5af2978f77
git-svn-id: https://swig.svn.sourceforge.net/svnroot/swig/trunk@12108 626c5289-ae23-0410-ae9c-e8d60b6d4f22
89 lines
1.8 KiB
HTML
89 lines
1.8 KiB
HTML
<html>
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<head>
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<title>SWIG:Examples:go:funcptr</title>
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</head>
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<body bgcolor="#ffffff">
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<tt>SWIG/Examples/go/funcptr/</tt>
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<hr>
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<H2>Pointers to Functions</H2>
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<p>
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Okay, just what in the heck does SWIG do with a declaration like this?
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<blockquote>
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<pre>
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int do_op(int a, int b, int (*op)(int, int));
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</pre>
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</blockquote>
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Well, it creates a wrapper as usual. Of course, that does raise some
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questions about the third argument (the pointer to a function).
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<p>
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In this case, SWIG will wrap the function pointer as it does for all
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other pointers. However, in order to actually call this function from
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a Go program, you will need to pass some kind of C function pointer
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object. In C, this is easy, you just supply a function name as an
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argument like this:
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<blockquote>
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<pre>
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/* Some callback function */
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int add(int a, int b) {
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return a+b;
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}
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...
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int r = do_op(x,y,add);
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</pre>
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</blockquote>
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To make this work with SWIG, you will need to do a little extra work.
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Specifically, you need to create some function pointer objects using
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the %constant directive like this:
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<blockquote>
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<pre>
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%constant(int (*)(int,int)) ADD = add;
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</pre>
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</blockquote>
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Now, in a Go program, you would do this:
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<blockquote>
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<pre>
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int r = do_op(x,y, example.ADD)
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</pre>
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</blockquote>
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where <tt>example</tt> is the module name.
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<h2>An Example</h2>
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Here are some files that illustrate this with a simple example:
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<ul>
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<li><a href="example.c">example.c</a>
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<li><a href="example.h">example.h</a>
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<li><a href="example.i">example.i</a> (SWIG interface)
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<li><a href="runme.go">runme.go</a> (Sample program)
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</ul>
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<h2>Notes</h2>
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<ul>
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<li>The value of a function pointer must correspond to a function
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written in C or C++. It is not possible to pass an arbitrary Go
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function in as a substitute for a C function pointer.
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</ul>
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<hr>
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</body>
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</html>
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