CODEWITHSUNDEEP
javac++android-ndkjava-native-interfacebytebuffer
Marcos Vasconcelos
Marcos Vasconcelos

Reputation: 18276

Get the pointer of a Java ByteBuffer though JNI

How can I get a pointer to the inner array of a Java ByteBuffer?

JNIEXPORT void JNICALL test(JNIEnv *env, jobject thiso) {
    jclass cls = env->FindClass("java/nio/ByteBuffer");
    jmethodID aloc = env->GetStaticMethodID(cls, "allocateDirect", "(I)Ljava/nio/ByteBuffer;");
    jobject obj = env->CallStaticObjectMethod(cls, aloc, 1000);
}

PS: I'm doing that to share the memory used by Java and C++.

Upvotes: 10

Views: 5732

Answers (2)

Alan Stokes
Alan Stokes

Reputation: 18964

void * data = env->GetDirectBufferAddress(obj);

The ByteBuffer must be a direct one for this to work.

Upvotes: 14

John Dibling
John Dibling

Reputation: 101456

If you're trying to return the address of the first element within m_buffer, then you can just do:

return m_buffer;

..or:

return &m_buffer[0]

Upvotes: 0

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