ceph/src/boost/libs/fiber/examples/barrier.hpp

   1
   2 //          Copyright Oliver Kowalke 2013.
   3 // Distributed under the Boost Software License, Version 1.0.
   4 //    (See accompanying file LICENSE_1_0.txt or copy at
   5 //          http://www.boost.org/LICENSE_1_0.txt)
   6
   7 #ifndef BARRIER_H
   8 #define BARRIER_H
   9
  10 #include <cstddef>
  11 #include <condition_variable>
  12 #include <mutex>
  13
  14 #include <boost/assert.hpp>
  15
  16 class barrier {
  17 private:
  18         std::size_t             initial_;
  19         std::size_t             current_;
  20         bool                    cycle_{ true };
  21     std::mutex              mtx_{};
  22     std::condition_variable cond_{};
  23
  24 public:
  25         explicit barrier( std::size_t initial) :
  26         initial_{ initial },
  27         current_{ initial_ } {
  28         BOOST_ASSERT ( 0 != initial);
  29     }
  30
  31     barrier( barrier const&) = delete;
  32     barrier & operator=( barrier const&) = delete;
  33
  34     bool wait() {
  35         std::unique_lock< std::mutex > lk( mtx_);
  36         const bool cycle = cycle_;
  37         if ( 0 == --current_) {
  38             cycle_ = ! cycle_;
  39             current_ = initial_;
  40             lk.unlock(); // no pessimization
  41             cond_.notify_all();
  42             return true;
  43         } else {
  44             cond_.wait( lk, [&](){ return cycle != cycle_; });
  45         }
  46         return false;
  47     }
  48 };
  49
  50 #endif // BARRIER_H