wtf/ParallelJobsLibdispatch.h

   1 /*
   2  * Copyright (C) 2011 University of Szeged
   3  * Copyright (C) 2011 Gabor Loki <loki@webkit.org>
   4  * All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions and the following disclaimer.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  *
  15  * THIS SOFTWARE IS PROVIDED BY UNIVERSITY OF SZEGED ``AS IS'' AND ANY
  16  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  17  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  18  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL UNIVERSITY OF SZEGED OR
  19  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  20  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  21  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  22  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  23  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  24  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  25  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  26  */
  27
  28 #ifndef ParallelJobsLibdispatch_h
  29 #define ParallelJobsLibdispatch_h
  30
  31 #if ENABLE(THREADING_LIBDISPATCH)
  32
  33 #include <dispatch/dispatch.h>
  34
  35 namespace WTF {
  36
  37 static const int maxParallelThreads = 2;
  38
  39 class ParallelEnvironment {
  40     WTF_MAKE_FAST_ALLOCATED;
  41 public:
  42     typedef void (*ThreadFunction)(void*);
  43
  44     ParallelEnvironment(ThreadFunction threadFunction, size_t sizeOfParameter, int requestedJobNumber) :
  45         m_threadFunction(threadFunction),
  46         m_sizeOfParameter(sizeOfParameter)
  47     {
  48         if (!requestedJobNumber || requestedJobNumber > maxParallelThreads)
  49             requestedJobNumber = maxParallelThreads;
  50
  51         ASSERT(requestedJobNumber > 0);
  52
  53         m_numberOfJobs = requestedJobNumber;
  54     }
  55
  56     int numberOfJobs()
  57     {
  58         return m_numberOfJobs;
  59     }
  60
  61     void execute(unsigned char* parameters)
  62     {
  63         // libdispatch is NOT supported inside a template
  64         dispatch_queue_t parallelJobsQueue = dispatch_queue_create("ParallelJobs", 0);
  65
  66         for (int i = 0; i < m_numberOfJobs - 1; ++i) {
  67             dispatch_async(parallelJobsQueue, ^{(*m_threadFunction)(parameters);});
  68             parameters += m_sizeOfParameter;
  69         }
  70
  71         // The work for the main thread. Wait until all jobs are done.
  72         dispatch_sync(parallelJobsQueue, ^{(*m_threadFunction)(parameters);});
  73     }
  74
  75 private:
  76     ThreadFunction m_threadFunction;
  77     size_t m_sizeOfParameter;
  78     int m_numberOfJobs;
  79 };
  80
  81 } // namespace WTF
  82
  83 #endif // ENABLE(THREADING_LIBDISPATCH)
  84
  85 #endif // ParallelJobsLibdispatch_h