// Copyright 2014 The Crashpad Authors. All rights reserved.
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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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#ifndef CRASHPAD_UTIL_SYNCHRONIZATION_SEMAPHORE_H_
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#define CRASHPAD_UTIL_SYNCHRONIZATION_SEMAPHORE_H_
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#include <limits>
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#include "build/build_config.h"
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#if defined(OS_APPLE)
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#include <dispatch/dispatch.h>
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#elif defined(OS_WIN)
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#include <windows.h>
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#elif defined(OS_ANDROID)
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#include <condition_variable>
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#include <mutex>
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#else
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#include <semaphore.h>
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#endif
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namespace crashpad {
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//! \brief An anonymous in-process counting sempahore.
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class Semaphore {
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public:
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//! \brief A TimedWait() argument that causes an indefinite wait.
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static constexpr double kIndefiniteWait =
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std::numeric_limits<double>::infinity();
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//! \brief Initializes the semaphore.
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//!
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//! \param[in] value The initial value of the semaphore.
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//!
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//! If the semaphore cannot be created, execution is terminated.
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explicit Semaphore(int value);
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~Semaphore();
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//! \brief Performs the wait (or “procure”) operation on the semaphore.
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//!
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//! Atomically decrements the value of the semaphore by 1. If the new value is
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//! negative, this function blocks and will not return until the semaphore’s
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//! value is incremented to 0 by Signal().
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//!
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//! \sa TimedWait()
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void Wait();
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//! \brief Performs a timed wait (or “procure”) operation on the semaphore.
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//!
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//! \param[in] seconds The maximum number of seconds to wait for the operation
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//! to complete. If \a seconds is #kIndefiniteWait, this method behaves as
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//! Wait(), and will not time out.
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//!
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//! \return `false` if the wait timed out, `true` otherwise.
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//!
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//! This method is simlar to Wait(), except that the amount of time that it
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//! blocks is limited.
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bool TimedWait(double seconds);
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//! \brief Performs the signal (or “post”) operation on the semaphore.
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//!
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//! Atomically increments the value of the semaphore by 1. If the new value is
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//! 0, a caller blocked in Wait() will be awakened.
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void Signal();
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private:
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#if defined(OS_APPLE)
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dispatch_semaphore_t semaphore_;
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#elif defined(OS_WIN)
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HANDLE semaphore_;
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#elif defined(OS_ANDROID)
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std::condition_variable cv_;
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std::mutex mutex_;
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int value_;
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#else
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sem_t semaphore_;
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#endif
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};
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} // namespace crashpad
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#endif // CRASHPAD_UTIL_SYNCHRONIZATION_SEMAPHORE_H_
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