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Make typemap fragments official - move the documentation in fragments.swg into Typemaps.html

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git-svn-id: https://swig.svn.sourceforge.net/svnroot/swig/trunk@11992 626c5289-ae23-0410-ae9c-e8d60b6d4f22
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William S Fulton 2010-04-14 22:22:16 +00:00
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@ -1,6 +1,9 @@
Version 2.0.0 (in progress) Version 2.0.0 (in progress)
============================ ============================
2010-04-14: wsfulton
Typemap fragments are now official and documented in Typemaps.html.
2010-04-09: wsfulton 2010-04-09: wsfulton
[Ruby] Fix #2048064 and #2408020. [Ruby] Fix #2048064 and #2408020.
Apply Ubuntu patch to fix Ruby and std::vector wrappers with -minherit. Apply Ubuntu patch to fix Ruby and std::vector wrappers with -minherit.

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@ -349,9 +349,8 @@
<li><a href="Typemaps.html#Typemaps_pattern_matching">Pattern matching rules</a> <li><a href="Typemaps.html#Typemaps_pattern_matching">Pattern matching rules</a>
<ul> <ul>
<li><a href="Typemaps.html#Typemaps_nn17">Basic matching rules</a> <li><a href="Typemaps.html#Typemaps_nn17">Basic matching rules</a>
<li><a href="Typemaps.html#Typemaps_typedef_reductions">Typedef reductions</a> <li><a href="Typemaps.html#Typemaps_typedef_reductions">Typedef reductions matching</a>
<li><a href="Typemaps.html#Typemaps_nn19">Default typemaps</a> <li><a href="Typemaps.html#Typemaps_nn19">Default typemap matching rules</a>
<li><a href="Typemaps.html#Typemaps_mixed_default">Mixed default typemaps</a>
<li><a href="Typemaps.html#Typemaps_multi_argument_typemaps_patterns">Multi-arguments typemaps</a> <li><a href="Typemaps.html#Typemaps_multi_argument_typemaps_patterns">Multi-arguments typemaps</a>
<li><a href="Typemaps.html#Typemaps_debugging_search">Debugging typemap pattern matching</a> <li><a href="Typemaps.html#Typemaps_debugging_search">Debugging typemap pattern matching</a>
</ul> </ul>
@ -390,14 +389,18 @@
<li><a href="Typemaps.html#Typemaps_nn43">Typemaps for multiple target languages</a> <li><a href="Typemaps.html#Typemaps_nn43">Typemaps for multiple target languages</a>
<li><a href="Typemaps.html#Typemaps_optimal">Optimal code generation when returning by value</a> <li><a href="Typemaps.html#Typemaps_optimal">Optimal code generation when returning by value</a>
<li><a href="Typemaps.html#Typemaps_multi_argument_typemaps">Multi-argument typemaps</a> <li><a href="Typemaps.html#Typemaps_multi_argument_typemaps">Multi-argument typemaps</a>
<li><a href="Typemaps.html#runtime_type_checker">The run-time type checker</a> <li><a href="Typemaps.html#Typemaps_fragments">Typemap fragments</a>
<ul>
<li><a href="Typemaps.html#Typemaps_fragment_type_specialization">Fragment type specialization</a>
<li><a href="Typemaps.html#Typemaps_automatic_specialization">Fragments and automatic typemap specialization</a>
</ul>
<li><a href="Typemaps.html#Typemaps_runtime_type_checker">The run-time type checker</a>
<ul> <ul>
<li><a href="Typemaps.html#Typemaps_nn45">Implementation</a> <li><a href="Typemaps.html#Typemaps_nn45">Implementation</a>
<li><a href="Typemaps.html#Typemaps_runtime_type_checker_usage">Usage</a> <li><a href="Typemaps.html#Typemaps_runtime_type_checker_usage">Usage</a>
</ul> </ul>
<li><a href="Typemaps.html#Typemaps_overloading">Typemaps and overloading</a> <li><a href="Typemaps.html#Typemaps_overloading">Typemaps and overloading</a>
<li><a href="Typemaps.html#Typemaps_nn48">More about <tt>%apply</tt> and <tt>%clear</tt></a> <li><a href="Typemaps.html#Typemaps_nn48">More about <tt>%apply</tt> and <tt>%clear</tt></a>
