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| <title>SWIG:Examples:java:simple</title> |
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| <body bgcolor="#ffffff"> |
| |
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| <tt>SWIG/Examples/java/simple/</tt> |
| <hr> |
| |
| <H2>Simple Java Example</H2> |
| |
| <p> |
| This example illustrates how you can hook Java to a very simple C program containing |
| a function and a global variable. |
| |
| <h2>The C Code</h2> |
| |
| Suppose you have the following C code: |
| |
| <blockquote> |
| <pre> |
| /* File : example.c */ |
| |
| /* A global variable */ |
| double Foo = 3.0; |
| |
| /* Compute the greatest common divisor of positive integers */ |
| int gcd(int x, int y) { |
| int g; |
| g = y; |
| while (x > 0) { |
| g = x; |
| x = y % x; |
| y = g; |
| } |
| return g; |
| } |
| </pre> |
| </blockquote> |
| |
| <h2>The SWIG interface</h2> |
| |
| Here is a simple SWIG interface file: |
| |
| <blockquote> |
| <pre> |
| /* File: example.i */ |
| %module example |
| |
| extern int gcd(int x, int y); |
| extern double Foo; |
| </pre> |
| </blockquote> |
| |
| <h2>Compilation</h2> |
| |
| <ol> |
| <li><tt>swig -java <a href="example.i">example.i</a></tt> |
| <p> |
| <li>Compile <tt><a href="example_wrap.c">example_wrap.c</a></tt> and <tt><a href="example.c">example.c</a></tt> |
| to create the extension <tt>libexample.so (unix)</tt>. |
| </ol> |
| |
| <h2>Using the extension</h2> |
| |
| Click <a href="main.java">here</a> to see a program that calls our C functions from Java. |
| <p> |
| Compile the java files <tt><a href="example.java">example.java</a></tt> and <tt><a href="main.java">main.java</a></tt> |
| to create the class files example.class and main.class before running main in the JVM. Ensure that the libexample.so file is in your LD_LIBRARY_PATH before running. For example: |
| <blockquote> |
| <pre> |
| export LD_LIBRARY_PATH=. #ksh |
| javac *.java |
| java main |
| </pre> |
| </blockquote> |
| |
| <h2>Key points</h2> |
| |
| <ul> |
| <li>Use the <tt>loadLibrary</tt> statement from java to load and access the generated java classes. For example: |
| <blockquote> |
| <pre> |
| System.loadLibrary("example"); |
| </pre> |
| </blockquote> |
| |
| <li>C functions work just like Java functions. For example: |
| <blockquote> |
| <pre> |
| int g = example.gcd(42,105); |
| </pre> |
| </blockquote> |
| |
| <li>C global variables are accessed through get and set functions in the module class. For example: |
| <blockquote> |
| <pre> |
| double a = example.get_Foo(); |
| example.set_Foo(20.0); |
| </pre> |
| </blockquote> |
| </ul> |
| |
| <hr> |
| </body> |
| </html> |
