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Diffstat (limited to 'Examples/java/typemap/example.i')
-rw-r--r-- | Examples/java/typemap/example.i | 101 |
1 files changed, 101 insertions, 0 deletions
diff --git a/Examples/java/typemap/example.i b/Examples/java/typemap/example.i new file mode 100644 index 0000000..7c97e66 --- /dev/null +++ b/Examples/java/typemap/example.i @@ -0,0 +1,101 @@ +/* File : example.i */ +%module example +%{ +/* + 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) { + f1(s); +} + +void f3(char *s) { + f1(s); +} + +%} + +/* default behaviour is that of input arg, Java cannot return a value in a + * string argument, so any changes made by f1(char*) will not be seen in the Java + * string passed to the f1 function. +*/ +void f1(char *s); + +%include various.i + +/* use the BYTE argout typemap to get around this. Changes in the string by + * f2 can be seen in Java. */ +void f2(char *BYTE); + + + +/* Alternative approach uses a StringBuffer typemap for argout */ + +/* Define the types to use in the generated JNI C code and Java code */ +%typemap(jni) char *SBUF "jobject" +%typemap(jtype) char *SBUF "StringBuffer" +%typemap(jstype) char *SBUF "StringBuffer" + +/* How to convert Java(JNI) type to requested C type */ +%typemap(in) char *SBUF { + + $1 = NULL; + if($input != NULL) { + /* Get the String from the StringBuffer */ + jmethodID setLengthID; + jclass sbufClass = (*jenv)->GetObjectClass(jenv, $input); + jmethodID toStringID = (*jenv)->GetMethodID(jenv, sbufClass, "toString", "()Ljava/lang/String;"); + jstring js = (jstring) (*jenv)->CallObjectMethod(jenv, $input, toStringID); + + /* Convert the String to a C string */ + const char *pCharStr = (*jenv)->GetStringUTFChars(jenv, js, 0); + + /* Take a copy of the C string as the typemap is for a non const C string */ + jmethodID capacityID = (*jenv)->GetMethodID(jenv, sbufClass, "capacity", "()I"); + jint capacity = (*jenv)->CallIntMethod(jenv, $input, capacityID); + $1 = (char *) malloc(capacity+1); + strcpy($1, pCharStr); + + /* Release the UTF string we obtained with GetStringUTFChars */ + (*jenv)->ReleaseStringUTFChars(jenv, js, pCharStr); + + /* Zero the original StringBuffer, so we can replace it with the result */ + setLengthID = (*jenv)->GetMethodID(jenv, sbufClass, "setLength", "(I)V"); + (*jenv)->CallVoidMethod(jenv, $input, setLengthID, (jint) 0); + } +} + +/* How to convert the C type to the Java(JNI) type */ +%typemap(argout) char *SBUF { + + if($1 != NULL) { + /* Append the result to the empty StringBuffer */ + jstring newString = (*jenv)->NewStringUTF(jenv, $1); + jclass sbufClass = (*jenv)->GetObjectClass(jenv, $input); + jmethodID appendStringID = (*jenv)->GetMethodID(jenv, sbufClass, "append", "(Ljava/lang/String;)Ljava/lang/StringBuffer;"); + (*jenv)->CallObjectMethod(jenv, $input, appendStringID, newString); + + /* Clean up the string object, no longer needed */ + free($1); + $1 = NULL; + } +} +/* Prevent the default freearg typemap from being used */ +%typemap(freearg) char *SBUF "" + +/* Convert the jstype to jtype typemap type */ +%typemap(javain) char *SBUF "$javainput" + +/* apply the new typemap to our function */ +void f3(char *SBUF); + |