barrier.hh

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/*
 * Copyright (c) 2013 ARM Limited
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 *
 * The license below extends only to copyright in the software and shall
 * not be construed as granting a license to any other intellectual
 * property including but not limited to intellectual property relating
 * to a hardware implementation of the functionality of the software
 * licensed hereunder.  You may use the software subject to the license
 * terms below provided that you ensure that this notice is replicated
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 * modified or unmodified, in source code or in binary form.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met: redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer;
 * redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
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 * this software without specific prior written permission.
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 * Authors: Ali Saidi
 */

#ifndef __BASE_BARRIER_HH__
#define __BASE_BARRIER_HH__

#include <condition_variable>

class Barrier
{
  private:
    std::mutex bMutex;
    std::condition_variable bCond;
    unsigned numWaiting;
    unsigned generation;
    unsigned numLeft;

  public:
    Barrier(unsigned _numWaiting)
        : numWaiting(_numWaiting), generation(0), numLeft(_numWaiting)
    {}

    bool
    wait()
    {
        std::unique_lock<std::mutex> lock(bMutex);
        unsigned int gen = generation;

        if (--numLeft == 0) {
            generation++;
            numLeft = numWaiting;
            bCond.notify_all();
            return true;
        }
        while (gen == generation)
            bCond.wait(lock);
        return false;
    }
};

#endif // __BASE_BARRIER_HH__