<li><a href="Typemaps.html#Typemaps_nn49">Reducing wrapper code size</a>
<li><a href="Typemaps.html#Typemaps_nn47">Passing data between typemaps</a> <li><a href="Typemaps.html#Typemaps_nn47">Passing data between typemaps</a>
<li><a href="Typemaps.html#Typemaps_nn52">C++ "this" pointer</a> <li><a href="Typemaps.html#Typemaps_nn52">C++ "this" pointer</a>
<li><a href="Typemaps.html#Typemaps_nn51">Where to go for more information?</a> <li><a href="Typemaps.html#Typemaps_nn51">Where to go for more information?</a>

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@ -31,9 +31,8 @@
<li><a href="#Typemaps_pattern_matching">Pattern matching rules</a> <li><a href="#Typemaps_pattern_matching">Pattern matching rules</a>
<ul> <ul>
<li><a href="#Typemaps_nn17">Basic matching rules</a> <li><a href="#Typemaps_nn17">Basic matching rules</a>
<li><a href="#Typemaps_typedef_reductions">Typedef reductions</a> <li><a href="#Typemaps_typedef_reductions">Typedef reductions matching</a>
<li><a href="#Typemaps_nn19">Default typemaps</a> <li><a href="#Typemaps_nn19">Default typemap matching rules</a>
<li><a href="#Typemaps_mixed_default">Mixed default typemaps</a>
<li><a href="#Typemaps_multi_argument_typemaps_patterns">Multi-arguments typemaps</a> <li><a href="#Typemaps_multi_argument_typemaps_patterns">Multi-arguments typemaps</a>
<li><a href="#Typemaps_debugging_search">Debugging typemap pattern matching</a> <li><a href="#Typemaps_debugging_search">Debugging typemap pattern matching</a>
</ul> </ul>
@ -72,14 +71,18 @@
<li><a href="#Typemaps_nn43">Typemaps for multiple target languages</a> <li><a href="#Typemaps_nn43">Typemaps for multiple target languages</a>
<li><a href="#Typemaps_optimal">Optimal code generation when returning by value</a> <li><a href="#Typemaps_optimal">Optimal code generation when returning by value</a>
<li><a href="#Typemaps_multi_argument_typemaps">Multi-argument typemaps</a> <li><a href="#Typemaps_multi_argument_typemaps">Multi-argument typemaps</a>
<li><a href="#runtime_type_checker">The run-time type checker</a> <li><a href="#Typemaps_fragments">Typemap fragments</a>
<ul>
<li><a href="#Typemaps_fragment_type_specialization">Fragment type specialization</a>
<li><a href="#Typemaps_automatic_specialization">Fragments and automatic typemap specialization</a>
</ul>
<li><a href="#Typemaps_runtime_type_checker">The run-time type checker</a>
<ul> <ul>
<li><a href="#Typemaps_nn45">Implementation</a> <li><a href="#Typemaps_nn45">Implementation</a>
<li><a href="#Typemaps_runtime_type_checker_usage">Usage</a> <li><a href="#Typemaps_runtime_type_checker_usage">Usage</a>
</ul> </ul>
<li><a href="#Typemaps_overloading">Typemaps and overloading</a> <li><a href="#Typemaps_overloading">Typemaps and overloading</a>
<li><a href="#Typemaps_nn48">More about <tt>%apply</tt> and <tt>%clear</tt></a> <li><a href="#Typemaps_nn48">More about <tt>%apply</tt> and <tt>%clear</tt></a>
<li><a href="#Typemaps_nn49">Reducing wrapper code size</a>
<li><a href="#Typemaps_nn47">Passing data between typemaps</a> <li><a href="#Typemaps_nn47">Passing data between typemaps</a>
<li><a href="#Typemaps_nn52">C++ "this" pointer</a> <li><a href="#Typemaps_nn52">C++ "this" pointer</a>
<li><a href="#Typemaps_nn51">Where to go for more information?</a> <li><a href="#Typemaps_nn51">Where to go for more information?</a>
@ -1408,7 +1411,7 @@ simpler scheme to match the current C++ template partial specialization matching
</p> </p>
<H3><a name="Typemaps_multi_argument_typemaps_patterns"></a>10.3.5 Multi-arguments typemaps</H3> <H3><a name="Typemaps_multi_argument_typemaps_patterns"></a>10.3.4 Multi-arguments typemaps</H3>
<p> <p>
@ -1438,7 +1441,7 @@ but all subsequent arguments must match exactly.
