e23ae76159
There were (a few) failures using 1.8.7, so document 1.9 and later as working in SWIG 4.0. Trusty failure in 2.3.0 was fixed in later versions of Ruby 2.3.x (expansion of RARRAY_PTR).
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5381 lines
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<title>SWIG and Ruby</title>
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<link rel="stylesheet" type="text/css" href="style.css">
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<H1><a name="Ruby">34 SWIG and Ruby</a></H1>
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<!-- INDEX -->
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<div class="sectiontoc">
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<ul>
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<li><a href="#Ruby_nn2">Preliminaries</a>
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<ul>
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<li><a href="#Ruby_nn3">Running SWIG</a>
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<li><a href="#Ruby_nn4">Getting the right header files</a>
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<li><a href="#Ruby_nn5">Compiling a dynamic module</a>
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<li><a href="#Ruby_nn6">Using your module</a>
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<li><a href="#Ruby_nn7">Static linking</a>
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<li><a href="#Ruby_nn8">Compilation of C++ extensions</a>
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</ul>
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<li><a href="#Ruby_nn9">Building Ruby Extensions under Windows 95/NT</a>
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<ul>
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<li><a href="#Ruby_nn10">Running SWIG from Developer Studio</a>
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</ul>
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<li><a href="#Ruby_nn11">The Ruby-to-C/C++ Mapping</a>
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<ul>
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<li><a href="#Ruby_nn12">Modules</a>
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<li><a href="#Ruby_nn13">Functions</a>
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<li><a href="#Ruby_nn14">Variable Linking</a>
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<li><a href="#Ruby_nn15">Constants</a>
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<li><a href="#Ruby_nn16">Pointers</a>
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<li><a href="#Ruby_nn17">Structures</a>
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<li><a href="#Ruby_nn18">C++ classes</a>
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<li><a href="#Ruby_nn19">C++ Inheritance</a>
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<li><a href="#Ruby_nn20">C++ Overloaded Functions</a>
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<li><a href="#Ruby_nn21">C++ Operators</a>
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<li><a href="#Ruby_nn22">C++ namespaces</a>
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<li><a href="#Ruby_nn23">C++ templates</a>
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<li><a href="#Ruby_nn23_1">C++ Standard Template Library (STL)</a>
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<li><a href="#Ruby_C_STL_Functors">C++ STL Functors</a>
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<li><a href="#Ruby_C_Iterators">C++ STL Iterators</a>
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<li><a href="#Ruby_nn24">C++ Smart Pointers</a>
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<ul>
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<li><a href="#Ruby_smart_pointers_shared_ptr">The shared_ptr Smart Pointer</a>
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<li><a href="#Ruby_smart_pointers_generic">Generic Smart Pointers</a>
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</ul>
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<li><a href="#Ruby_nn25">Cross-Language Polymorphism</a>
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<ul>
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<li><a href="#Ruby_nn26">Exception Unrolling</a>
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</ul>
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</ul>
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<li><a href="#Ruby_nn27">Naming</a>
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<ul>
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<li><a href="#Ruby_nn28">Defining Aliases</a>
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<li><a href="#Ruby_nn29">Predicate Methods</a>
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<li><a href="#Ruby_nn30">Bang Methods</a>
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<li><a href="#Ruby_nn31">Getters and Setters</a>
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</ul>
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<li><a href="#Ruby_nn32">Input and output parameters</a>
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<li><a href="#Ruby_nn33">Exception handling </a>
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<ul>
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<li><a href="#Ruby_nn34">Using the %exception directive </a>
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<li><a href="#Ruby_nn34_2">Handling Ruby Blocks </a>
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<li><a href="#Ruby_nn35">Raising exceptions </a>
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<li><a href="#Ruby_nn36">Exception classes </a>
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</ul>
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<li><a href="#Ruby_nn37">Typemaps</a>
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<ul>
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<li><a href="#Ruby_nn38">What is a typemap?</a>
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<li><a href="#Ruby_Typemap_scope">Typemap scope</a>
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<li><a href="#Ruby_Copying_a_typemap">Copying a typemap</a>
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<li><a href="#Ruby_Deleting_a_typemap">Deleting a typemap</a>
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<li><a href="#Ruby_Placement_of_typemaps">Placement of typemaps</a>
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<li><a href="#Ruby_nn39">Ruby typemaps</a>
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<ul>
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<li><a href="#Ruby_in_typemap">"in" typemap</a>
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<li><a href="#Ruby_typecheck_typemap">"typecheck" typemap</a>
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<li><a href="#Ruby_out_typemap">"out" typemap</a>
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<li><a href="#Ruby_arginit_typemap">"arginit" typemap</a>
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<li><a href="#Ruby_default_typemap">"default" typemap</a>
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<li><a href="#Ruby_check_typemap">"check" typemap</a>
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<li><a href="#Ruby_argout_typemap_">"argout" typemap</a>
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<li><a href="#Ruby_freearg_typemap_">"freearg" typemap</a>
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<li><a href="#Ruby_newfree_typemap">"newfree" typemap</a>
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<li><a href="#Ruby_memberin_typemap">"memberin" typemap</a>
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<li><a href="#Ruby_varin_typemap">"varin" typemap</a>
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<li><a href="#Ruby_varout_typemap_">"varout" typemap</a>
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<li><a href="#Ruby_throws_typemap">"throws" typemap</a>
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<li><a href="#Ruby_directorin_typemap">directorin typemap</a>
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<li><a href="#Ruby_directorout_typemap">directorout typemap</a>
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<li><a href="#Ruby_directorargout_typemap">directorargout typemap</a>
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<li><a href="#Ruby_ret_typemap">ret typemap</a>
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<li><a href="#Ruby_globalin_typemap">globalin typemap</a>
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</ul>
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<li><a href="#Ruby_nn40">Typemap variables</a>
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<li><a href="#Ruby_nn41">Useful Functions</a>
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<ul>
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<li><a href="#Ruby_nn42">C Datatypes to Ruby Objects</a>
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<li><a href="#Ruby_nn43">Ruby Objects to C Datatypes</a>
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<li><a href="#Ruby_nn44">Macros for VALUE</a>
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<li><a href="#Ruby_nn45">Exceptions</a>
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<li><a href="#Ruby_nn46">Iterators</a>
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</ul>
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<li><a href="#Ruby_nn47">Typemap Examples</a>
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<li><a href="#Ruby_nn48">Converting a Ruby array to a char **</a>
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<li><a href="#Ruby_nn49">Collecting arguments in a hash</a>
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<li><a href="#Ruby_nn50">Pointer handling</a>
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<ul>
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<li><a href="#Ruby_nn51">Ruby Datatype Wrapping</a>
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</ul>
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<li><a href="#Ruby_nn52">Example: STL Vector to Ruby Array</a>
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</ul>
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<li><a href="#Ruby_nn65">Docstring Features</a>
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<ul>
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<li><a href="#Ruby_nn66">Module docstring</a>
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<li><a href="#Ruby_nn67">%feature("autodoc")</a>
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<ul>
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<li><a href="#Ruby_nn68">%feature("autodoc", "0")</a>
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<li><a href="#Ruby_autodoc1">%feature("autodoc", "1")</a>
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<li><a href="#Ruby_autodoc2">%feature("autodoc", "2")</a>
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<li><a href="#Ruby_feature_autodoc3">%feature("autodoc", "3")</a>
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<li><a href="#Ruby_nn70">%feature("autodoc", "docstring")</a>
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</ul>
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<li><a href="#Ruby_nn71">%feature("docstring")</a>
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</ul>
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<li><a href="#Ruby_nn53">Advanced Topics</a>
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<ul>
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<li><a href="#Ruby_operator_overloading">Operator overloading</a>
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<li><a href="#Ruby_nn55">Creating Multi-Module Packages</a>
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<li><a href="#Ruby_nn56">Specifying Mixin Modules</a>
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</ul>
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<li><a href="#Ruby_nn57">Memory Management</a>
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<ul>
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<li><a href="#Ruby_nn58">Mark and Sweep Garbage Collector </a>
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<li><a href="#Ruby_nn59">Object Ownership</a>
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<li><a href="#Ruby_nn60">Object Tracking</a>
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<li><a href="#Ruby_nn61">Mark Functions</a>
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<li><a href="#Ruby_nn62">Free Functions</a>
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<li><a href="#Ruby_nn63">Embedded Ruby and the C++ Stack</a>
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</ul>
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</ul>
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</div>
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<!-- INDEX -->
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<p>This chapter describes SWIG's support of Ruby.</p>
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<H2><a name="Ruby_nn2">34.1 Preliminaries</a></H2>
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<p> SWIG 4.0 is known to work with Ruby versions 1.9 and later.
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Given the choice, you should use the latest stable version of Ruby. You
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should also determine if your system supports shared libraries and
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dynamic loading. SWIG will work with or without dynamic loading, but
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the compilation process will vary. </p>
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<p>This chapter covers most SWIG features, but in less depth than
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is found in earlier chapters. At the very least, make sure you also
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read the "<a href="SWIG.html#SWIG">SWIG Basics</a>"
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chapter. It is also assumed that the reader has a basic understanding
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of Ruby. </p>
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<H3><a name="Ruby_nn3">34.1.1 Running SWIG</a></H3>
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<p> To build a Ruby module, run SWIG using the <tt>-ruby</tt>
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option:</p>
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<div class="code shell">
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<pre>$ swig -ruby example.i
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</pre>
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</div>
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<p> If building a C++ extension, add the <tt>-c++</tt>
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option: </p>
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<div class="code shell">
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<pre>$ swig -c++ -ruby example.i
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</pre>
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</div>
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<p> This creates a file <tt>example_wrap.c</tt> (<tt>example_wrap.cxx</tt>
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if compiling a C++ extension) that contains all of the code needed to
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build a Ruby extension module. To finish building the module, you need
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to compile this file and link it with the rest of your program. </p>
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<H3><a name="Ruby_nn4">34.1.2 Getting the right header files</a></H3>
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<p> In order to compile the wrapper code, the compiler needs the <tt>ruby.h</tt>
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header file and its dependencies, notably <tt>ruby/config.h</tt> which is
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found in a different, architecture-dependent, directory. The best way to find
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the compiler options needed to compile the code is to ask Ruby itself:</p>
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<div class="code shell">
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<pre>$ ruby -rrbconfig -e 'puts "-I#{RbConfig::CONFIG[%q{rubyhdrdir}]} -I#{RbConfig::CONFIG[%q{rubyarchhdrdir}]}"'
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-I/usr/include/ruby-2.1.0 -I/usr/include/x86_64-linux-gnu/ruby-2.1.0
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</pre>
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</div>
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<H3><a name="Ruby_nn5">34.1.3 Compiling a dynamic module</a></H3>
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<p> Ruby extension modules are typically compiled into shared
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libraries that the interpreter loads dynamically at runtime. Since the
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exact commands for doing this vary from platform to platform, your best
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bet is to follow the steps described in the <tt>README.EXT</tt>
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file from the Ruby distribution: </p>
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<ol>
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<li>
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<p>Create a file called <tt>extconf.rb</tt> that
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looks like the following:</p>
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<div class="code targetlang">
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<pre>require 'mkmf'
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create_makefile('example')</pre>
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</div>
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</li>
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<li>
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<p>Type the following to build the extension:</p>
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<div class="code shell">
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<pre>
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$ ruby extconf.rb
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$ make
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$ make install
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</pre>
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</div>
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</li>
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</ol>
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<p> Of course, there is the problem that mkmf does not work
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correctly on all platforms, e.g, HPUX. If you need to add your own make
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rules to the file that <tt>extconf.rb</tt> produces, you
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can add this: </p>
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<div class="code targetlang">
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<pre>open("Makefile", "a") { |mf|
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puts <<EOM
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# Your make rules go here
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EOM
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}
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</pre>
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</div>
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<p> to the end of the <tt>extconf.rb</tt> file. If
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for some reason you don't want to use the standard approach, you'll
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need to determine the correct compiler and linker flags for your build
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platform. For example, assuming you have code you need to link to in a file
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called <tt>example.c</tt>, a typical sequence of commands for the Linux
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operating system would look something like this: </p>
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<div class="code shell">
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<pre>$ swig -ruby example.i
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$ gcc -O2 -fPIC -c example.c
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$ gcc -O2 -fPIC -c example_wrap.c -I/usr/include/ruby-2.1.0
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$ gcc -shared example.o example_wrap.o -o example.so
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</pre>
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</div>
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<p>
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The -fPIC option tells GCC to generate position-independent code (PIC)
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which is required for most architectures (it's not vital on x86, but
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still a good idea as it allows code pages from the library to be shared between
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processes). Other compilers may need a different option specified instead of
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-fPIC.
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</p>
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<p>
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If in doubt, consult the
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manual pages for your compiler and linker to determine the correct set
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of options. You might also check the <a href="https://github.com/swig/swig/wiki">SWIG Wiki</a>
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for additional information. </p>
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<H3><a name="Ruby_nn6">34.1.4 Using your module</a></H3>
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|
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<p> Ruby <i>module</i> names must be capitalized,
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but the convention for Ruby <i>feature</i> names is to use
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lowercase names. So, for example, the <b>Etc</b> extension
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module is imported by requiring the <b>etc</b> feature: </p>
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<div class="code targetlang">
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<pre># The feature name begins with a lowercase letter...
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require 'etc'
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# ... but the module name begins with an uppercase letter
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puts "Your login name: #{Etc.getlogin}"
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</pre>
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</div>
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<p> To stay consistent with this practice, you should always
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specify a <b>lowercase</b> module name with SWIG's <tt>%module</tt>
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directive. SWIG will automatically correct the resulting Ruby module
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name for your extension. So for example, a SWIG interface file that
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begins with: </p>
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<div class="code">
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<pre>%module example</pre>
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</div>
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<p> will result in an extension module using the feature name
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"example" and Ruby module name "Example". </p>
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<H3><a name="Ruby_nn7">34.1.5 Static linking</a></H3>
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|
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<p> An alternative approach to dynamic linking is to rebuild the
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Ruby interpreter with your extension module added to it. In the past,
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this approach was sometimes necessary due to limitations in dynamic
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loading support on certain machines. However, the situation has
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improved greatly over the last few years and you should not consider
|
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this approach unless there is really no other option. </p>
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<p>The usual procedure for adding a new module to Ruby involves
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finding the Ruby source, adding an entry to the <tt>ext/Setup</tt>
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file, adding your directory to the list of extensions in the file, and
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finally rebuilding Ruby. </p>
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<H3><a name="Ruby_nn8">34.1.6 Compilation of C++ extensions</a></H3>
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|
|
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<p> On most machines, C++ extension modules should be linked
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using the C++ compiler. For example: </p>
|
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<div class="code shell">
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<pre>
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$ swig -c++ -ruby example.i
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$ g++ -fPIC -c example.cxx
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$ g++ -fPIC -c example_wrap.cxx -I/usr/include/ruby-2.1.0
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$ g++ -shared example.o example_wrap.o -o example.so
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</pre>
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</div>
|
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<p> If you've written an <tt>extconf.rb</tt> script
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to automatically generate a <tt>Makefile</tt> for your C++
|
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extension module, keep in mind that (as of this writing) Ruby still
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|
uses <tt>gcc</tt> and not <tt>g++</tt> as its
|
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linker. As a result, the required C++ runtime library support will not
|
|
be automatically linked into your extension module and it may fail to
|
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load on some platforms. A workaround for this problem is use the <tt>mkmf</tt>
|
|
module's <tt>append_library()</tt> method to add one of
|
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the C++ runtime libraries to the list of libraries linked into your
|
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extension, e.g. </p>
|
|
|
|
<div class="code targetlang">
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<pre>require 'mkmf'
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$libs = append_library($libs, "supc++")
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create_makefile('example')</pre>
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</div>
|
|
|
|
<H2><a name="Ruby_nn9">34.2 Building Ruby Extensions under Windows 95/NT</a></H2>
|
|
|
|
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<p> Building a SWIG extension to Ruby under Windows 95/NT is
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roughly similar to the process used with Unix. Normally, you will want
|
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to produce a DLL that can be loaded into the Ruby interpreter. For all
|
|
recent versions of Ruby, the procedure described above (i.e. using an <tt>extconf.rb</tt>
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script) will work with Windows as well; you should be able to build
|
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your code into a DLL by typing: </p>
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<div class="code shell">
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<pre>
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C:\swigtest> ruby extconf.rb
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C:\swigtest> nmake
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C:\swigtest> nmake install
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</pre>
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</div>
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<p> The remainder of this section covers the process of compiling
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SWIG-generated Ruby extensions with Microsoft Visual C++ 6 (i.e. within
|
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the Developer Studio IDE, instead of using the command line tools). In
|
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order to build extensions, you may need to download the source
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distribution to the Ruby package, as you will need the Ruby header
|
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files. </p>
|
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|
|
<H3><a name="Ruby_nn10">34.2.1 Running SWIG from Developer Studio</a></H3>
|
|
|
|
|
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<p> If you are developing your application within Microsoft
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|
developer studio, SWIG can be invoked as a custom build option. The
|
|
process roughly follows these steps : </p>
|
|
<ul>
|
|
<li> Open up a new workspace and use the AppWizard to select a
|
|
DLL project. </li>
|
|
<li> Add both the SWIG interface file (the .i file), any
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supporting C files, and the name of the wrapper file that will be
|
|
created by SWIG (i.e. <tt>example_wrap.c</tt>). Note : If
|
|
using C++, choose a different suffix for the wrapper file such as <tt>example_wrap.cxx</tt>.
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Don't worry if the wrapper file doesn't exist yet--Developer Studio
|
|
will keep a reference to it around. </li>
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<li> Select the SWIG interface file and go to the settings
|
|
menu. Under settings, select the "Custom Build" option. </li>
|
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<li> Enter "SWIG" in the description field. </li>
|
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<li> Enter "<tt>swig -ruby -o
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$(ProjDir)\$(InputName)_wrap.c $(InputPath)</tt>" in the "Build
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command(s) field". You may have to include the path to swig.exe. </li>
|
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<li> Enter "<tt>$(ProjDir)\$(InputName)_wrap.c</tt>"
|
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in the "Output files(s) field". </li>
|
|
<li> Next, select the settings for the entire project and go to
|
|
the C/C++ tab and select the Preprocessor category. Add NT=1 to the
|
|
Preprocessor definitions. This must be set else you will get
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|
compilation errors. Also add IMPORT to the preprocessor definitions,
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else you may get runtime errors. Also add the include directories for
|
|
your Ruby installation under "Additional include directories". </li>
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<li> Next, select the settings for the entire project and go to
|
|
the Link tab and select the General category. Set the name of the
|
|
output file to match the name of your Ruby module (i.e.. example.dll).
|
|
Next add the Ruby library file to your link libraries under
|
|
Object/Library modules. For example "mswin32-ruby16.lib. You also need
|
|
to add the path to the library under the Input tab - Additional library
|
|
path. </li>
|
|
<li> Build your project. </li>
|
|
</ul>
|
|
|
|
<p> Now, assuming all went well, SWIG will be automatically
|
|
invoked when you build your project. Any changes made to the interface
|
|
file will result in SWIG being automatically invoked to produce a new
|
|
version of the wrapper file. To run your new Ruby extension, simply run
|
|
Ruby and use the <tt>require</tt> command as normal. For
|
|
example if you have this ruby file run.rb:</p>
|
|
|
|
<div class="code targetlang">
|
|
<pre># file: run.rb
|
|
require 'Example'
|
|
|
|
# Call a c function
|
|
print "Foo = ", Example.Foo, "\n"</pre>
|
|
</div>
|
|
|
|
<p> Ensure the dll just built is in your path or current
|
|
directory, then run the Ruby script from the DOS/Command prompt: </p>
|
|
|
|
<div class="code shell">
|
|
<pre>
|
|
C:\swigtest> ruby run.rb
|
|
Foo = 3.0
|
|
</pre>
|
|
</div>
|
|
|
|
<H2><a name="Ruby_nn11">34.3 The Ruby-to-C/C++ Mapping</a></H2>
|
|
|
|
|
|
<p> This section describes the basics of how SWIG maps C or C++
|
|
declarations in your SWIG interface files to Ruby constructs. </p>
|
|
|
|
<H3><a name="Ruby_nn12">34.3.1 Modules</a></H3>
|
|
|
|
|
|
<p> The SWIG <tt>%module</tt> directive specifies
|
|
the name of the Ruby module. If you specify: </p>
|
|
|
|
<div class="code">
|
|
<pre>%module example</pre>
|
|
</div>
|
|
|
|
<p> then everything is wrapped into a Ruby module named <tt>Example</tt>
|
|
that is nested directly under the global module. You can specify a more
|
|
deeply nested module by specifying the fully-qualified module name in
|
|
quotes, e.g. </p>
|
|
|
|
<div class="code">
|
|
<pre>%module "foo::bar::spam"</pre>
|
|
</div>
|
|
|
|
<p> An alternate method of specifying a nested module name is to
|
|
use the <tt>-prefix</tt>
|
|
option on the SWIG command line. The prefix that you specify with this
|
|
option will be prepended to the module name specified with the <tt>%module</tt>
|
|
directive in your SWIG interface file. So for example, this declaration
|
|
at the top of your SWIG interface file:
|
|
</p>
|
|
|
|
<div class="code">
|
|
<pre>%module "foo::bar::spam"</pre>
|
|
</div>
|
|
|
|
<p> will result in a nested module name of <tt>Foo::Bar::Spam</tt>,
|
|
but you can achieve the <span style="font-style: italic;">same</span>
|
|
effect by specifying:
|
|
</p>
|
|
|
|
<div class="code">
|
|
<pre>%module spam</pre>
|
|
</div>
|
|
|
|
<p> and then running SWIG with the <tt>-prefix</tt> command
|
|
line option:
|
|
</p>
|
|
|
|
<div class="code shell">
|
|
<pre>
|
|
$ swig -ruby -prefix "foo::bar::" example.i
|
|
</pre>
|
|
</div>
|
|
|
|
<p> Starting with SWIG 1.3.20, you can also choose to wrap
|
|
everything into the global module by specifying the <tt>-globalmodule</tt>
|
|
option on the SWIG command line, i.e. </p>
|
|
|
|
<div class="code shell">
|
|
<pre>
|
|
$ swig -ruby -globalmodule example.i
|
|
</pre>
|
|
</div>
|
|
|
|
<p> Note that this does not relieve you of the requirement of
|
|
specifying the SWIG module name with the <tt>%module</tt>
|
|
directive (or the <tt>-module</tt> command-line option) as
|
|
described earlier. </p>
|
|
|
|
<p>When choosing a module name, do not use the same name as a
|
|
built-in Ruby command or standard module name, as the results may be
|
|
unpredictable. Similarly, if you're using the <tt>-globalmodule</tt>
|
|
option to wrap everything into the global module, take care that the
|
|
names of your constants, classes and methods don't conflict with any of
|
|
Ruby's built-in names. </p>
|
|
|
|
<H3><a name="Ruby_nn13">34.3.2 Functions</a></H3>
|
|
|
|
|
|
<p> Global functions are wrapped as Ruby module methods. For
|
|
example, given the SWIG interface file <tt>example.i</tt>:
|
|
</p>
|
|
|
|
<div class="code">
|
|
<pre>%module example
|
|
|
|
int fact(int n);</pre>
|
|
</div>
|
|
|
|
<p> and C source file <tt>example.c</tt>: </p>
|
|
|
|
<div class="code">
|
|
<pre>int fact(int n) {
|
|
if (n == 0)
|
|
return 1;
|
|
return (n * fact(n-1));
|
|
}</pre>
|
|
</div>
|
|
|
|
<p> SWIG will generate a method <i>fact</i> in the <i>Example</i>
|
|
module that can be used like so: </p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>$ <b>irb</b>
|
|
irb(main):001:0> <b>require 'example'</b>
|
|
true
|
|
irb(main):002:0> <b>Example.fact(4)</b>
|
|
24</pre>
|
|
</div>
|
|
|
|
<H3><a name="Ruby_nn14">34.3.3 Variable Linking</a></H3>
|
|
|
|
|
|
<p> C/C++ global variables are wrapped as a pair of singleton
|
|
methods for the module: one to get the value of the global variable and
|
|
one to set it. For example, the following SWIG interface file declares
|
|
two global variables: </p>
|
|
|
|
<div class="code">
|
|
<pre>// SWIG interface file with global variables
|
|
%module example
|
|
...
|
|
%inline %{
|
|
extern int variable1;
|
|
extern double Variable2;
|
|
%}
|
|
...</pre>
|
|
</div>
|
|
|
|
<p> Now look at the Ruby interface:</p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>$ <b>irb</b>
|
|
irb(main):001:0> <b>require 'Example'</b>
|
|
true
|
|
irb(main):002:0> <b>Example.variable1 = 2</b>
|
|
2
|
|
irb(main):003:0> <b>Example.Variable2 = 4 * 10.3</b>
|
|
41.2
|
|
irb(main):004:0> <b>Example.Variable2</b>
|
|
41.2</pre>
|
|
</div>
|
|
|
|
<p> If you make an error in variable assignment, you will receive
|
|
an error message. For example: </p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>irb(main):005:0> <b>Example.Variable2 = "hello"</b>
|
|
TypeError: no implicit conversion to float from string
|
|
from (irb):5:in `Variable2='
|
|
from (irb):5</pre>
|
|
</div>
|
|
|
|
<p> If a variable is declared as <tt>const</tt>, it
|
|
is wrapped as a read-only variable. Attempts to modify its value will
|
|
result in an error. </p>
|
|
|
|
<p>To make ordinary variables read-only, you can also use the <tt>%immutable</tt>
|
|
directive. For example: </p>
|
|
|
|
<div class="code">
|
|
<pre>%immutable;
|
|
%inline %{
|
|
extern char *path;
|
|
%}
|
|
%mutable;</pre>
|
|
</div>
|
|
|
|
<p> The <tt>%immutable</tt> directive stays in
|
|
effect until it is explicitly disabled using <tt>%mutable</tt>.
