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// Copyright 2020 Google LLC
//
// 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
//
// https://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.
#ifndef PLATFORM_IMPL_SHARED_COUNT_DOWN_LATCH_H_
#define PLATFORM_IMPL_SHARED_COUNT_DOWN_LATCH_H_
#include "absl/base/thread_annotations.h"
#include "absl/synchronization/mutex.h"
#include "absl/time/clock.h"
#include "platform/api/count_down_latch.h"
namespace location {
namespace nearby {
namespace shared {
// A synchronization aid that allows one or more threads to wait until a set of
// operations being performed in other threads completes.
//
// https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/CountDownLatch.html
class CountDownLatch final : public api::CountDownLatch {
public:
explicit CountDownLatch(int count);
CountDownLatch(const CountDownLatch&) = delete;
CountDownLatch& operator=(const CountDownLatch&) = delete;
CountDownLatch(CountDownLatch&&) = delete;
CountDownLatch& operator=(CountDownLatch&&) = delete;
ExceptionOr<bool> Await(absl::Duration timeout) override;
Exception Await() override;
void CountDown() override;
private:
absl::Mutex mutex_; // Mutex to be used with cond_.Wait...() method family.
absl::CondVar cond_; // Condition to synchronize up to N waiting threads.
int count_
ABSL_GUARDED_BY(mutex_); // When zero, latch should release all waiters.
};
} // namespace shared
} // namespace nearby
} // namespace location
#endif // PLATFORM_IMPL_G3_COUNT_DOWN_LATCH_H_