</p> </p>
<H3><a name="Typemaps_debugging_search"></a>10.3.6 Debugging typemap pattern matching</H3> <H3><a name="Typemaps_debugging_search"></a>10.3.5 Debugging typemap pattern matching</H3>
<p> <p>
@ -3404,7 +3407,335 @@ with non-consecutive C/C++ arguments; a workaround such as a helper function re-
the arguments to make them consecutive will need to be written. the arguments to make them consecutive will need to be written.
</p> </p>
<H2><a name="runtime_type_checker"></a>10.10 The run-time type checker</H2> <H2><a name="Typemaps_fragments"></a>10.10 Typemap fragments</H2>
<p>
The primary purpose of fragments is to reduce code bloat that repeated use of typemap code can lead to.
Fragments are snippets of code that can be thought of as code dependencies of a typemap.
If a fragment is used by more than one typemap, then the snippet of code within the fragment is only generated once.
Code bloat is typically reduced by moving typemap code into a support function
and then placing the support function into a fragment.
</p>
<p>
For example, if you have a very long typemap
</p>
<div class="code">
<pre>
%typemap(in) MyClass * {
MyClass *value = 0;
... many lines of marshalling code ...
$result = value;
}
</pre>
</div>
<p>
the same marshalling code is often repeated in several typemaps, such as "in", "varin", "directorout", etc.
SWIG copies the code for each argument that requires the typemap code, easily leading to code bloat
in the generated code.
To eliminate this, define a fragment that includes the common marshalling code:
</p>
<div class="code">
<pre>
%fragment("AsMyClass", "header") {
MyClass *AsMyClass(PyObject *obj) {
MyClass *value = 0;
... many lines of marshalling code ...
return value;
}
}
%typemap(in, fragment="AsMyClass") MyClass * {
$result = AsMyClass($input);
}
%typemap(varin, fragment="AsMyClass") MyClass * {
$result = AsMyClass($input);
}
</pre>
</div>
<p>
When the "in" or "varin" typemaps for MyClass are required, the
contents of the fragment called "AsMyClass" is added to the "header" section within the generated code, and then the
typemap code is emitted. Hence, the method <tt>AsMyClass</tt> will be
generated into the wrapper code before any typemap code that calls it.
</p>
<p>
To define a fragment you need a fragment name, a section name for generating the fragment code into, and the code itself.
See <a href="SWIG.html#SWIG_nn42">Code insertion blocks</a> for a full list of section names.
Usually the section name used is "header". Both string and curly braces can be used:
</p>
<div class="code">
<pre>
%fragment("my_name", "header") { ... }
%fragment("my_name", "header") " ... "
</pre>
</div>
<p>
The following are some rules and guidelines for using fragments:
</p>
<ol>
<li>
<p>
A fragment is added to the wrapping code only once. When using the <tt>MyClass *</tt> typemaps above and wrapping the method:
</p>
<div class="code">
<pre>
void foo(MyClass *a, MyClass *b);
</pre>
</div>
<p>
the generated code will look something like:
</p>
<div class="code">
<pre>
MyClass *AsMyClass(PyObject *obj) {
...