|
|
</p>
|
|
|
|
<H3><a name="Ruby_nn15">34.3.4 Constants</a></H3>
|
|
|
|
|
|
<p> C/C++ constants are wrapped as module constants initialized
|
|
to the appropriate value. To create a constant, use <tt>#define</tt>
|
|
or the <tt>%constant</tt> directive. For example: </p>
|
|
|
|
<div class="code">
|
|
<pre>#define PI 3.14159
|
|
#define VERSION "1.0"
|
|
|
|
%constant int FOO = 42;
|
|
%constant const char *path = "/usr/local";
|
|
|
|
const int BAR = 32;</pre>
|
|
</div>
|
|
|
|
<p> Remember to use the :: operator in Ruby to get at these
|
|
constant values, e.g. </p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>$ <b>irb</b>
|
|
irb(main):001:0> <b>require 'Example'</b>
|
|
true
|
|
irb(main):002:0> <b>Example::PI</b>
|
|
3.14159</pre>
|
|
</div>
|
|
|
|
<H3><a name="Ruby_nn16">34.3.5 Pointers</a></H3>
|
|
|
|
|
|
<p> "Opaque" pointers to arbitrary C/C++ types (i.e. types that
|
|
aren't explicitly declared in your SWIG interface file) are wrapped as
|
|
data objects. So, for example, consider a SWIG interface file
|
|
containing only the declarations: </p>
|
|
|
|
<div class="code">
|
|
<pre>Foo *get_foo();
|
|
void set_foo(Foo *foo);</pre>
|
|
</div>
|
|
|
|
<p> For this case, the <i>get_foo()</i> method
|
|
returns an instance of an internally generated Ruby class: </p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>irb(main):001:0> <b>foo = Example::get_foo()</b>
|
|
#<SWIG::TYPE_p_Foo:0x402b1654></pre>
|
|
</div>
|
|
|
|
<p> A <tt>NULL</tt> pointer is always represented by
|
|
the Ruby <tt>nil</tt> object. </p>
|
|
|
|
<H3><a name="Ruby_nn17">34.3.6 Structures</a></H3>
|
|
|
|
|
|
<p> C/C++ structs are wrapped as Ruby classes, with accessor
|
|
methods (i.e. "getters" and "setters") for all of the struct members.
|
|
For example, this struct declaration: </p>
|
|
|
|
<div class="code">
|
|
<pre>struct Vector {
|
|
double x, y;
|
|
};</pre>
|
|
</div>
|
|
|
|
<p> gets wrapped as a <tt>Vector</tt> class, with
|
|
Ruby instance methods <tt>x</tt>, <tt>x=</tt>,
|
|
<tt>y</tt> and <tt>y=</tt>. These methods can
|
|
be used to access structure data from Ruby as follows: </p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>$ <b>irb</b>
|
|
irb(main):001:0> <b>require 'Example'</b>
|
|
true
|
|
irb(main):002:0> <b>f = Example::Vector.new</b>
|
|
#<Example::Vector:0x4020b268>
|
|
irb(main):003:0> <b>f.x = 10</b>
|
|
nil
|
|
irb(main):004:0> <b>f.x</b>
|
|
10.0</pre>
|
|
</div>
|
|
|
|
<p> Similar access is provided for unions and the public data
|
|
members of C++ classes.</p>
|
|
|
|
<p><tt>const</tt> members of a structure are
|
|
read-only. Data members can also be forced to be read-only using the <tt>%immutable</tt>
|
|
directive (in C++, <tt>private</tt> may also be used). For
|
|
example: </p>
|
|
|
|
<div class="code">
|
|
<pre>struct Foo {
|
|
...
|
|
%immutable;
|
|
int x; /* Read-only members */
|
|
char *name;
|
|
%mutable;
|
|
...
|
|
};</pre>
|
|
</div>
|
|
|
|
<p> When <tt>char *</tt> members of a structure are
|
|
wrapped, the contents are assumed to be dynamically allocated using <tt>malloc</tt>
|
|
or <tt>new</tt> (depending on whether or not SWIG is run
|
|
with the <tt>-c++</tt> option). When the structure member
|
|
is set, the old contents will be released and a new value created. If
|
|
this is not the behavior you want, you will have to use a typemap
|
|
(described shortly). </p>
|
|
|
|
<p>Array members are normally wrapped as read-only. For example,
|
|
this code: </p>
|
|
|
|
<div class="code">
|
|
<pre>struct Foo {
|
|
int x[50];
|
|
};</pre>
|
|
</div>
|
|
|
|
<p> produces a single accessor function like this: </p>
|
|
|
|
<div class="code">
|
|
<pre>int *Foo_x_get(Foo *self) {
|
|
return self->x;
|
|
};</pre>
|
|
</div>
|
|
|
|
<p> If you want to set an array member, you will need to supply a
|
|
"memberin" typemap described in the <a href="#Ruby_memberin_typemap">section on typemaps</a>.
|
|
As a special case, SWIG does generate code to set array members of type
|
|
<tt>char</tt> (allowing you to store a Ruby string in the
|
|
structure). </p>
|
|
|
|
<p>When structure members are wrapped, they are handled as
|
|
pointers. For example, </p>
|
|
|
|
<div class="code">
|
|
<pre>struct Foo {
|
|
...
|
|
};
|
|
|
|
struct Bar {
|
|
Foo f;
|
|
};</pre>
|
|
</div>
|
|
|
|
<p> generates accessor functions such as this: </p>
|
|
|
|
<div class="code">
|
|
<pre>Foo *Bar_f_get(Bar *b) {
|
|
return &b->f;
|
|
}
|
|
|
|
void Bar_f_set(Bar *b, Foo *val) {
|
|
b->f = *val;
|
|
}</pre>
|
|
</div>
|
|
|
|
<H3><a name="Ruby_nn18">34.3.7 C++ classes</a></H3>
|
|
|
|
|
|
<p> Like structs, C++ classes are wrapped by creating a new Ruby
|
|
class of the same name with accessor methods for the public class
|
|
member data. Additionally, public member functions for the class are
|
|
wrapped as Ruby instance methods, and public static member functions
|
|
are wrapped as Ruby singleton methods. So, given the C++ class
|
|
declaration: </p>
|
|
|
|
<div class="code">
|
|
<pre>class List {
|
|
public:
|
|
List();
|
|
~List();
|
|
int search(char *item);
|
|
void insert(char *item);
|
|
void remove(char *item);
|
|
char *get(int n);
|
|
int length;
|
|
static void print(List *l);
|
|
};</pre>
|
|
</div>
|
|
|
|
<p> SWIG would create a <tt>List</tt> class with: </p>
|
|
|
|
<ul>
|
|
<li> instance methods <i>search</i>, <i>insert</i>,
|
|
<i>remove</i>, and <i>get</i>; </li>
|
|
<li> instance methods <i>length</i> and <i>length=</i>
|
|
(to get and set the value of the <i>length</i> data
|
|
member); and, </li>
|
|
<li> a <i>print</i> singleton method for the
|
|
class. </li>
|
|
</ul>
|
|
|
|
<p> In Ruby, these functions are used as follows: </p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>require 'Example'
|
|
|
|
l = Example::List.new
|
|
|
|
l.insert("Ale")
|
|
l.insert("Stout")
|
|
l.insert("Lager")
|
|
Example.print(l)
|
|
l.length()
|
|
----- produces the following output
|
|
Lager
|
|
Stout
|
|
Ale
|
|
3</pre>
|
|
</div>
|
|
|
|
<H3><a name="Ruby_nn19">34.3.8 C++ Inheritance</a></H3>
|
|
|
|
|
|
<p> The SWIG type-checker is fully aware of C++ inheritance.
|
|
Therefore, if you have classes like this: </p>
|
|
|
|
<div class="code">
|
|
<pre>class Parent {
|
|
...
|
|
};
|
|
|
|
class Child : public Parent {
|
|
...
|
|
};</pre>
|
|
</div>
|
|
|
|
<p> those classes are wrapped into a hierarchy of Ruby classes
|
|
that reflect the same inheritance structure. All of the usual Ruby
|
|
utility methods work normally: </p>
|
|
|
|
<div class="code">
|
|
<pre>irb(main):001:0> <b>c = Child.new</b>
|
|
#<Bar:0x4016efd4>
|
|
irb(main):002:0> <b>c.instance_of? Child</b>
|
|
true
|
|
irb(main):003:0> <b>b.instance_of? Parent</b>
|
|
false
|
|
irb(main):004:0> <b>b.is_a? Child</b>
|
|
true
|
|
irb(main):005:0> <b>b.is_a? Parent</b>
|
|
true
|
|
irb(main):006:0> <b>Child < Parent</b>
|
|
true
|
|
irb(main):007:0> <b>Child > Parent</b>
|
|
false</pre>
|
|
</div>
|
|
|
|
<p> Furthermore, if you have a function like this: </p>
|
|
|
|
<div class="code">
|
|
<pre>void spam(Parent *f);</pre>
|
|
</div>
|
|
|
|
<p> then the function <tt>spam()</tt> accepts <tt>Parent</tt>*
|
|
or a pointer to any class derived from <tt>Parent</tt>. </p>
|
|
|
|
<p>Until recently, the Ruby module for SWIG didn't support
|
|
multiple inheritance, and this is still the default behavior. This
|
|
doesn't mean that you can't wrap C++ classes which inherit from
|
|
multiple base classes; it simply means that only the <b>first</b>
|
|
base class listed in the class declaration is considered, and any
|
|
additional base classes are ignored. As an example, consider a SWIG
|
|
interface file with a declaration like this: </p>
|
|
|
|
<div class="code">
|
|
<pre>class Derived : public Base1, public Base2
|
|
{
|
|
...
|
|
};</pre>
|
|
</div>
|
|
|
|
<p> For this case, the resulting Ruby class (<tt>Derived</tt>)
|
|
will only consider <tt>Base1</tt> as its superclass. It
|
|
won't inherit any of <tt>Base2</tt>'s member functions or
|
|
data and it won't recognize <tt>Base2</tt> as an
|
|
"ancestor" of <tt>Derived</tt> (i.e. the <em>is_a?</em>
|
|
relationship would fail). When SWIG processes this interface file,
|
|
you'll see a warning message like: </p>
|
|
|
|
<div class="code shell">
|
|
<pre>example.i:5: Warning 802: Warning for Derived: Base Base2 ignored.
|
|
Multiple inheritance is not supported in Ruby.</pre>
|
|
</div>
|
|
|
|
<p> Starting with SWIG 1.3.20, the Ruby module for SWIG provides
|
|
limited support for multiple inheritance. Because the approach for
|
|
dealing with multiple inheritance introduces some limitations, this is
|
|
an optional feature that you can activate with the <tt>-minherit</tt>
|
|
command-line option: </p>
|
|
|
|
<div class="code shell">
|
|
<pre>
|
|
$ swig -c++ -ruby -minherit example.i
|
|
</pre>
|
|
</div>
|
|
|
|
<p> Using our previous example, if your SWIG interface file
|
|
contains a declaration like this: </p>
|
|
|
|
<div class="code">
|
|
<pre>class Derived : public Base1, public Base2
|
|
{
|
|
...
|
|
};</pre>
|
|
</div>
|
|
|
|
<p> and you run SWIG with the <tt>-minherit</tt>
|
|
command-line option, then you will end up with a Ruby class <tt>Derived</tt>
|
|
that appears to "inherit" the member data and functions from both <tt>Base1</tt>
|
|
and <tt>Base2</tt>. What actually happens is that three
|
|
different top-level classes are created, with Ruby's <tt>Object</tt>
|
|
class as their superclass. Each of these classes defines a nested
|
|
module named <tt>Impl</tt>, and it's in these nested <tt>Impl</tt>
|
|
modules that the actual instance methods for the classes are defined,
|
|
i.e. </p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>class Base1
|
|
module Impl
|
|
# Define Base1 methods here
|
|
end
|
|
include Impl
|
|
end
|
|
|
|
class Base2
|
|
module Impl
|
|
# Define Base2 methods here
|
|
end
|
|
include Impl
|
|
end
|
|
|
|
class Derived
|
|
module Impl
|
|
include Base1::Impl
|
|
include Base2::Impl
|
|
# Define Derived methods here
|
|
end
|
|
include Impl
|
|
end</pre>
|
|
</div>
|
|
|
|
<p> Observe that after the nested <tt>Impl</tt>
|
|
module for a class is defined, it is mixed-in to the class itself. Also
|
|
observe that the <tt>Derived::Impl</tt> module first
|
|
mixes-in its base classes' <tt>Impl</tt> modules, thus
|
|
"inheriting" all of their behavior. </p>
|
|
|
|
<p>The primary drawback is that, unlike the default mode of
|
|
operation, neither <tt>Base1</tt> nor <tt>Base2</tt>
|
|
is a true superclass of <tt>Derived</tt> anymore: </p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>obj = Derived.new
|
|
obj.is_a? Base1 # this will return false...
|
|
obj.is_a? Base2 # ... and so will this</pre>
|
|
</div>
|
|
|
|
<p> In most cases, this is not a serious problem since objects of
|
|
type <tt>Derived</tt> will otherwise behave as though they
|
|
inherit from both <tt>Base1</tt> and <tt>Base2</tt>
|
|
(i.e. they exhibit <a href="http://c2.com/cgi/wiki?DuckTyping">"Duck
|
|
Typing"</a>). </p>
|
|
|
|
<H3><a name="Ruby_nn20">34.3.9 C++ Overloaded Functions</a></H3>
|
|
|
|
|
|
<p> C++ overloaded functions, methods, and constructors are
|
|
mostly supported by SWIG. For example, if you have two functions like
|
|
this: </p>
|
|
|
|
<div class="code">
|
|
<pre>void foo(int);
|
|
void foo(char *c);</pre>
|
|
</div>
|
|
|
|
<p> You can use them in Ruby in a straightforward manner: </p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>irb(main):001:0> <b>foo(3)</b> # foo(int)
|
|
irb(main):002:0> <b>foo("Hello")</b> # foo(char *c)</pre>
|
|
</div>
|
|
|
|
<p>Similarly, if you have a class like this, </p>
|
|
|
|
<div class="code">
|
|
<pre>class Foo {
|
|
public:
|
|
Foo();
|
|
Foo(const Foo &);
|
|
...
|
|
};</pre>
|
|
</div>
|
|
|
|
<p>you can write Ruby code like this:</p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>irb(main):001:0> <b>f = Foo.new</b> # Create a Foo
|
|
irb(main):002:0> <b>g = Foo.new(f)</b> # Copy f</pre>
|
|
</div>
|
|
|
|
<p> Overloading support is not quite as flexible as in C++.
|
|
Sometimes there are methods that SWIG can't disambiguate. For example: </p>
|
|
|
|
<div class="code">
|
|
<pre>void spam(int);
|
|
void spam(short);</pre>
|
|
</div>
|
|
|
|
<p>or</p>
|
|
|
|
<div class="code">
|
|
<pre>void foo(Bar *b);
|
|
void foo(Bar &b);</pre>
|
|
</div>
|
|
|
|
<p> If declarations such as these appear, you will get a warning
|
|
message like this: </p>
|
|
|
|
<div class="code shell">
|
|
<pre>
|
|
example.i:12: Warning 509: Overloaded method spam(short) effectively ignored,
|
|
example.i:11: Warning 509: as it is shadowed by spam(int).
|
|
</pre>
|
|
</div>
|
|
|
|
<p> To fix this, you either need to ignore or rename one of the
|
|
methods. For example: </p>
|
|
|
|
<div class="code">
|
|
<pre>%rename(spam_short) spam(short);
|
|
...
|
|
void spam(int);
|
|
void spam(short); // Accessed as spam_short</pre>
|
|
</div>
|
|
|
|
<p>or</p>
|
|
|
|
<div class="code">
|
|
<pre>%ignore spam(short);
|
|
...
|
|
void spam(int);
|
|
void spam(short); // Ignored</pre>
|
|
</div>
|
|
|
|
<p> SWIG resolves overloaded functions and methods using a
|
|
disambiguation scheme that ranks and sorts declarations according to a
|
|
set of type-precedence rules. The order in which declarations appear in
|
|
the input does not matter except in situations where ambiguity
|
|
arises--in this case, the first declaration takes precedence. </p>
|
|
|
|
<p>Please refer to the <a href="SWIGPlus.html#SWIGPlus">"SWIG
|
|
and C++"</a> chapter for more information about overloading. </p>
|
|
|
|
<H3><a name="Ruby_nn21">34.3.10 C++ Operators</a></H3>
|
|
|
|
|
|
<p> For the most part, overloaded operators are handled
|
|
automatically by SWIG and do not require any special treatment on your
|
|
part. So if your class declares an overloaded addition operator, e.g. </p>
|
|
|
|
<div class="code">
|
|
<pre>class Complex {
|
|
...
|
|
Complex operator+(Complex &);
|
|
...
|
|
};</pre>
|
|
</div>
|
|
|
|
<p> the resulting Ruby class will also support the addition (+)
|
|
method correctly. </p>
|
|
|
|
<p>For cases where SWIG's built-in support is not sufficient, C++
|
|
operators can be wrapped using the <tt>%rename</tt>
|
|
directive (available on SWIG 1.3.10 and later releases). All you need
|
|
to do is give the operator the name of a valid Ruby identifier. For
|
|
example: </p>
|
|
|
|
<div class="code">
|
|
<pre>%rename(add_complex) operator+(Complex &, Complex &);
|
|
...
|
|
Complex operator+(Complex &, Complex &);</pre>
|
|
</div>
|
|
|
|
<p>Now, in Ruby, you can do this:</p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>a = Example::Complex.new(2, 3)
|
|
b = Example::Complex.new(4, -1)
|
|
c = Example.add_complex(a, b)</pre>
|
|
</div>
|
|
|
|
<p> More details about wrapping C++ operators into Ruby operators
|
|
is discussed in the <a href="#Ruby_operator_overloading">section
|
|
on operator overloading</a>. </p>
|
|
|
|
<H3><a name="Ruby_nn22">34.3.11 C++ namespaces</a></H3>
|
|
|
|
|
|
<p> SWIG is aware of C++ namespaces, but namespace names do not
|
|
appear in the module nor do namespaces result in a module that is
|
|
broken up into submodules or packages. For example, if you have a file
|
|
like this, </p>
|
|
|
|
<div class="code">
|
|
<pre>%module example
|
|
|
|
namespace foo {
|
|
int fact(int n);
|
|
struct Vector {
|
|
double x, y, z;
|
|
};
|
|
};</pre>
|
|
</div>
|
|
|
|
<p>it works in Ruby as follows:</p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>irb(main):001:0> <b>require 'example'</b>
|
|
true
|
|
irb(main):002:0> <b>Example.fact(3)</b>
|
|
6
|
|
irb(main):003:0> <b>v = Example::Vector.new</b>
|
|
#<Example::Vector:0x4016f4d4>
|
|
irb(main):004:0> <b>v.x = 3.4</b>
|
|
3.4
|
|
irb(main):004:0> <b>v.y</b>
|
|
0.0</pre>
|
|
</div>
|
|
|
|
<p> If your program has more than one namespace, name conflicts
|
|
(if any) can be resolved using <tt>%rename</tt> For
|
|
example: </p>
|
|
|
|
<div class="code">
|
|
<pre>%rename(Bar_spam) Bar::spam;
|
|
|
|
namespace Foo {
|
|
int spam();
|
|
}
|
|
|
|
namespace Bar {
|
|
int spam();
|
|
}</pre>
|
|
</div>
|
|
|
|
<p> If you have more than one namespace and your want to keep
|
|
their symbols separate, consider wrapping them as separate SWIG
|
|
modules. For example, make the module name the same as the namespace
|
|
and create extension modules for each namespace separately. If your
|
|
program utilizes thousands of small deeply nested namespaces each with
|
|
identical symbol names, well, then you get what you deserve. </p>
|
|
|
|
<H3><a name="Ruby_nn23">34.3.12 C++ templates</a></H3>
|
|
|
|
|
|
<p> C++ templates don't present a huge problem for SWIG. However,
|
|
in order to create wrappers, you have to tell SWIG to create wrappers
|
|
for a particular template instantiation. To do this, you use the <tt>%template</tt>
|
|
directive. For example: </p>
|
|
|
|
<div class="code">
|
|
<pre>%module example
|
|
|
|
%{
|
|
#include "pair.h"
|
|
%}
|
|
|
|
template<class T1, class T2>
|
|
struct pair {
|
|
typedef T1 first_type;
|
|
typedef T2 second_type;
|
|
T1 first;
|
|
T2 second;
|
|
pair();
|
|
pair(const T1&, const T2&);
|
|
~pair();
|
|
};
|
|
|
|
%template(Pairii) pair<int, int>;</pre>
|
|
</div>
|
|
|
|
<p>In Ruby:</p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>irb(main):001:0> <b>require 'example'</b>
|
|
true
|
|
irb(main):002:0> <b>p = Example::Pairii.new(3, 4)</b>
|
|
#<Example:Pairii:0x4016f4df>
|
|
irb(main):003:0> <b>p.first</b>
|
|
3
|
|
irb(main):004:0> <b>p.second</b>
|
|
4</pre>
|
|
</div>
|
|
|
|
<H3><a name="Ruby_nn23_1">34.3.13 C++ Standard Template Library (STL)</a></H3>
|
|
|
|
|
|
<p> On a related note, the standard SWIG library contains a
|
|
number of modules that provide typemaps for standard C++ library
|
|
classes (such as <tt>std::pair</tt>, <tt>std::string</tt>
|
|
and <tt>std::vector</tt>). These library modules don't
|
|
provide wrappers around the templates themselves, but they do make it
|
|
convenient for users of your extension module to pass Ruby objects
|
|
(such as arrays and strings) to wrapped C++ code that expects instances
|
|
of standard C++ templates. For example, suppose the C++ library you're
|
|
wrapping has a function that expects a vector of floats: </p>
|
|
|
|
<div class="code">
|
|
<pre>%module example
|
|
|
|
float sum(const std::vector<float>& values);</pre>
|
|
</div>
|
|
|
|
<p> Rather than go through the hassle of writing an "in" typemap
|
|
to convert an array of Ruby numbers into a
|
|
std::vector<float>, you can just use the <tt>std_vector.i</tt>
|
|
module from the standard SWIG library: </p>
|
|
|
|
<div class="code">
|
|
<pre>%module example
|
|
|
|
%include std_vector.i
|
|
float sum(const std::vector<float>& values);</pre>
|
|
</div>
|
|
|
|
<p>Ruby's STL wrappings provide additional methods to make them
|
|
behave more similarly to Ruby's native classes.</p>
|
|
|
|
<p>Thus, you can do, for example:</p>
|
|
|
|
<div class="targetlang">
|
|
<pre>v = IntVector.new
|
|
v << 2
|
|
v << 3
|
|
v << 4
|
|
v.each { |x| puts x }
|
|
|
|
=> 2
|
|
3
|
|
4
|
|
v.delete_if { |x| x == 3 }
|
|
=> [2, 4]</pre>
|
|
</div>
|
|
|
|
<p>The SWIG Ruby module provides also the ability for all the STL
|
|
containers to carry around Ruby native objects (Fixnum, Classes, etc)
|
|
making them act almost like Ruby's own Array, Hash, etc. To
|
|
do
|
|
that, you need to define a container that contains a swig::GC_VALUE,
|
|
like:</p>
|
|
|
|
<div class="code"><pre>
|
|
%module nativevector
|
|
|
|
%{
|
|
std::vector< swig::GC_VALUE > NativeVector;
|
|
%}
|
|
|
|
%template(NativeVector) std::vector< swig::GC_VALUE >;
|
|
</pre>
|
|
</div>
|
|
|
|
<p>This vector can then contain any Ruby object, making them
|
|
almost identical to Ruby's own Array class.</p>
|
|
|
|
<div class="targetlang">
|
|
<pre>require 'nativevector'
|
|
include NativeVector
|
|
|
|
v = NativeVector.new
|
|
v << 1
|
|
v << [1, 2]
|
|
v << 'hello'
|
|
|
|
class A; end
|
|
|
|
v << A.new
|
|
|
|
puts v
|
|
=> [1, [1, 2], 'hello', #<A:0x245325>]
|
|
</pre>
|
|
</div>
|
|
|
|
<p>Obviously, there is a lot more to template wrapping than
|
|
shown in these examples. More details can be found in the <a href="SWIGPlus.html#SWIGPlus">SWIG and C++</a>
|
|
chapter.</p>
|
|
|
|
<H3><a name="Ruby_C_STL_Functors">34.3.14 C++ STL Functors</a></H3>
|
|
|
|
|
|
<p>Some containers in the STL allow you to modify their default
|
|
behavior by using so called functors or function objects.
|
|
Functors are often just a very simple struct with <tt>operator()</tt>
|
|
redefined or an actual C/C++ function. This allows you, for
|
|
example, to always keep the sort order of a STL container to your
|
|
liking.</p>
|
|
|
|
<p>The Ruby STL mappings allows you to modify those containers
|
|
that
|
|
support functors using Ruby procs or methods, instead.
