new example
git-svn-id: https://swig.svn.sourceforge.net/svnroot/swig/trunk/SWIG@806 626c5289-ae23-0410-ae9c-e8d60b6d4f22
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Dave Beazley
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6 changed files with 273 additions and 0 deletions
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@ -20,6 +20,7 @@ certain C declarations are turned into constants.
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<li><a href="value/index.html">value</a>. How to pass and return structures by value.
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<li><a href="class/index.html">class</a>. How to wrap a simple C++ class.
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<li><a href="reference/index.html">reference</a>. C++ references.
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<li><a href="pointer/index.html">pointer</a>. Simple pointer handling.
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</ul>
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<h2>Compilation Issues</h2>
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18
Examples/perl5/pointer/Makefile
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18
Examples/perl5/pointer/Makefile
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@ -0,0 +1,18 @@
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TOP = ../..
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SWIG = $(TOP)/../swig
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SRCS = example.c
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TARGET = example
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INTERFACE = example.i
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SWIGOPT =
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all::
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$(MAKE) -f $(TOP)/Makefile SRCS='$(SRCS)' SWIG='$(SWIG)' \
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SWIGOPT='$(SWIGOPT)' TARGET='$(TARGET)' INTERFACE='$(INTERFACE)' perl5
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static::
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$(MAKE) -f $(TOP)/Makefile SRCS='$(SRCS)' SWIG='$(SWIG)' \
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SWIGOPT='$(SWIGOPT)' TARGET='myperl' INTERFACE='$(INTERFACE)' perl5_static
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clean::
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rm -f *_wrap* *.o core *~ *.so *.pm myperl
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check: all
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16
Examples/perl5/pointer/example.c
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16
Examples/perl5/pointer/example.c
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@ -0,0 +1,16 @@
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/* File : example.c */
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void add(int *x, int *y, int *result) {
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*result = *x + *y;
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}
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void sub(int *x, int *y, int *result) {
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*result = *x - *y;
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}
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int divide(int n, int d, int *r) {
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int q;
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q = n/d;
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*r = n - q*d;
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return q;
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}
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23
Examples/perl5/pointer/example.i
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23
Examples/perl5/pointer/example.i
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@ -0,0 +1,23 @@
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/* File : example.i */
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%module example
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/* This example illustrates a couple of different techniques
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for manipulating C pointers */
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/* First we'll use the pointer library */
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extern void add(int *x, int *y, int *result);
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%include pointer.i
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/* Next we'll use some typemaps */
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%include typemaps.i
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extern void sub(int *INPUT, int *INPUT, int *OUTPUT);
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/* Next we'll use typemaps and the %apply directive */
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%apply int *OUTPUT { int *r };
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extern int divide(int n, int d, int *r);
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42
Examples/perl5/pointer/example.pl
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42
Examples/perl5/pointer/example.pl
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@ -0,0 +1,42 @@
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# file: example.pl
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use example;
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# First create some objects using the pointer library.
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print "Testing the pointer library\n";
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$a = example::ptrcreate("int",37);
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$b = example::ptrcreate("int",42);
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$c = example::ptrcreate("int");
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print " a = $a\n";
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print " b = $b\n";
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print " c = $c\n";
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# Call the add() function with some pointers
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example::add($a,$b,$c);
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# Now get the result
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$r = example::ptrvalue($c);
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print " 37 + 42 = $r\n";
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# Clean up the pointers
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example::ptrfree($a);
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example::ptrfree($b);
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example::ptrfree($c);
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# Now try the typemap library
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# This should be much easier. Now how it is no longer
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# necessary to manufacture pointers.
