mirror of
https://github.com/kidfromjupiter/nearby.git
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74 lines
2.4 KiB
C++
74 lines
2.4 KiB
C++
// Copyright 2020 Google LLC
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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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// https://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 PLATFORM_IMPL_G3_COUNT_DOWN_LATCH_H_
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#define PLATFORM_IMPL_G3_COUNT_DOWN_LATCH_H_
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#include "absl/base/thread_annotations.h"
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#include "absl/synchronization/mutex.h"
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#include "absl/time/clock.h"
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#include "platform/api/count_down_latch.h"
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namespace location {
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namespace nearby {
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namespace g3 {
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// A synchronization aid that allows one or more threads to wait until a set of
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// operations being performed in other threads completes.
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//
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// https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/CountDownLatch.html
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class CountDownLatch final : public api::CountDownLatch {
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public:
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explicit CountDownLatch(int count) : count_(count) {}
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CountDownLatch(const CountDownLatch&) = delete;
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CountDownLatch& operator=(const CountDownLatch&) = delete;
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CountDownLatch(CountDownLatch&&) = delete;
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CountDownLatch& operator=(CountDownLatch&&) = delete;
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ExceptionOr<bool> Await(absl::Duration timeout) override {
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absl::MutexLock lock(&mutex_);
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absl::Time deadline = absl::Now() + timeout;
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while (count_ > 0) {
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if (cond_.WaitWithDeadline(&mutex_, deadline)) {
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return ExceptionOr<bool>(false);
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}
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}
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return ExceptionOr<bool>(true);
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}
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Exception Await() override {
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absl::MutexLock lock(&mutex_);
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while (count_ > 0) {
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cond_.Wait(&mutex_);
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}
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return {Exception::kSuccess};
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}
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void CountDown() override {
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absl::MutexLock lock(&mutex_);
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if (count_ > 0 && --count_ == 0) {
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cond_.SignalAll();
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}
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}
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private:
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absl::Mutex mutex_; // Mutex to be used with cond_.Wait...() method family.
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absl::CondVar cond_; // Condition to synchronize up to N waiting threads.
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int count_
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ABSL_GUARDED_BY(mutex_); // When zero, latch should release all waiters.
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};
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} // namespace g3
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} // namespace nearby
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} // namespace location
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#endif // PLATFORM_IMPL_G3_COUNT_DOWN_LATCH_H_
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