[Boost-commit] svn:boost r85849 - trunk/boost/sync/detail/event

Subject: [Boost-commit] svn:boost r85849 - trunk/boost/sync/detail/event
From: tim_at_[hidden]
Date: 2013-09-23 05:27:35

Author: timblechmann
Date: 2013-09-23 05:27:34 EDT (Mon, 23 Sep 2013)
New Revision: 85849
URL: http://svn.boost.org/trac/boost/changeset/85849

Log:
sync: implement autoreset event for sync semaphores

Added:
   trunk/boost/sync/detail/event/event_autoreset_semaphore.hpp   (contents, props changed)

Added: trunk/boost/sync/detail/event/event_autoreset_semaphore.hpp
==============================================================================
--- /dev/null	00:00:00 1970	(empty, because file is newly added)
+++ trunk/boost/sync/detail/event/event_autoreset_semaphore.hpp	2013-09-23 05:27:34 EDT (Mon, 23 Sep 2013)	(r85849)
@@ -0,0 +1,128 @@
+// autoreset event for generic semaphores
+//
+// Copyright (C) 2013 Tim Blechmann
+// Copyright (C) 2013 Andrey Semashev
+//
+// 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)
+
+#ifndef BOOST_SYNC_DETAIL_EVENT_EVENT_AUTORESET_SEMAPHORE_HPP
+#define BOOST_SYNC_DETAIL_EVENT_EVENT_AUTORESET_SEMAPHORE_HPP
+
+#include <cstddef>
+#include <boost/assert.hpp>
+#include <boost/cstdint.hpp>
+
+#include <boost/sync/detail/config.hpp>
+#include <boost/sync/detail/atomic.hpp>
+#include <boost/sync/detail/pause.hpp>
+#include <boost/sync/semaphore.hpp>
+
+
+#include <boost/sync/detail/header.hpp>
+
+namespace boost {
+
+namespace sync {
+
+BOOST_SYNC_DETAIL_OPEN_ABI_NAMESPACE {
+
+class event
+{
+    BOOST_DELETED_FUNCTION(event(event const&))
+    BOOST_DELETED_FUNCTION(event& operator=(event const&));
+
+public:
+    explicit event():
+        m_state(0)
+    {}
+
+    void post() BOOST_NOEXCEPT
+    {
+        using namespace boost::sync::detail; // for memory_order
+        int32_t old_state = m_state.load(memory_order_acquire);
+        if (old_state >= 0) {
+            for (;;) {
+                if (m_state.compare_exchange_weak( old_state, old_state - 1, memory_order_release, memory_order_acquire)) {
+                    m_sem.post();
+                    return; // avoid unnecessary fence
+                }
+
+                if (old_state < 0)
+                    break; // someone else has set the event with no waiters
+
+                detail::pause();
+            }
+        }
+
+        atomic_thread_fence( memory_order_release );
+    }
+
+    void reset() BOOST_NOEXCEPT
+    {
+        m_state = 0;
+    }
+
+    void wait()
+    {
+        m_state.fetch_add(1, memory_order_acquire);
+        m_sem.wait();
+    }
+
+    bool try_wait()
+    {
+        using namespace boost::sync::detail; // for memory_order
+
+        m_state.fetch_add(1, memory_order_acquire);
+
+        const bool wait_successful = m_sem.try_wait();
+        if (wait_successful)
+            return true;
+
+        m_state.fetch_add(-1, memory_order_relaxed);
+        return false;
+    }
+
+    template <typename Duration>
+    bool try_wait_for(const chrono::duration<Rep, Period> & duration)
+    {
+        using namespace boost::sync::detail; // for memory_order
+
+        m_state.fetch_add(1, memory_order_acquire);
+
+        const bool wait_successful = m_sem.try_wait_for( duration );
+        if (wait_successful)
+            return true;
+
+        m_state.fetch_add(-1, memory_order_relaxed);
+        return false;
+    }
+
+    template <typename Timepoint>
+    bool try_wait_until(const Timepoint & timeout )
+    {
+        using namespace boost::sync::detail; // for memory_order
+
+        m_state.fetch_add(1, memory_order_acquire);
+
+        const bool wait_successful = m_sem.try_wait_until( timeout );
+        if (wait_successful)
+            return true;
+
+        m_state.fetch_add(-1, memory_order_relaxed);
+        return false;
+    }
+
+private:
+    semaphore m_sem;
+    detail::atomic<int32_t> m_state;
+};
+
+}
+}
+}
+
+#include <boost/sync/detail/footer.hpp>
+
+#endif // BOOST_SYNC_DETAIL_EVENT_EVENT_AUTORESET_SEMAPHORE_HPP