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+// Distributed under the Boost Software License, Version 1.0. (See
+// accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+// (C) Copyright 2013 Vicente J. Botet Escriba
+
+#ifndef BOOST_THREAD_COMPLETION_LATCH_HPP
+#define BOOST_THREAD_COMPLETION_LATCH_HPP
+
+#include <boost/thread/detail/config.hpp>
+#include <boost/thread/detail/delete.hpp>
+#include <boost/thread/detail/counter.hpp>
+
+#include <boost/thread/mutex.hpp>
+#include <boost/thread/lock_types.hpp>
+#include <boost/thread/condition_variable.hpp>
+#include <boost/chrono/duration.hpp>
+#include <boost/chrono/time_point.hpp>
+#include <boost/assert.hpp>
+//#include <boost/thread/detail/nullary_function.hpp>
+#include <boost/thread/csbl/functional.hpp>
+
+#include <boost/config/abi_prefix.hpp>
+
+namespace boost
+{
+  namespace thread_detail
+  {
+    void noop()
+    {
+    }
+  }
+  class completion_latch
+  {
+  public:
+    /// the implementation defined completion function type
+    //typedef detail::nullary_function<void()> completion_function;
+    typedef csbl::function<void()> completion_function;
+    /// noop completion function factory
+    static completion_function noop()
+    {
+      return completion_function(&thread_detail::noop);
+    }
+
+  private:
+    struct around_wait;
+    friend struct around_wait;
+    struct around_wait
+    {
+      completion_latch &that_;
+      boost::unique_lock<boost::mutex> &lk_;
+      around_wait(completion_latch &that, boost::unique_lock<boost::mutex> &lk)
+      : that_(that), lk_(lk)
+      {
+        that_.leavers_.cond_.wait(lk, detail::counter_is_zero(that_.leavers_));
+        that_.waiters_.inc_and_notify_all();
+        that_.leavers_.cond_.wait(lk, detail::counter_is_not_zero(that_.leavers_));
+      }
+      ~around_wait()
+      {
+        that_.waiters_.dec_and_notify_all();
+      }
+    };
+
+    bool count_down(unique_lock<mutex> &lk)
+    {
+      BOOST_ASSERT(count_ > 0);
+      if (--count_ == 0)
+      {
+        waiters_.cond_.wait(lk, detail::counter_is_not_zero(waiters_));
+        leavers_.assign_and_notify_all(waiters_);
+        count_.cond_.notify_all();
+        waiters_.cond_.wait(lk, detail::counter_is_zero(waiters_));
+        leavers_.assign_and_notify_all(0);
+        lk.unlock();
+        funct_();
+        return true;
+      }
+      return false;
+    }
+
+  public:
+    BOOST_THREAD_NO_COPYABLE( completion_latch )
+
+    /// Constructs a latch with a given count.
+    completion_latch(std::size_t count) :
+      count_(count), funct_(noop()), waiters_(0), leavers_(0)
+    {
+    }
+
+    /// Constructs a latch with a given count and a completion function.
+    template <typename F>
+    completion_latch(std::size_t count, BOOST_THREAD_RV_REF(F) funct) :
+    count_(count),
+    funct_(boost::move(funct)),
+    waiters_(0),
+    leavers_(0)
+    {
+    }
+    template <typename F>
+    completion_latch(std::size_t count, void(*funct)()) :
+      count_(count), funct_(funct), waiters_(0), leavers_(0)
+    {
+    }
+
+    ///
+    ~completion_latch()
+    {
+    }
+
+    /// Blocks until the latch has counted down to zero.
+    void wait()
+    {
+      boost::unique_lock<boost::mutex> lk(mutex_);
+      around_wait aw(*this, lk);
+      count_.cond_.wait(lk, detail::counter_is_zero(count_));
+    }
+
+    /// @return true if the internal counter is already 0, false otherwise
+    bool try_wait()
+    {
+      boost::unique_lock<boost::mutex> lk(mutex_);
+      around_wait aw(*this, lk);
+      return (count_ == 0);
+    }
+
+    /// try to wait for a specified amount of time
+    /// @return whether there is a timeout or not.
+    template <class Rep, class Period>
+    cv_status wait_for(const chrono::duration<Rep, Period>& rel_time)
+    {
+      boost::unique_lock<boost::mutex> lk(mutex_);
+      around_wait aw(*this, lk);
+      return count_.cond_.wait_for(lk, rel_time, detail::counter_is_zero(count_))
+              ? cv_status::no_timeout
+              : cv_status::timeout;
+    }
+
+    /// try to wait until the specified time_point is reached
+    /// @return whether there is a timeout or not.
+    template <class Clock, class Duration>
+    cv_status wait_until(const chrono::time_point<Clock, Duration>& abs_time)
+    {
+      boost::unique_lock<boost::mutex> lk(mutex_);
+      around_wait aw(*this, lk);
+      return count_.cond_.wait_until(lk, abs_time, detail::counter_is_zero(count_))
+          ? cv_status::no_timeout
+          : cv_status::timeout;
+    }
+
+    /// Decrement the count and notify anyone waiting if we reach zero.
+    /// @Requires count must be greater than 0
+    void count_down()
+    {
+      unique_lock<mutex> lk(mutex_);
+      count_down(lk);
+    }
+    void signal()
+    {
+      count_down();
+    }
+
+    /// Decrement the count and notify anyone waiting if we reach zero.
+    /// Blocks until the latch has counted down to zero.
+    /// @Requires count must be greater than 0
+    void count_down_and_wait()
+    {
+      boost::unique_lock<boost::mutex> lk(mutex_);
+      if (count_down(lk))
+      {
+        return;
+      }
+      around_wait aw(*this, lk);
+      count_.cond_.wait(lk, detail::counter_is_zero(count_));
+    }
+    void sync()
+    {
+      count_down_and_wait();
+    }
+
+    /// Reset the counter
+    /// #Requires This method may only be invoked when there are no other threads currently inside the count_down_and_wait() method.
+    void reset(std::size_t count)
+    {
+      boost::lock_guard<boost::mutex> lk(mutex_);
+      //BOOST_ASSERT(count_ == 0);
+      count_ = count;
+    }
+
+    /// Resets the latch with the new completion function.
+    /// The next time the internal count reaches 0, this function will be invoked.
+    /// This completion function may only be invoked when there are no other threads
+    /// currently inside the count_down and wait related functions.
+    /// It may also be invoked from within the registered completion function.
+    /// @Returns the old completion function if any or noop if
+
+#ifdef BOOST_NO_CXX11_HDR_FUNCTIONAL
+    template <typename F>
+    completion_function then(BOOST_THREAD_RV_REF(F) funct)
+    {
+      boost::lock_guard<boost::mutex> lk(mutex_);
+      completion_function tmp(funct_);
+      funct_ = boost::move(funct);
+      return tmp;
+    }
+#endif
+    completion_function then(void(*funct)())
+    {
+      boost::lock_guard<boost::mutex> lk(mutex_);
+      completion_function tmp(funct_);
+      funct_ = completion_function(funct);
+      return tmp;
+    }
+
+  private:
+    mutex mutex_;
+    detail::counter count_;
+    completion_function funct_;
+    detail::counter waiters_;
+    detail::counter leavers_;
+  };
+
+} // namespace boost
+
+#include <boost/config/abi_suffix.hpp>
+
+#endif