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//
// detail/conditionally_enabled_mutex.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 BOOST_ASIO_DETAIL_CONDITIONALLY_ENABLED_MUTEX_HPP
#define BOOST_ASIO_DETAIL_CONDITIONALLY_ENABLED_MUTEX_HPP
#if defined(_MSC_VER) && (_MSC_VER >= 1200)
# pragma once
#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
#include <boost/asio/detail/config.hpp>
#include <boost/asio/detail/mutex.hpp>
#include <boost/asio/detail/noncopyable.hpp>
#include <boost/asio/detail/scoped_lock.hpp>
#include <boost/asio/detail/push_options.hpp>
namespace boost {
namespace asio {
namespace detail {
// Mutex adapter used to conditionally enable or disable locking.
class conditionally_enabled_mutex
: private noncopyable
{
public:
// Helper class to lock and unlock a mutex automatically.
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(conditionally_enabled_mutex& m, adopt_lock_t)
: mutex_(m),
locked_(m.enabled_)
{
}
// Constructor acquires the lock.
explicit scoped_lock(conditionally_enabled_mutex& m)
: mutex_(m)
{
if (m.enabled_)
{
mutex_.mutex_.lock();
locked_ = true;
}
else
locked_ = false;
}
// Destructor releases the lock.
~scoped_lock()
{
if (locked_)
mutex_.mutex_.unlock();
}
// Explicitly acquire the lock.
void lock()
{
if (mutex_.enabled_ && !locked_)
{
mutex_.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.
boost::asio::detail::mutex& mutex()
{
return mutex_.mutex_;
}
private:
friend class conditionally_enabled_event;
conditionally_enabled_mutex& mutex_;
bool locked_;
};
// Constructor.
explicit conditionally_enabled_mutex(bool enabled)
: enabled_(enabled)
{
}
// Destructor.
~conditionally_enabled_mutex()
{
}
// Determine whether locking is enabled.
bool enabled() const
{
return enabled_;
}
// Lock the mutex.
void lock()
{
if (enabled_)
mutex_.lock();
}
// Unlock the mutex.
void unlock()
{
if (enabled_)
mutex_.unlock();
}
private:
friend class scoped_lock;
friend class conditionally_enabled_event;
boost::asio::detail::mutex mutex_;
const bool enabled_;
};
} // namespace detail
} // namespace asio
} // namespace boost
#include <boost/asio/detail/pop_options.hpp>
#endif // BOOST_ASIO_DETAIL_CONDITIONALLY_ENABLED_MUTEX_HPP
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