58 lines
1.8 KiB
C++
58 lines
1.8 KiB
C++
// Copyright 2017 The Abseil Authors.
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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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#include "absl/synchronization/blocking_counter.h"
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#include "absl/base/internal/raw_logging.h"
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namespace absl {
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ABSL_NAMESPACE_BEGIN
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// Return whether int *arg is zero.
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static bool IsZero(void *arg) {
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return 0 == *reinterpret_cast<int *>(arg);
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}
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bool BlockingCounter::DecrementCount() {
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MutexLock l(&lock_);
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count_--;
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if (count_ < 0) {
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ABSL_RAW_LOG(
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FATAL,
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"BlockingCounter::DecrementCount() called too many times. count=%d",
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count_);
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}
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return count_ == 0;
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}
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void BlockingCounter::Wait() {
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MutexLock l(&this->lock_);
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ABSL_RAW_CHECK(count_ >= 0, "BlockingCounter underflow");
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// only one thread may call Wait(). To support more than one thread,
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// implement a counter num_to_exit, like in the Barrier class.
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ABSL_RAW_CHECK(num_waiting_ == 0, "multiple threads called Wait()");
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num_waiting_++;
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this->lock_.Await(Condition(IsZero, &this->count_));
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// At this point, We know that all threads executing DecrementCount have
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// released the lock, and so will not touch this object again.
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// Therefore, the thread calling this method is free to delete the object
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// after we return from this method.
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}
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ABSL_NAMESPACE_END
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} // namespace absl
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