mirror of https://github.com/swig/swig
103 lines
2.3 KiB
HTML
103 lines
2.3 KiB
HTML
<html>
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<head>
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<title>SWIG:Examples:java:template</title>
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</head>
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<body bgcolor="#ffffff">
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<tt>SWIG/Examples/java/template/</tt>
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<hr>
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<H2>C++ template support</H2>
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<p>
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This example illustrates how C++ templates can be used from Java using SWIG.
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<h2>The C++ Code</h2>
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Let's take a templated function and a templated class as follows:
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<blockquote>
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<pre>
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/* File : example.h */
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// Some template definitions
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template<class T> T max(T a, T b) { return a>b ? a : b; }
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template<class T> class vector {
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T *v;
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int sz;
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public:
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vector(int _sz) {
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v = new T[_sz];
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sz = _sz;
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}
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T &get(int index) {
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return v[index];
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}
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void set(int index, T &val) {
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v[index] = val;
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}
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#ifdef SWIG
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%extend {
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T getitem(int index) {
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return self->get(index);
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}
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void setitem(int index, T val) {
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self->set(index,val);
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}
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}
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#endif
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};
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</pre>
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</blockquote>
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The %extend is used for a neater interface from Java as the functions <tt>get</tt> and <tt>set</tt> use C++ references to primitive types. These are tricky to use from Java as they end up as a pointer in Java (Java long).
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<h2>The SWIG interface</h2>
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A simple SWIG interface for this can be built by simply grabbing the header file
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like this:
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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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%{
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#include "example.h"
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%}
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/* Let's just grab the original header file here */
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%include "example.h"
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/* Now instantiate some specific template declarations */
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%template(maxint) max<int>;
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%template(maxdouble) max<double>;
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%template(vecint) vector<int>;
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%template(vecdouble) vector<double>;
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</pre>
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</blockquote>
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Note that SWIG parses the templated function <tt>max</tt> and templated class <tt>vector</tt> and so knows about them. However to generate code for use from Java, SWIG has to be told which class/type to use as the template parameter. The SWIG directive %template is used for this.
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<h2>A sample Java program</h2>
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Click <a href="runme.java">here</a> to see a Java program that calls the C++ functions from Java.
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<h2>Notes</h2>
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Use templated classes just like you would any other SWIG generated Java class. Use the classnames specified by the %template directive.
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<blockquote>
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<pre>
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vecdouble dv = new vecdouble(1000);
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dv.setitem(i, 12.34));
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</pre>
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</blockquote>
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<hr>
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</body>
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</html>
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