|
|
Currently,
|
|
this includes <tt>std::set</tt>,
|
|
<tt>set::map</tt>,
|
|
<tt>std::multiset</tt>
|
|
and <tt>std::multimap</tt>.</p>
|
|
|
|
<p>The functors in swig are called <tt>swig::UnaryFunction</tt>
|
|
and <tt>swig::BinaryFunction</tt>.
|
|
|
|
For C++ predicates (ie. functors that must return bool as a result) <tt>swig::UnaryPredicate</tt>
|
|
and <tt>swig::BinaryPredicate</tt>
|
|
are provided.</p>
|
|
|
|
<p>As an example, if given this swig file:</p>
|
|
|
|
<div class="code"><pre>
|
|
%module intset;
|
|
|
|
%include <std_set.i>
|
|
|
|
%template(IntSet) std::set< int, swig::BinaryPredicate >;
|
|
</pre></div>
|
|
|
|
<p>You can then use the set from Ruby with or without a proc
|
|
object as a predicate:</p>
|
|
|
|
<div class="targetlang"><pre>
|
|
require 'intset'
|
|
include Intset
|
|
|
|
# Default sorting behavior defined in C++
|
|
a = IntSet.new
|
|
a << 1
|
|
a << 2
|
|
a << 3
|
|
a
|
|
<b>=> [1, 2, 3]</b>
|
|
|
|
# Custom sorting behavior defined by a Ruby proc
|
|
b = IntSet.new( proc { |a, b| a > b } )
|
|
b << 1
|
|
b << 2
|
|
b << 3
|
|
b
|
|
<b>=> [3, 2, 1]</b>
|
|
</pre>
|
|
</div>
|
|
|
|
<H3><a name="Ruby_C_Iterators">34.3.15 C++ STL Iterators</a></H3>
|
|
|
|
|
|
<p>The STL is well known for the use of iterators. There
|
|
are a number of iterators possible with different properties, but in
|
|
general there are two main categories: const iterators and non-const
|
|
iterators. The const iterators can access and not modify the
|
|
values they point at, while the non-const iterators can both read and
|
|
modify the values.</p>
|
|
|
|
<p>The Ruby STL wrappings support both type of iterators by using
|
|
a proxy class in-between. This proxy class is <tt>swig::Iterator</tt> or
|
|
<tt>swig::ConstIterator</tt>. Derived from them are template
|
|
classes that need to be initialized with the actual iterator for the
|
|
container you are wrapping and often times with the beginning and
|
|
ending points of the iteration range.</p>
|
|
|
|
<p>The SWIG STL library already provides typemaps to all the
|
|
standard containers to do this wrapping automatically for you, but if
|
|
you have your own STL-like iterator, you will need to write your own
|
|
typemap for them. For out typemaps, the special functions <tt>make_const_iterator</tt> and <tt>make_nonconst_iterator</tt> are provided.</p>
|
|
|
|
<p>These can be used either like:</p>
|
|
|
|
<div class="code"><pre>
|
|
make_const_iterator( iterator, rubyclass );
|
|
make_const_iterator( iterator, iterator_begin, iterator_end, rubyclass );
|
|
</pre></div>
|
|
|
|
<p>The iterators support a <tt>next()</tt> and <tt>previous()</tt> member function to
|
|
just change the iterator without returning anything. <tt>previous()</tt>
|
|
should obviously only be used for bidirectional iterators. You
|
|
can also advance the iterator multiple steps by using standard math
|
|
operations like <tt>+=</tt>.</p>
|
|
|
|
<p>The
|
|
value the iterator points at can be accessed with <tt>value()</tt> -- this is equivalent to dereferencing it with <tt>*i</tt>.
|
|
For non-const iterators, a <tt>value=()</tt> function
|
|
is also provided which allows you to change the value pointed by the
|
|
iterator. This is equivalent to the C++ construct of dereferencing and assignment, like <tt>*i = something</tt>. </p>
|
|
|
|
<p>Thus, given say a vector class of doubles defined as:</p>
|
|
|
|
<div class="code">
|
|
<pre>
|
|
%module doublevector
|
|
|
|
%include std_vector.i
|
|
|
|
%template(DoubleVector) std::vector<double>;
|
|
</pre>
|
|
</div>
|
|
|
|
<p>Its iterator can then be used from Ruby like:</p>
|
|
|
|
<div class="targetlang">
|
|
<pre>
|
|
require 'doublevector'
|
|
include Doublevector
|
|
|
|
v = DoubleVector.new
|
|
v << 1
|
|
v << 2
|
|
v << 3
|
|
|
|
#
|
|
# an elaborate and less efficient way of doing v.map! { |x| x+2 }
|
|
#
|
|
i = v.begin
|
|
e = v.end
|
|
while i != e
|
|
val = i.value
|
|
val += 2
|
|
i.value = val
|
|
i.next
|
|
end
|
|
i
|
|
<b>>> [3, 4, 5 ]</b>
|
|
</pre>
|
|
</div>
|
|
|
|
<p>If you'd rather have STL classes without any iterators, you should define <tt>-DSWIG_NO_EXPORT_ITERATOR_METHODS</tt> when running swig.</p>
|
|
|
|
<H3><a name="Ruby_nn24">34.3.16 C++ Smart Pointers</a></H3>
|
|
|
|
|
|
<H4><a name="Ruby_smart_pointers_shared_ptr">34.3.16.1 The shared_ptr Smart Pointer</a></H4>
|
|
|
|
|
|
<p>
|
|
The C++11 standard provides <tt>std::shared_ptr</tt> which was derived from the Boost
|
|
implementation, <tt>boost::shared_ptr</tt>.
|
|
Both of these are available for Ruby in the SWIG library and usage is outlined
|
|
in the <a href="Library.html#Library_std_shared_ptr">shared_ptr smart pointer</a> library section.
|
|
</p>
|
|
|
|
|
|
<H4><a name="Ruby_smart_pointers_generic">34.3.16.2 Generic Smart Pointers</a></H4>
|
|
|
|
|
|
<p> In certain C++ programs, it is common to use classes that
|
|
have been wrapped by so-called "smart pointers." Generally, this
|
|
involves the use of a template class that implements <tt>operator->()</tt>
|
|
like this: </p>
|
|
|
|
<div class="code">
|
|
<pre>template<class T> class SmartPtr {
|
|
...
|
|
T *operator->();
|
|
...
|
|
}</pre>
|
|
</div>
|
|
|
|
<p>Then, if you have a class like this, </p>
|
|
|
|
<div class="code">
|
|
<pre>class Foo {
|
|
public:
|
|
int x;
|
|
int bar();
|
|
};</pre>
|
|
</div>
|
|
|
|
<p>A smart pointer would be used in C++ as follows:</p>
|
|
|
|
<div class="code">
|
|
<pre>SmartPtr<Foo> p = CreateFoo(); // Created somehow (not shown)
|
|
...
|
|
p->x = 3; // Foo::x
|
|
int y = p->bar(); // Foo::bar</pre>
|
|
</div>
|
|
|
|
<p> To wrap this in Ruby, simply tell SWIG about the <tt>SmartPtr</tt>
|
|
class and the low-level <tt>Foo</tt> object. Make sure you
|
|
instantiate <tt>SmartPtr</tt> using <tt>%template</tt>
|
|
if necessary. For example: </p>
|
|
|
|
<div class="code">
|
|
<pre>%module example
|
|
...
|
|
%template(SmartPtrFoo) SmartPtr<Foo>;
|
|
...</pre>
|
|
</div>
|
|
|
|
<p>Now, in Ruby, everything should just "work":</p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>irb(main):001:0> <b>p = Example::CreateFoo()</b> # Create a smart-pointer somehow
|
|
#<Example::SmartPtrFoo:0x4016f4df>
|
|
irb(main):002:0> <b>p.x = 3</b> # Foo::x
|
|
3
|
|
irb(main):003:0> <b>p.bar()</b> # Foo::bar</pre>
|
|
</div>
|
|
|
|
<p> If you ever need to access the underlying pointer returned by
|
|
<tt>operator->()</tt> itself, simply use the <tt>__deref__()</tt>
|
|
method. For example: </p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>irb(main):004:0> <b>f = p.__deref__()</b> # Returns underlying Foo *</pre>
|
|
</div>
|
|
|
|
<H3><a name="Ruby_nn25">34.3.17 Cross-Language Polymorphism</a></H3>
|
|
|
|
|
|
<p> SWIG's Ruby module supports cross-language polymorphism
|
|
(a.k.a. the "directors" feature) similar to that for SWIG's Python
|
|
module. Rather than duplicate the information presented in the <a href="Python.html#Python">Python</a> chapter, this
|
|
section just notes the differences that you need to be aware of when
|
|
using this feature with Ruby. </p>
|
|
|
|
<H4><a name="Ruby_nn26">34.3.17.1 Exception Unrolling</a></H4>
|
|
|
|
|
|
<p> Whenever a C++ director class routes one of its virtual
|
|
member function calls to a Ruby instance method, there's always the
|
|
possibility that an exception will be raised in the Ruby code. By
|
|
default, those exceptions are ignored, which simply means that the
|
|
exception will be exposed to the Ruby interpreter. If you would like to
|
|
change this behavior, you can use the <tt>%feature("director:except")</tt>
|
|
directive to indicate what action should be taken when a Ruby exception
|
|
is raised. The following code should suffice in most cases: </p>
|
|
|
|
<div class="code">
|
|
<pre>%feature("director:except") {
|
|
throw Swig::DirectorMethodException($error);
|
|
}</pre>
|
|
</div>
|
|
|
|
<p> When this feature is activated, the call to the Ruby instance
|
|
method is "wrapped" using the <tt>rb_rescue2()</tt>
|
|
function from Ruby's C API. If any Ruby exception is raised, it will be
|
|
caught here and a C++ exception is raised in its place. </p>
|
|
|
|
<H2><a name="Ruby_nn27">34.4 Naming</a></H2>
|
|
|
|
|
|
<p>Ruby has several common naming conventions. Constants are
|
|
generally
|
|
in upper case, module and class names are in camel case and methods are
|
|
in lower case with underscores. For example: </p>
|
|
|
|
<div class="code">
|
|
<ul>
|
|
<li><strong>MATH::PI</strong> is a constant name</li>
|
|
<li><strong>MyClass</strong> is a class name</li>
|
|
<li><strong>my_method</strong> is a method name</li>
|
|
</ul>
|
|
</div>
|
|
|
|
<p>Prior to version 1.3.28, SWIG did not support these Ruby
|
|
conventions. The only modifications it made to names was to capitalize
|
|
the first letter of constants (which includes module and class names).</p>
|
|
|
|
<p>SWIG 1.3.28 introduces the new -autorename command line
|
|
parameter.
|
|
When this parameter is specified, SWIG will automatically change
|
|
constant, class and method names to conform with the standard Ruby
|
|
naming conventions. For example: </p>
|
|
|
|
<div class="code shell">
|
|
<pre>$ swig -ruby -autorename example.i
|
|
</pre>
|
|
</div>
|
|
|
|
<p>To disable renaming use the -noautorename command line option.</p>
|
|
|
|
<p>Since this change significantly changes the wrapper code
|
|
generated
|
|
by SWIG, it is turned off by default in SWIG 1.3.28. However, it is
|
|
planned to become the default option in future releases.</p>
|
|
|
|
<H3><a name="Ruby_nn28">34.4.1 Defining Aliases</a></H3>
|
|
|
|
|
|
<p> It's a fairly common practice in the Ruby built-ins and
|
|
standard library to provide aliases for method names. For example, <em>Array#size</em>
|
|
is an alias for <em>Array#length</em>. If you would like
|
|
to provide an alias for one of your class' instance methods, one
|
|
approach is to use SWIG's <tt>%extend</tt> directive to
|
|
add a new method of the aliased name that calls the original function.
|
|
For example: </p>
|
|
|
|
<div class="code">
|
|
<pre>class MyArray {
|
|
public:
|
|
// Construct an empty array
|
|
MyArray();
|
|
|
|
// Return the size of this array
|
|
size_t length() const;
|
|
};
|
|
|
|
%extend MyArray {
|
|
// MyArray#size is an alias for MyArray#length
|
|
size_t size() const {
|
|
return $self->length();
|
|
}
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<p> A better solution is to use the <tt>%alias</tt>
|
|
directive (unique to SWIG's Ruby module). The previous example could
|
|
then be rewritten as: </p>
|
|
|
|
<div class="code">
|
|
<pre>// MyArray#size is an alias for MyArray#length
|
|
%alias MyArray::length "size";
|
|
|
|
class MyArray {
|
|
public:
|
|
// Construct an empty array
|
|
MyArray();
|
|
|
|
// Return the size of this array
|
|
size_t length() const;
|
|
};</pre>
|
|
</div>
|
|
|
|
<p> Multiple aliases can be associated with a method by providing
|
|
a comma-separated list of aliases to the <tt>%alias</tt>
|
|
directive, e.g. </p>
|
|
|
|
<div class="code">
|
|
<pre>%alias MyArray::length "amount, quantity, size";</pre>
|
|
</div>
|
|
|
|
<p> From an end-user's standpoint, there's no functional
|
|
difference between these two approaches; i.e. they should get the same
|
|
result from calling either <em>MyArray#size</em> or <em>MyArray#length</em>.
|
|
However, when the <tt>%alias</tt> directive is used, SWIG
|
|
doesn't need to generate all of the wrapper code that's usually
|
|
associated with added methods like our <em>MyArray::size()</em>
|
|
example. </p>
|
|
|
|
<p>Note that the <tt>%alias</tt> directive is
|
|
implemented using SWIG's "features" mechanism and so the same name
|
|
matching rules used for other kinds of features apply (see the chapter
|
|
on <a href="Customization.html#Customization">"Customization
|
|
Features"</a>) for more details).</p>
|
|
|
|
<H3><a name="Ruby_nn29">34.4.2 Predicate Methods</a></H3>
|
|
|
|
|
|
<p> Ruby methods that return a boolean value and end in a
|
|
question mark
|
|
are known as predicate methods. Examples of predicate methods in
|
|
standard Ruby classes include <em>Array#empty?</em> (which
|
|
returns <tt>true</tt> for an array containing no elements)
|
|
and <em>Object#instance_of?</em> (which returns <tt>true</tt>
|
|
if the object is an instance of the specified class). For consistency
|
|
with Ruby conventions, methods that return boolean values should be
|
|
marked as predicate methods.</p>
|
|
|
|
<p>One cumbersome solution to this problem is to rename the
|
|
method (using SWIG's <tt>%rename</tt> directive) and
|
|
provide a custom typemap that converts the function's actual return
|
|
type to Ruby's <tt>true</tt> or <tt>false</tt>.
|
|
For example: </p>
|
|
|
|
<div class="code">
|
|
<pre>%rename("is_it_safe?") is_it_safe();
|
|
|
|
%typemap(out) int is_it_safe "$result = ($1 != 0) ? Qtrue : Qfalse;";
|
|
|
|
int is_it_safe();</pre>
|
|
</div>
|
|
|
|
<p> A better solution is to use the <tt>%predicate</tt>
|
|
directive (unique to SWIG's Ruby module) to designate a method as a
|
|
predicate method. For the previous example, this would look like: </p>
|
|
|
|
<div class="code">
|
|
<pre>%predicate is_it_safe();
|
|
|
|
int is_it_safe();</pre>
|
|
</div>
|
|
|
|
<p>This method would be invoked from Ruby code like this:</p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>irb(main):001:0> <b>Example::is_it_safe?</b>
|
|
true</pre>
|
|
</div>
|
|
|
|
<p> The <tt>%predicate</tt> directive is implemented
|
|
using SWIG's "features" mechanism and so the same name matching rules
|
|
used for other kinds of features apply (see the chapter on <a href="Customization.html#Customization">"Customization
|
|
Features"</a>) for more details). </p>
|
|
|
|
<H3><a name="Ruby_nn30">34.4.3 Bang Methods</a></H3>
|
|
|
|
|
|
<p> Ruby methods that modify an object in-place and end in an
|
|
exclamation mark are known as bang methods. An example of a bang method
|
|
is <em>Array#sort!</em> which changes the ordering of
|
|
items in an array. Contrast this with <em>Array#sort</em>,
|
|
which returns a copy of the array with the items sorted instead of
|
|
modifying the original array. For consistency with Ruby conventions,
|
|
methods that modify objects in place should be marked as bang methods.</p>
|
|
|
|
<p>Bang methods can be marked using the <tt>%bang</tt>
|
|
directive which is unique to the Ruby module and was introduced in SWIG
|
|
1.3.28. For example:</p>
|
|
|
|
<div class="code">
|
|
<pre>%bang sort(int arr[]);
|
|
|
|
int sort(int arr[]); </pre>
|
|
</div>
|
|
|
|
<p>This method would be invoked from Ruby code like this:</p>
|
|
|
|
<div class="code">
|
|
<pre>irb(main):001:0> <b>Example::sort!(arr)</b></pre>
|
|
</div>
|
|
|
|
<p> The <tt>%bang</tt> directive is implemented
|
|
using SWIG's "features" mechanism and so the same name matching rules
|
|
used for other kinds of features apply (see the chapter on <a href="Customization.html#Customization">"Customization
|
|
Features"</a>) for more details). </p>
|
|
|
|
<H3><a name="Ruby_nn31">34.4.4 Getters and Setters</a></H3>
|
|
|
|
|
|
<p> Often times a C++ library will expose properties through
|
|
getter and setter methods. For example:</p>
|
|
|
|
<div class="code">
|
|
<pre>class Foo {
|
|
Foo() {}
|
|
int getValue() { return value_; }
|
|
void setValue(int value) { value_ = value; }
|
|
|
|
private:
|
|
int value_;
|
|
};</pre>
|
|
</div>
|
|
|
|
<p>By default, SWIG will expose these methods to Ruby as <tt>get_value</tt>
|
|
and <tt>set_value.</tt> However, it more natural for these
|
|
methods to be exposed in Ruby as <tt>value</tt> and <tt>value=.
|
|
</tt> That allows the methods to be used like this:</p>
|
|
|
|
<div class="code">
|
|
<pre>irb(main):001:0> <b>foo = Foo.new()</b>
|
|
irb(main):002:0> <b>foo.value = 5</b>
|
|
irb(main):003:0> <b>puts foo.value</b></pre>
|
|
</div>
|
|
|
|
<p> This can be done by using the %rename directive:</p>
|
|
|
|
<div class="code">
|
|
<pre>%rename("value") Foo::getValue();
|
|
%rename("value=") Foo::setValue(int value);</pre>
|
|
</div>
|
|
|
|
<H2><a name="Ruby_nn32">34.5 Input and output parameters</a></H2>
|
|
|
|
|
|
<p> A common problem in some C programs is handling parameters
|
|
passed as simple pointers. For example: </p>
|
|
|
|
<div class="code">
|
|
<pre>void add(int x, int y, int *result) {
|
|
*result = x + y;
|
|
}</pre>
|
|
</div>
|
|
|
|
<p>
|
|
or
|
|
</p>
|
|
|
|
<div class="code">
|
|
<pre>
|
|
int sub(int *x, int *y) {
|
|
return *x-*y;
|
|
}</pre>
|
|
</div>
|
|
|
|
<p> The easiest way to handle these situations is to use the <tt>typemaps.i</tt>
|
|
file. For example: </p>
|
|
|
|
<div class="code">
|
|
<pre>%module Example
|
|
%include "typemaps.i"
|
|
|
|
void add(int, int, int *OUTPUT);
|
|
int sub(int *INPUT, int *INPUT);</pre>
|
|
</div>
|
|
|
|
<p>In Ruby, this allows you to pass simple values. For example:</p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>a = Example.add(3, 4)
|
|
puts a
|
|
7
|
|
b = Example.sub(7, 4)
|
|
puts b
|
|
3</pre>
|
|
</div>
|
|
|
|
<p> Notice how the <tt>INPUT</tt> parameters allow
|
|
integer values to be passed instead of pointers and how the <tt>OUTPUT</tt>
|
|
parameter creates a return result. </p>
|
|
|
|
<p>If you don't want to use the names <tt>INPUT</tt>
|
|
or <tt>OUTPUT</tt>, use the <tt>%apply</tt>
|
|
directive. For example: </p>
|
|
|
|
<div class="code">
|
|
<pre>%module Example
|
|
%include "typemaps.i"
|
|
|
|
%apply int *OUTPUT { int *result };
|
|
%apply int *INPUT { int *x, int *y};
|
|
|
|
void add(int x, int y, int *result);
|
|
int sub(int *x, int *y);</pre>
|
|
</div>
|
|
|
|
<p> If a function mutates one of its parameters like this, </p>
|
|
|
|
<div class="code">
|
|
<pre>void negate(int *x) {
|
|
*x = -(*x);
|
|
}</pre>
|
|
</div>
|
|
|
|
<p>you can use <tt>INOUT</tt> like this:</p>
|
|
|
|
<div class="code">
|
|
<pre>%include "typemaps.i"
|
|
...
|
|
void negate(int *INOUT);</pre>
|
|
</div>
|
|
|
|
<p>In Ruby, a mutated parameter shows up as a return value. For
|
|
example:</p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>a = Example.negate(3)
|
|
print a
|
|
-3</pre>
|
|
</div>
|
|
|
|
<p> The most common use of these special typemap rules is to
|
|
handle functions that return more than one value. For example,
|
|
sometimes a function returns a result as well as a special error code: </p>
|
|
|
|
<div class="code">
|
|
<pre>/* send message, return number of bytes sent, success code, and error_code */
|
|
int send_message(char *text, int *success, int *error_code);</pre>
|
|
</div>
|
|
|
|
<p> To wrap such a function, simply use the <tt>OUTPUT</tt>
|
|
rule above. For example: </p>
|
|
|
|
<div class="code">
|
|
<pre>%module example
|
|
%include "typemaps.i"
|
|
...
|
|
int send_message(char *, int *OUTPUT, int *OUTPUT);</pre>
|
|
</div>
|
|
|
|
<p> When used in Ruby, the function will return an array of
|
|
multiple values. </p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>bytes, success, error_code = send_message("Hello World")
|
|
if not success
|
|
print "error #{error_code} : in send_message"
|
|
else
|
|
print "Sent", bytes
|
|
end</pre>
|
|
</div>
|
|
|
|
<p> Another way to access multiple return values is to use the <tt>%apply</tt>
|
|
rule. In the following example, the parameters rows and columns are
|
|
related to SWIG as <tt>OUTPUT</tt> values through the use
|
|
of <tt>%apply</tt> </p>
|
|
|
|
<div class="code">
|
|
<pre>%module Example
|
|
%include "typemaps.i"
|
|
%apply int *OUTPUT { int *rows, int *columns };
|
|
...
|
|
void get_dimensions(Matrix *m, int *rows, int*columns);</pre>
|
|
</div>
|
|
|
|
<p>In Ruby:</p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>r, c = Example.get_dimensions(m)</pre>
|
|
</div>
|
|
|
|
<H2><a name="Ruby_nn33">34.6 Exception handling </a></H2>
|
|
|
|
|
|
<H3><a name="Ruby_nn34">34.6.1 Using the %exception directive </a></H3>
|
|
|
|
|
|
<p>The SWIG <tt>%exception</tt> directive can be
|
|
used to define a user-definable exception handler that can convert
|
|
C/C++ errors into Ruby exceptions. The chapter on <a href="Customization.html#Customization">Customization
|
|
Features</a> contains more details, but suppose you have a C++
|
|
class like the following : </p>
|
|
|
|
<div class="code">
|
|
<pre>class DoubleArray {
|
|
private:
|
|
int n;
|
|
double *ptr;
|
|
public:
|
|
// Create a new array of fixed size
|
|
DoubleArray(int size) {
|
|
ptr = new double[size];
|
|
n = size;
|
|
}
|
|
|
|
// Destroy an array
|
|
~DoubleArray() {
|
|
delete ptr;
|
|
}
|
|
|
|
// Return the length of the array
|
|
int length() {
|
|
return n;
|
|
}
|
|
|
|
// Get an array item and perform bounds checking.
|
|
double getitem(int i) {
|
|
if ((i >= 0) && (i < n))
|
|
return ptr[i];
|
|
else
|
|
throw RangeError();
|
|
}
|
|
|
|
// Set an array item and perform bounds checking.
|
|
void setitem(int i, double val) {
|
|
if ((i >= 0) && (i < n))
|
|
ptr[i] = val;
|
|
else {
|
|
throw RangeError();
|
|
}
|
|
}
|
|
};</pre>
|
|
</div>
|
|
|
|
<p> Since several methods in this class can throw an exception
|
|
for an out-of-bounds access, you might want to catch this in the Ruby
|
|
extension by writing the following in an interface file: </p>
|
|
|
|
<div class="code">
|
|
<pre>%exception {
|
|
try {
|
|
$action
|
|
}
|
|
catch (const RangeError&) {
|
|
static VALUE cpperror = rb_define_class("CPPError", rb_eStandardError);
|
|
rb_raise(cpperror, "Range error.");
|
|
}
|
|
}
|
|
|
|
class DoubleArray {
|
|
...
