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+//
+// detail/scoped_lock.hpp
+// ~~~~~~~~~~~~~~~~~~~~~~
+//
+// Copyright (c) 2003-2018 Christopher M. Kohlhoff (chris at kohlhoff 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)
+//
+
+#ifndef ASIO_DETAIL_SCOPED_LOCK_HPP
+#define ASIO_DETAIL_SCOPED_LOCK_HPP
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1200)
+# pragma once
+#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
+
+#include "asio/detail/noncopyable.hpp"
+
+#include "asio/detail/push_options.hpp"
+
+namespace asio {
+namespace detail {
+
+// Helper class to lock and unlock a mutex automatically.
+template <typename Mutex>
+class scoped_lock
+ : private noncopyable
+{
+public:
+ // Tag type used to distinguish constructors.
+ enum adopt_lock_t { adopt_lock };
+
+ // Constructor adopts a lock that is already held.
+ scoped_lock(Mutex& m, adopt_lock_t)
+ : mutex_(m),
+ locked_(true)
+ {
+ }
+
+ // Constructor acquires the lock.
+ explicit scoped_lock(Mutex& m)
+ : mutex_(m)
+ {
+ mutex_.lock();
+ locked_ = true;
+ }
+
+ // Destructor releases the lock.
+ ~scoped_lock()
+ {
+ if (locked_)
+ mutex_.unlock();
+ }
+
+ // Explicitly acquire the lock.
+ void lock()
+ {
+ if (!locked_)
+ {
+ mutex_.lock();
+ locked_ = true;
+ }
+ }
+
+ // Explicitly release the lock.
+ void unlock()
+ {
+ if (locked_)
+ {
+ mutex_.unlock();
+ locked_ = false;
+ }
+ }
+
+ // Test whether the lock is held.
+ bool locked() const
+ {
+ return locked_;
+ }
+
+ // Get the underlying mutex.
+ Mutex& mutex()
+ {
+ return mutex_;
+ }
+
+private:
+ // The underlying mutex.
+ Mutex& mutex_;
+
+ // Whether the mutex is currently locked or unlocked.
+ bool locked_;
+};
+
+} // namespace detail
+} // namespace asio
+
+#include "asio/detail/pop_options.hpp"
+
+#endif // ASIO_DETAIL_SCOPED_LOCK_HPP