added a typemap example for java

git-svn-id: https://swig.svn.sourceforge.net/svnroot/swig/trunk/SWIG@334 626c5289-ae23-0410-ae9c-e8d60b6d4f22

Examples/java/typemap/Makefile

@@ -0,0 +1,16 @@
+TOP        = ../..
+SWIG       = $(TOP)/../swig
+SRCS       = 
+TARGET     = libexample
+INTERFACE  = example.i
+SWIGOPT    = 
+
+all::	java
+
+java::
+	$(MAKE) -f $(TOP)/Makefile SRCS='$(SRCS)' SWIG='$(SWIG)' \
+	SWIGOPT='$(SWIGOPT)' TARGET='$(TARGET)' INTERFACE='$(INTERFACE)' java
+
+clean::
+	rm -f *_wrap* *.o core *~ *.so *.class example.java
+

Examples/java/typemap/README

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+Example of a typemap to handle return values in char * arguments.
+
+type:
+make
+javac *.java
+export LD_LIBRARY_PATH=. # sh
+setenv LD_LIBRARY_PATH . # csh
+java main

Examples/java/typemap/example.i

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+/* File : example.i */
+%module example
+%{
+/* Put headers and other declarations here */
+
+/*
+   example of a function that returns a value in the char * argument
+   normally used like:
+
+   char buf[bigenough];
+   f1(buf);
+*/
+
+void f1(char *s) {
+  if(s != NULL) {
+    sprintf(s, "hello world");
+  }
+}
+
+void f2(char *s) {
+  return f1(s);
+}
+
+void f3(char *s) {
+  return f1(s);
+}
+
+%}
+
+/* default behaviour is that of input arg, besides java cannot return
+   a value in a string argument
+*/
+void f1(char *s);
+
+%include typemaps.i
+
+/* use the BYTE typemap to get around this, but the resulting code is ugly */
+void f2(char *BYTE);
+
+/* make a StringBuffer typemap to handle this case */
+
+/* what type to use in java source code */
+%typemap(java,jtype) char *SBUF {StringBuffer}
+
+/* what is the corresponding jni type */
+%typemap(java,jni) char *SBUF {jobject}
+
+/* how to convert java type to requested c type */
+%typemap(java,in) char *SBUF {
+  jclass sbufClass;
+  jmethodID toStringID;
+  jmethodID setLengthID;
+  jstring js;
+
+  $target = NULL;
+  if($source != NULL) {
+    /* get the String from the StringBuffer */
+    sbufClass = (*jenv)->GetObjectClass(jenv, $source);
+    toStringID = (*jenv)->GetMethodID(jenv, sbufClass, "toString", "()Ljava/lang/String;");
+    js = (jstring) (*jenv)->CallObjectMethod(jenv, $source, toStringID);
+    /* convert the String to a char * */
+    $target =  (char *)(*jenv)->GetStringUTFChars(jenv, js, 0); 
+    /* zero the original StringBuffer, so we can replace it with the result */
+    setLengthID = (*jenv)->GetMethodID(jenv, sbufClass, "setLength", "(I)V");
+    (*jenv)->CallVoidMethod(jenv, $source, setLengthID, (jint) 0);
+  }
+}
+
+/* how to convert the c type to the java type */
+%typemap(java,argout) char *SBUF {
+  jclass sbufClass;
+  jmethodID appendStringID;
+
+  if($target != NULL) {
+    /* append the result to the empty StringBuffer */
+    sbufClass = (*jenv)->GetObjectClass(jenv, $source);
+    appendStringID = (*jenv)->GetMethodID(jenv, sbufClass, "append", "(Ljava/lang/String;)Ljava/lang/StringBuffer;");
+    (*jenv)->CallObjectMethod(jenv, $source, appendStringID, (*jenv)->NewStringUTF(jenv, $target));
+    if($source != NULL) (*jenv)->ReleaseStringUTFChars(jenv, $source, $target);
+  }  
+}
+
+/* apply the new typemap to our function */
+void f3(char *SBUF);

Examples/java/typemap/main.java

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+import example;
+
+public class main {
+
+  static {
+    try {
+	System.loadLibrary("example");
+    } catch (UnsatisfiedLinkError e) {
+      System.err.println("Cannot load the example native code.\nMake sure your LD_LIBRARY_PATH contains \'.\'\n" + e);
+      System.exit(1);
+    }
+  }
+
+  public static void main(String argv[]) {
+    String s = "brave new world";
+    example.f1(s);
+    System.out.println("f1(String): " + s);
+
+    byte b[] = new byte[25];
+    example.f2(b);
+    System.out.println("f2(byte[]): " + new String(b));
+
+    StringBuffer sb = new StringBuffer(20);
+    example.f3(sb);
+    System.out.println("f3(StringBuffer): " + sb);
+  }
+}