|
|
};</pre>
|
|
</div>
|
|
|
|
<p> The exception handling code is inserted directly into
|
|
generated wrapper functions. When an exception handler is defined,
|
|
errors can be caught and used to gracefully raise a Ruby exception
|
|
instead of forcing the entire program to terminate with an uncaught
|
|
error. </p>
|
|
|
|
<p>As shown, the exception handling code will be added to every
|
|
wrapper function. Because this is somewhat inefficient, you might
|
|
consider refining the exception handler to only apply to specific
|
|
methods like this: </p>
|
|
|
|
<div class="code">
|
|
<pre>%exception getitem {
|
|
try {
|
|
$action
|
|
} catch (const RangeError&) {
|
|
static VALUE cpperror = rb_define_class("CPPError", rb_eStandardError);
|
|
rb_raise(cpperror, "Range error in getitem.");
|
|
}
|
|
}
|
|
|
|
%exception setitem {
|
|
try {
|
|
$action
|
|
} catch (const RangeError&) {
|
|
static VALUE cpperror = rb_define_class("CPPError", rb_eStandardError);
|
|
rb_raise(cpperror, "Range error in setitem.");
|
|
}
|
|
}</pre>
|
|
</div>
|
|
|
|
<p> In this case, the exception handler is only attached to
|
|
methods and functions named <tt>getitem</tt> and <tt>setitem</tt>.
|
|
</p>
|
|
|
|
<p>Since SWIG's exception handling is user-definable, you are not
|
|
limited to C++ exception handling. See the chapter on <a href="Customization.html#Customization">Customization
|
|
Features</a> for more examples.</p>
|
|
|
|
<H3><a name="Ruby_nn34_2">34.6.2 Handling Ruby Blocks </a></H3>
|
|
|
|
|
|
<p>One of the highlights of Ruby and most of its standard library
|
|
is
|
|
the use of blocks, which allow the easy creation of continuations and
|
|
other niceties. Blocks in ruby are also often used to
|
|
simplify the passing of many arguments to a class.</p>
|
|
|
|
<p>In order to make your class constructor support blocks, you
|
|
can take advantage of the %exception directive, which will get run
|
|
after the C++ class' constructor was called. </p>
|
|
|
|
<p>For example, this yields the class over after its
|
|
construction:
|
|
</p>
|
|
|
|
<div class="code">
|
|
<pre>class Window
|
|
{
|
|
public:
|
|
Window(int x, int y, int w, int h);
|
|
// .... other methods here ....
|
|
};
|
|
|
|
// Add support for yielding self in the Class' constructor.
|
|
%exception Window::Window {
|
|
$action
|
|
if (rb_block_given_p()) {
|
|
rb_yield(self);
|
|
}
|
|
}</pre>
|
|
</div>
|
|
|
|
<p> Then, in ruby, it can be used like:</p>
|
|
|
|
<div class="targetlang"><pre>
|
|
Window.new(0, 0, 360, 480) { |w|
|
|
w.color = Fltk::RED
|
|
w.border = false
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>For other methods, you can usually use a dummy parameter with
|
|
a special in typemap, like:</p>
|
|
|
|
<div class="code" ><pre>
|
|
//
|
|
// original function was:
|
|
//
|
|
// void func(int x);
|
|
|
|
%typemap(in, numinputs=0) int RUBY_YIELD_SELF {
|
|
if ( !rb_block_given_p() )
|
|
rb_raise("No block given");
|
|
return rb_yield(self);
|
|
}
|
|
|
|
%extend {
|
|
void func(int x, int RUBY_YIELD_SELF );
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>For more information on typemaps, see <a href="#Ruby_nn37">Typemaps</a>.</p>
|
|
|
|
<H3><a name="Ruby_nn35">34.6.3 Raising exceptions </a></H3>
|
|
|
|
|
|
<p>There are three ways to raise exceptions from C++ code to
|
|
Ruby. </p>
|
|
|
|
<p>The first way is to use <tt>SWIG_exception(int code,
|
|
const char *msg)</tt>. The following table shows the mappings
|
|
from SWIG error codes to Ruby exceptions:</p>
|
|
|
|
<div class="diagram">
|
|
<table class="diagram" summary="Mapping between SWIG error codes and Ruby exceptions." border="1" width="80%">
|
|
<tbody>
|
|
<tr>
|
|
<td class="diagram">
|
|
<div>SWIG_MemoryError</div>
|
|
</td>
|
|
<td>
|
|
<div>rb_eNoMemError</div>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td class="diagram">
|
|
<div>SWIG_IOError</div>
|
|
</td>
|
|
<td>
|
|
<div>rb_eIOError</div>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td class="diagram">
|
|
<div>SWIG_RuntimeError</div>
|
|
</td>
|
|
<td>
|
|
<div>rb_eRuntimeError</div>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td class="diagram">
|
|
<div>SWIG_IndexError</div>
|
|
</td>
|
|
<td>
|
|
<div>rb_eIndexError</div>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td class="diagram">
|
|
<div>SWIG_TypeError</div>
|
|
</td>
|
|
<td>
|
|
<div>rb_eTypeError</div>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td class="diagram">
|
|
<div>SWIG_DivisionByZero</div>
|
|
</td>
|
|
<td>
|
|
<div>rb_eZeroDivError</div>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td class="diagram">
|
|
<div>SWIG_OverflowError</div>
|
|
</td>
|
|
<td>
|
|
<div>rb_eRangeError</div>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td class="diagram">
|
|
<div>SWIG_SyntaxError</div>
|
|
</td>
|
|
<td>
|
|
<div>rb_eSyntaxError</div>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td class="diagram">
|
|
<div>SWIG_ValueError</div>
|
|
</td>
|
|
<td>
|
|
<div>rb_eArgError</div>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td class="diagram">
|
|
<div>SWIG_SystemError</div>
|
|
</td>
|
|
<td>
|
|
<div>rb_eFatal</div>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td class="diagram">
|
|
<div>SWIG_AttributeError</div>
|
|
</td>
|
|
<td>
|
|
<div>rb_eRuntimeError</div>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td class="diagram">
|
|
<div>SWIG_NullReferenceError</div>
|
|
</td>
|
|
<td>
|
|
<div>rb_eNullReferenceError*</div>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td class="diagram">
|
|
<div>SWIG_ObjectPreviouslyDeletedError</div>
|
|
</td>
|
|
<td>
|
|
<div>rb_eObjectPreviouslyDeleted*</div>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td class="diagram">
|
|
<div>SWIG_UnknownError</div>
|
|
</td>
|
|
<td>
|
|
<div>rb_eRuntimeError</div>
|
|
</td>
|
|
</tr>
|
|
<tr class="diagram">
|
|
<td colspan="2">
|
|
<div>* These error classes are created by
|
|
SWIG and are not built-in Ruby exception classes </div>
|
|
</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
</div>
|
|
|
|
<p>The second way to raise errors is to use <tt>SWIG_Raise(obj,
|
|
type, desc)</tt>.
|
|
Obj is a C++ instance of an exception class, type is a string
|
|
specifying the type of exception (for example, "MyError") and desc is
|
|
the SWIG description of the exception class. For example: </p>
|
|
|
|
<div class="code"><pre>
|
|
%raise(SWIG_NewPointerObj(e, SWIGTYPE_p_AssertionFailedException, 0), ":AssertionFailedException", SWIGTYPE_p_AssertionFailedException);
|
|
</pre></div>
|
|
|
|
<p>This is useful when you want to pass the current exception
|
|
object
|
|
directly to Ruby, particularly when the object is an instance of class
|
|
marked as an <tt>%exceptionclass</tt> (see the next
|
|
section for more information).</p>
|
|
|
|
<p>Last, you can raise an exception by directly calling Ruby's C
|
|
api. This is done by invoking the <tt>rb_raise()</tt>
|
|
function. The first argument passed to <tt>rb_raise()</tt>
|
|
is the exception type. You can raise a custom exception type or one of
|
|
the built-in Ruby exception types.</p>
|
|
|
|
<H3><a name="Ruby_nn36">34.6.4 Exception classes </a></H3>
|
|
|
|
|
|
<p>Starting with SWIG 1.3.28, the Ruby module supports the <tt>%exceptionclass</tt>
|
|
directive, which is used to identify C++ classes that are used as
|
|
exceptions. Classes that are marked with the <tt>%exceptionclass</tt>
|
|
directive are exposed in Ruby as child classes of <tt>rb_eRuntimeError</tt>.
|
|
This allows C++ exceptions to be directly mapped to Ruby exceptions,
|
|
providing for a more natural integration between C++ code and Ruby code.</p>
|
|
|
|
<div class="code">
|
|
<pre>%exceptionclass CustomError;
|
|
|
|
%inline %{
|
|
class CustomError { };
|
|
|
|
class Foo {
|
|
public:
|
|
void test() { throw CustomError; }
|
|
};
|
|
%}</pre>
|
|
</div>
|
|
|
|
<p>From Ruby you can now call this method like this: </p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>foo = Foo.new
|
|
begin
|
|
foo.test()
|
|
rescue CustomError => e
|
|
puts "Caught custom error"
|
|
end </pre>
|
|
</div>
|
|
|
|
<p>For another example look at swig/Examples/ruby/exception_class.
|
|
</p>
|
|
|
|
<H2><a name="Ruby_nn37">34.7 Typemaps</a></H2>
|
|
|
|
|
|
<p> This section describes how you can modify SWIG's default
|
|
wrapping behavior for various C/C++ datatypes using the <tt>%typemap</tt>
|
|
directive. This is an advanced topic that assumes familiarity with the
|
|
Ruby C API as well as the material in the "<a href="Typemaps.html#Typemaps">Typemaps</a>"
|
|
chapter.
|
|
</p>
|
|
|
|
<p>Before proceeding, it should be stressed that typemaps are not
|
|
a required part of using SWIG---the default wrapping behavior is enough
|
|
in most cases. Typemaps are only used if you want to change some aspect
|
|
of the primitive C-Ruby interface.</p>
|
|
|
|
<H3><a name="Ruby_nn38">34.7.1 What is a typemap?</a></H3>
|
|
|
|
|
|
<p> A typemap is nothing more than a code generation rule that is
|
|
attached to a specific C datatype. The general form of this declaration
|
|
is as follows ( parts enclosed in [...] are optional
|
|
): </p>
|
|
|
|
<div class="code">
|
|
<pre>
|
|
%typemap( method [, modifiers...] ) typelist code;
|
|
</pre>
|
|
</div>
|
|
|
|
<p><em> method</em> is a simply a name that specifies
|
|
what kind of typemap is being defined. It is usually a name like <tt>"in"</tt>,
|
|
<tt>"out"</tt>, or <tt>"argout"</tt> (or its
|
|
director variations). The purpose of these methods is described later.</p>
|
|
|
|
<p><em> modifiers</em> is an optional comma separated
|
|
list of <tt>
|
|
name="value"</tt> values. These are sometimes to attach extra
|
|
information to a typemap and is often target-language dependent.</p>
|
|
|
|
<p><em> typelist</em> is a list of the C++ type
|
|
patterns that the typemap will match. The general form of this list is
|
|
as follows:</p>
|
|
|
|
<div class="diagram">
|
|
<pre>typelist : typepattern [, typepattern, typepattern, ... ] ;
|
|
|
|
typepattern : type [ (parms) ]
|
|
| type name [ (parms) ]
|
|
| ( typelist ) [ (parms) ]</pre>
|
|
</div>
|
|
|
|
<p> Each type pattern is either a simple type, a simple type and
|
|
argument name, or a list of types in the case of multi-argument
|
|
typemaps. In addition, each type pattern can be parameterized with a
|
|
list of temporary variables (parms). The purpose of these variables
|
|
will be explained shortly.</p>
|
|
|
|
<p><em>code</em> specifies the C code used in the
|
|
typemap. It can take any one of the following forms:</p>
|
|
|
|
<div class="diagram">
|
|
<pre>code : { ... }
|
|
| " ... "
|
|
| %{ ... %}</pre>
|
|
</div>
|
|
|
|
<p>For example, to convert integers
|
|
from Ruby to C, you might define a typemap like this: </p>
|
|
|
|
<div class="code">
|
|
<pre>%module example
|
|
|
|
%typemap(in) int {
|
|
$1 = (int) NUM2INT($input);
|
|
printf("Received an integer : %d\n", $1);
|
|
}
|
|
|
|
%inline %{
|
|
extern int fact(int n);
|
|
%}</pre>
|
|
</div>
|
|
|
|
<p> Typemaps are always associated with some specific aspect of
|
|
code generation. In this case, the "in" method refers to the conversion
|
|
of input arguments to C/C++. The datatype <tt>int</tt> is
|
|
the datatype to which the typemap will be applied. The supplied C code
|
|
is used to convert values. In this code a number of special variables
|
|
prefaced by a <tt>$</tt> are used. The <tt>$1</tt>
|
|
variable is placeholder for a local variable of type <tt>int</tt>.
|
|
The <tt>$input</tt> variable is the input Ruby object. </p>
|
|
|
|
<p>When this example is compiled into a Ruby module, the
|
|
following sample code: </p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>require 'example'
|
|
|
|
puts Example.fact(6)</pre>
|
|
</div>
|
|
|
|
<p>prints the result:</p>
|
|
|
|
<div class="code shell">
|
|
<pre>
|
|
Received an integer : 6
|
|
720
|
|
</pre>
|
|
</div>
|
|
|
|
<p> In this example, the typemap is applied to all occurrences of
|
|
the <tt>int</tt> datatype. You can refine this by
|
|
supplying an optional parameter name. For example: </p>
|
|
|
|
<div class="code">
|
|
<pre>%module example
|
|
|
|
%typemap(in) int n {
|
|
$1 = (int) NUM2INT($input);
|
|
printf("n = %d\n", $1);
|
|
}
|
|
|
|
%inline %{
|
|
extern int fact(int n);
|
|
%}</pre>
|
|
</div>
|
|
|
|
<p> In this case, the typemap code is only attached to arguments
|
|
that exactly match "<tt>int n</tt>". </p>
|
|
|
|
<p>The application of a typemap to specific datatypes and
|
|
argument names involves more than simple text-matching--typemaps are
|
|
fully integrated into the SWIG type-system. When you define a typemap
|
|
for <tt>int</tt>, that typemap applies to <tt>int</tt>
|
|
and qualified variations such as <tt>const int</tt>. In
|
|
addition, the typemap system follows <tt>typedef</tt>
|
|
declarations. For example: </p>
|
|
|
|
<div class="code">
|
|
<pre>%typemap(in) int n {
|
|
$1 = (int) NUM2INT($input);
|
|
printf("n = %d\n", $1);
|
|
}
|
|
|
|
typedef int Integer;
|
|
extern int fact(Integer n); // Above typemap is applied</pre>
|
|
</div>
|
|
|
|
<p> However, the matching of <tt>typedef</tt> only
|
|
occurs in one direction. If you defined a typemap for <tt>Integer</tt>,
|
|
it is not applied to arguments of type <tt>int</tt>. </p>
|
|
|
|
<p>Typemaps can also be defined for groups of consecutive
|
|
arguments. For example: </p>
|
|
|
|
<div class="code">
|
|
<pre>%typemap(in) (char *str, int len) {
|
|
$1 = StringValuePtr($input);
|
|
$2 = (int) RSTRING($input)->len;
|
|
};
|
|
|
|
int count(char c, char *str, int len);</pre>
|
|
</div>
|
|
|
|
<p> When a multi-argument typemap is defined, the arguments are
|
|
always handled as a single Ruby object. This allows the function <tt>count</tt>
|
|
to be used as follows (notice how the length parameter is omitted): </p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>puts Example.count('o', 'Hello World')
|
|
2</pre>
|
|
</div>
|
|
|
|
<H3><a name="Ruby_Typemap_scope">34.7.2 Typemap scope</a></H3>
|
|
|
|
|
|
<p> Once defined, a typemap remains in effect for all of the
|
|
declarations that follow. A typemap may be redefined for different
|
|
sections of an input file. For example:</p>
|
|
|
|
<div class="code">
|
|
<pre>// typemap1
|
|
%typemap(in) int {
|
|
...
|
|
}
|
|
|
|
int fact(int); // typemap1
|
|
int gcd(int x, int y); // typemap1
|
|
|
|
// typemap2
|
|
%typemap(in) int {
|
|
...
|
|
}
|
|
|
|
int isprime(int); // typemap2</pre>
|
|
</div>
|
|
|
|
<p> One exception to the typemap scoping rules pertains to the <tt>
|
|
%extend</tt> declaration. <tt>%extend</tt> is used
|
|
to attach new declarations to a class or structure definition. Because
|
|
of this, all of the declarations in an <tt>%extend</tt>
|
|
block are subject to the typemap rules that are in effect at the point
|
|
where the class itself is defined. For example:</p>
|
|
|
|
<div class="code">
|
|
<pre>class Foo {
|
|
...
|
|
};
|
|
|
|
%typemap(in) int {
|
|
...
|
|
}
|
|
|
|
%extend Foo {
|
|
int blah(int x); // typemap has no effect. Declaration is attached to Foo which
|
|
// appears before the %typemap declaration.
|
|
};</pre>
|
|
</div>
|
|
|
|
<H3><a name="Ruby_Copying_a_typemap">34.7.3 Copying a typemap</a></H3>
|
|
|
|
|
|
<p> A typemap is copied by using assignment. For example:</p>
|
|
|
|
<div class="code">
|
|
<pre>%typemap(in) Integer = int;</pre>
|
|
</div>
|
|
|
|
<p> or this:</p>
|
|
|
|
<div class="code">
|
|
<pre>%typemap(in) Integer, Number, int32_t = int;</pre>
|
|
</div>
|
|
|
|
<p> Types are often managed by a collection of different
|
|
typemaps. For example:</p>
|
|
|
|
<div class="code">
|
|
<pre>%typemap(in) int { ... }
|
|
%typemap(out) int { ... }
|
|
%typemap(varin) int { ... }
|
|
%typemap(varout) int { ... }</pre>
|
|
</div>
|
|
|
|
<p> To copy all of these typemaps to a new type, use <tt>%apply</tt>.
|
|
For example:</p>
|
|
|
|
<div class="code">
|
|
<pre>%apply int { Integer }; // Copy all int typemaps to Integer
|
|
%apply int { Integer, Number }; // Copy all int typemaps to both Integer and Number</pre>
|
|
</div>
|
|
|
|
<p> The patterns for <tt>%apply</tt> follow the same
|
|
rules as for <tt>
|
|
%typemap</tt>. For example:</p>
|
|
|
|
<div class="code">
|
|
<pre>%apply int *output { Integer *output }; // Typemap with name
|
|
%apply (char *buf, int len) { (char *buffer, int size) }; // Multiple arguments</pre>
|
|
</div>
|
|
|
|
<H3><a name="Ruby_Deleting_a_typemap">34.7.4 Deleting a typemap</a></H3>
|
|
|
|
|
|
<p> A typemap can be deleted by simply defining no code. For
|
|
example:</p>
|
|
|
|
<div class="code">
|
|
<pre>%typemap(in) int; // Clears typemap for int
|
|
%typemap(in) int, long, short; // Clears typemap for int, long, short
|
|
%typemap(in) int *output; </pre>
|
|
</div>
|
|
|
|
<p> The <tt>%clear</tt> directive clears all
|
|
typemaps for a given type. For example:</p>
|
|
|
|
<div class="code">
|
|
<pre>%clear int; // Removes all types for int
|
|
%clear int *output, long *output;</pre>
|
|
</div>
|
|
|
|
<p><b> Note:</b> Since SWIG's default behavior is
|
|
defined by typemaps, clearing a fundamental type like <tt>int</tt>
|
|
will make that type unusable unless you also define a new set of
|
|
typemaps immediately after the clear operation.</p>
|
|
|
|
<H3><a name="Ruby_Placement_of_typemaps">34.7.5 Placement of typemaps</a></H3>
|
|
|
|
|
|
<p> Typemap declarations can be declared in the global scope,
|
|
within a C++ namespace, and within a C++ class. For example:</p>
|
|
|
|
<div class="code">
|
|
<pre>%typemap(in) int {
|
|
...
|
|
}
|
|
|
|
namespace std {
|
|
class string;
|
|
%typemap(in) string {
|
|
...
|
|
}
|
|
}
|
|
|
|
class Bar {
|
|
public:
|
|
typedef const int & const_reference;
|
|
%typemap(out) const_reference {
|
|
...
|
|
}
|
|
};</pre>
|
|
</div>
|
|
|
|
<p> When a typemap appears inside a namespace or class, it stays
|
|
in effect until the end of the SWIG input (just like before). However,
|
|
the typemap takes the local scope into account. Therefore, this code</p>
|
|
|
|
<div class="code">
|
|
<pre>namespace std {
|
|
class string;
|
|
%typemap(in) string {
|
|
...
|
|
}
|
|
}</pre>
|
|
</div>
|
|
|
|
<p> is really defining a typemap for the type <tt>std::string</tt>.
|
|
You could have code like this:</p>
|
|
|
|
<div class="code">
|
|
<pre>namespace std {
|
|
class string;
|
|
%typemap(in) string { /* std::string */
|
|
...
|
|
}
|
|
}
|
|
|
|
namespace Foo {
|
|
class string;
|
|
%typemap(in) string { /* Foo::string */
|
|
...
|
|
}
|
|
}</pre>
|
|
</div>
|
|
|
|
<p> In this case, there are two completely distinct typemaps that
|
|
apply to two completely different types (<tt>std::string</tt>
|
|
and <tt>
|
|
Foo::string</tt>).</p>
|
|
|
|
<p> It should be noted that for scoping to work, SWIG has to know
|
|
that <tt>
|
|
string</tt> is a typename defined within a particular namespace.
|
|
In this example, this is done using the class declaration <tt>class
|
|
string</tt>
|
|
.</p>
|
|
|
|
<H3><a name="Ruby_nn39">34.7.6 Ruby typemaps</a></H3>
|
|
|
|
|
|
<p>The following list details all of the typemap methods that
|
|
can be used by the Ruby module: </p>
|
|
|
|
<H4><a name="Ruby_in_typemap">34.7.6.1 "in" typemap</a></H4>
|
|
|
|
|
|
<p>Converts Ruby objects to input
|
|
function arguments. For example:
|
|
</p>
|
|
|
|
<div class="code">
|
|
<pre>%typemap(in) int {
|
|
$1 = NUM2INT($input);
|
|
}</pre>
|
|
</div>
|
|
|
|
<p> The following special variables are available:</p>
|
|
|
|
<div class="diagram">
|
|
<table border="1" cellpadding="2" cellspacing="2" width="100%" summary="Special variables - in typemap">
|
|
<tbody>
|
|
<tr>
|
|
<td>$input </td>
|
|
<td> Input object
|
|
holding value to be converted.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>$symname </td>
|
|
<td> Name of
|
|
function/method being wrapped</td>
|
|
</tr>
|
|
<tr>
|
|
<td>$1...n </td>
|
|
<td> Argument being
|
|
sent to the function</td>
|
|
</tr>
|
|
<tr>
|
|
<td>$1_name </td>
|
|
<td> Name of the
|
|
argument (if provided)</td>
|
|
</tr>
|
|
<tr>
|
|
<td>$1_type </td>
|
|
<td> The actual C
|
|
datatype matched by the typemap.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>$1_ltype </td>
|
|
<td> The assignable
|
|
version of the C datatype matched by the typemap.</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
</div>
|
|
|
|
<p> This is probably the most commonly redefined typemap because
|
|
it can be used to implement customized conversions.</p>
|
|
|
|
<p> In addition, the "in" typemap allows the number of converted
|
|
arguments to be specified. For example:</p>
|
|
|
|
<div class="code">
|
|
<pre>// Ignored argument.
|
|
%typemap(in, numinputs=0) int *out (int temp) {
|
|
$1 = &temp;
|
|
}</pre>
|
|
</div>
|
|
|
|
<p> At this time, only zero or one arguments may be converted.</p>
|
|
|
|
<H4><a name="Ruby_typecheck_typemap">34.7.6.2 "typecheck" typemap</a></H4>
|
|
|
|
|
|
<p> The "typecheck" typemap is used to support overloaded
|
|
functions and methods. It merely checks an argument to see whether or
|
|
not it matches a specific type. For example:</p>
|
|
|
|
<div class="code">
|
|
<pre>%typemap(typecheck, precedence=SWIG_TYPECHECK_INTEGER) int {
|
|
$1 = FIXNUM_P($input) ? 1 : 0;
|
|
}</pre>
|
|
</div>
|
|
|
|
<p> For typechecking, the $1 variable is always a simple integer
|
|
that is set to 1 or 0 depending on whether or not the input argument is
|
|
the correct type.</p>
|
|
|
|
<p> If you define new "in" typemaps<em> and</em> your
|
|
program uses overloaded methods, you should also define a collection of
|
|
"typecheck" typemaps. More details about this follow in a later section
|
|
on "Typemaps and Overloading."</p>
|
|
|
|
<H4><a name="Ruby_out_typemap">34.7.6.3 "out" typemap</a></H4>
|
|
|
|
|
|
<p>Converts return value of a C function
|
|
to a Ruby object.</p>
|
|
|
|
<div class="code">
|
|
<pre>%typemap(out) int {
|
|
$result = INT2NUM( $1 );
|
|
}
|
|
</pre></div>
|
|
|
|
<p> The following special variables are available.</p>
|
|
|
|
<div class="diagram">
|
|
<table border="1" cellpadding="2" cellspacing="2" width="100%" summary="Special variables - out typemap">
|
|
<tbody>
|
|
<tr>
|
|
<td>$result </td>
|
|
<td> Result object
|
|
returned to target language.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>$symname </td>
|
|
<td> Name of
|
|
function/method being wrapped</td>
|
|
</tr>
|
|
<tr>
|
|
<td>$1...n </td>
|
|
<td> Argument being
|
|
wrapped</td>
|
|
</tr>
|
|
<tr>
|
|
<td>$1_name </td>
|
|
<td> Name of the
|
|
argument (if provided)</td>
|
|
</tr>
|
|
<tr>
|
|
<td>$1_type </td>
|
|
<td> The actual C
|
|
datatype matched by the typemap.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>$1_ltype </td>
|
|
<td> The assignable
|
|
version of the C datatype matched by the typemap.</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
</div>
|
|
|
|
<H4><a name="Ruby_arginit_typemap">34.7.6.4 "arginit" typemap</a></H4>
|
|
|
|
|
|
<p> The "arginit" typemap is used to set the initial value of a
|
|
function argument--before any conversion has occurred. This is not
|
|
normally necessary, but might be useful in highly specialized
|
|
applications. For example:</p>
|
|
|
|
<div class="code">
|
|
<pre>// Set argument to NULL before any conversion occurs
|
|
%typemap(arginit) int *data {
|
|
$1 = NULL;
|
|
}</pre>
|
|
</div>
|
|
|
|
<H4><a name="Ruby_default_typemap">34.7.6.5 "default" typemap</a></H4>
|
|
|
|
|
|
<p> The "default" typemap is used to turn an argument into a
|
|
default argument. For example:</p>
|
|
|
|
<div class="code">
|
|
<pre>%typemap(default) int flags {
|
|
$1 = DEFAULT_FLAGS;
|
|
}
|
|
...
