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+//
+// Copyright (c) 2016-2019 Vinnie Falco (vinnie dot falco at gmail dot com)
+//
+// 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)
+//
+// Official repository: https://github.com/boostorg/beast
+//
+
+#ifndef BOOST_BEAST_WEBSOCKET_DETAIL_SOFT_MUTEX_HPP
+#define BOOST_BEAST_WEBSOCKET_DETAIL_SOFT_MUTEX_HPP
+
+#include <boost/assert.hpp>
+
+namespace boost {
+namespace beast {
+namespace websocket {
+namespace detail {
+
+// used to order reads, writes in websocket streams
+
+class soft_mutex
+{
+ int id_ = 0;
+
+public:
+ soft_mutex() = default;
+ soft_mutex(soft_mutex const&) = delete;
+ soft_mutex& operator=(soft_mutex const&) = delete;
+
+ soft_mutex(soft_mutex&& other) noexcept
+ : id_(boost::exchange(other.id_, 0))
+ {
+ }
+
+ soft_mutex& operator=(soft_mutex&& other) noexcept
+ {
+ id_ = other.id_;
+ other.id_ = 0;
+ return *this;
+ }
+
+ // VFALCO I'm not too happy that this function is needed
+ void
+ reset()
+ {
+ id_ = 0;
+ }
+
+ bool
+ is_locked() const noexcept
+ {
+ return id_ != 0;
+ }
+
+ template<class T>
+ bool
+ is_locked(T const*) const noexcept
+ {
+ return id_ == T::id;
+ }
+
+ template<class T>
+ void
+ lock(T const*)
+ {
+ BOOST_ASSERT(id_ == 0);
+ id_ = T::id;
+ }
+
+ template<class T>
+ void
+ unlock(T const*)
+ {
+ BOOST_ASSERT(id_ == T::id);
+ id_ = 0;
+ }
+
+ template<class T>
+ bool
+ try_lock(T const*)
+ {
+ // If this assert goes off it means you are attempting to
+ // simultaneously initiate more than one of same asynchronous
+ // operation, which is not allowed. For example, you must wait
+ // for an async_read to complete before performing another
+ // async_read.
+ //
+ BOOST_ASSERT(id_ != T::id);
+ if(id_ != 0)
+ return false;
+ id_ = T::id;
+ return true;
+ }
+
+ template<class T>
+ bool
+ try_unlock(T const*) noexcept
+ {
+ if(id_ != T::id)
+ return false;
+ id_ = 0;
+ return true;
+ }
+};
+
+} // detail
+} // websocket
+} // beast
+} // boost
+
+#endif