62 lines
1.9 KiB
C++
62 lines
1.9 KiB
C++
/*
|
|
* Licensed under the Apache License, Version 2.0 (the "License");
|
|
* you may not use this file except in compliance with the License.
|
|
* You may obtain a copy of the License at
|
|
*
|
|
* http://www.apache.org/licenses/LICENSE-2.0
|
|
*
|
|
* Unless required by applicable law or agreed to in writing, software
|
|
* distributed under the License is distributed on an "AS IS" BASIS,
|
|
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
* See the License for the specific language governing permissions and
|
|
* limitations under the License.
|
|
*
|
|
* Copyright 2018 Danny Robson <danny@nerdcruft.net>
|
|
*/
|
|
|
|
#ifndef CRUFT_UTIL_THREAD_EVENT_HPP
|
|
#define CRUFT_UTIL_THREAD_EVENT_HPP
|
|
|
|
#include <atomic>
|
|
|
|
namespace util::thread {
|
|
/// a reusable synchronisation object that allows threads to wait until
|
|
/// notify is called.
|
|
///
|
|
/// there is no internal state so it is easy to create races between wait
|
|
/// and notify calls. this makes the class mostly suitable for recurring
|
|
/// events.
|
|
///
|
|
/// the user should ensure no callers are waiting at destruction time
|
|
/// otherwise they may remain blocked indefinitely.
|
|
///
|
|
/// the address of the object is important so it must _never_ be
|
|
/// relocated in any manner if any caller may be waiting. it may be safe
|
|
/// to do so if there are no callers waiting (but the relevant functions
|
|
/// are deleted for safety anyway).
|
|
class event {
|
|
public:
|
|
event ();
|
|
|
|
event (const event&) = delete;
|
|
event (event&&) = delete;
|
|
event& operator= (const event&) = delete;
|
|
event& operator= (event&&) = delete;
|
|
|
|
/// block until notified
|
|
void wait (void);
|
|
|
|
/// wake all threads that are waiting
|
|
int notify (void);
|
|
|
|
/// wait `count' threads that are waiting
|
|
int notify (int count);
|
|
|
|
private:
|
|
alignas (4) std::atomic<int> value;
|
|
};
|
|
}
|
|
|
|
#endif
|
|
|