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// Copyright 2023 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
//
// 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.
#include "absl/synchronization/internal/stdcpp_waiter.h"
#ifdef ABSL_INTERNAL_HAVE_STDCPP_WAITER
#include <chrono> // NOLINT(build/c++11)
#include <condition_variable> // NOLINT(build/c++11)
#include <mutex> // NOLINT(build/c++11)
#include "absl/base/config.h"
#include "absl/base/internal/raw_logging.h"
#include "absl/base/internal/thread_identity.h"
#include "absl/base/optimization.h"
#include "absl/synchronization/internal/kernel_timeout.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace synchronization_internal {
#ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
constexpr char StdcppWaiter::kName[];
#endif
StdcppWaiter::StdcppWaiter() : waiter_count_(0), wakeup_count_(0) {}
bool StdcppWaiter::Wait(KernelTimeout t) {
std::unique_lock<std::mutex> lock(mu_);
++waiter_count_;
// Loop until we find a wakeup to consume or timeout.
// Note that, since the thread ticker is just reset, we don't need to check
// whether the thread is idle on the very first pass of the loop.
bool first_pass = true;
while (wakeup_count_ == 0) {
if (!first_pass) MaybeBecomeIdle();
// No wakeups available, time to wait.
if (!t.has_timeout()) {
cv_.wait(lock);
} else {
auto wait_result = t.SupportsSteadyClock() && t.is_relative_timeout()
? cv_.wait_for(lock, t.ToChronoDuration())
: cv_.wait_until(lock, t.ToChronoTimePoint());
if (wait_result == std::cv_status::timeout) {
--waiter_count_;
return false;
}
}
first_pass = false;
}
// Consume a wakeup and we're done.
--wakeup_count_;
--waiter_count_;
return true;
}
void StdcppWaiter::Post() {
std::lock_guard<std::mutex> lock(mu_);
++wakeup_count_;
InternalCondVarPoke();
}
void StdcppWaiter::Poke() {
std::lock_guard<std::mutex> lock(mu_);
InternalCondVarPoke();
}
void StdcppWaiter::InternalCondVarPoke() {
if (waiter_count_ != 0) {
cv_.notify_one();
}
}
} // namespace synchronization_internal
ABSL_NAMESPACE_END
} // namespace absl
#endif // ABSL_INTERNAL_HAVE_STDCPP_WAITER
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