54 lines
1.7 KiB
C++
54 lines
1.7 KiB
C++
|
// 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"
|
||
|
|
|
||
|
|
namespace absl {
|
||
|
|
|
||
|
|
// 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.
|
||
|
|
}
|
||
|
|
|
||
|
|
} // namespace absl
|