}
void _wrap_foo(...) {
....
arg1 = AsMyClass(obj1);
arg2 = AsMyClass(obj2);
...
foo(arg1, arg2);
}
</pre>
</div>
<p>
even as there is duplicated typemap code to process both <tt>a</tt> and
<tt>b</tt>, the <tt>AsMyClass</tt> method will be defined only once.
</p>
<li>
<p>
A fragment should only be defined once. If there is more than
one definition, the first definition is the one used.
All other definitions are silently ignored. For example, if you have
</p>
<div class="code">
<pre>
%fragment("AsMyClass", "header") { ...definition 1... }
....
%fragment("AsMyClass", "header") { ...definition 2... }
</pre>
</div>
<p>
only the first definition is used. In this way
you can override the default fragments in a SWIG library by defining your fragment before the library <tt>%include</tt>.
Note that this behavior is the opposite to typemaps, where the last typemap defined/applied prevails.
Fragments follow the first-in-first-out convention since they are intended to be global,
while typemaps are intended to be locally specialized.
</p>
<li>
<p>
Fragment names cannot contain commas.
</p>
<li>
<p>
A fragment can use one or more additional fragments, for example:
</p>
<div class="code">
<pre>
%fragment("&lt;limits.h&gt;", "header") {
#include &lt;limits.h&gt;
}
%fragment("AsMyClass", "header", fragment="&lt;limits.h&gt;") {
MyClass *AsMyClass(PyObject *obj) {
MyClass *value = 0;
... some marshalling code ...
if (ival &lt; CHAR_MIN /*defined in &lt;limits.h&gt;*/) {
...
} else {
...
}
...
return value;
}
}
</pre>
</div>
<p>
in this case, when the "AsMyClass" fragment is emitted, it also
triggers the inclusion of the "&lt;limits.h&gt;" fragment.
</p>
<li>
<p>
A fragment can have dependencies on a number of other fragments, for example:
</p>
<div class="code">
<pre>
%fragment("bigfragment", "header", fragment="frag1", fragment="frag2", fragment="frag3") "";
</pre>
</div>
<p>
When the "bigfragment" is used, the three dependent fragments "frag1",
"frag2" and "frag3" are also pulled in. Note that as "bigframent" is
empty (the empty string - ""), it does not add any code itself, but merely triggers the
inclusion of the other fragments.
</p>
<li>
<p>
A typemap can also use more than one fragment, but since the
syntax is different, you need to specify the dependent fragments in a comma separated
list. Consider:
</p>
<div class="code">
<pre>
%typemap(in, fragment="frag1,frag2,frag3") {...}
</pre>
</div>
<p>
which is equivalent to:
</p>
<div class="code">
<pre>
%typemap(in, fragment="bigfragment") {...}
</pre>
</div>
<p>
when used with the "bigfragment" defined above.
</p>
<li>
<p>
Finally, you can force the inclusion of a fragment at any point in the generated code as follows:
</p>
<div class="code">
<pre>
%fragment("bigfragment");
</pre>
</div>
<p>
which is very useful inside a template class, for example.
</p>
</ol>
<p>
Most readers will probably want to skip the next two sub-sections on advanced
fragment usage unless a desire to really get to grips
with some powerful but tricky macro and fragment usage that is used in parts of the SWIG typemap library.
</p>
<H3><a name="Typemaps_fragment_type_specialization"></a>10.10.1 Fragment type specialization</H3>
<p>
Fragments can be <i>type specialized</i>. The syntax is as follows:
</p>
<div class="code">
<pre>
%fragment("name", "header") { ...a type independent fragment... }
%fragment("name"{type}, "header") { ...a type dependent fragment... }
</pre>
</div>
<p>
where <tt>type</tt> is a C/C++ type. Like typemaps, fragments can also be used inside templates, for example:
</p>
<div class="code">
<pre>
template &lt;class T&gt;
struct A {
%fragment("incode"{A&lt;T&gt;}, "header") {
... 'incode' specialized fragment ...
