Java example source code file (Dispatch.m)

This example Java source code file (Dispatch.m) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

java_com_apple_concurrent_libdispatchnative_nativecreateserialqueue, java_com_apple_concurrent_libdispatchnative_nativeexecutesync, java_com_apple_concurrent_libdispatchnative_nativereleasequeue, jnf_cocoa_enter, jnf_cocoa_exit, jnfcallobjectmethod, jnfjobjectwrapper, jnfobtainenv, jnfthreadcontext, jni_true, jnicall, jnienv, jniexport, null

The Dispatch.m Java example source code

/*
 * Copyright (c) 2011, 2012, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

#import "com_apple_concurrent_LibDispatchNative.h"

#import <dispatch/dispatch.h>
#import <JavaNativeFoundation/JavaNativeFoundation.h>


/*
 * Class:     com_apple_concurrent_LibDispatchNative
 * Method:    nativeIsDispatchSupported
 * Signature: ()Z
 */
JNIEXPORT jboolean JNICALL Java_com_apple_concurrent_LibDispatchNative_nativeIsDispatchSupported
(JNIEnv *env, jclass clazz)
{
        return JNI_TRUE;
}


/*
 * Class:     com_apple_concurrent_LibDispatchNative
 * Method:    nativeGetMainQueue
 * Signature: ()J
 */
JNIEXPORT jlong JNICALL Java_com_apple_concurrent_LibDispatchNative_nativeGetMainQueue
(JNIEnv *env, jclass clazz)
{
        dispatch_queue_t queue = dispatch_get_main_queue();
        return ptr_to_jlong(queue);
}


/*
 * Class:     com_apple_concurrent_LibDispatchNative
 * Method:    nativeCreateConcurrentQueue
 * Signature: (I)J
 */
JNIEXPORT jlong JNICALL Java_com_apple_concurrent_LibDispatchNative_nativeCreateConcurrentQueue
(JNIEnv *env, jclass clazz, jint priority)
{
        dispatch_queue_t queue = dispatch_get_global_queue((long)priority, 0);
        return ptr_to_jlong(queue);
}


/*
 * Class:     com_apple_concurrent_LibDispatchNative
 * Method:    nativeCreateSerialQueue
 * Signature: (Ljava/lang/String;)J
 */
JNIEXPORT jlong JNICALL Java_com_apple_concurrent_LibDispatchNative_nativeCreateSerialQueue
(JNIEnv *env, jclass clazz, jstring name)
{
        if (name == NULL) return 0L;

        jboolean isCopy;
        const char *queue_name = (*env)->GetStringUTFChars(env, name, &isCopy);
        dispatch_queue_t queue = dispatch_queue_create(queue_name, NULL);
        (*env)->ReleaseStringUTFChars(env, name, queue_name);

        return ptr_to_jlong(queue);
}


/*
 * Class:     com_apple_concurrent_LibDispatchNative
 * Method:    nativeReleaseQueue
 * Signature: (J)V
 */
JNIEXPORT void JNICALL Java_com_apple_concurrent_LibDispatchNative_nativeReleaseQueue
(JNIEnv *env, jclass clazz, jlong nativeQueue)
{
        if (nativeQueue == 0L) return;
        dispatch_release((dispatch_queue_t)jlong_to_ptr(nativeQueue));
}


static JNF_CLASS_CACHE(jc_Runnable, "java/lang/Runnable");
static JNF_MEMBER_CACHE(jm_run, jc_Runnable, "run", "()V");

static void perform_dispatch(JNIEnv *env, jlong nativeQueue, jobject runnable, void (*dispatch_fxn)(dispatch_queue_t, dispatch_block_t))
{
JNF_COCOA_ENTER(env);
        dispatch_queue_t queue = (dispatch_queue_t)jlong_to_ptr(nativeQueue);
        if (queue == NULL) return; // shouldn't happen

        // create a global-ref around the Runnable, so it can be safely passed to the dispatch thread
        JNFJObjectWrapper *wrappedRunnable = [[JNFJObjectWrapper alloc] initWithJObject:runnable withEnv:env];

        dispatch_fxn(queue, ^{
                // attach the dispatch thread to the JVM if necessary, and get an env
                JNFThreadContext ctx = JNFThreadDetachOnThreadDeath | JNFThreadSetSystemClassLoaderOnAttach | JNFThreadAttachAsDaemon;
                JNIEnv *blockEnv = JNFObtainEnv(&ctx);

        JNF_COCOA_ENTER(blockEnv);

                // call the user's runnable
                JNFCallObjectMethod(blockEnv, [wrappedRunnable jObject], jm_run);

                // explicitly clear object while we have an env (it's cheaper that way)
                [wrappedRunnable setJObject:NULL withEnv:blockEnv];

        JNF_COCOA_EXIT(blockEnv);

                // let the env go, but leave the thread attached as a daemon
                JNFReleaseEnv(blockEnv, &ctx);
        });

        // release this thread's interest in the Runnable, the block
        // will have retained the it's own interest above
        [wrappedRunnable release];

JNF_COCOA_EXIT(env);
}


/*
 * Class:     com_apple_concurrent_LibDispatchNative
 * Method:    nativeExecuteAsync
 * Signature: (JLjava/lang/Runnable;)V
 */
JNIEXPORT void JNICALL Java_com_apple_concurrent_LibDispatchNative_nativeExecuteAsync
(JNIEnv *env, jclass clazz, jlong nativeQueue, jobject runnable)
{
        // enqueues and returns
        perform_dispatch(env, nativeQueue, runnable, dispatch_async);
}


/*
 * Class:     com_apple_concurrent_LibDispatchNative
 * Method:    nativeExecuteSync
 * Signature: (JLjava/lang/Runnable;)V
 */
JNIEXPORT void JNICALL Java_com_apple_concurrent_LibDispatchNative_nativeExecuteSync
(JNIEnv *env, jclass clazz, jlong nativeQueue, jobject runnable)
{
        // blocks until the Runnable completes
        perform_dispatch(env, nativeQueue, runnable, dispatch_sync);
}