fiber/detail/thread_barrier.hpp

0001
0002 //          Copyright Oliver Kowalke 2013.
0003 // Distributed under the Boost Software License, Version 1.0.
0004 //    (See accompanying file LICENSE_1_0.txt or copy at
0005 //          http://www.boost.org/LICENSE_1_0.txt)
0006
0007 #ifndef BOOST_FIBER_DETAIL_THREAD_BARRIER_H
0008 #define BOOST_FIBER_DETAIL_THREAD_BARRIER_H
0009
0010 #include <cstddef>
0011 #include <condition_variable>
0012 #include <mutex>
0013
0014 #include <boost/assert.hpp>
0015 #include <boost/config.hpp>
0016
0017 #include <boost/fiber/detail/config.hpp>
0018
0019 #ifdef BOOST_HAS_ABI_HEADERS
0020 # include BOOST_ABI_PREFIX
0021 #endif
0022
0023 namespace boost {
0024 namespace fibers {
0025 namespace detail {
0026
0027 class thread_barrier {
0028 private:
0029     std::size_t             initial_;
0030     std::size_t             current_;
0031     bool                    cycle_{ true };
0032     std::mutex              mtx_{};
0033     std::condition_variable cond_{};
0034
0035 public:
0036     explicit thread_barrier( std::size_t initial) :
0037         initial_{ initial },
0038         current_{ initial_ } {
0039         BOOST_ASSERT ( 0 != initial);
0040     }
0041
0042     thread_barrier( thread_barrier const&) = delete;
0043     thread_barrier & operator=( thread_barrier const&) = delete;
0044
0045     bool wait() {
0046         std::unique_lock< std::mutex > lk( mtx_);
0047         const bool cycle = cycle_;
0048         if ( 0 == --current_) {
0049             cycle_ = ! cycle_;
0050             current_ = initial_;
0051             lk.unlock(); // no pessimization
0052             cond_.notify_all();
0053             return true;
0054         }
0055         cond_.wait( lk, [&](){ return cycle != cycle_; });
0056         return false;
0057     }
0058 };
0059
0060 }}}
0061
0062 #endif // BOOST_FIBER_DETAIL_THREAD_BARRIER_H