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//
// detail/std_event.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_STD_EVENT_HPP
#define ASIO_DETAIL_STD_EVENT_HPP
#if defined(_MSC_VER) && (_MSC_VER >= 1200)
# pragma once
#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
#include "asio/detail/config.hpp"
#if defined(ASIO_HAS_STD_MUTEX_AND_CONDVAR)
#include <chrono>
#include <condition_variable>
#include "asio/detail/assert.hpp"
#include "asio/detail/noncopyable.hpp"
#include "asio/detail/push_options.hpp"
namespace asio {
namespace detail {
class std_event
: private noncopyable
{
public:
// Constructor.
std_event()
: state_(0)
{
}
// Destructor.
~std_event()
{
}
// Signal the event. (Retained for backward compatibility.)
template <typename Lock>
void signal(Lock& lock)
{
this->signal_all(lock);
}
// Signal all waiters.
template <typename Lock>
void signal_all(Lock& lock)
{
ASIO_ASSERT(lock.locked());
(void)lock;
state_ |= 1;
cond_.notify_all();
}
// Unlock the mutex and signal one waiter.
template <typename Lock>
void unlock_and_signal_one(Lock& lock)
{
ASIO_ASSERT(lock.locked());
state_ |= 1;
bool have_waiters = (state_ > 1);
lock.unlock();
if (have_waiters)
cond_.notify_one();
}
// If there's a waiter, unlock the mutex and signal it.
template <typename Lock>
bool maybe_unlock_and_signal_one(Lock& lock)
{
ASIO_ASSERT(lock.locked());
state_ |= 1;
if (state_ > 1)
{
lock.unlock();
cond_.notify_one();
return true;
}
return false;
}
// Reset the event.
template <typename Lock>
void clear(Lock& lock)
{
ASIO_ASSERT(lock.locked());
(void)lock;
state_ &= ~std::size_t(1);
}
// Wait for the event to become signalled.
template <typename Lock>
void wait(Lock& lock)
{
ASIO_ASSERT(lock.locked());
unique_lock_adapter u_lock(lock);
while ((state_ & 1) == 0)
{
waiter w(state_);
cond_.wait(u_lock.unique_lock_);
}
}
// Timed wait for the event to become signalled.
template <typename Lock>
bool wait_for_usec(Lock& lock, long usec)
{
ASIO_ASSERT(lock.locked());
unique_lock_adapter u_lock(lock);
if ((state_ & 1) == 0)
{
waiter w(state_);
cond_.wait_for(u_lock.unique_lock_, std::chrono::microseconds(usec));
}
return (state_ & 1) != 0;
}
private:
// Helper class to temporarily adapt a scoped_lock into a unique_lock so that
// it can be passed to std::condition_variable::wait().
struct unique_lock_adapter
{
template <typename Lock>
explicit unique_lock_adapter(Lock& lock)
: unique_lock_(lock.mutex().mutex_, std::adopt_lock)
{
}
~unique_lock_adapter()
{
unique_lock_.release();
}
std::unique_lock<std::mutex> unique_lock_;
};
// Helper to increment and decrement the state to track outstanding waiters.
class waiter
{
public:
explicit waiter(std::size_t& state)
: state_(state)
{
state_ += 2;
}
~waiter()
{
state_ -= 2;
}
private:
std::size_t& state_;
};
std::condition_variable cond_;
std::size_t state_;
};
} // namespace detail
} // namespace asio
#include "asio/detail/pop_options.hpp"
#endif // defined(ASIO_HAS_STD_MUTEX_AND_CONDVAR)
#endif // ASIO_DETAIL_STD_EVENT_HPP
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