Chris@16: // Distributed under the Boost Software License, Version 1.0. (See
Chris@16: // accompanying file LICENSE_1_0.txt or copy at
Chris@16: // http://www.boost.org/LICENSE_1_0.txt)
Chris@16: // (C) Copyright 2013 Vicente J. Botet Escriba
Chris@16: 
Chris@16: #ifndef BOOST_THREAD_LATCH_HPP
Chris@16: #define BOOST_THREAD_LATCH_HPP
Chris@16: 
Chris@16: #include <boost/thread/detail/config.hpp>
Chris@16: #include <boost/thread/detail/delete.hpp>
Chris@16: #include <boost/thread/detail/counter.hpp>
Chris@16: 
Chris@16: #include <boost/thread/mutex.hpp>
Chris@16: #include <boost/thread/lock_types.hpp>
Chris@16: #include <boost/thread/condition_variable.hpp>
Chris@16: #include <boost/chrono/duration.hpp>
Chris@16: #include <boost/chrono/time_point.hpp>
Chris@16: #include <boost/assert.hpp>
Chris@16: 
Chris@16: #include <boost/config/abi_prefix.hpp>
Chris@16: 
Chris@16: namespace boost
Chris@16: {
Chris@16:   class latch
Chris@16:   {
Chris@16:     /// @Requires: count_ must be greater than 0
Chris@16:     /// Effect: Decrement the count. Unlocks the lock and notify anyone waiting if we reached zero.
Chris@16:     /// Returns: true if count_ reached the value 0.
Chris@16:     /// @ThreadSafe ensured by the @c lk parameter
Chris@101:     bool count_down(unique_lock<mutex> &)
Chris@16:     /// pre_condition (count_ > 0)
Chris@16:     {
Chris@16:       BOOST_ASSERT(count_ > 0);
Chris@16:       if (--count_ == 0)
Chris@16:       {
Chris@16:         ++generation_;
Chris@101:         //lk.unlock();
Chris@16:         cond_.notify_all();
Chris@16:         return true;
Chris@16:       }
Chris@16:       return false;
Chris@16:     }
Chris@16:     /// Effect: Decrement the count is > 0. Unlocks the lock notify anyone waiting if we reached zero.
Chris@16:     /// Returns: true if count_ is 0.
Chris@16:     /// @ThreadSafe ensured by the @c lk parameter
Chris@16:     bool try_count_down(unique_lock<mutex> &lk)
Chris@16:     {
Chris@16:       if (count_ > 0)
Chris@16:       {
Chris@16:         return count_down(lk);
Chris@16:       }
Chris@16:       return true;
Chris@16:     }
Chris@16:   public:
Chris@16:     BOOST_THREAD_NO_COPYABLE( latch)
Chris@16: 
Chris@16:     /// Constructs a latch with a given count.
Chris@16:     latch(std::size_t count) :
Chris@16:       count_(count), generation_(0)
Chris@16:     {
Chris@16:     }
Chris@16: 
Chris@16:     /// Destructor
Chris@16:     /// Precondition: No threads are waiting or invoking count_down on @c *this.
Chris@16: 
Chris@16:     ~latch()
Chris@16:     {
Chris@16: 
Chris@16:     }
Chris@16: 
Chris@16:     /// Blocks until the latch has counted down to zero.
Chris@16:     void wait()
Chris@16:     {
Chris@16:       boost::unique_lock<boost::mutex> lk(mutex_);
Chris@16:       std::size_t generation(generation_);
Chris@16:       cond_.wait(lk, detail::not_equal(generation, generation_));
Chris@16:     }
Chris@16: 
Chris@16:     /// @return true if the internal counter is already 0, false otherwise
Chris@16:     bool try_wait()
Chris@16:     {
Chris@16:       boost::unique_lock<boost::mutex> lk(mutex_);
Chris@16:       return (count_ == 0);
Chris@16:     }
Chris@16: 
Chris@16:     /// try to wait for a specified amount of time is elapsed.
Chris@16:     /// @return whether there is a timeout or not.
Chris@16:     template <class Rep, class Period>
Chris@16:     cv_status wait_for(const chrono::duration<Rep, Period>& rel_time)
Chris@16:     {
Chris@16:       boost::unique_lock<boost::mutex> lk(mutex_);
Chris@16:       std::size_t generation(generation_);
Chris@16:       return cond_.wait_for(lk, rel_time, detail::not_equal(generation, generation_))
Chris@16:               ? cv_status::no_timeout
Chris@16:               : cv_status::timeout;
Chris@16:     }
Chris@16: 
Chris@16:     /// try to wait until the specified time_point is reached
Chris@16:     /// @return whether there were a timeout or not.
Chris@16:     template <class Clock, class Duration>
Chris@16:     cv_status wait_until(const chrono::time_point<Clock, Duration>& abs_time)
Chris@16:     {
Chris@16:       boost::unique_lock<boost::mutex> lk(mutex_);
Chris@16:       std::size_t generation(generation_);
Chris@16:       return cond_.wait_until(lk, abs_time, detail::not_equal(generation, generation_))
Chris@16:           ? cv_status::no_timeout
Chris@16:           : cv_status::timeout;
Chris@16:     }
Chris@16: 
Chris@16:     /// Decrement the count and notify anyone waiting if we reach zero.
Chris@16:     /// @Requires count must be greater than 0
Chris@16:     void count_down()
Chris@16:     {
Chris@16:       boost::unique_lock<boost::mutex> lk(mutex_);
Chris@16:       count_down(lk);
Chris@16:     }
Chris@16:     /// Effect: Decrement the count if it is > 0 and notify anyone waiting if we reached zero.
Chris@16:     /// Returns: true if count_ was 0 or reached 0.
Chris@16:     bool try_count_down()
Chris@16:     {
Chris@16:       boost::unique_lock<boost::mutex> lk(mutex_);
Chris@16:       return try_count_down(lk);
Chris@16:     }
Chris@16:     void signal()
Chris@16:     {
Chris@16:       count_down();
Chris@16:     }
Chris@16: 
Chris@16:     /// Decrement the count and notify anyone waiting if we reach zero.
Chris@16:     /// Blocks until the latch has counted down to zero.
Chris@16:     /// @Requires count must be greater than 0
Chris@16:     void count_down_and_wait()
Chris@16:     {
Chris@16:       boost::unique_lock<boost::mutex> lk(mutex_);
Chris@16:       std::size_t generation(generation_);
Chris@16:       if (count_down(lk))
Chris@16:       {
Chris@16:         return;
Chris@16:       }
Chris@16:       cond_.wait(lk, detail::not_equal(generation, generation_));
Chris@16:     }
Chris@16:     void sync()
Chris@16:     {
Chris@16:       count_down_and_wait();
Chris@16:     }
Chris@16: 
Chris@16:     /// Reset the counter
Chris@16:     /// #Requires This method may only be invoked when there are no other threads currently inside the count_down_and_wait() method.
Chris@16:     void reset(std::size_t count)
Chris@16:     {
Chris@16:       boost::lock_guard<boost::mutex> lk(mutex_);
Chris@16:       //BOOST_ASSERT(count_ == 0);
Chris@16:       count_ = count;
Chris@16:     }
Chris@16: 
Chris@16:   private:
Chris@16:     mutex mutex_;
Chris@16:     condition_variable cond_;
Chris@16:     std::size_t count_;
Chris@16:     std::size_t generation_;
Chris@16:   };
Chris@16: 
Chris@16: } // namespace boost
Chris@16: 
Chris@16: #include <boost/config/abi_suffix.hpp>
Chris@16: 
Chris@16: #endif