|
|
int foo(int x, int y, int flags);</pre>
|
|
</div>
|
|
|
|
<p> The primary use of this typemap is to either change the
|
|
wrapping of default arguments or specify a default argument in a
|
|
language where they aren't supported (like C). Target languages that do
|
|
not support optional arguments, such as Java and C#, effectively ignore
|
|
the value specified by this typemap as all arguments must be given.</p>
|
|
|
|
<p> Once a default typemap has been applied to an argument, all
|
|
arguments that follow must have default values. See the <a href="SWIG.html#SWIG_default_args">
|
|
Default/optional arguments</a> section for further information on
|
|
default argument wrapping.</p>
|
|
|
|
<H4><a name="Ruby_check_typemap">34.7.6.6 "check" typemap</a></H4>
|
|
|
|
|
|
<p> The "check" typemap is used to supply value checking code
|
|
during argument conversion. The typemap is applied<em> after</em>
|
|
arguments have been converted. For example:</p>
|
|
|
|
<div class="code">
|
|
<pre>%typemap(check) int positive {
|
|
if ($1 <= 0) {
|
|
SWIG_exception(SWIG_ValueError, "Expected positive value.");
|
|
}
|
|
}</pre>
|
|
</div>
|
|
|
|
<H4><a name="Ruby_argout_typemap_">34.7.6.7 "argout" typemap</a></H4>
|
|
|
|
|
|
<p> The "argout" typemap is used to return values from arguments.
|
|
This is most commonly used to write wrappers for C/C++ functions that
|
|
need to return multiple values. The "argout" typemap is almost always
|
|
combined with an "in" typemap---possibly to ignore the input value. For
|
|
example:</p>
|
|
|
|
<div class="code">
|
|
<pre>/* Set the input argument to point to a temporary variable */
|
|
%typemap(in, numinputs=0) int *out (int temp) {
|
|
$1 = &temp;
|
|
}
|
|
|
|
%typemap(argout, fragment="output_helper") int *out {
|
|
// Append output value $1 to $result (assuming a single integer in this case)
|
|
$result = output_helper( $result, INT2NUM(*$1) );
|
|
}</pre>
|
|
</div>
|
|
|
|
<p> The following special variables are available.</p>
|
|
|
|
<div class="diagram">
|
|
<table border="1" cellpadding="2" cellspacing="2" width="100%" summary="Special variables - argout typemap">
|
|
<tbody>
|
|
<tr>
|
|
<td>$result </td>
|
|
<td> Result object
|
|
returned to target language.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>$input </td>
|
|
<td> The original
|
|
input object passed.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>$symname </td>
|
|
<td> Name of
|
|
function/method being wrapped.</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
</div>
|
|
|
|
<p> The code supplied to the "argout" typemap is always placed
|
|
after the "out" typemap. If multiple return values are used, the extra
|
|
return values are often appended to return value of the function.</p>
|
|
|
|
<p>Output helper is a fragment that usually defines a macro to
|
|
some function like SWIG_Ruby_AppendOutput.</p>
|
|
|
|
<p> See the <tt>typemaps.i</tt> library for examples.</p>
|
|
|
|
<H4><a name="Ruby_freearg_typemap_">34.7.6.8 "freearg" typemap</a></H4>
|
|
|
|
|
|
<p> The "freearg" typemap is used to cleanup argument data. It is
|
|
only used when an argument might have allocated resources that need to
|
|
be cleaned up when the wrapper function exits. The "freearg" typemap
|
|
usually cleans up argument resources allocated by the "in" typemap. For
|
|
example:</p>
|
|
|
|
<div class="code">
|
|
<pre>// Get a list of integers
|
|
%typemap(in) int *items {
|
|
int nitems = Length($input);
|
|
$1 = (int *) malloc(sizeof(int)*nitems);
|
|
}
|
|
// Free the list
|
|
%typemap(freearg) int *items {
|
|
free($1);
|
|
}</pre>
|
|
</div>
|
|
|
|
<p> The "freearg" typemap inserted at the end of the wrapper
|
|
function, just before control is returned back to the target language.
|
|
This code is also placed into a special variable <tt>$cleanup</tt>
|
|
that may be used in other typemaps whenever a wrapper function needs to
|
|
abort prematurely.</p>
|
|
|
|
<H4><a name="Ruby_newfree_typemap">34.7.6.9 "newfree" typemap</a></H4>
|
|
|
|
|
|
<p> The "newfree" typemap is used in conjunction with the <tt>%newobject</tt>
|
|
directive and is used to deallocate memory used by the return result of
|
|
a function. For example:</p>
|
|
|
|
<div class="code">
|
|
<pre>%typemap(newfree) string * {
|
|
delete $1;
|
|
}
|
|
%typemap(out) string * {
|
|
$result = PyString_FromString($1->c_str());
|
|
}
|
|
...
|
|
|
|
%newobject foo;
|
|
...
|
|
string *foo();</pre>
|
|
</div>
|
|
|
|
<p> See <a href="Customization.html#Customization_ownership">Object
|
|
ownership and %newobject</a> for further details.</p>
|
|
|
|
<H4><a name="Ruby_memberin_typemap">34.7.6.10 "memberin" typemap</a></H4>
|
|
|
|
|
|
<p> The "memberin" typemap is used to copy data from<em> an
|
|
already converted input value</em> into a structure member. It is
|
|
typically used to handle array members and other special cases. For
|
|
example:</p>
|
|
|
|
<div class="code">
|
|
<pre>%typemap(memberin) int [4] {
|
|
memmove($1, $input, 4*sizeof(int));
|
|
}</pre>
|
|
</div>
|
|
|
|
<p> It is rarely necessary to write "memberin" typemaps---SWIG
|
|
already provides a default implementation for arrays, strings, and
|
|
other objects.</p>
|
|
|
|
<H4><a name="Ruby_varin_typemap">34.7.6.11 "varin" typemap</a></H4>
|
|
|
|
|
|
<p> The "varin" typemap is used to convert objects in the target
|
|
language to C for the purposes of assigning to a C/C++ global variable.
|
|
This is implementation specific.</p>
|
|
|
|
<H4><a name="Ruby_varout_typemap_">34.7.6.12 "varout" typemap</a></H4>
|
|
|
|
|
|
<p> The "varout" typemap is used to convert a C/C++ object to an
|
|
object in the target language when reading a C/C++ global variable.
|
|
This is implementation specific.</p>
|
|
|
|
<H4><a name="Ruby_throws_typemap">34.7.6.13 "throws" typemap</a></H4>
|
|
|
|
|
|
<p> The "throws" typemap is only used when SWIG parses a C++
|
|
method with an exception specification or has the <tt>%catches</tt>
|
|
feature attached to the method. It provides a default mechanism for
|
|
handling C++ methods that have declared the exceptions they will throw.
|
|
The purpose of this typemap is to convert a C++ exception into an error
|
|
or exception in the target language. It is slightly different to the
|
|
other typemaps as it is based around the exception type rather than the
|
|
type of a parameter or variable. For example:</p>
|
|
|
|
<div class="code">
|
|
<pre>%typemap(throws) const char * %{
|
|
rb_raise(rb_eRuntimeError, $1);
|
|
SWIG_fail;
|
|
%}
|
|
void bar() throw (const char *);</pre>
|
|
</div>
|
|
|
|
<p> As can be seen from the generated code below, SWIG generates
|
|
an exception handler with the catch block comprising the "throws"
|
|
typemap content.</p>
|
|
|
|
<div class="code">
|
|
<pre>...
|
|
try {
|
|
bar();
|
|
}
|
|
catch(char const *_e) {
|
|
rb_raise(rb_eRuntimeError, _e);
|
|
SWIG_fail;
|
|
}
|
|
...</pre>
|
|
</div>
|
|
|
|
<p> Note that if your methods do not have an exception
|
|
specification yet they do throw exceptions, SWIG cannot know how to
|
|
deal with them. For a neat way to handle these, see the <a href="Customization.html#Customization_exception">Exception
|
|
handling with %exception</a> section.</p>
|
|
|
|
<H4><a name="Ruby_directorin_typemap">34.7.6.14 directorin typemap</a></H4>
|
|
|
|
|
|
<p>Converts C++ objects in director
|
|
member functions to ruby objects. It is roughly the opposite
|
|
of the "in" typemap, making its typemap rule often similar to the "out"
|
|
typemap.
|
|
</p>
|
|
|
|
<div class="code"><pre>
|
|
%typemap(directorin) int {
|
|
$result = INT2NUM($1);
|
|
}
|
|
</pre></div>
|
|
|
|
<p> The following special variables are available.</p>
|
|
|
|
<div class="diagram">
|
|
<table border="1" cellpadding="2" cellspacing="2" width="100%" summary="Special variables - directorin typemap">
|
|
<tbody>
|
|
<tr>
|
|
<td>$result </td>
|
|
<td> Result object
|
|
returned to target language.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>$symname </td>
|
|
<td> Name of
|
|
function/method being wrapped</td>
|
|
</tr>
|
|
<tr>
|
|
<td>$1...n </td>
|
|
<td> Argument being
|
|
wrapped</td>
|
|
</tr>
|
|
<tr>
|
|
<td>$1_name </td>
|
|
<td> Name of the
|
|
argument (if provided)</td>
|
|
</tr>
|
|
<tr>
|
|
<td>$1_type </td>
|
|
<td> The actual C
|
|
datatype matched by the typemap.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>$1_ltype </td>
|
|
<td> The assignable
|
|
version of the C datatype matched by the typemap.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>this </td>
|
|
<td> C++ this,
|
|
referring to the class itself.</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
</div>
|
|
|
|
<H4><a name="Ruby_directorout_typemap">34.7.6.15 directorout typemap</a></H4>
|
|
|
|
|
|
<p>Converts Ruby objects in director
|
|
member functions to C++ objects. It is roughly the opposite
|
|
of the "out" typemap, making its rule often similar to the "in"
|
|
typemap.
|
|
</p>
|
|
|
|
<div class="code"><pre>
|
|
%typemap(directorout) int {
|
|
$result = NUM2INT($1);
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<p> The following special variables are available:</p>
|
|
|
|
<div class="diagram">
|
|
<table border="1" cellpadding="2" cellspacing="2" width="100%" summary="Special variables - directorout typemap">
|
|
<tbody>
|
|
<tr>
|
|
<td>$input</td>
|
|
<td>Ruby object being sent to the function</td>
|
|
</tr>
|
|
<tr>
|
|
<td>$symname </td>
|
|
<td>Name of function/method being wrapped</td>
|
|
</tr>
|
|
<tr>
|
|
<td>$1...n </td>
|
|
<td>Argument being sent to the function</td>
|
|
</tr>
|
|
<tr>
|
|
<td>$1_name </td>
|
|
<td> Name of the
|
|
argument (if provided)</td>
|
|
</tr>
|
|
<tr>
|
|
<td>$1_type </td>
|
|
<td> The actual C
|
|
datatype matched by the typemap.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>$1_ltype </td>
|
|
<td> The assignable
|
|
version of the C datatype matched by the typemap.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>this </td>
|
|
<td> C++ this,
|
|
referring to the class itself.</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
</div>
|
|
|
|
<p>Currently, the directorout nor the out typemap support the
|
|
option <tt>numoutputs</tt>,
|
|
but the Ruby module provides that functionality through a %feature
|
|
directive. Thus, a function can be made to return "nothing"
|
|
if you do:</p>
|
|
|
|
<div class="code"><pre>
|
|
%feature("numoutputs", "0") MyClass::function;
|
|
</pre></div>
|
|
|
|
<p>This feature can be useful if a function returns a status
|
|
code, which you want to discard but still use the typemap to raise an
|
|
exception.
|
|
|
|
</p>
|
|
|
|
<H4><a name="Ruby_directorargout_typemap">34.7.6.16 directorargout typemap</a></H4>
|
|
|
|
|
|
<p>Output argument processing in director
|
|
member functions.</p>
|
|
|
|
<div class="code"><pre>
|
|
%typemap(directorargout,
|
|
fragment="output_helper") int {
|
|
$result = output_helper( $result, NUM2INT($1) );
|
|
}
|
|
</pre></div>
|
|
|
|
<p> The following special variables are available:</p>
|
|
|
|
<div class="diagram">
|
|
<table style="text-align: left; width: 100%;" border="1" cellpadding="2" cellspacing="2" summary="Special variables - directorargout typemap">
|
|
<tbody>
|
|
<tr>
|
|
<td>$result</td>
|
|
<td>Result that the director function returns</td>
|
|
</tr>
|
|
<tr>
|
|
<td>$input</td>
|
|
<td>Ruby object being sent to the function</td>
|
|
</tr>
|
|
<tr>
|
|
<td>$symname</td>
|
|
<td>name of the function/method being wrapped</td>
|
|
</tr>
|
|
<tr>
|
|
<td>$1...n</td>
|
|
<td>Argument being sent to the function</td>
|
|
</tr>
|
|
<tr>
|
|
<td>$1_name</td>
|
|
<td>Name of the
|
|
argument (if provided)</td>
|
|
</tr>
|
|
<tr>
|
|
<td>$1_type</td>
|
|
<td>The actual C
|
|
datatype matched by the typemap</td>
|
|
</tr>
|
|
<tr>
|
|
<td>$1_ltype</td>
|
|
<td>The assignable
|
|
version of the C datatype matched by the typemap</td>
|
|
</tr>
|
|
<tr>
|
|
<td>this</td>
|
|
<td>C++ this,
|
|
referring to the instance of the class itself</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
</div>
|
|
|
|
<H4><a name="Ruby_ret_typemap">34.7.6.17 ret typemap</a></H4>
|
|
|
|
|
|
<p>Cleanup of function return values
|
|
</p>
|
|
|
|
<H4><a name="Ruby_globalin_typemap">34.7.6.18 globalin typemap</a></H4>
|
|
|
|
|
|
<p>Setting of C global variables
|
|
</p>
|
|
|
|
<H3><a name="Ruby_nn40">34.7.7 Typemap variables</a></H3>
|
|
|
|
|
|
<p>
|
|
Within a typemap, a number of special variables prefaced with a <tt>$</tt>
|
|
may appear. A full list of variables can be found in the "<a href="Typemaps.html#Typemaps">Typemaps</a>" chapter.
|
|
This is a list of the most common variables:
|
|
</p>
|
|
|
|
<p><tt>$1</tt> </p>
|
|
|
|
<div class="indent">A C local variable corresponding to
|
|
the actual type specified in the <tt>%typemap</tt>
|
|
directive. For input values, this is a C local variable that is
|
|
supposed to hold an argument value. For output values, this is the raw
|
|
result that is supposed to be returned to Ruby. </div>
|
|
|
|
<p><tt>$input</tt></p>
|
|
|
|
<div class="indent">A <tt>VALUE</tt> holding
|
|
a raw Ruby object with an argument or variable value. </div>
|
|
|
|
<p><tt>$result</tt></p>
|
|
|
|
<div class="indent">A <tt>VALUE</tt> that
|
|
holds the result to be returned to Ruby. </div>
|
|
|
|
<p><tt>$1_name</tt></p>
|
|
|
|
<div class="indent">The parameter name that was matched. </div>
|
|
|
|
<p><tt>$1_type</tt></p>
|
|
|
|
<div class="indent">The actual C datatype matched by the
|
|
typemap. </div>
|
|
|
|
<p><tt>$1_ltype</tt></p>
|
|
|
|
<div class="indent">An assignable version of the datatype
|
|
matched by the typemap (a type that can appear on the left-hand-side of
|
|
a C assignment operation). This type is stripped of qualifiers and may
|
|
be an altered version of <tt>$1_type</tt>. All arguments
|
|
and local variables in wrapper functions are declared using this type
|
|
so that their values can be properly assigned. </div>
|
|
|
|
<p><tt>$symname</tt></p>
|
|
|
|
<div class="indent">The Ruby name of the wrapper function
|
|
being created. </div>
|
|
|
|
<H3><a name="Ruby_nn41">34.7.8 Useful Functions</a></H3>
|
|
|
|
|
|
<p> When you write a typemap, you usually have to work directly
|
|
with Ruby objects. The following functions may prove to be useful.
|
|
(These functions plus many more can be found in <em>Programming
|
|
Ruby</em> book, by David Thomas and Andrew Hunt.)</p>
|
|
<p>In addition, we list equivalent functions that SWIG defines, which
|
|
provide a language neutral conversion (these functions are defined for
|
|
each swig language supported). If you are trying to create a swig
|
|
file that will work under multiple languages, it is recommended you
|
|
stick to the swig functions instead of the native Ruby functions.
|
|
That should help you avoid having to rewrite a lot of typemaps
|
|
across multiple languages.</p>
|
|
|
|
<H4><a name="Ruby_nn42">34.7.8.1 C Datatypes to Ruby Objects</a></H4>
|
|
|
|
|
|
<div class="diagram">
|
|
<table style="width: 100%;" border="1" cellpadding="2" cellspacing="2" summary="Datatypes">
|
|
|
|
<tbody>
|
|
<tr>
|
|
<th><b>RUBY</b></th>
|
|
<th><b>SWIG</b></th>
|
|
<td></td>
|
|
</tr>
|
|
<tr>
|
|
<td>INT2NUM(long or int) </td>
|
|
<td>SWIG_From_int(int x)</td>
|
|
<td> int to Fixnum or Bignum</td>
|
|
</tr>
|
|
<tr>
|
|
<td>INT2FIX(long or int) </td>
|
|
<td></td>
|
|
<td> int to Fixnum (faster than INT2NUM)</td>
|
|
</tr>
|
|
<tr>
|
|
<td>CHR2FIX(char) </td>
|
|
<td>SWIG_From_char(char x)</td>
|
|
<td> char to Fixnum</td>
|
|
</tr>
|
|
<tr>
|
|
<td>rb_str_new2(char*) </td>
|
|
<td>SWIG_FromCharPtrAndSize(char*, size_t)</td>
|
|
<td> char* to String</td>
|
|
</tr>
|
|
<tr>
|
|
<td>rb_float_new(double) </td>
|
|
<td>SWIG_From_double(double), <br>
|
|
SWIG_From_float(float)</td>
|
|
<td>float/double to Float</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
</div>
|
|
|
|
<H4><a name="Ruby_nn43">34.7.8.2 Ruby Objects to C Datatypes</a></H4>
|
|
|
|
|
|
<p>Here, while the Ruby versions return the value directly, the SWIG
|
|
versions do not, but return a status value to indicate success (<tt>SWIG_OK</tt>). While more awkward to use, this allows you to write typemaps that report more helpful error messages, like:</p>
|
|
|
|
<div class="code">
|
|
<pre>
|
|
%typemap(in) size_t (int ok)
|
|
ok = SWIG_AsVal_size_t($input, &$1);
|
|
if (!SWIG_IsOK(ok)) {
|
|
SWIG_exception_fail(SWIG_ArgError(ok), Ruby_Format_TypeError( "$1_name", "$1_type", "$symname", $argnum, $input));
|
|
}
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<div class="diagram">
|
|
<table border="1" cellpadding="2" cellspacing="2" width="100%" summary="Ruby objects">
|
|
<tbody>
|
|
<tr>
|
|
<td>int NUM2INT(Numeric)</td>
|
|
<td>SWIG_AsVal_int(VALUE, int*)</td>
|
|
</tr>
|
|
<tr>
|
|
<td>int FIX2INT(Numeric)</td>
|
|
<td>SWIG_AsVal_int(VALUE, int*)</td>
|
|
</tr>
|
|
<tr>
|
|
<td>unsigned int NUM2UINT(Numeric)</td>
|
|
<td>SWIG_AsVal_unsigned_SS_int(VALUE, int*)</td>
|
|
</tr>
|
|
<tr>
|
|
<td>unsigned int FIX2UINT(Numeric)</td>
|
|
<td>SWIG_AsVal_unsigned_SS_int(VALUE, int*)</td>
|
|
</tr>
|
|
<tr>
|
|
<td>long NUM2LONG(Numeric)</td>
|
|
<td>SWIG_AsVal_long(VALUE, long*)</td>
|
|
</tr>
|
|
<tr>
|
|
<td>long FIX2LONG(Numeric)</td>
|
|
<td>SWIG_AsVal_long(VALUE, long*)</td>
|
|
</tr>
|
|
<tr>
|
|
<td>unsigned long FIX2ULONG(Numeric)</td>
|
|
<td>SWIG_AsVal_unsigned_SS_long(VALUE, unsigned long*)</td>
|
|
</tr>
|
|
<tr>
|
|
<td>char NUM2CHR(Numeric or String)</td>
|
|
<td>SWIG_AsVal_char(VALUE, int*)</td>
|
|
</tr>
|
|
<tr>
|
|
<td>char * StringValuePtr(String)</td>
|
|
<td>SWIG_AsCharPtrAndSize(VALUE, char*, size_t, int* alloc)</td>
|
|
</tr>
|
|
<tr>
|
|
<td>char * rb_str2cstr(String, int*length)</td>
|
|
<td></td>
|
|
</tr>
|
|
<tr>
|
|
<td>double NUM2DBL(Numeric)</td>
|
|
<td>(double) SWIG_AsVal_int(VALUE) or similar</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
</div>
|
|
|
|
<H4><a name="Ruby_nn44">34.7.8.3 Macros for VALUE</a></H4>
|
|
|
|
|
|
<p> <tt>RSTRING_LEN(str)</tt> </p>
|
|
|
|
<div class="indent">length of the Ruby string</div>
|
|
|
|
<p><tt>RSTRING_PTR(str)</tt></p>
|
|
|
|
<div class="indent">pointer to string storage</div>
|
|
|
|
<p><tt>RARRAY_LEN(arr)</tt></p>
|
|
|
|
<div class="indent">length of the Ruby array</div>
|
|
|
|
<p><tt>RARRAY(arr)->capa</tt></p>
|
|
|
|
<div class="indent">capacity of the Ruby array</div>
|
|
|
|
<p><tt>RARRAY_PTR(arr)</tt></p>
|
|
|
|
<div class="indent">pointer to array storage</div>
|
|
|
|
<H4><a name="Ruby_nn45">34.7.8.4 Exceptions</a></H4>
|
|
|
|
|
|
<p> <tt>void rb_raise(VALUE exception, const char *fmt,
|
|
...)</tt> </p>
|
|
|
|
<div class="indent"> Raises an exception. The given format
|
|
string <i>fmt</i> and remaining arguments are interpreted
|
|
as with <tt>printf()</tt>. </div>
|
|
|
|
<p><tt>void rb_fatal(const char *fmt, ...)</tt></p>
|
|
|
|
<div class="indent"> Raises a fatal exception, terminating
|
|
the process. No rescue blocks are called, but ensure blocks will be
|
|
called. The given format string <i>fmt</i> and remaining
|
|
arguments are interpreted as with <tt>printf()</tt>. </div>
|
|
|
|
<p><tt>void rb_bug(const char *fmt, ...)</tt></p>
|
|
|
|
<div class="indent"> Terminates the process immediately --
|
|
no handlers of any sort will be called. The given format string <i>fmt</i>
|
|
and remaining arguments are interpreted as with <tt>printf()</tt>.
|
|
You should call this function only if a fatal bug has been exposed. </div>
|
|
|
|
<p><tt>void rb_sys_fail(const char *msg)</tt></p>
|
|
|
|
<div class="indent"> Raises a platform-specific exception
|
|
corresponding to the last known system error, with the given string <i>msg</i>.
