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// Copyright 2017 The Abseil Authors.
//
// 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
//
// http://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.
#include "absl/synchronization/blocking_counter.h"
#include "absl/base/internal/raw_logging.h"
namespace absl {
inline namespace lts_2018_06_20 {
// Return whether int *arg is zero.
static bool IsZero(void *arg) {
return 0 == *reinterpret_cast<int *>(arg);
}
bool BlockingCounter::DecrementCount() {
MutexLock l(&lock_);
count_--;
if (count_ < 0) {
ABSL_RAW_LOG(
FATAL,
"BlockingCounter::DecrementCount() called too many times. count=%d",
count_);
}
return count_ == 0;
}
void BlockingCounter::Wait() {
MutexLock l(&this->lock_);
ABSL_RAW_CHECK(count_ >= 0, "BlockingCounter underflow");
// only one thread may call Wait(). To support more than one thread,
// implement a counter num_to_exit, like in the Barrier class.
ABSL_RAW_CHECK(num_waiting_ == 0, "multiple threads called Wait()");
num_waiting_++;
this->lock_.Await(Condition(IsZero, &this->count_));
// At this point, We know that all threads executing DecrementCount have
// released the lock, and so will not touch this object again.
// Therefore, the thread calling this method is free to delete the object
// after we return from this method.
}
} // inline namespace lts_2018_06_20
} // namespace absl
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