[zeromq-dev] Zero Copy in Java jzmq

[gonzalo diethelm]

I remembered that I did implement this for a tentative Java binding for Crossroads IO. The relevant methods where send() and recv(). This all worked and performed MUCH better that current binding. Some details follow; if more is required, let me know.

Usage:

            int size = 128;
            ByteBuffer bb = ByteBuffer.allocateDirect(size);
...
            int rc = xs.xs_recv(sock, bb, 0, size, 0);
...
            int rc = xs.xs_recv(sock, bb, 0, size, 0);

---------------------
In Java:

public class XsLibrary {
...
    public native int xs_send(long socket,
                              ByteBuffer buffer,
                              int offset,
                              int length,
                              int flags);
    public native int xs_recv(long socket,
                              ByteBuffer buffer,
                              int offset,
                              int length,
                              int flags);
}

---------------------
In C (the JNI part):

JNIEXPORT jint JNICALL Java_io_crossroads_jni_XsLibrary_xs_1send(JNIEnv* env,
                                                                 jobject obj,
                                                                 jlong socket,
                                                                 jobject buffer,
                                                                 jint offset,
                                                                 jint length,
                                                                 jint flags)
{
    void* sock = 0;
    jbyte* buf = 0;
    int ret = 0;

    sock = (void*) socket;
    XS_ASSERT(sock);
    buf = (jbyte*) (*env)->GetDirectBufferAddress(env, buffer);
    XS_ASSERT(buf);
    ret = xs_send(sock, buf, length, flags);
    return ret;
}

JNIEXPORT jint JNICALL Java_io_crossroads_jni_XsLibrary_xs_1recv(JNIEnv* env,
                                                                 jobject obj,
                                                                 jlong socket,
                                                                 jobject buffer,
                                                                 jint offset,
                                                                 jint length,
                                                                 jint flags)
{
    void* sock = 0;
    jbyte* buf = 0;
    int ret = 0;

    sock = (void*) socket;
    XS_ASSERT(sock);
    buf = (jbyte*) (*env)->GetDirectBufferAddress(env, buffer);
    XS_ASSERT(buf);
    ret = xs_recv(sock, buf, length, flags);
    return ret;
}

---------------------

-- 
Gonzalo Diethelm
DCV Chile


> -----Original Message-----
> From: zeromq-dev-bounces at lists.zeromq.org [mailto:zeromq-dev-
> bounces at lists.zeromq.org] On Behalf Of Trevor Bernard
> Sent: Friday, February 15, 2013 2:02 PM
> To: thecarrolls at jiminger.com; ZeroMQ development list
> Subject: Re: [zeromq-dev] Zero Copy in Java jzmq
> 
> > I'm thinking of extending jzmq to optionally allow the zero-copy
> > technique using the concepts outlined by Martin Thompson here:
> 
> That's awesome
> 
> > I'm not 100% sure I'll do it, I need some more experimentation first,
> > but is there any interest or words of advice if someone's tried this
> > already?
> 
> I'd love for send/recv to have a ByteBuffer API.
> 
> Some resources and general suggestions:
> 
> Have a peak at zmq_msg_t in zmq.h.
> 
> Defines ZMTP/2.0 Spec:
> * http://rfc.zeromq.org/spec:15
> 
> Also depending on the size of the msg, it may be allocated on the stack or
> heap.
> * http://api.zeromq.org/3-2:zmq-msg-init-size
> 
> At some point you'll have to access a malloc'ed array from Java/JNI.
> *
> http://docs.oracle.com/javase/6/docs/technotes/guides/jni/spec/functions.
> html#nio_support
> 
> Something like this would do the trick. This wraps a native pointer in a
> ByteBufer
> 
> void *data = ...
> jobject bb = (*env)->NewDirectByteBuffer(env, (void*) data,
> sizeof(zmq_msg_t));
> 
> Here is another option: Use a library like javolution to do your mapping:
> 
> http://javolution.org/target/site/apidocs/javolution/io/Struct.html
> 
> class Message extends Struct {
>    Unsigned8 _ = new Unsigned8(32);
>     Message() {
>         setByteBuffer(Message.nativeBuffer(), 0);
>     }
>     private static native ByteBuffer nativeBuffer(); }
> 
> Something along those lines.
> 
> Hope this helps.
> 
> -Trev
> _______________________________________________
> zeromq-dev mailing list
> zeromq-dev at lists.zeromq.org
> http://lists.zeromq.org/mailman/listinfo/zeromq-dev


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