|
|
</div>
|
|
|
|
<p><tt>VALUE rb_rescue(VALUE (*body)(VALUE), VALUE args,
|
|
VALUE(*rescue)(VALUE, VALUE), VALUE rargs)</tt></p>
|
|
|
|
<div class="indent"> Executes <i>body</i>
|
|
with the given <i>args</i>. If a <tt>StandardError</tt>
|
|
exception is raised, then execute <i>rescue</i> with the
|
|
given <i>rargs</i>. </div>
|
|
|
|
<p><tt>VALUE rb_ensure(VALUE(*body)(VALUE), VALUE args,
|
|
VALUE(*ensure)(VALUE), VALUE eargs)</tt></p>
|
|
|
|
<div class="indent"> Executes <i>body</i>
|
|
with the given <i>args</i>. Whether or not an exception is
|
|
raised, execute <i>ensure</i> with the given <i>rargs</i>
|
|
after <i>body</i> has completed. </div>
|
|
|
|
<p><tt>VALUE rb_protect(VALUE (*body)(VALUE), VALUE args,
|
|
int *result)</tt></p>
|
|
|
|
<div class="indent"> Executes <i>body</i>
|
|
with the given <i>args</i> and returns nonzero in result
|
|
if any exception was raised. </div>
|
|
|
|
<p><tt>void rb_notimplement()</tt></p>
|
|
|
|
<div class="indent"> Raises a <tt>NotImpError</tt>
|
|
exception to indicate that the enclosed function is not implemented
|
|
yet, or not available on this platform. </div>
|
|
|
|
<p><tt>void rb_exit(int status)</tt></p>
|
|
|
|
<div class="indent"> Exits Ruby with the given <i>status</i>.
|
|
Raises a <tt>SystemExit</tt> exception and calls
|
|
registered exit functions and finalizers. </div>
|
|
|
|
<p><tt>void rb_warn(const char *fmt, ...)</tt></p>
|
|
|
|
<div class="indent"> Unconditionally issues a warning
|
|
message to standard error. The given format string <i>fmt</i>
|
|
and remaining arguments are interpreted as with <tt>printf()</tt>.
|
|
</div>
|
|
|
|
<p><tt>void rb_warning(const char *fmt, ...)</tt></p>
|
|
|
|
<div class="indent"> Conditionally issues a warning
|
|
message to standard error if Ruby was invoked with the <tt>-w</tt>
|
|
flag. The given format string <i>fmt</i> and remaining
|
|
arguments are interpreted as with <tt>printf()</tt>. </div>
|
|
|
|
<H4><a name="Ruby_nn46">34.7.8.5 Iterators</a></H4>
|
|
|
|
|
|
<p> <tt>void rb_iter_break()</tt> </p>
|
|
|
|
<div class="indent"> Breaks out of the enclosing iterator
|
|
block. </div>
|
|
|
|
<p><tt>VALUE rb_each(VALUE obj)</tt></p>
|
|
|
|
<div class="indent"> Invokes the <tt>each</tt>
|
|
method of the given <i>obj</i>. </div>
|
|
|
|
<p><tt>VALUE rb_yield(VALUE arg)</tt></p>
|
|
|
|
<div class="indent"> Transfers execution to the iterator
|
|
block in the current context, passing <i>arg</i> as an
|
|
argument. Multiple values may be passed in an array. </div>
|
|
|
|
<p><tt>int rb_block_given_p()</tt></p>
|
|
|
|
<div class="indent"> Returns <tt>true</tt> if
|
|
<tt>yield</tt> would execute a block in the current
|
|
context; that is, if a code block was passed to the current method and
|
|
is available to be called. </div>
|
|
|
|
<p><tt>VALUE rb_iterate(VALUE (*method)(VALUE), VALUE args,
|
|
VALUE (*block)(VALUE, VALUE), VALUE arg2)</tt></p>
|
|
|
|
<div class="indent"> Invokes <i>method</i>
|
|
with argument <i>args</i> and block <i>block</i>.
|
|
A <tt>yield</tt> from that method will invoke <i>block</i>
|
|
with the argument given to <tt>yield</tt>, and a second
|
|
argument <i>arg2</i>. </div>
|
|
|
|
<p><tt>VALUE rb_catch(const char *tag, VALUE (*proc)(VALUE,
|
|
VALUE), VALUE value)</tt></p>
|
|
|
|
<div class="indent"> Equivalent to Ruby's <tt>catch</tt>.
|
|
</div>
|
|
|
|
<p><tt>void rb_throw(const char *tag, VALUE value)</tt></p>
|
|
|
|
<div class="indent"> Equivalent to Ruby's <tt>throw</tt>.
|
|
</div>
|
|
|
|
<H3><a name="Ruby_nn47">34.7.9 Typemap Examples</a></H3>
|
|
|
|
|
|
<p> This section includes a few examples of typemaps. For more
|
|
examples, you might look at the examples in the <tt>Example/ruby</tt>
|
|
directory. </p>
|
|
|
|
<H3><a name="Ruby_nn48">34.7.10 Converting a Ruby array to a char **</a></H3>
|
|
|
|
|
|
<p> A common problem in many C programs is the processing of
|
|
command line arguments, which are usually passed in an array of <tt>NULL</tt>
|
|
terminated strings. The following SWIG interface file allows a Ruby
|
|
Array instance to be used as a <tt>char **</tt> object. </p>
|
|
|
|
<div class="code">
|
|
<pre>%module argv
|
|
|
|
// This tells SWIG to treat char ** as a special case
|
|
%typemap(in) char ** {
|
|
/* Get the length of the array */
|
|
int size = RARRAY($input)->len;
|
|
int i;
|
|
$1 = (char **) malloc((size+1)*sizeof(char *));
|
|
/* Get the first element in memory */
|
|
VALUE *ptr = RARRAY($input)->ptr;
|
|
for (i=0; i < size; i++, ptr++) {
|
|
/* Convert Ruby Object String to char* */
|
|
$1[i]= StringValuePtr(*ptr);
|
|
}
|
|
$1[i]=NULL; /* End of list */
|
|
}
|
|
|
|
// This cleans up the char ** array created before
|
|
// the function call
|
|
|
|
%typemap(freearg) char ** {
|
|
free((char *) $1);
|
|
}
|
|
|
|
// Now a test function
|
|
%inline %{
|
|
int print_args(char **argv) {
|
|
int i = 0;
|
|
while (argv[i]) {
|
|
printf("argv[%d] = %s\n", i, argv[i]);
|
|
i++;
|
|
}
|
|
return i;
|
|
}
|
|
%}</pre>
|
|
</div>
|
|
|
|
<p> When this module is compiled, the wrapped C function now
|
|
operates as follows : </p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>require 'Argv'
|
|
Argv.print_args(["Dave", "Mike", "Mary", "Jane", "John"])
|
|
argv[0] = Dave
|
|
argv[1] = Mike
|
|
argv[2] = Mary
|
|
argv[3] = Jane
|
|
argv[4] = John</pre>
|
|
</div>
|
|
|
|
<p> In the example, two different typemaps are used. The "in"
|
|
typemap is used to receive an input argument and convert it to a C
|
|
array. Since dynamic memory allocation is used to allocate memory for
|
|
the array, the "freearg" typemap is used to later release this memory
|
|
after the execution of the C function. </p>
|
|
|
|
<H3><a name="Ruby_nn49">34.7.11 Collecting arguments in a hash</a></H3>
|
|
|
|
|
|
<p> Ruby's solution to the "keyword arguments" capability of some
|
|
other languages is to allow the programmer to pass in one or more
|
|
key-value pairs as arguments to a function. All of those key-value
|
|
pairs are collected in a single <tt>Hash</tt> argument
|
|
that's presented to the function. If it makes sense, you might want to
|
|
provide similar functionality for your Ruby interface. For example,
|
|
suppose you'd like to wrap this C function that collects information
|
|
about people's vital statistics: </p>
|
|
|
|
<div class="code">
|
|
<pre>void setVitalStats(const char *person, int nattributes, const char **names, int *values);</pre>
|
|
</div>
|
|
|
|
<p> and you'd like to be able to call it from Ruby by passing in
|
|
an arbitrary number of key-value pairs as inputs, e.g. </p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>setVitalStats("Fred",
|
|
'weight' => 270,
|
|
'age' => 42
|
|
)</pre>
|
|
</div>
|
|
|
|
<p> To make this work, you need to write a typemap that expects a
|
|
Ruby <tt>Hash</tt> as its input and somehow extracts the
|
|
last three arguments (<i>nattributes</i>, <i>names</i>
|
|
and <i>values</i>) needed by your C function. Let's start
|
|
with the basics: </p>
|
|
|
|
<div class="code">
|
|
<pre>%typemap(in) (int nattributes, const char **names, const int *values)
|
|
(VALUE keys_arr, int i, VALUE key, VALUE val) {
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<p> This <tt>%typemap</tt> directive tells SWIG that
|
|
we want to match any function declaration that has the specified types
|
|
and names of arguments somewhere in the argument list. The fact that we
|
|
specified the argument names (<i>nattributes</i>, <i>names</i>
|
|
and <i>values</i>) in our typemap is significant; this
|
|
ensures that SWIG won't try to apply this typemap to <i>other</i>
|
|
functions it sees that happen to have a similar declaration with
|
|
different argument names. The arguments that appear in the second set
|
|
of parentheses (<i>keys_arr</i>, <i>i</i>, <i>key</i>
|
|
and <i>val</i>) define local variables that our typemap
|
|
will need. </p>
|
|
|
|
<p>Since we expect the input argument to be a <tt>Hash</tt>,
|
|
let's next add a check for that: </p>
|
|
|
|
<div class="code">
|
|
<pre>%typemap(in) (int nattributes, const char **names, const int *values)
|
|
(VALUE keys_arr, int i, VALUE key, VALUE val) {
|
|
<b>Check_Type($input, T_HASH);</b>
|
|
}</pre>
|
|
</div>
|
|
|
|
<p> <tt>Check_Type()</tt> is just a macro (defined
|
|
in the Ruby header files) that confirms that the input argument is of
|
|
the correct type; if it isn't, an exception will be raised. </p>
|
|
|
|
<p>The next task is to determine how many key-value pairs are
|
|
present in the hash; we'll assign this number to the first typemap
|
|
argument (<tt>$1</tt>). This is a little tricky since the
|
|
Ruby/C API doesn't provide a public function for querying the size of a
|
|
hash, but we can get around that by calling the hash's <i>size</i>
|
|
method directly and converting its result to a C <tt>int</tt>
|
|
value: </p>
|
|
|
|
<div class="code">
|
|
<pre>%typemap(in) (int nattributes, const char **names, const int *values)
|
|
(VALUE keys_arr, int i, VALUE key, VALUE val) {
|
|
Check_Type($input, T_HASH);
|
|
<b>$1 = NUM2INT(rb_funcall($input, rb_intern("size"), 0, Qnil));</b>
|
|
}</pre>
|
|
</div>
|
|
|
|
<p> So now we know the number of attributes. Next we need to
|
|
initialize the second and third typemap arguments (i.e. the two C
|
|
arrays) to <tt>NULL</tt> and set the stage for extracting
|
|
the keys and values from the hash: </p>
|
|
|
|
<div class="code">
|
|
<pre>%typemap(in) (int nattributes, const char **names, const int *values)
|
|
(VALUE keys_arr, int i, VALUE key, VALUE val) {
|
|
Check_Type($input, T_HASH);
|
|
$1 = NUM2INT(rb_funcall($input, rb_intern("size"), 0, Qnil));
|
|
<b>$2 = NULL;
|
|
$3 = NULL;
|
|
if ($1 > 0) {
|
|
$2 = (char **) malloc($1*sizeof(char *));
|
|
$3 = (int *) malloc($1*sizeof(int));
|
|
}</b>
|
|
}</pre>
|
|
</div>
|
|
|
|
<p> There are a number of ways we could extract the keys and
|
|
values from the input hash, but the simplest approach is to first call
|
|
the hash's <i>keys</i> method (which returns a Ruby array
|
|
of the keys) and then start looping over the elements in that array: </p>
|
|
|
|
<div class="code">
|
|
<pre>%typemap(in) (int nattributes, const char **names, const int *values)
|
|
(VALUE keys_arr, int i, VALUE key, VALUE val) {
|
|
Check_Type($input, T_HASH);
|
|
$1 = NUM2INT(rb_funcall($input, rb_intern("size"), 0, Qnil));
|
|
$2 = NULL;
|
|
$3 = NULL;
|
|
if ($1 > 0) {
|
|
$2 = (char **) malloc($1*sizeof(char *));
|
|
$3 = (int *) malloc($1*sizeof(int));
|
|
<b>keys_arr = rb_funcall($input, rb_intern("keys"), 0, Qnil);
|
|
for (i = 0; i < $1; i++) {
|
|
}</b>
|
|
}
|
|
}</pre>
|
|
</div>
|
|
|
|
<p> Recall that <i>keys_arr</i> and <i>i</i>
|
|
are local variables for this typemap. For each element in the <i>keys_arr</i>
|
|
array, we want to get the key itself, as well as the value
|
|
corresponding to that key in the hash: </p>
|
|
|
|
<div class="code">
|
|
<pre>%typemap(in) (int nattributes, const char **names, const int *values)
|
|
(VALUE keys_arr, int i, VALUE key, VALUE val) {
|
|
Check_Type($input, T_HASH);
|
|
$1 = NUM2INT(rb_funcall($input, rb_intern("size"), 0, Qnil));
|
|
$2 = NULL;
|
|
$3 = NULL;
|
|
if ($1 > 0) {
|
|
$2 = (char **) malloc($1*sizeof(char *));
|
|
$3 = (int *) malloc($1*sizeof(int));
|
|
keys_arr = rb_funcall($input, rb_intern("keys"), 0, Qnil);
|
|
for (i = 0; i < $1; i++) {
|
|
<b>key = rb_ary_entry(keys_arr, i);
|
|
val = rb_hash_aref($input, key);</b>
|
|
}
|
|
}
|
|
}</pre>
|
|
</div>
|
|
|
|
<p> To be safe, we should again use the <tt>Check_Type()</tt>
|
|
macro to confirm that the key is a <tt>String</tt> and the
|
|
value is a <tt>Fixnum</tt>: </p>
|
|
|
|
<div class="code">
|
|
<pre>%typemap(in) (int nattributes, const char **names, const int *values)
|
|
(VALUE keys_arr, int i, VALUE key, VALUE val) {
|
|
Check_Type($input, T_HASH);
|
|
$1 = NUM2INT(rb_funcall($input, rb_intern("size"), 0, Qnil));
|
|
$2 = NULL;
|
|
$3 = NULL;
|
|
if ($1 > 0) {
|
|
$2 = (char **) malloc($1*sizeof(char *));
|
|
$3 = (int *) malloc($1*sizeof(int));
|
|
keys_arr = rb_funcall($input, rb_intern("keys"), 0, Qnil);
|
|
for (i = 0; i < $1; i++) {
|
|
key = rb_ary_entry(keys_arr, i);
|
|
val = rb_hash_aref($input, key);
|
|
<b>Check_Type(key, T_STRING);
|
|
Check_Type(val, T_FIXNUM);</b>
|
|
}
|
|
}
|
|
}</pre>
|
|
</div>
|
|
|
|
<p> Finally, we can convert these Ruby objects into their C
|
|
equivalents and store them in our local C arrays: </p>
|
|
|
|
<div class="code">
|
|
<pre>%typemap(in) (int nattributes, const char **names, const int *values)
|
|
(VALUE keys_arr, int i, VALUE key, VALUE val) {
|
|
Check_Type($input, T_HASH);
|
|
$1 = NUM2INT(rb_funcall($input, rb_intern("size"), 0, Qnil));
|
|
$2 = NULL;
|
|
$3 = NULL;
|
|
if ($1 > 0) {
|
|
$2 = (char **) malloc($1*sizeof(char *));
|
|
$3 = (int *) malloc($1*sizeof(int));
|
|
keys_arr = rb_funcall($input, rb_intern("keys"), 0, Qnil);
|
|
for (i = 0; i < $1; i++) {
|
|
key = rb_ary_entry(keys_arr, i);
|
|
val = rb_hash_aref($input, key);
|
|
Check_Type(key, T_STRING);
|
|
Check_Type(val, T_FIXNUM);
|
|
<b>$2[i] = StringValuePtr(key);
|
|
$3[i] = NUM2INT(val);</b>
|
|
}
|
|
}
|
|
}</pre>
|
|
</div>
|
|
|
|
<p> We're not done yet. Since we used <tt>malloc()</tt>
|
|
to dynamically allocate the memory used for the <i>names</i>
|
|
and <i>values</i> arguments, we need to provide a
|
|
corresponding "freearg" typemap to free that memory so that there is no
|
|
memory leak. Fortunately, this typemap is a lot easier to write: </p>
|
|
|
|
<div class="code">
|
|
<pre>%typemap(freearg) (int nattributes, const char **names, const int *values) {
|
|
free((void *) $2);
|
|
free((void *) $3);
|
|
}</pre>
|
|
</div>
|
|
|
|
<p> All of the code for this example, as well as a sample Ruby
|
|
program that uses the extension, can be found in the <tt>Examples/ruby/hashargs</tt>
|
|
directory of the SWIG distribution. </p>
|
|
|
|
<H3><a name="Ruby_nn50">34.7.12 Pointer handling</a></H3>
|
|
|
|
|
|
<p> Occasionally, it might be necessary to convert pointer values
|
|
that have been stored using the SWIG typed-pointer representation.
|
|
Since there are several ways in which pointers can be represented, the
|
|
following two functions are used to safely perform this conversion: </p>
|
|
|
|
<p><tt>int SWIG_ConvertPtr(VALUE obj, void **ptr,
|
|
swig_type_info *ty, int flags)</tt> </p>
|
|
|
|
<div class="indent">Converts a Ruby object <i>obj</i>
|
|
to a C pointer whose address is <i>ptr</i> (i.e. <i>ptr</i>
|
|
is a pointer to a pointer). The third argument, <i>ty</i>,
|
|
is a pointer to a SWIG type descriptor structure. If <i>ty</i>
|
|
is not <tt>NULL</tt>, that type information is used to
|
|
validate type compatibility and other aspects of the type conversion.
|
|
If <i>flags</i> is non-zero, any type errors encountered
|
|
during this validation result in a Ruby <tt>TypeError</tt>
|
|
exception being raised; if <i>flags</i> is zero, such type
|
|
errors will cause <tt>SWIG_ConvertPtr()</tt> to return -1
|
|
but not raise an exception. If <i>ty</i> is <tt>NULL</tt>,
|
|
no type-checking is performed. </div>
|
|
|
|
<p> <tt>VALUE SWIG_NewPointerObj(void *ptr, swig_type_info
|
|
*ty, int own)</tt> </p>
|
|
|
|
<div class="indent">Creates a new Ruby pointer object.
|
|
Here, <i>ptr</i> is the pointer to convert, <i>ty</i>
|
|
is the SWIG type descriptor structure that describes the type, and <i>own</i>
|
|
is a flag that indicates whether or not Ruby should take ownership of
|
|
the pointer (i.e. whether Ruby should free this data when the
|
|
corresponding Ruby instance is garbage-collected). </div>
|
|
|
|
<p> Both of these functions require the use of a special SWIG
|
|
type-descriptor structure. This structure contains information about
|
|
the mangled name of the datatype, type-equivalence information, as well
|
|
as information about converting pointer values under C++ inheritance.
|
|
For a type of <tt>Foo *</tt>, the type descriptor
|
|
structure is usually accessed as follows: </p>
|
|
|
|
<div class="indent code">
|
|
<pre>Foo *foo;
|
|
SWIG_ConvertPtr($input, (void **) &foo, SWIGTYPE_p_Foo, 1);
|
|
|
|
VALUE obj;
|
|
obj = SWIG_NewPointerObj(f, SWIGTYPE_p_Foo, 0);</pre>
|
|
</div>
|
|
|
|
<p> In a typemap, the type descriptor should always be accessed
|
|
using the special typemap variable <tt>$1_descriptor</tt>.
|
|
For example: </p>
|
|
|
|
<div class="indent code">
|
|
<pre>%typemap(in) Foo * {
|
|
SWIG_ConvertPtr($input, (void **) &$1, $1_descriptor, 1);
|
|
}</pre>
|
|
</div>
|
|
|
|
<H4><a name="Ruby_nn51">34.7.12.1 Ruby Datatype Wrapping</a></H4>
|
|
|
|
|
|
<p> <tt>VALUE Data_Wrap_Struct(VALUE class, void
|
|
(*mark)(void *), void (*free)(void *), void *ptr)</tt> </p>
|
|
|
|
<div class="indent">Given a pointer <i>ptr</i>
|
|
to some C data, and the two garbage collection routines for this data (<i>mark</i>
|
|
and <i>free</i>), return a <tt>VALUE</tt> for
|
|
the Ruby object. </div>
|
|
|
|
<p><tt>VALUE Data_Make_Struct(VALUE class, <i>c-type</i>,
|
|
void (*mark)(void *), void (*free)(void *), <i>c-type</i>
|
|
*ptr)</tt></p>
|
|
|
|
<div class="indent">Allocates a new instance of a C data
|
|
type <i>c-type</i>, assigns it to the pointer <i>ptr</i>,
|
|
then wraps that pointer with <tt>Data_Wrap_Struct()</tt>
|
|
as above. </div>
|
|
|
|
<p><tt>Data_Get_Struct(VALUE obj, <i>c-type</i>,
|
|
<i>c-type</i> *ptr)</tt></p>
|
|
|
|
<div class="indent">Retrieves the original C pointer of
|
|
type <i>c-type</i> from the data object <i>obj</i>
|
|
and assigns that pointer to <i>ptr</i>. </div>
|
|
|
|
<H3><a name="Ruby_nn52">34.7.13 Example: STL Vector to Ruby Array</a></H3>
|
|
|
|
|
|
<p>Another use for macros and type maps is to create a Ruby array
|
|
from a STL vector of pointers. In essence, copy of all the pointers in
|
|
the vector into a Ruby array. The use of the macro is to make the
|
|
typemap so generic that any vector with pointers can use the type map.
|
|
The following is an example of how to construct this type of
|
|
macro/typemap and should give insight into constructing similar
|
|
typemaps for other STL structures: </p>
|
|
|
|
<div class="code">
|
|
<pre>%define PTR_VECTOR_TO_RUBY_ARRAY(vectorclassname, classname)
|
|
%typemap(out) vectorclassname &, const vectorclassname & {
|
|
VALUE arr = rb_ary_new2($1->size());
|
|
vectorclassname::iterator i = $1->begin(), iend = $1->end();
|
|
for ( ; i!=iend; i++ )
|
|
rb_ary_push(arr, Data_Wrap_Struct(c ## classname.klass, 0, 0, *i));
|
|
$result = arr;
|
|
}
|
|
%typemap(out) vectorclassname, const vectorclassname {
|
|
VALUE arr = rb_ary_new2($1.size());
|
|
vectorclassname::iterator i = $1.begin(), iend = $1.end();
|
|
for ( ; i!=iend; i++ )
|
|
rb_ary_push(arr, Data_Wrap_Struct(c ## classname.klass, 0, 0, *i));
|
|
$result = arr;
|
|
}
|
|
%enddef</pre>
|
|
</div>
|
|
|
|
<p> Note, that the "<tt>c ## classname.klass"</tt> is
|
|
used in the preprocessor step to determine the actual object from the
|
|
class name. </p>
|
|
|
|
<p>To use the macro with a class Foo, the following is used: </p>
|
|
|
|
<div class="code">
|
|
<pre>PTR_VECTOR_TO_RUBY_ARRAY(vector<foo *="">, Foo)</pre>
|
|
</div>
|
|
|
|
<p> It is also possible to create a STL vector of Ruby objects: </p>
|
|
|
|
<div class="code">
|
|
<pre>%define RUBY_ARRAY_TO_PTR_VECTOR(vectorclassname, classname)
|
|
%typemap(in) vectorclassname &, const vectorclassname & {
|
|
Check_Type($input, T_ARRAY);
|
|
vectorclassname *vec = new vectorclassname;
|
|
int len = RARRAY($input)->len;
|
|
for (int i=0; i!=len; i++) {
|
|
VALUE inst = rb_ary_entry($input, i);
|
|
//The following _should_ work but doesn't on HPUX
|
|
// Check_Type(inst, T_DATA);
|
|
classname *element = NULL;
|
|
Data_Get_Struct(inst, classname, element);
|
|
vec->push_back(element);
|
|
}
|
|
$1 = vec;
|
|
}
|
|
|
|
%typemap(freearg) vectorclassname &, const vectorclassname & {
|
|
delete $1;
|
|
}
|
|
%enddef</pre>
|
|
</div>
|
|
|
|
<p> It is also possible to create a Ruby array from a vector of
|
|
static data types: </p>
|
|
|
|
<div class="code">
|
|
<pre>%define VECTOR_TO_RUBY_ARRAY(vectorclassname, classname)
|
|
%typemap(out) vectorclassname &, const vectorclassname & {
|
|
VALUE arr = rb_ary_new2($1->size());
|
|
vectorclassname::iterator i = $1->begin(), iend = $1->end();
|
|
for ( ; i!=iend; i++ )
|
|
rb_ary_push(arr, Data_Wrap_Struct(c ## classname.klass, 0, 0, &(*i)));
|
|
$result = arr;
|
|
}
|
|
%typemap(out) vectorclassname, const vectorclassname {
|
|
VALUE arr = rb_ary_new2($1.size());
|
|
vectorclassname::iterator i = $1.begin(), iend = $1.end();
|
|
for ( ; i!=iend; i++ )
|
|
rb_ary_push(arr, Data_Wrap_Struct(c ## classname.klass, 0, 0, &(*i)));
|
|
$result = arr;
|
|
}
|
|
%enddef</pre>
|
|
</div>
|
|
|
|
Note that this is mostly an example of typemaps. If you want to use the
|
|
STL with ruby, you are advised to use the standard swig STL library,
|
|
which does much more than this. Refer to the section called
|
|
the<a href="#Ruby_nn23_1"> C++ Standard Template Library</a>.