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print "Trying the typemap library\n";
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$r = example::sub(37,42);
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print " 37 - 42 = $r\n";
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# Now try the version with multiple return values
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print "Testing multiple return values\n";
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($q,$r) = example::divide(42,37);
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print " 42/37 = $q remainder $r\n";
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173
Examples/perl5/pointer/index.html
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173
Examples/perl5/pointer/index.html
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@ -0,0 +1,173 @@
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<html>
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<head>
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<title>SWIG:Examples:perl5:pointer</title>
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</head>
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<body bgcolor="#ffffff">
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<tt>SWIG/Examples/perl5/pointer/</tt>
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<hr>
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<H2>Simple Pointer Handling</H2>
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<tt>$Header$</tt><br>
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<p>
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This example illustrates a couple of techniques for handling
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simple pointers in SWIG. The prototypical example is a C function
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that operates on pointers such as this:
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<blockquote>
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<pre>
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void add(int *x, int *y, int *r) {
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*r = *x + *y;
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}
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</pre>
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</blockquote>
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By default, SWIG wraps this function exactly as specified and creates
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an interface that expects pointer objects for arguments. The only
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problem is how does one go about creating these objects from a script?
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<h2>Possible Solutions</h2>
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<ul>
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<li>Write some helper functions to explicitly create objects. For
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example:
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<blockquote>
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<pre>
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int *new_int(int ivalue) {
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int *i = (int *) malloc(sizeof(ivalue));
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*i = ivalue;
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return i;
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}
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int get_int(int *i) {
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return *i;
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}
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void delete_int(int *i) {
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free(i);
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}
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</pre>
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</blockquote>
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Now, in a script you would do this:
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<blockquote>
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<pre>
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$a = new_int(37);
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$b = new_int(42);
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$c = new_int(0):
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add($a,$b,$c);
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$r = get_int($c);
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print "Result = $r\n";
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delete_int($a);
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delete_int($b);
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delete_int($c);
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</pre>
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</blockquote>
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<p>
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<li>Use the SWIG pointer library. For example, in the interface file
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you would do this:
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<blockquote>
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<pre>
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%include "pointer.i"
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</pre>
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</blockquote?
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and in a script you would do this:
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<blockquote>
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<pre>
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$a = ptrcreate("int",37);
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$b = ptrcreate("int",42);
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$c = ptrcreate("int");
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add($a,$b,$c);
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$r = ptrvalue($c);
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print "Result = $r\n";
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ptrfree($a);
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ptrfree($b);
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ptrfree($c);
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</pre>
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</blockquote>
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The advantage to using the pointer library is that it unifies some of the helper
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functions behind a common set of names. For example, the same set of functions work
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with int, double, float, and other fundamental types.
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<p>
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<li>Use the SWIG typemap library. This library allows you to completely
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change the way arguments are processed by SWIG. For example:
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<blockquote>
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<pre>
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%include "typemaps.i"
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void add(int *INPUT, int *INPUT, int *OUTPUT);
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</pre>
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</blockquote>
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And in a script:
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<blockquote>
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<pre>
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$r = add(37,42);
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print "Result = $r\n";
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</pre>
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</blockquote>
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Needless to say, this is substantially easier.
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<p>
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<li>A final alternative is to use the typemaps library in combination
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with the %apply directive. This allows you to change the names of parameters
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that behave as input or output parameters. For example:
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<blockquote>
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<pre>
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%include "typemaps.i"
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%apply int *INPUT {int *x, int *y};
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%apply int *OUTPUT {int *r};
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void add(int *x, int *y, int *r);
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void sub(int *x, int *y, int *r);
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void mul(int *x, int *y, int *r);
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... etc ...
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</pre>
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</blockquote>
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</ul>
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<h2>Example</h2>
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The following example illustrates the use of these features for pointer
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extraction.
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<ul>
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<li> <a href="example.c">example.c</a> (C Source)
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<li> <a href="example.i">example.i</a> (Swig interface)
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<li> <a href="example.pl">example.pl</a> (Perl Script)
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</ul>
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<h2>Notes</h2>
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<ul>
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<li>Since pointers are used for so many different things (arrays, output values,
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etc...) the complexity of pointer handling can be as complicated as you want to
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make it.
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<p>
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<li>More documentation on the typemaps.i and pointer.i library files can be
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found in the SWIG user manual. The files also contain documentation.
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<p>
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<li>The pointer.i library is designed primarily for convenience. If you
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are concerned about performance, you probably want to use a different
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approach.
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</ul>
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<hr>
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</body>
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</html>
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