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itself. git-svn-id: https://swig.svn.sourceforge.net/svnroot/swig/trunk@12133 626c5289-ae23-0410-ae9c-e8d60b6d4f22
128 lines
3.1 KiB
HTML
128 lines
3.1 KiB
HTML
<html>
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<head>
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<title>SWIG:Examples:go:simple</title>
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</head>
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<body bgcolor="#ffffff">
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<tt>SWIG/Examples/go/simple/</tt>
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<hr>
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<H2>Simple Go Example</H2>
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<p>
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This example illustrates how you can hook Go to a very simple C program containing
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a function and a global variable.
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<h2>The C Code</h2>
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Suppose you have the following C code:
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<blockquote>
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<pre>
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/* File : example.c */
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/* A global variable */
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double Foo = 3.0;
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/* Compute the greatest common divisor of positive integers */
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int gcd(int x, int y) {
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int g;
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g = y;
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while (x > 0) {
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g = x;
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x = y % x;
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y = g;
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}
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return g;
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}
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</pre>
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</blockquote>
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<h2>The SWIG interface</h2>
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Here is a simple SWIG interface file:
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<blockquote>
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<pre>
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/* File: example.i */
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%module example
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extern int gcd(int x, int y);
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extern double Foo;
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</pre>
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</blockquote>
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<h2>Compilation</h2>
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These are the instructions if you are using <tt>6g</tt>/<tt>8g</tt>
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rather than <tt>gccgo</tt>.
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<ol>
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<li>Run <tt>swig -go <a href="example.i">example.i</a></tt>. This
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will create the three
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files <tt>example.go</tt>, <tt>example_gc.c</tt>,
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and <tt>example_wrap.c</tt>.
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<li>Compile <tt><a href="example.go">example.go</a></tt>
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using <tt>6g</tt> or <tt>8g</tt>; e.g., <tt>6g example.go</tt>.
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<li>Compile <tt><a href="example_gc.c">example_gc.c</a></tt>
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using <tt>6c</tt> or <tt>8c</tt>; e.g., <tt>6c example_gc.c</tt>.
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<li>Put the two object files together into an archive
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named <tt>example.a</tt>; e.g., <tt>gopack grc example.a example.6
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example_gc.6</tt>.
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<li>Compile the <tt><a href="example_wrap.c">example_wrap.c</a></tt>
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file using your standard C compiler with the <tt>-fpic</tt> option;
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e.g., <tt>gcc -c -O -fpic example_wrap.c</tt>.
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<li>Also compile the actual code, not generated by SWIG; e.g., <tt>gcc
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-c -O -fpic example.c</tt>.
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<li>Put the gcc compiled object files into a shared library;
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e.g., <tt>gcc -shared -o example.so example_wrap.o example.o</tt>.
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<li>Compile the program which demonstrates how to use the library;
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e.g., <tt>6g runme.go</tt>.
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<li>Link the program; e.g., <tt>6l -o runme runme.6</tt>.
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<li>Now you should have a program <tt>runme</tt>.
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</ol>
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<h2>Using the extension</h2>
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The Go program which demonstrates calling the C functions from Go
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is <a href="runme.go">runme.go</a>.
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<h2>Key points</h2>
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<ul>
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<li>Use the <tt>import</tt> statement to load your extension module from Go. For example:
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<blockquote>
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<pre>
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import "example"
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</pre>
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</blockquote>
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<li>C functions work just like Go functions. However, the function
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names are automatically capitalized in order to make the names
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visible from other Go packages. For example:
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<blockquote>
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<pre>
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g := example.Gcd(42,105)
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</pre>
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</blockquote>
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(If there are name conflicts, you can use the <tt>%rename</tt>
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directive in the .i file or the <tt>-rename</tt> option to Go to
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rename one or the other symbol).
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<li>C global variables are accessed using getter and setter
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functions. The getter function is named <tt>Get</tt> followed by
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the capitalized name of the C variable. The Setter function
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uses <tt>Set</tt> instead of <tt>Get</tt>.
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<blockquote>
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<pre>
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a = example.GetFoo()
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</pre>
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</blockquote>
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</ul>
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<hr>
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</body>
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</html>
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