|
|
|
|
<H2><a name="Ruby_nn65">34.8 Docstring Features</a></H2>
|
|
|
|
|
|
<p>
|
|
Using ri and rdoc web pages in Ruby libraries is a common practice.
|
|
Given the way that SWIG generates the extensions by default, your users
|
|
will normally not get
|
|
any documentation for it, even if they run 'rdoc' on the resulting .c
|
|
or .cxx file.</p>
|
|
|
|
<p>The features described in this section make it easy for you to
|
|
add
|
|
rdoc strings to your modules, functions and methods that can then be
|
|
read by Ruby's rdoc tool to generate html web pages, ri documentation,
|
|
Windows chm file and an .xml description.</p>
|
|
|
|
<p>rdoc can then be run from a console or shell window on a swig
|
|
generated file.</p>
|
|
|
|
<p>For example, to generate html web pages from a C++ file, you'd
|
|
do:</p>
|
|
|
|
<div class="code shell">
|
|
<pre>
|
|
$ rdoc -E cxx=c -f html file_wrap.cxx
|
|
</pre></div>
|
|
|
|
<p>To
|
|
generate ri documentation from a c wrap file, you could do:</p>
|
|
|
|
<div class="code shell"><pre>
|
|
$ rdoc -r file_wrap.c
|
|
</pre></div>
|
|
|
|
<H3><a name="Ruby_nn66">34.8.1 Module docstring</a></H3>
|
|
|
|
|
|
<p>
|
|
Ruby allows a docstring at the beginning of the file
|
|
before any other statements, and it is typically used to give a
|
|
general description of the entire module. SWIG supports this by
|
|
setting an option of the <tt>%module</tt> directive. For
|
|
example:
|
|
</p>
|
|
|
|
<div class="code">
|
|
<pre>%module(docstring="This is the example module's docstring") example</pre>
|
|
</div>
|
|
|
|
<p>
|
|
When you have more than just a line or so then you can retain the easy
|
|
readability of the <tt>%module</tt> directive by using a
|
|
macro. For example:
|
|
</p>
|
|
|
|
<div class="code">
|
|
<pre>%define DOCSTRING
|
|
"The `XmlResource` class allows program resources defining menus,
|
|
layout of controls on a panel, etc. to be loaded from an XML file."
|
|
%enddef
|
|
|
|
%module(docstring=DOCSTRING) xrc</pre>
|
|
</div>
|
|
|
|
<H3><a name="Ruby_nn67">34.8.2 %feature("autodoc")</a></H3>
|
|
|
|
|
|
<p>Since SWIG does know everything about the function it wraps,
|
|
it is possible to generate an rdoc containing the parameter types,
|
|
names
|
|
and default values. Since Ruby ships with one of the best documentation
|
|
systems of any language, it makes sense to take advantage of it.
|
|
</p>
|
|
|
|
<p>SWIG's Ruby module provides support for the "autodoc"
|
|
feature,
|
|
which when attached to a node in the parse tree will cause an rdoc
|
|
comment
|
|
to be generated in the wrapper file that includes the name of the
|
|
function, parameter
|
|
names, default values if any, and return type if any. There are also
|
|
several options for autodoc controlled by the value given to the
|
|
feature, described below.
|
|
</p>
|
|
|
|
<H4><a name="Ruby_nn68">34.8.2.1 %feature("autodoc", "0")</a></H4>
|
|
|
|
|
|
<p>
|
|
When the "0" option is given then the types of the parameters will
|
|
<em>not</em> be included in the autodoc string. For
|
|
example, given
|
|
this function prototype:
|
|
</p>
|
|
|
|
<div class="code">
|
|
<pre>%feature("autodoc", "0");
|
|
bool function_name(int x, int y, Foo* foo=NULL, Bar* bar=NULL);</pre>
|
|
</div>
|
|
|
|
<p>
|
|
Then Ruby code like this will be generated:
|
|
</p>
|
|
|
|
<div class="targetlang">
|
|
<pre>function_name(x, y, foo=nil, bar=nil) -> bool
|
|
...</pre>
|
|
</div>
|
|
|
|
<H4><a name="Ruby_autodoc1">34.8.2.2 %feature("autodoc", "1")</a></H4>
|
|
|
|
|
|
<p>
|
|
When the "1" option is used then the parameter types <em>will</em>
|
|
be used in the rdoc string. In addition, an attempt is made to
|
|
simplify the type name such that it makes more sense to the Ruby
|
|
user. Pointer, reference and const info is removed,
|
|
<tt>%rename</tt>'s are evaluated, etc. (This is not always
|
|
successful, but works most of the time. See the next section for what
|
|
to do when it doesn't.) Given the example above, then turning on the
|
|
parameter types with the "1" option will result in rdoc code like
|
|
this:
|
|
</p>
|
|
|
|
<div class="targetlang">
|
|
<pre>function_name(int x, int y, Foo foo=nil, Bar bar=nil) -> bool
|
|
...</pre>
|
|
</div>
|
|
|
|
<H4><a name="Ruby_autodoc2">34.8.2.3 %feature("autodoc", "2")</a></H4>
|
|
|
|
|
|
<p>
|
|
When the "2" option is used then the parameter types will not
|
|
be
|
|
used in the rdoc string. However, they will be listed in full after the
|
|
function. Given the example above, then turning on the
|
|
parameter types with the "2" option will result in Ruby code like
|
|
this:
|
|
</p>
|
|
|
|
<H4><a name="Ruby_feature_autodoc3">34.8.2.4 %feature("autodoc", "3")</a></H4>
|
|
|
|
|
|
<p>
|
|
When the "3" option is used then the function will be documented using
|
|
a combination of "1" and "2" above. Given the example above,
|
|
then turning on the
|
|
parameter types with the "2" option will result in Ruby code like
|
|
this:
|
|
</p>
|
|
|
|
<div class="targetlang">
|
|
<pre>function_name(int x, int y, Foo foo=nil, Bar bar=nil) -> bool
|
|
|
|
Parameters:
|
|
x - int
|
|
y - int
|
|
foo - Foo
|
|
bar - Bar</pre>
|
|
</div>
|
|
|
|
<H4><a name="Ruby_nn70">34.8.2.5 %feature("autodoc", "docstring")</a></H4>
|
|
|
|
|
|
<p>
|
|
Finally, there are times when the automatically generated autodoc
|
|
string will make no sense for a Ruby programmer, particularly when a
|
|
typemap is involved. So if you give an explicit value for the autodoc
|
|
feature then that string will be used in place of the automatically
|
|
generated string. For example:
|
|
</p>
|
|
|
|
<div class="code">
|
|
<pre>%feature("autodoc", "GetPosition() -> (x, y)") GetPosition;
|
|
void GetPosition(int* OUTPUT, int* OUTPUT);</pre>
|
|
</div>
|
|
|
|
<H3><a name="Ruby_nn71">34.8.3 %feature("docstring")</a></H3>
|
|
|
|
|
|
<p>
|
|
In addition to the autodoc strings described above, you can also
|
|
attach any arbitrary descriptive text to a node in the parse tree with
|
|
the "docstring" feature. When the proxy module is generated then any
|
|
docstring associated with classes, function or methods are output.
|
|
If an item already has an autodoc string then it is combined with the
|
|
docstring and they are output together. </p>
|
|
|
|
<H2><a name="Ruby_nn53">34.9 Advanced Topics</a></H2>
|
|
|
|
|
|
<H3><a name="Ruby_operator_overloading">34.9.1 Operator overloading</a></H3>
|
|
|
|
|
|
<p> SWIG allows operator overloading with, by using the <tt>%extend</tt>
|
|
or <tt>%rename</tt> commands in SWIG and the following
|
|
operator names (derived from Python): </p>
|
|
|
|
<div class="code diagram">
|
|
<table style="width: 100%; font-family: monospace;" border="1" cellpadding="2" cellspacing="2" summary="operator names">
|
|
<tbody>
|
|
<tr>
|
|
<td><b> General</b></td>
|
|
</tr>
|
|
<tr>
|
|
<td>__repr__ </td>
|
|
<td> inspect</td>
|
|
</tr>
|
|
<tr>
|
|
<td>__str__ </td>
|
|
<td> to_s</td>
|
|
</tr>
|
|
<tr>
|
|
<td>__cmp__ </td>
|
|
<td> <=></td>
|
|
</tr>
|
|
<tr>
|
|
<td>__hash__ </td>
|
|
<td> hash</td>
|
|
</tr>
|
|
<tr>
|
|
<td>__nonzero__ </td>
|
|
<td> nonzero?</td>
|
|
</tr>
|
|
<tr>
|
|
<td></td>
|
|
</tr>
|
|
<tr>
|
|
<td><b> Callable</b></td>
|
|
</tr>
|
|
<tr>
|
|
<td>__call__ </td>
|
|
<td> call</td>
|
|
</tr>
|
|
<tr>
|
|
<td></td>
|
|
</tr>
|
|
<tr>
|
|
<td><b> Collection</b></td>
|
|
</tr>
|
|
<tr>
|
|
<td>__len__ </td>
|
|
<td> length</td>
|
|
</tr>
|
|
<tr>
|
|
<td>__getitem__ </td>
|
|
<td> []</td>
|
|
</tr>
|
|
<tr>
|
|
<td>__setitem__ </td>
|
|
<td> []=</td>
|
|
</tr>
|
|
<tr>
|
|
<td></td>
|
|
</tr>
|
|
<tr>
|
|
<td><b> Numeric</b></td>
|
|
</tr>
|
|
<tr>
|
|
<td>__add__ </td>
|
|
<td> +</td>
|
|
</tr>
|
|
<tr>
|
|
<td>__sub__ </td>
|
|
<td> -</td>
|
|
<td></td>
|
|
</tr>
|
|
<tr>
|
|
<td>__mul__ </td>
|
|
<td> *</td>
|
|
</tr>
|
|
<tr>
|
|
<td>__div__ </td>
|
|
<td> /</td>
|
|
</tr>
|
|
<tr>
|
|
<td>__mod__ </td>
|
|
<td> %</td>
|
|
</tr>
|
|
<tr>
|
|
<td>__divmod__ </td>
|
|
<td> divmod</td>
|
|
</tr>
|
|
<tr>
|
|
<td>__pow__ </td>
|
|
<td> **</td>
|
|
</tr>
|
|
<tr>
|
|
<td>__lshift__ </td>
|
|
<td> <<</td>
|
|
</tr>
|
|
<tr>
|
|
<td>__rshift__ </td>
|
|
<td> >></td>
|
|
</tr>
|
|
<tr>
|
|
<td>__and__ </td>
|
|
<td> &</td>
|
|
</tr>
|
|
<tr>
|
|
<td>__xor__ </td>
|
|
<td> ^</td>
|
|
</tr>
|
|
<tr>
|
|
<td>__or__ </td>
|
|
<td> |</td>
|
|
</tr>
|
|
<tr>
|
|
<td>__neg__ </td>
|
|
<td> -@</td>
|
|
<td></td>
|
|
</tr>
|
|
<tr>
|
|
<td>__pos__ </td>
|
|
<td> +@</td>
|
|
</tr>
|
|
<tr>
|
|
<td>__abs__ </td>
|
|
<td> abs</td>
|
|
</tr>
|
|
<tr>
|
|
<td>__invert__ </td>
|
|
<td> ~</td>
|
|
</tr>
|
|
<tr>
|
|
<td>__int__ </td>
|
|
<td> to_i</td>
|
|
</tr>
|
|
<tr>
|
|
<td>__float__ </td>
|
|
<td> to_f</td>
|
|
</tr>
|
|
<tr>
|
|
<td>__coerce__ </td>
|
|
<td> coerce</td>
|
|
</tr>
|
|
<tr>
|
|
<td></td>
|
|
</tr>
|
|
<tr>
|
|
<td><b>Additions in 1.3.13 </b></td>
|
|
</tr>
|
|
<tr>
|
|
<td>__lt__ </td>
|
|
<td> <</td>
|
|
</tr>
|
|
<tr>
|
|
<td>__le__ </td>
|
|
<td> <=</td>
|
|
</tr>
|
|
<tr>
|
|
<td>__eq__ </td>
|
|
<td> ==</td>
|
|
</tr>
|
|
<tr>
|
|
<td>__gt__ </td>
|
|
<td> ></td>
|
|
</tr>
|
|
<tr>
|
|
<td>__ge__ </td>
|
|
<td> >=</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
</div>
|
|
|
|
<p> Note that although SWIG supports the <tt>__eq__</tt>
|
|
magic method name for defining an equivalence operator, there is no
|
|
separate method for handling <i>inequality</i> since Ruby
|
|
parses the expression <i>a != b</i> as <i>!(a == b)</i>.
|
|
</p>
|
|
|
|
<H3><a name="Ruby_nn55">34.9.2 Creating Multi-Module Packages</a></H3>
|
|
|
|
|
|
<p> The chapter on <a href="Modules.html#Modules">Working
|
|
with Modules</a> discusses the basics of creating multi-module
|
|
extensions with SWIG, and in particular the considerations for sharing
|
|
runtime type information among the different modules. </p>
|
|
|
|
<p>As an example, consider one module's interface file (<tt>shape.i</tt>)
|
|
that defines our base class: </p>
|
|
|
|
<div class="code">
|
|
<pre>%module shape
|
|
|
|
%{
|
|
#include "Shape.h"
|
|
%}
|
|
|
|
class Shape {
|
|
protected:
|
|
double xpos;
|
|
double ypos;
|
|
protected:
|
|
Shape(double x, double y);
|
|
public:
|
|
double getX() const;
|
|
double getY() const;
|
|
};</pre>
|
|
</div>
|
|
|
|
<p> We also have a separate interface file (<tt>circle.i</tt>)
|
|
that defines a derived class: </p>
|
|
|
|
<div class="code">
|
|
<pre>%module circle
|
|
|
|
%{
|
|
#include "Shape.h"
|
|
#include "Circle.h"
|
|
%}
|
|
|
|
// Import the base class definition from Shape module
|
|
%import shape.i
|
|
|
|
class Circle : public Shape {
|
|
protected:
|
|
double radius;
|
|
public:
|
|
Circle(double x, double y, double r);
|
|
double getRadius() const;
|
|
};</pre>
|
|
</div>
|
|
|
|
<p> We'll start by building the <b>Shape</b>
|
|
extension module: </p>
|
|
|
|
<div class="code shell">
|
|
<pre>$ swig -c++ -ruby shape.i
|
|
</pre>
|
|
</div>
|
|
|
|
<p> SWIG generates a wrapper file named <tt>shape_wrap.cxx</tt>.
|
|
To compile this into a dynamically loadable extension for Ruby, prepare
|
|
an <tt>extconf.rb</tt> script using this template: </p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>require 'mkmf'
|
|
|
|
# Since the SWIG runtime support library for Ruby
|
|
# depends on the Ruby library, make sure it's in the list
|
|
# of libraries.
|
|
$libs = append_library($libs, Config::CONFIG['RUBY_INSTALL_NAME'])
|
|
|
|
# Create the makefile
|
|
create_makefile('shape')</pre>
|
|
</div>
|
|
|
|
<p> Run this script to create a <tt>Makefile</tt>
|
|
and then type <tt>make</tt> to build the shared library: </p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>$ <b>ruby extconf.rb</b>
|
|
creating Makefile
|
|
$ <b>make</b>
|
|
g++ -fPIC -g -O2 -I. -I/usr/include/ruby-2.1.0 \
|
|
-I. -c shape_wrap.cxx
|
|
gcc -shared -L/usr/local/lib -o shape.so shape_wrap.o -L. \
|
|
-lruby -lruby -lc</pre>
|
|
</div>
|
|
|
|
<p> Note that depending on your installation, the outputs may be
|
|
slightly different; these outputs are those for a Linux-based
|
|
development environment. The end result should be a shared library
|
|
(here, <tt>shape.so</tt>) containing the extension module
|
|
code. Now repeat this process in a separate directory for the <b>Circle</b>
|
|
module: </p>
|
|
|
|
<ol>
|
|
<li> Run SWIG to generate the wrapper code (<tt>circle_wrap.cxx</tt>);
|
|
</li>
|
|
<li> Write an <tt>extconf.rb</tt> script that your
|
|
end-users can use to create a platform-specific <tt>Makefile</tt>
|
|
for the extension; </li>
|
|
<li> Build the shared library for this extension by typing <tt>make</tt>.
|
|
</li>
|
|
</ol>
|
|
|
|
<p> Once you've built both of these extension modules, you can
|
|
test them interactively in IRB to confirm that the <tt>Shape</tt>
|
|
and <tt>Circle</tt> modules are properly loaded and
|
|
initialized: </p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>$ <b>irb</b>
|
|
irb(main):001:0> <b>require 'shape'</b>
|
|
true
|
|
irb(main):002:0> <b>require 'circle'</b>
|
|
true
|
|
irb(main):003:0> <b>c = Circle::Circle.new(5, 5, 20)</b>
|
|
#<Circle::Circle:0xa097208>
|
|
irb(main):004:0> <b>c.kind_of? Shape::Shape</b>
|
|
true
|
|
irb(main):005:0> <b>c.getX()</b>
|
|
5.0</pre>
|
|
</div>
|
|
|
|
<H3><a name="Ruby_nn56">34.9.3 Specifying Mixin Modules</a></H3>
|
|
|
|
|
|
<p> The Ruby language doesn't support multiple inheritance, but
|
|
it does allow you to mix one or more modules into a class using Ruby's <tt>include</tt>
|
|
method. For example, if you have a Ruby class that defines an <em>each</em>
|
|
instance method, e.g. </p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>class Set
|
|
def initialize
|
|
@members = []
|
|
end
|
|
|
|
def each
|
|
@members.each { |m| yield m }
|
|
end
|
|
end</pre>
|
|
</div>
|
|
|
|
<p> then you can mix-in Ruby's <tt>Enumerable</tt>
|
|
module to easily add a lot of functionality to your class: </p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>class Set
|
|
<b>include Enumerable</b>
|
|
def initialize
|
|
@members = []
|
|
end
|
|
def each
|
|
@members.each { |m| yield m }
|
|
end
|
|
end</pre>
|
|
</div>
|
|
|
|
<p> To get the same benefit for your SWIG-wrapped classes, you
|
|
can use the <tt>%mixin</tt> directive to specify the names
|
|
of one or more modules that should be mixed-in to a class. For the
|
|
above example, the SWIG interface specification might look like this: </p>
|
|
|
|
<div class="code">
|
|
<pre>%mixin Set "Enumerable";
|
|
|
|
class Set {
|
|
public:
|
|
// Constructor
|
|
Set();
|
|
|
|
// Iterates through set members
|
|
void each();
|
|
};</pre>
|
|
</div>
|
|
|
|
<p> Multiple modules can be mixed into a class by providing a
|
|
comma-separated list of module names to the <tt>%mixin</tt>
|
|
directive, e.g. </p>
|
|
|
|
<div class="code">
|
|
<pre>%mixin Set "Fee, Fi, Fo, Fum";</pre>
|
|
</div>
|
|
|
|
<p> Note that the <tt>%mixin</tt> directive is
|
|
implemented using SWIG's "features" mechanism and so the same name
|
|
matching rules used for other kinds of features apply (see the chapter
|
|
on <a href="Customization.html#Customization">"Customization
|
|
Features"</a>) for more details). </p>
|
|
|
|
<H2><a name="Ruby_nn57">34.10 Memory Management</a></H2>
|
|
|
|
|
|
<p>One of the most common issues in generating SWIG bindings for
|
|
Ruby is proper memory management. The key to proper memory management
|
|
is clearly defining whether a wrapper Ruby object owns the underlying C
|
|
struct or C++ class. There are two possibilities:</p>
|
|
|
|
<ul>
|
|
|
|
<li> The Ruby object is responsible for freeing the C struct or
|
|
C++ object </li>
|
|
|
|
<li> The Ruby object should not free the C struct or C++ object
|
|
because it will be freed by the underlying C or C++ code</li>
|
|
|
|
</ul>
|
|
|
|
<p>To complicate matters, object ownership may transfer from Ruby
|
|
to C++ (or vice versa) depending on what function or methods are
|
|
invoked. Clearly, developing a SWIG wrapper requires a thorough
|
|
understanding of how the underlying library manages memory.</p>
|
|
|
|
<H3><a name="Ruby_nn58">34.10.1 Mark and Sweep Garbage Collector </a></H3>
|
|
|
|
|
|
<p>Ruby uses a mark and sweep garbage collector. When the garbage
|
|
collector runs, it finds all the "root" objects, including local
|
|
variables, global variables, global constants, hardware registers and
|
|
the C stack. For each root object, the garbage collector sets its mark
|
|
flag to true and calls <tt>rb_gc_mark</tt> on the object.
|
|
The job of <tt>rb_gc_mark</tt> is to recursively mark all
|
|
the objects that a Ruby object has a reference to (ignoring those
|
|
objects that have already been marked). Those objects, in turn, may
|
|
reference other objects. This process will continue until all active
|
|
objects have been "marked." After the mark phase comes the sweep phase.
|
|
In the sweep phase, all objects that have not been marked will be
|
|
garbage collected. </p>
|
|
|
|
<p>The Ruby C/API provides extension developers two hooks into
|
|
the garbage collector - a "mark" function and a "sweep" function. By
|
|
default these functions are set to NULL.</p>
|
|
|
|
<p>If a C struct or C++ class references any other Ruby objects,
|
|
then it must provide a "mark" function. The "mark" function should
|
|
identify any referenced Ruby objects by calling the rb_gc_mark function
|
|
for each one. Unsurprisingly, this function will be called by the Ruby
|
|
garbage during the "mark" phase.</p>
|
|
|
|
<p>During the sweep phase, Ruby destroys any unused objects. If
|
|
any memory has been allocated in creating the underlying C struct or
|
|
C++ struct, then a "free" function must be defined that deallocates
|
|
this memory. </p>
|
|
|
|
<H3><a name="Ruby_nn59">34.10.2 Object Ownership</a></H3>
|
|
|
|
|
|
<p>As described above, memory management depends on clearly
|
|
defining who is responsible for freeing the underlying C struct or C++
|
|
class. If the Ruby object is responsible for freeing the C++ object,
|
|
then a "free" function must be registered for the object. If the Ruby
|
|
object is not responsible for freeing the underlying memory, then a
|
|
"free" function must not be registered for the object.</p>
|
|
|
|
<p>For the most part, SWIG takes care of memory management
|
|
issues. The rules it uses are:</p>
|
|
|
|
<ul>
|
|
|
|
<li> When calling a C++ object's constructor from Ruby, SWIG
|
|
will assign a "free" function thereby making the Ruby object
|
|
responsible for freeing the C++ object</li>
|
|
|
|
<li> When calling a C++ member function that returns a pointer,
|
|
SWIG will not assign a "free" function thereby making the underlying
|
|
library responsible for freeing the object.</li>
|
|
|
|
</ul>
|
|
|
|
<p>To make this clearer, let's look at an example. Assume we have
|
|
a Foo and a Bar class. </p>
|
|
|
|
<div class="code">
|
|
<pre>/* File "RubyOwernshipExample.h" */
|
|
|
|
class Foo
|
|
{
|
|
public:
|
|
Foo() {}
|
|
~Foo() {}
|
|
};
|
|
|
|
class Bar
|
|
{
|
|
Foo *foo_;
|
|
public:
|
|
Bar(): foo_(new Foo) {}
|
|
~Bar() { delete foo_; }
|
|
Foo* get_foo() { return foo_; }
|
|
Foo* get_new_foo() { return new Foo; }
|
|
void set_foo(Foo *foo) { delete foo_; foo_ = foo; }
|
|
};</pre>
|
|
</div>
|
|
|
|
<p>First, consider this Ruby code: </p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>foo = Foo.new</pre>
|
|
</div>
|
|
|
|
<p>In this case, the Ruby code calls the underlying <tt>Foo</tt>
|
|
C++ constructor, thus creating a new <tt>foo</tt> object.
|
|
By default, SWIG will assign the new Ruby object a "free" function.
|
|
When the Ruby object is garbage collected, the "free" function will be
|
|
called. It in turn will call <tt>Foo</tt>'s destructor.</p>
|
|
|
|
<p>Next, consider this code: </p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>bar = Bar.new
|
|
foo = bar.get_foo()</pre>
|
|
</div>
|
|
|
|
<p>In this case, the Ruby code calls a C++ member function, <tt>get_foo</tt>.
|
|
By default, SWIG will not assign the Ruby object a "free" function.
|
|
Thus, when the Ruby object is garbage collected the underlying C++ <tt>foo</tt>
|
|
object is not affected.</p>
|
|
|
|
<p>Unfortunately, the real world is not as simple as the examples
|
|
above. For example:</p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>bar = Bar.new
|
|
foo = bar.get_new_foo()</pre>
|
|
</div>
|
|
|
|
<p>In this case, the default SWIG behavior for calling member
|
|
functions is incorrect. The Ruby object should assume ownership of the
|
|
returned object. This can be done by using the %newobject directive.
