// 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

//

//      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.

// This file is a no-op if the required LowLevelAlloc support is missing.

#include "absl/base/internal/low_level_alloc.h"

#ifndef ABSL_LOW_LEVEL_ALLOC_MISSING

#include "absl/synchronization/internal/per_thread_sem.h"

#include <atomic>

#include "absl/base/attributes.h"

#include "absl/base/internal/thread_identity.h"

#include "absl/synchronization/internal/waiter.h"

namespace absl {

ABSL_NAMESPACE_BEGIN

namespace synchronization_internal {

void PerThreadSem::SetThreadBlockedCounter(std::atomic<int> *counter) {

  base_internal::ThreadIdentity *identity;

  identity = GetOrCreateCurrentThreadIdentity();

  identity->blocked_count_ptr = counter;

}

std::atomic<int> *PerThreadSem::GetThreadBlockedCounter() {

  base_internal::ThreadIdentity *identity;

  identity = GetOrCreateCurrentThreadIdentity();

  return identity->blocked_count_ptr;

}

void PerThreadSem::Tick(base_internal::ThreadIdentity *identity) {

  const int ticker =

      identity->ticker.fetch_add(1, std::memory_order_relaxed) + 1;

  const int wait_start = identity->wait_start.load(std::memory_order_relaxed);

  const bool is_idle = identity->is_idle.load(std::memory_order_relaxed);

  if (wait_start && (ticker - wait_start > Waiter::kIdlePeriods) && !is_idle) {

    // Wakeup the waiting thread since it is time for it to become idle.

    ABSL_INTERNAL_C_SYMBOL(AbslInternalPerThreadSemPoke)(identity);

  }

}

}  // namespace synchronization_internal

ABSL_NAMESPACE_END

}  // namespace absl

extern "C" {

ABSL_ATTRIBUTE_WEAK void ABSL_INTERNAL_C_SYMBOL(AbslInternalPerThreadSemInit)(

    absl::base_internal::ThreadIdentity *identity) {

  new (absl::synchronization_internal::Waiter::GetWaiter(identity))

      absl::synchronization_internal::Waiter();

}

ABSL_ATTRIBUTE_WEAK void ABSL_INTERNAL_C_SYMBOL(AbslInternalPerThreadSemPost)(

    absl::base_internal::ThreadIdentity *identity) {

  absl::synchronization_internal::Waiter::GetWaiter(identity)->Post();

}

ABSL_ATTRIBUTE_WEAK void ABSL_INTERNAL_C_SYMBOL(AbslInternalPerThreadSemPoke)(

    absl::base_internal::ThreadIdentity *identity) {

  absl::synchronization_internal::Waiter::GetWaiter(identity)->Poke();

}

ABSL_ATTRIBUTE_WEAK bool ABSL_INTERNAL_C_SYMBOL(AbslInternalPerThreadSemWait)(

    absl::synchronization_internal::KernelTimeout t) {

  bool timeout = false;

  absl::base_internal::ThreadIdentity *identity;

  identity = absl::synchronization_internal::GetOrCreateCurrentThreadIdentity();

  // Ensure wait_start != 0.

  int ticker = identity->ticker.load(std::memory_order_relaxed);

  identity->wait_start.store(ticker ? ticker : 1, std::memory_order_relaxed);

  identity->is_idle.store(false, std::memory_order_relaxed);

  if (identity->blocked_count_ptr != nullptr) {

    // Increment count of threads blocked in a given thread pool.

    identity->blocked_count_ptr->fetch_add(1, std::memory_order_relaxed);

  }

  timeout =

      !absl::synchronization_internal::Waiter::GetWaiter(identity)->Wait(t);

  if (identity->blocked_count_ptr != nullptr) {

    identity->blocked_count_ptr->fetch_sub(1, std::memory_order_relaxed);

  }

  identity->is_idle.store(false, std::memory_order_relaxed);

  identity->wait_start.store(0, std::memory_order_relaxed);

  return !timeout;

}

}  // extern "C"

#endif  // ABSL_LOW_LEVEL_ALLOC_MISSING