/* * Copyright (c) 2009 Apple Inc. All rights reserved. * * @APPLE_DTS_LICENSE_HEADER_START@ * * IMPORTANT: This Apple software is supplied to you by Apple Computer, Inc. * ("Apple") in consideration of your agreement to the following terms, and your * use, installation, modification or redistribution of this Apple software * constitutes acceptance of these terms. If you do not agree with these terms, * please do not use, install, modify or redistribute this Apple software. * * In consideration of your agreement to abide by the following terms, and * subject to these terms, Apple grants you a personal, non-exclusive license, * under Apple's copyrights in this original Apple software (the "Apple Software"), * to use, reproduce, modify and redistribute the Apple Software, with or without * modifications, in source and/or binary forms; provided that if you redistribute * the Apple Software in its entirety and without modifications, you must retain * this notice and the following text and disclaimers in all such redistributions * of the Apple Software. Neither the name, trademarks, service marks or logos of * Apple Computer, Inc. may be used to endorse or promote products derived from * the Apple Software without specific prior written permission from Apple. Except * as expressly stated in this notice, no other rights or licenses, express or * implied, are granted by Apple herein, including but not limited to any patent * rights that may be infringed by your derivative works or by other works in * which the Apple Software may be incorporated. * * The Apple Software is provided by Apple on an "AS IS" basis. APPLE MAKES NO * WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION THE IMPLIED * WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY AND FITNESS FOR A PARTICULAR * PURPOSE, REGARDING THE APPLE SOFTWARE OR ITS USE AND OPERATION ALONE OR IN * COMBINATION WITH YOUR PRODUCTS. * * IN NO EVENT SHALL APPLE BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL OR * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * ARISING IN ANY WAY OUT OF THE USE, REPRODUCTION, MODIFICATION AND/OR * DISTRIBUTION OF THE APPLE SOFTWARE, HOWEVER CAUSED AND WHETHER UNDER THEORY OF * CONTRACT, TORT (INCLUDING NEGLIGENCE), STRICT LIABILITY OR OTHERWISE, EVEN IF * APPLE HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. * * @APPLE_DTS_LICENSE_HEADER_END@ */ /* * nWide.c * Samples project * * Created by Mensch on 5/1/09. * Copyright 2009 Apple, Inc. All rights reserved. * */ #include <stdio.h> #include <unistd.h> #include <stdlib.h> #include <sys/errno.h> #include <assert.h> #include <dispatch/dispatch.h> #include <mach/mach_time.h> #import <libkern/OSAtomic.h> #include <string.h> /* * Demonstrate using dispatch_semaphore to create a concurrent queue that * allows only a fixed number of blocks to be in flight at any given time */ int main (int argc, const char * argv[]) { dispatch_group_t mg = dispatch_group_create(); dispatch_semaphore_t ds; __block int numRunning = 0; int qWidth = 5; int numWorkBlocks = 100; if (argc >= 2) { qWidth = atoi(argv[1]); // use the command 1st line parameter as the queue width if (qWidth==0) qWidth==1; // protect against bad values } if (argc >=3) { numWorkBlocks = atoi(argv[2]); // use the 2nd command line parameter as the queue width if (numWorkBlocks==0) numWorkBlocks==1; // protect against bad values } printf("Starting dispatch semaphore test to simulate a %d wide dispatch queue\n", qWidth ); ds = dispatch_semaphore_create(qWidth); int i; for (i=0; i<numWorkBlocks; i++) { // synchronize the whole shebang every 25 work units... if (i % 25 == 24) { dispatch_group_async(mg,dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT,0), ^{ int x; // wait for all pending work units to finish up... for (int x=0; x<qWidth; x++) dispatch_semaphore_wait(ds, DISPATCH_TIME_FOREVER); // do the thing that is critical here printf("doing something critical...while %d work units are running \n",numRunning); // and let work continue unimpeeded for (int x=0; x<qWidth; x++) dispatch_semaphore_signal(ds); }); } else { // schedule the next block waiting when there are qWidth blocks running dispatch_semaphore_wait(ds, DISPATCH_TIME_FOREVER); dispatch_group_async(mg,dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT,0), ^{ OSAtomicIncrement32( &numRunning ); usleep(random() % 10000); // simulate some random amount of work printf("Value of i is %d Number of blocks in flight %d\n",i, numRunning); // tell the loop it's time to schedule the next block if there is one OSAtomicDecrement32( &numRunning ); dispatch_semaphore_signal(ds); }); } } dispatch_group_notify(mg, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ printf("And we are done!\n"); dispatch_release(mg); dispatch_release(ds); exit(0); }); dispatch_main(); return 0; }