|
|
See <a href="Customization.html#Customization_ownership">
|
|
Object ownership and %newobject</a> for more information. </p>
|
|
|
|
<p>The SWIG default mappings are also incorrect in this case:</p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>foo = Foo.new
|
|
bar = Bar.new
|
|
bar.set_foo(foo)</pre>
|
|
</div>
|
|
|
|
<p>Without modification, this code will cause a segmentation
|
|
fault. When the Ruby <tt>foo</tt> object goes out of
|
|
scope, it will free the underlying C++ <tt>foo</tt>
|
|
object. However, when the Ruby bar object goes out of scope, it will
|
|
call the C++ bar destructor which will also free the C++ <tt>foo</tt>
|
|
object. The problem is that object ownership is transferred from the
|
|
Ruby object to the C++ object when the <tt>set_foo</tt>
|
|
method is called. This can be done by using the special DISOWN type
|
|
map, which was added to the Ruby bindings in SWIG-1.3.26.</p>
|
|
|
|
<p>Thus, a correct SWIG interface file correct mapping for these
|
|
classes is:</p>
|
|
|
|
<div class="code">
|
|
<pre>/* File RubyOwnershipExample.i */
|
|
|
|
%module RubyOwnershipExample
|
|
|
|
%{
|
|
#include "RubyOwnershipExample.h"
|
|
%}
|
|
|
|
class Foo
|
|
{
|
|
public:
|
|
Foo();
|
|
~Foo();
|
|
};
|
|
|
|
class Bar
|
|
{
|
|
Foo *foo_;
|
|
public:
|
|
Bar();
|
|
~Bar();
|
|
Foo* get_foo();
|
|
|
|
<b> %newobject get_new_foo;</b>
|
|
Foo* get_new_foo();
|
|
|
|
<b> %apply SWIGTYPE *DISOWN {Foo *foo};</b>
|
|
void set_foo(Foo *foo);
|
|
<b> %clear Foo *foo;</b>
|
|
};
|
|
</pre>
|
|
</div>
|
|
|
|
<p> This code can be seen in swig/examples/ruby/tracking.</p>
|
|
|
|
<H3><a name="Ruby_nn60">34.10.3 Object Tracking</a></H3>
|
|
|
|
|
|
<p>The remaining parts of this section will use the class library
|
|
shown below to illustrate different memory management techniques. The
|
|
class library models a zoo and the animals it contains. </p>
|
|
|
|
<div class="code">
|
|
<pre>%module zoo
|
|
|
|
%{
|
|
#include <string>
|
|
#include <vector>
|
|
|
|
#include "zoo.h"
|
|
%}
|
|
|
|
class Animal
|
|
{
|
|
private:
|
|
typedef std::vector<Animal*> AnimalsType;
|
|
typedef AnimalsType::iterator IterType;
|
|
protected:
|
|
AnimalsType animals;
|
|
protected:
|
|
std::string name_;
|
|
public:
|
|
// Construct an animal with this name
|
|
Animal(const char* name) : name_(name) {}
|
|
|
|
// Return the animal's name
|
|
const char* get_name() const { return name.c_str(); }
|
|
};
|
|
|
|
class Zoo
|
|
{
|
|
protected:
|
|
std::vector<Animal *> animals;
|
|
|
|
public:
|
|
// Construct an empty zoo
|
|
Zoo() {}
|
|
|
|
/* Create a new animal. */
|
|
static Animal* Zoo::create_animal(const char* name) {
|
|
return new Animal(name);
|
|
}
|
|
|
|
// Add a new animal to the zoo
|
|
void add_animal(Animal* animal) {
|
|
animals.push_back(animal);
|
|
}
|
|
|
|
Animal* remove_animal(size_t i) {
|
|
Animal* result = this->animals[i];
|
|
IterType iter = this->animals.begin();
|
|
std::advance(iter, i);
|
|
this->animals.erase(iter);
|
|
|
|
return result;
|
|
}
|
|
|
|
// Return the number of animals in the zoo
|
|
size_t get_num_animals() const {
|
|
return animals.size();
|
|
}
|
|
|
|
// Return a pointer to the ith animal
|
|
Animal* get_animal(size_t i) const {
|
|
return animals[i];
|
|
}
|
|
};</pre>
|
|
</div>
|
|
|
|
<p>Let's say you SWIG this code and then run IRB:
|
|
|
|
</p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>$ <b>irb</b>
|
|
irb(main):001:0> <b>require 'example'</b>
|
|
=> true
|
|
|
|
irb(main):002:0> <b>tiger1 = Example::Animal.new("tiger1")</b>
|
|
=> #<Example::Animal:0x2be3820>
|
|
|
|
irb(main):004:0> <b>tiger1.get_name()</b>
|
|
=> "tiger1"
|
|
|
|
irb(main):003:0> <b>zoo = Example::Zoo.new()</b>
|
|
=> #<Example::Zoo:0x2be0a60>
|
|
|
|
irb(main):006:0> <b>zoo.add_animal(tiger)</b>
|
|
=> nil
|
|
|
|
irb(main):007:0> <b>zoo.get_num_animals()</b>
|
|
=> 1
|
|
|
|
irb(main):007:0> <b>tiger2 = zoo.remove_animal(0)</b>
|
|
=> #<Example::Animal:0x2bd4a18>
|
|
|
|
irb(main):008:0> <b>tiger2.get_name()</b>
|
|
=> "tiger1"
|
|
|
|
irb(main):009:0> <b>tiger1.equal?(tiger2)</b>
|
|
=> false
|
|
</pre>
|
|
</div>
|
|
|
|
<p>Pay particular attention to the code <tt>tiger1.equal?(tiger2)</tt>.
|
|
Note that the two Ruby objects are not the same - but they reference
|
|
the same underlying C++ object. This can cause problems. For example:
|
|
</p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>irb(main):010:0> <b>tiger1 = nil</b>
|
|
=> nil
|
|
|
|
irb(main):011:0> <b>GC.start</b>
|
|
=> nil
|
|
|
|
irb(main):012:0> <b>tiger2.get_name()</b>
|
|
(irb):12: [BUG] Segmentation fault
|
|
</pre>
|
|
</div>
|
|
|
|
<p>After the garbage collector runs, as a result of our call
|
|
to <tt>GC.start</tt>, calling<tt>tiger2.get_name()</tt>
|
|
causes a segmentation fault. The problem is that when <tt>tiger1</tt>
|
|
is garbage collected, it frees the underlying C++ object. Thus, when <tt>tiger2</tt>
|
|
calls the <tt>get_name()</tt> method it invokes it on a
|
|
destroyed object.</p>
|
|
|
|
<p>This problem can be avoided if SWIG enforces a one-to-one
|
|
mapping between Ruby objects and C++ classes. This can be done via the
|
|
use of the <tt>%trackobjects</tt> functionality available
|
|
in SWIG-1.3.26. and later.</p>
|
|
|
|
<p>When the <tt>%trackobjects</tt> is turned on,
|
|
SWIG automatically keeps track of mappings between C++ objects and Ruby
|
|
objects. Note that enabling object tracking causes a slight performance
|
|
degradation. Test results show this degradation to be about 3% to 5%
|
|
when creating and destroying 100,000 animals in a row.</p>
|
|
|
|
<p>Since <tt>%trackobjects</tt> is implemented as a <tt>%feature</tt>,
|
|
it uses the same name matching rules as other kinds of features (see
|
|
the chapter on <a href="Customization.html#Customization">
|
|
"Customization Features"</a>) . Thus it can be applied on a
|
|
class-by-class basis if needed. To fix the example above:</p>
|
|
|
|
<div class="code">
|
|
<pre>%module example
|
|
|
|
%{
|
|
#include "example.h"
|
|
%}
|
|
|
|
<b>/* Tell SWIG that create_animal creates a new object */</b>
|
|
<b>%newobject Zoo::create_animal;</b>
|
|
|
|
<b>/* Tell SWIG to keep track of mappings between C/C++ structs/classes. */</b>
|
|
<b>%trackobjects;</b>
|
|
|
|
%include "example.h"</pre>
|
|
</div>
|
|
|
|
<p>When this code runs we see:
|
|
</p>
|
|
|
|
<div class="code targetlang">
|
|
<pre>$ <b>irb</b>
|
|
irb(main):001:0> <b>require 'example'</b>
|
|
=> true
|
|
|
|
irb(main):002:0> <b>tiger1 = Example::Animal.new("tiger1")</b>
|
|
=> #<Example::Animal:0x2be37d8>
|
|
|
|
irb(main):003:0> <b>zoo = Example::Zoo.new()</b>
|
|
=> #<Example::Zoo:0x2be0a18>
|
|
|
|
irb(main):004:0> <b>zoo.add_animal(tiger1)</b>
|
|
=> nil
|
|
|
|
irb(main):006:0> <b>tiger2 = zoo.remove_animal(0)</b>
|
|
=> #<Example::Animal:0x2be37d8>
|
|
|
|
irb(main):007:0> <b>tiger1.equal?(tiger2)</b>
|
|
=> true
|
|
|
|
irb(main):008:0> <b>tiger1 = nil</b>
|
|
=> nil
|
|
|
|
irb(main):009:0> <b>GC.start</b>
|
|
=> nil
|
|
|
|
irb(main):010:0> <b>tiger.get_name()</b>
|
|
=> "tiger1"
|
|
irb(main):011:0></pre>
|
|
</div>
|
|
|
|
<p>For those who are interested, object tracking is implemented
|
|
by storing Ruby objects in a hash table and keying them on C++
|
|
pointers. The underlying API is:
|
|
|
|
</p>
|
|
|
|
<div class="code">
|
|
<pre>static void SWIG_RubyAddTracking(void* ptr, VALUE object);
|
|
static VALUE SWIG_RubyInstanceFor(void* ptr) ;
|
|
static void SWIG_RubyRemoveTracking(void* ptr);
|
|
static void SWIG_RubyUnlinkObjects(void* ptr);</pre>
|
|
</div>
|
|
|
|
<p>When an object is created, SWIG will automatically call the <tt>SWIG_RubyAddTracking</tt>
|
|
method. Similarly, when an object is deleted, SWIG will call the <tt>SWIG_RubyRemoveTracking</tt>.
|
|
When an object is returned to Ruby from C++, SWIG will use the <tt>SWIG_RubyInstanceFor</tt>
|
|
method to ensure a one-to-one mapping from Ruby to C++ objects. Last,
|
|
the <tt>RubyUnlinkObjects</tt> method unlinks a Ruby
|
|
object from its underlying C++ object.</p>
|
|
|
|
<p>In general, you will only need to use the <tt>SWIG_RubyInstanceFor</tt>,
|
|
which is required for implementing mark functions as shown below.
|
|
However, if you implement your own free functions (see below) you may
|
|
also have to call the <tt>SWIG_RubyRemoveTracking</tt> and <tt>RubyUnlinkObjects</tt>
|
|
methods.</p>
|
|
|
|
<H3><a name="Ruby_nn61">34.10.4 Mark Functions</a></H3>
|
|
|
|
|
|
<p>With a bit more testing, we see that our class library still
|
|
has problems. For example:
|
|
|
|
</p>
|
|
|
|
<div class="targetlang">
|
|
<pre>$ <b>irb</b>
|
|
irb(main):001:0> <b>require 'example'</b>
|
|
=> true
|
|
|
|
irb(main):002:0> tiger1 = <b>Example::Animal.new("tiger1")</b>
|
|
=> #<Example::Animal:0x2bea6a8>
|
|
|
|
irb(main):003:0> zoo = <b>Example::Zoo.new()</b>
|
|
=> #<Example::Zoo:0x2be7960>
|
|
|
|
irb(main):004:0> <b>zoo.add_animal(tiger1)</b>
|
|
=> nil
|
|
|
|
irb(main):007:0> <b>tiger1 = nil</b>
|
|
=> nil
|
|
|
|
irb(main):007:0> <b>GC.start</b>
|
|
=> nil
|
|
|
|
irb(main):005:0> <b>tiger2 = zoo.get_animal(0)</b>
|
|
(irb):12: [BUG] Segmentation fault</pre>
|
|
</div>
|
|
|
|
<p>The problem is that Ruby does not know that the <tt>zoo</tt>
|
|
object contains a reference to a Ruby object. Thus, when Ruby garbage
|
|
collects <tt>tiger1</tt>
|
|
it frees the underlying C++ object.</p>
|
|
|
|
<p>This can be fixed by implementing a <tt>mark</tt>
|
|
function as described above in the <a href="Ruby.html#Ruby_nn52">Mark
|
|
and Sweep Garbage Collector</a> section. You can specify a mark
|
|
function by using the <tt>%markfunc</tt> directive. Since
|
|
the <tt>%markfunc</tt> directive is implemented using
|
|
SWIG's' "features" mechanism it uses the same name matching rules as
|
|
other kinds of features (see the chapter on <a href="Customization.html#Customization">"Customization
|
|
Features"</a> for more details). </p>
|
|
|
|
<p>A <tt>mark</tt> function takes a single argument,
|
|
which is a pointer to the C++ object being marked; it should, in turn,
|
|
call <tt>rb_gc_mark()</tt> for any instances that are
|
|
reachable from the current object. The mark function for our <tt>
|
|
Zoo</tt> class should therefore loop over all of the C++ animal
|
|
objects in the zoo object, look up their Ruby object equivalent, and
|
|
then call <tt>rb_gc_mark()</tt>. One possible
|
|
implementation is:</p>
|
|
|
|
<div class="code">
|
|
<pre>%module example
|
|
|
|
%{
|
|
#include "example.h"
|
|
%}
|
|
|
|
/* Keep track of mappings between C/C++ structs/classes
|
|
and Ruby objects so we can implement a mark function. */
|
|
<b>%trackobjects;</b>
|
|
|
|
/* Specify the mark function */
|
|
<b>%markfunc Zoo "mark_Zoo";</b>
|
|
|
|
%include "example.h"
|
|
|
|
%header %{
|
|
|
|
static void mark_Zoo(void* ptr) {
|
|
Zoo* zoo = (Zoo*) ptr;
|
|
|
|
/* Loop over each object and tell the garbage collector
|
|
that we are holding a reference to them. */
|
|
int count = zoo->get_num_animals();
|
|
|
|
for(int i = 0; i < count; ++i) {
|
|
Animal* animal = zoo->get_animal(i);
|
|
VALUE object = SWIG_RubyInstanceFor(animal);
|
|
|
|
if (object != Qnil) {
|
|
rb_gc_mark(object);
|
|
}
|
|
}
|
|
}
|
|
%}</pre>
|
|
</div>
|
|
|
|
<p> Note the <tt>mark</tt> function is dependent on
|
|
the <tt>SWIG_RUBY_InstanceFor</tt> method, and thus
|
|
requires that <tt>%trackobjects</tt> is enabled. For more
|
|
information, please refer to the ruby_track_objects.i test case in the SWIG
|
|
test suite.</p>
|
|
|
|
<p>When this code is compiled we now see:</p>
|
|
|
|
<div class="targetlang">
|
|
<pre>$ <b>irb
|
|
</b>irb(main):002:0> <b>tiger1=Example::Animal.new("tiger1")</b>
|
|
=> #<Example::Animal:0x2be3bf8>
|
|
|
|
irb(main):003:0> <b>Example::Zoo.new()</b>
|
|
=> #<Example::Zoo:0x2be1780>
|
|
|
|
irb(main):004:0> <b>zoo = Example::Zoo.new()</b>
|
|
=> #<Example::Zoo:0x2bde9c0>
|
|
|
|
irb(main):005:0> <b>zoo.add_animal(tiger1)</b>
|
|
=> nil
|
|
|
|
irb(main):009:0> <b>tiger1 = nil</b>
|
|
=> nil
|
|
|
|
irb(main):010:0> <b>GC.start</b>
|
|
=> nil
|
|
irb(main):014:0> <b>tiger2 = zoo.get_animal(0)</b>
|
|
=> #<Example::Animal:0x2be3bf8>
|
|
|
|
irb(main):015:0> <b>tiger2.get_name()</b>
|
|
=> "tiger1"
|
|
irb(main):016:0></pre>
|
|
</div>
|
|
|
|
<p>This code can be seen in swig/examples/ruby/mark_function.</p>
|
|
|
|
<H3><a name="Ruby_nn62">34.10.5 Free Functions</a></H3>
|
|
|
|
|
|
<p>By default, SWIG creates a "free" function that is called when
|
|
a Ruby object is garbage collected. The free function simply calls the
|
|
C++ object's destructor.</p>
|
|
|
|
<p>However, sometimes an appropriate destructor does not exist or
|
|
special processing needs to be performed before the destructor is
|
|
called. Therefore, SWIG allows you to manually specify a "free"
|
|
function via the use of the <tt>%freefunc</tt> directive.
|
|
The <tt>%freefunc</tt> directive is implemented using
|
|
SWIG's' "features" mechanism and so the same name matching rules used
|
|
for other kinds of features apply (see the chapter on <a href="Customization.html#Customization">"Customization
|
|
Features"</a>) for more details).</p>
|
|
|
|
<p>IMPORTANT ! - If you define your own free function, then you
|
|
must ensure that you call the underlying C++ object's destructor. In
|
|
addition, if object tracking is activated for the object's class, you
|
|
must also call the <tt>SWIG_RubyRemoveTracking</tt>
|
|
function (of course call this before you destroy the C++ object). Note
|
|
that it is harmless to call this method if object tracking if off so it
|
|
is advised to always call it.</p>
|
|
|
|
<p>Note there is a subtle interaction between object ownership
|
|
and free functions. A custom defined free function will only be called
|
|
if the Ruby object owns the underlying C++ object. This also to Ruby
|
|
objects which are created, but then transfer ownership to C++ objects
|
|
via the use of the <tt>disown</tt> typemap described
|
|
above. </p>
|
|
|
|
<p>To show how to use the <tt>%freefunc</tt>
|
|
directive, let's slightly change our example. Assume that the zoo
|
|
object is responsible for freeing any animal that it contains. This means
|
|
that the <tt>Zoo::add_animal</tt>
|
|
function should be marked with a <tt>DISOWN</tt> typemap
|
|
and the destructor should be updated as below:</p>
|
|
|
|
<div class="code">
|
|
<pre>
|
|
Zoo::~Zoo() {
|
|
IterType iter = this->animals.begin();
|
|
IterType end = this->animals.end();
|
|
|
|
for(iter; iter != end; ++iter) {
|
|
Animal* animal = *iter;
|
|
delete animal;
|
|
}
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>When we use these objects in IRB we see:</p>
|
|
|
|
<div class="code targetlang">
|
|
<pre class="targetlang"><b>$irb</b>
|
|
irb(main):002:0> <b>require 'example'</b>
|
|
=> true
|
|
|
|
irb(main):003:0> <b>zoo = Example::Zoo.new()</b>
|
|
=> #<Example::Zoo:0x2be0fe8>
|
|
|
|
irb(main):005:0> <b>tiger1 = Example::Animal.new("tiger1")</b>
|
|
=> #<Example::Animal:0x2bda760>
|
|
|
|
irb(main):006:0> <b>zoo.add_animal(tiger1)</b>
|
|
=> nil
|
|
|
|
irb(main):007:0> <b>zoo = nil</b>
|
|
=> nil
|
|
|
|
irb(main):008:0> <b>GC.start</b>
|
|
=> nil
|
|
|
|
irb(main):009:0> <b>tiger1.get_name()</b>
|
|
(irb):12: [BUG] Segmentation fault
|
|
</pre>
|
|
</div>
|
|
|
|
<p>The error happens because the C++ <tt>animal</tt>
|
|
object is freed when the <tt>zoo</tt> object is freed.
|
|
Although this error is unavoidable, we can at least prevent the
|
|
segmentation fault. To do this requires enabling object tracking and
|
|
implementing a custom free function that calls the <tt>SWIG_RubyUnlinkObjects</tt>
|
|
function for each animal object that is destroyed. The <tt>SWIG_RubyUnlinkObjects</tt>
|
|
function notifies SWIG that a Ruby object's underlying C++ object is no
|
|
longer valid. Once notified, SWIG will intercept any calls from the
|
|
existing Ruby object to the destroyed C++ object and raise an exception.
|
|
</p>
|
|
|
|
<div class="code">
|
|
<pre>%module example
|
|
|
|
%{
|
|
#include "example.h"
|
|
%}
|
|
|
|
/* Specify that ownership is transferred to the zoo when calling add_animal */
|
|
%apply SWIGTYPE *DISOWN { Animal* animal };
|
|
|
|
/* Track objects */
|
|
%trackobjects;
|
|
|
|
/* Specify the mark function */
|
|
%freefunc Zoo "free_Zoo";
|
|
|
|
%include "example.h"
|
|
|
|
%header %{
|
|
static void free_Zoo(void* ptr) {
|
|
Zoo* zoo = (Zoo*) ptr;
|
|
|
|
/* Loop over each animal */
|
|
int count = zoo->get_num_animals();
|
|
|
|
for(int i = 0; i < count; ++i) {
|
|
/* Get an animal */
|
|
Animal* animal = zoo->get_animal(i);
|
|
|
|
/* Unlink the Ruby object from the C++ object */
|
|
SWIG_RubyUnlinkObjects(animal);
|
|
|
|
/* Now remove the tracking for this animal */
|
|
SWIG_RubyRemoveTracking(animal);
|
|
}
|
|
|
|
/* Now call SWIG_RubyRemoveTracking for the zoo */
|
|
SWIG_RubyRemoveTracking(ptr);
|
|
/* Now free the zoo which will free the animals it contains */
|
|
delete zoo;
|
|
}
|
|
%} </pre>
|
|
</div>
|
|
|
|
<p>Now when we use these objects in IRB we see:</p>
|
|
|
|
<div class="code targetlang">
|
|
<pre><b>$irb</b>
|
|
irb(main):002:0> <b>require 'example'</b>
|
|
=> true
|
|
|
|
irb(main):003:0> <b>zoo = Example::Zoo.new()</b>
|
|
=> #<Example::Zoo:0x2be0fe8>
|
|
|
|
irb(main):005:0> <b>tiger1 = Example::Animal.new("tiger1")</b>
|
|
=> #<Example::Animal:0x2bda760>
|
|
|
|
irb(main):006:0> <b>zoo.add_animal(tiger1)</b>
|
|
=> nil
|
|
|
|
irb(main):007:0> <b>zoo = nil</b>
|
|
=> nil
|
|
|
|
irb(main):008:0> <b>GC.start</b>
|
|
=> nil
|
|
|
|
irb(main):009:0> <b>tiger1.get_name()</b>
|
|
RuntimeError: This Animal * already released
|
|
from (irb):10:in `get_name'
|
|
from (irb):10
|
|
irb(main):011:0></pre>
|
|
</div>
|
|
|
|
<p>Notice that SWIG can now detect the underlying C++ object has
|
|
been freed, and thus raises a runtime exception.</p>
|
|
|
|
<p>This code can be seen in swig/examples/ruby/free_function.</p>
|
|
|
|
<H3><a name="Ruby_nn63">34.10.6 Embedded Ruby and the C++ Stack</a></H3>
|
|
|
|
|
|
<p>As has been said, the Ruby GC runs and marks objects before
|
|
its
|
|
sweep phase. When the garbage collector is called, it will
|
|
also
|
|
try to mark any Ruby objects (VALUE) it finds in the machine registers
|
|
and in the C++ stack.</p>
|
|
|
|
<p>The stack is basically the history of the functions that have
|
|
been
|
|
called and also contains local variables, such as the ones you define
|
|
whenever you do inside a function:</p>
|
|
|
|
<div class="diagram">VALUE obj; </div>
|
|
|
|
<p>For ruby to determine where its stack space begins, during
|
|
initialization a normal Ruby interpreter will call the ruby_init()
|
|
function which in turn will call a function called Init_stack or
|
|
similar. This function will store a pointer to the location
|
|
where
|
|
the stack points at that point in time.</p>
|
|
|
|
<p>ruby_init() is presumed to always be called within the main()
|
|
function of your program and whenever the GC is called, ruby will
|
|
assume that the memory between the current location in memory and the
|
|
pointer that was stored previously represents the stack, which may
|
|
contain local (and temporary) VALUE ruby objects. Ruby will
|
|
then be careful not to remove any of those objects in that location.</p>
|
|
|
|
<p>So far so good. For a normal Ruby session, all the
|
|
above is
|
|
completely transparent and magic to the extensions developer.
|
|
</p>
|
|
|
|
<p>However, with an embedded Ruby, it may not always be possible
|
|
to
|
|
modify main() to make sure ruby_init() is called there. As
|
|
such,
|
|
ruby_init() will likely end up being called from within some other
|
|
function. This can lead Ruby to measure incorrectly where the
|
|
stack begins and can result in Ruby incorrectly collecting
|
|
those
|
|
temporary VALUE objects that are created once another function
|
|
is
|
|
called. The end result: random crashes and segmentation
|
|
faults.</p>
|
|
|
|
<p>This problem will often be seen in director functions that are
|
|
used for callbacks, for example. </p>
|
|
|
|
<p>To solve the problem, SWIG can now generate code with director
|
|
functions containing the optional macros SWIG_INIT_STACK and
|
|
SWIG_RELEASE_STACK. These macros will try to force Ruby to
|
|
reinitialize the beginning of the stack the first time a
|
|
director
|
|
function is called. This will lead Ruby to measure and not
|
|
collect any VALUE objects defined from that point on. </p>
|
|
|
|
<p>To mark functions to either reset the ruby stack or not, you
|
|
can use:</p>
|
|
|
|
<div class="code"><pre>
|
|
%initstack Class::memberfunction; // only re-init the stack in this director method
|
|
%ignorestack Class::memberfunction; // do not re-init the stack in this director method
|
|
%initstack Class; // init the stack on all the methods of this class
|
|
%initstack; // all director functions will re-init the stack
|
|
</pre></div>
|
|
|
|
</body>
|
|
</html>
|