[JNI] how to modify java array in the C++ code ?

[yomgui]

in the java code :

byte [ ] aPictArrayUnpac ked = new byte [ 3 ] ;

in the c++ code :

JNIEXPORT void JNICALL Java_tracker_Un packPict (
JNIEnv * aEnv ,
jobject aObj ,
jbyteArray aPictArrayUnpac ked )
{
jbyte * lBodyUnpacked = aEnv -> GetByteArrayEle ments (
aPictArrayUnpac ked , 0 ) ;

memset ( lBodyUnpacked , 0 , 3 ) ;

aEnv -> ReleaseByteArra yElements ( aPictArrayPacke d , lBodyPacked ,
0 ) ;
}

it crash on the memset.

what should I do ?

thanks

yomgui