}
%typemap(in, fragment="incode"{A&lt;T&gt;}) {
... here we use the 'type specialized' fragment "incode"{A&lt;T&gt;} ...
}
};
</pre>
</div>
<H3><a name="Typemaps_automatic_specialization"></a>10.10.2 Fragments and automatic typemap specialization</H3>
<p>
Since fragments can be type specialized, they can be elegantly used
to specialize typemaps. For example, if you have something like:
</p>
<div class="code">
<pre>
%fragment("incode"{float}, "header") {
float in_method_float(PyObject *obj) {
...
}
}
%fragment("incode"{long}, "header") {
float in_method_long(PyObject *obj) {
...
}
}
// %my_typemaps macro definition
%define %my_typemaps(Type)
%typemap(in, fragment="incode"{Type}) Type {
value = in_method_##Type(obj);
}
%enddef
%my_typemaps(float);
%my_typemaps(long);
</pre>
</div>
<p>
then the proper <tt>"incode"{float}</tt> or <tt>"incode"{long}</tt> fragment will be used,
and the <tt>in_method_float</tt> and <tt>in_method_long</tt> methods will be called whenever
the <tt>float</tt> or <tt>long</tt> types are used as input parameters.
</p>
<p>
This feature is used a lot in the typemaps shipped in the SWIG library for some scripting languages.
The interested (or very brave) reader can take a look at the fragments.swg file shipped with SWIG to see this in action.
</p>
<H2><a name="Typemaps_runtime_type_checker"></a>10.11 The run-time type checker</H2>
<p> <p>
@ -3430,7 +3761,7 @@ language modules.</li>
<li>Modules can be unloaded from the type system.</li> <li>Modules can be unloaded from the type system.</li>
</ul> </ul>
<H3><a name="Typemaps_nn45"></a>10.10.1 Implementation</H3> <H3><a name="Typemaps_nn45"></a>10.11.1 Implementation</H3>
<p> <p>
@ -3616,7 +3947,7 @@ structures rather than creating new ones. These <tt>swig_module_info</tt>
structures are chained together in a circularly linked list. structures are chained together in a circularly linked list.
</p> </p>
<H3><a name="Typemaps_runtime_type_checker_usage"></a>10.10.2 Usage</H3> <H3><a name="Typemaps_runtime_type_checker_usage"></a>10.11.2 Usage</H3>
<p>This section covers how to use these functions from typemaps. To learn how to <p>This section covers how to use these functions from typemaps. To learn how to
@ -3710,7 +4041,7 @@ probably just look at the output of SWIG to get a better sense for how types are
managed. managed.
</p> </p>
<H2><a name="Typemaps_overloading"></a>10.11 Typemaps and overloading</H2> <H2><a name="Typemaps_overloading"></a>10.12 Typemaps and overloading</H2>
<p> <p>
@ -4021,7 +4352,7 @@ Subsequent "in" typemaps would then perform more extensive type-checking.
