85 lines
2.3 KiB
C++
85 lines
2.3 KiB
C++
/*
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* Copyright (C) 2015 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef TNT_UTILS_CYCLIC_BARRIER_H
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#define TNT_UTILS_CYCLIC_BARRIER_H
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#include <stddef.h>
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// note: we use our version of mutex/condition to keep this public header STL free
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#include <utils/Condition.h>
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#include <utils/Mutex.h>
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namespace utils {
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/**
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* A cyclic barrier is used to synchronize several threads to a particular execution point.
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*
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* Threads entering the barrier are halted until all threads reach the barrier.
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*
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* @see CountDownLatch
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*/
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class CyclicBarrier {
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public:
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/**
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* Creates a cyclic barrier with a specified number of threads to synchronize. The minimum
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* useful value is 2. A value of 0 is invalid and is silently changed to 1.
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* @param num_threads Number of threads to synchronize.
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*/
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explicit CyclicBarrier(size_t num_threads) noexcept;
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/**
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* @return The number of thread that are synchronized.
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*/
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size_t getThreadCount() const noexcept;
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/**
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* @return Number of threads currently waiting on the barrier.
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*/
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size_t getWaitingThreadCount() const noexcept;
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/**
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* Blocks until getThreadCount()-1 other threads reach await().
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*/
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void await() noexcept;
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/**
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* Resets the cyclic barrier to its original state and releases all waiting threads.
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*/
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void reset() noexcept;
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CyclicBarrier() = delete;
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CyclicBarrier(const CyclicBarrier&) = delete;
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CyclicBarrier& operator=(const CyclicBarrier&) = delete;
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private:
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enum class State {
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TRAP, RELEASE
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};
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const size_t m_num_threads;
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mutable Mutex m_lock;
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mutable Condition m_cv;
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State m_state = State::TRAP;
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size_t m_trapped_threads = 0;
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size_t m_released_threads = 0;
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};
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} // namespace utils
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#endif // TNT_UTILS_CYCLIC_BARRIER_H
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