67 lines
2 KiB
C++
67 lines
2 KiB
C++
/*
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* SPDX-License-Identifier: GPL-2.0-or-later
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*
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* Copyright (C) 2021-2023 The DOSBox Staging Team
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*/
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#include <condition_variable>
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#include <mutex>
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/*
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* A Semaphore class for synchronizing threads.
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*
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* This Semaphore implementation uses a count to represent the number of
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* available resources, along with a mutex and a condition variable to
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* handle synchronization between threads.
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*/
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class Semaphore {
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public:
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/**
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* Constructs a new Semaphore.
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*
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* @param count The initial count. Defaults to 0.
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*/
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Semaphore(const int initial_count = 0) : count(initial_count) {}
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/**
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* Decrements (acquires) the semaphore. If the count is 0, this will
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* block until another thread calls notify().
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*/
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void wait()
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{
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std::unique_lock lock(mtx);
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while (count == 0) {
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cv.wait(lock);
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}
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--count;
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}
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/**
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* Increments (releases) the semaphore, potentially unblocking a thread
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* currently waiting on wait().
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*/
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void notify() {
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std::unique_lock lock(mtx);
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++count;
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cv.notify_one();
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}
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private:
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std::mutex mtx = {}; // Mutex to protect count.
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std::condition_variable cv = {}; // Condition variable for the count.
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int count = 0; // Current count.
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};
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