</li> </li>
</ul> </ul>
<H2><a name="Typemaps_nn48"></a>10.12 More about <tt>%apply</tt> and <tt>%clear</tt></H2> <H2><a name="Typemaps_nn48"></a>10.13 More about <tt>%apply</tt> and <tt>%clear</tt></H2>
<p> <p>
@ -4106,86 +4437,6 @@ example:
</pre> </pre>
</div> </div>
<H2><a name="Typemaps_nn49"></a>10.13 Reducing wrapper code size</H2>
<p>
Since the code supplied to a typemap is inlined directly into wrapper functions, typemaps can result
in a tremendous amount of code bloat. For example, consider this typemap for an array:
</p>
<div class="code">
<pre>
%typemap(in) float [ANY] {
int i;
if (!PySequence_Check($input)) {
PyErr_SetString(PyExc_ValueError,"Expected a sequence");
return NULL;
}
if (PySequence_Length($input) != $1_dim0) {
PyErr_SetString(PyExc_ValueError,"Size mismatch. Expected $1_dim0 elements");
return NULL;
}
$1 = (float) malloc($1_dim0*sizeof(float));
for (i = 0; i &lt; $1_dim0; i++) {
PyObject *o = PySequence_GetItem($input,i);
if (PyNumber_Check(o)) {
$1[i] = (float) PyFloat_AsDouble(o);
} else {
PyErr_SetString(PyExc_ValueError,"Sequence elements must be numbers");
free(result);
return NULL;
}
}
}
</pre>
</div>
<p>
If you had a large interface with hundreds of functions all accepting
array parameters, this typemap would be replicated
repeatedly--generating a huge amount of code. A better approach might
be to consolidate some of the typemap into a function. For example:
</p>
<div class="code">
<pre>
%{
/* Define a helper function */
static float *
convert_float_array(PyObject *input, int size) {
int i;
float *result;
if (!PySequence_Check(input)) {
PyErr_SetString(PyExc_ValueError,"Expected a sequence");
return NULL;
}
if (PySequence_Length(input) != size) {
PyErr_SetString(PyExc_ValueError,"Size mismatch. ");
return NULL;
}
result = (float) malloc(size*sizeof(float));
for (i = 0; i &lt; size; i++) {
PyObject *o = PySequence_GetItem(input,i);
if (PyNumber_Check(o)) {
result[i] = (float) PyFloat_AsDouble(o);
} else {
PyErr_SetString(PyExc_ValueError,"Sequence elements must be numbers");
free(result);
return NULL;
}
}
return result;
}
%}
%typemap(in) float [ANY] {
$1 = convert_float_array($input, $1_dim0);
if (!$1) return NULL;
}
%}
</pre>
</div>
<H2><a name="Typemaps_nn47"></a>10.14 Passing data between typemaps</H2> <H2><a name="Typemaps_nn47"></a>10.14 Passing data between typemaps</H2>

237
Lib/typemaps/fragments.swg
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@ -1,236 +1,13 @@
/* /*
Fragments: Fragments
========== =========
See the "Typemap fragments" section in the documentation for understanding
fragments. Below is some info on how fragments and automatic type
specialization is used.
Second to typemaps, fragments are one the most powerful and Macros that make the automatic generation of typemaps easier are provided.
dangerous swig features. So, if you are starting to read about them,
make sure you read all of this document.
Basics: Consider the following code:
=======
Fragments provide a way to include or generate code into "on-demand"
as the typemaps could require.
For example, if you have a very long typemap
%typemap(in) MyClass * {
MyClass *value = 0;
<very long typemap>
....
value = somewhere_converted_from_input_object_here($input);
...
<very long typemap>
$result = value;
}
very soon you will discover yourself copying the same long
conversion code in several typemaps, such as varin, directorout,
etc. Also, you will discover that swig copes verbatim the same very
long conversion code for every argument that requires it, making the
code very large too.
To eliminate this automatic or manual code copying, we define a
fragment that includes the common conversion code:
%fragment("AsMyClass","header") {
MyClass *AsMyClass(PyObject *obj) {
MyClass *value = 0;
<very long conversion>
....
value = somewhere_converted_from_input_object_here(obj);
...
<very long conversion>
return value;
}
}
%typemap(in,fragment="AsMyClass") MyClass * {
$result = AsMyClass($input);
}
%typemap(varin,fragment="AsMyClass") MyClass * {
$result = AsMyClass($input);
}
When the 'in' or 'varin' typemaps for MyClass are invoked, the
fragment "AsMyClass" is added to the "header" section, and then the
typemap code is emitted. Hence, the method AsMyClass will be
included in the wrapping code and it will be available at the time
the typemap is applied.
To define a fragment then you need a name, a section where it goes,
and the code. Usually the section refers to the "header" part, and
both string and braces forms are accepted, ie:
%fragment("my_name","header") { ... }
%fragment("my_name","header") "...";
To ensure all the fragment/typemap engine works as expected, there
are some rules that fragments follow:
1.- A fragment is added to the wrapping code only once, ie, for the
method:
int foo(MyClass *a, MyClass *b);
the wrapped code will look as much as:
MyClass *AsMyClass(PyObject *obj) {
.....
}
int _wrap_foo(...) {
....
arg1 = AsMyClass(obj1);
arg2 = AsMyClass(obj2);
...
result = foo(arg1, arg2);
}
even when there will be duplicated typemap to process 'a' and
'b', the 'AsMyClass' method will be defined only once.
2.- A fragment can only defined once, and the first definition
is the only one taking in account. All other definitions of the
same fragments are silently ignored. For example, you can have
%fragment("AsMyClass","header") { <definition 1> }
....
%fragment("AsMyClass","header") { <definition 2> }
and then only the first definition is considered. In this way
you can change the 'system' fragments by including yours first.
Note that this behavior is opposite to the typemaps, where the
last typemap applied or defined prevails. Fragment follows the
first-in-first-out convention since they are intended to be
"global", while typemaps intend to be "locally" specialized.
3.- Fragments names can not contain commas.
A fragment can include one or more additional fragments, for example:
%fragment("<limits.h>", "header") {
#include <limits.h>
}
%fragment("AsMyClass", "header", fragment="<limits.h>") {
MyClass *AsMyClass(PyObject *obj) {
MyClass *value = 0;
int ival = somewhere_converted_from_input_object_here(obj)
...
if (ival < CHAR_MIN) {
value = something_from_ival(ival);
} else {
...
}
...
return value;
}
}
in this case, when the "AsMyClass" fragment is emitted, it also
trigger the inclusion of the "<limits.h>" fragment.
You can add as many fragments as you want, for example
%fragment("bigfragment","header", fragment="frag1", fragment="frag2", fragment="frag3") "";
here, when the "bigfragment" is included, the three fragments "frag1",
"frag2" and "frag3" are included. Note that as "bigframent" is defined
empty, "", it does not add any code by itself, buy only trigger the
inclusion of the other fragments.
In a typemap you can also include more than one fragment, but since the
syntax is different, you need to specify them in a 'comma separated'
list, for example, considering the previous example:
%typemap(in,fragment="frag1,frag2,frag3") {...}
is equivalent to
%typemap(in,fragment="bigfragment") {...}
Finally, you can force the inclusion of a fragment at any moment as follow:
%fragment("bigfragment");
which is very useful inside a template class, for example.
Fragment type specialization
============================
Fragments can be "type specialized". The syntax is as follows
%fragment("name","header") { a type independent fragment }
%fragment("name" {Type}, "header") { a type dependent fragment }
and they can also, as typemaps, be used inside templates, for exampe:
template <class T>
struct A {
%fragment("incode"{A<T>},"header") {
'incode' specialized fragment
}
%typemap(in,fragment="incode"{A<T>}) {
here we use the 'type specialized'
fragment "incode"{A<T>}
}
};
which could seems a not much interesting feature, but is
fundamental for automatic typemap and template specialization.
Fragments and automatic typemap specialization:
===============================================
Since fragments can be type specialized, they can be elegantly used
to specialized typemaps .
For example, if you have something like:
%fragment("incode"{float}, "header") {
float in_method_float(PyObject *obj) {
...
}
}
%fragment("incode"{long}, "header") {
float in_method_long(PyObject *obj) {
...
}
}
%define %my_typemaps(Type)
%typemaps(in,fragment="incode"{Type}) {
value = in_method_##Type(obj);
}
%enddef
%my_typemaps(float);
%my_typemaps(long);
then the proper "incode"{float,double} fragment will be included,
and the proper in_method_{float,double} will be called.
Since this is a recurrent fragment use, we provide a couple of
macros that make the automatic generation of typemaps easier:
Consider for example the following code:
%fragment(SWIG_From_frag(bool), "header") { %fragment(SWIG_From_frag(bool), "header") {
static PyObject* static PyObject*