my_semaphore.h

// MIT License

// Copyright (c) 2021 CyanHill

// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:

// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

#pragma once

#include <cassert>
#include <chrono>
#include <condition_variable>
#include <cstddef>
#include <limits>
#include <mutex>

namespace cyan {

template <std::ptrdiff_t least_max_value = std::numeric_limits<std::ptrdiff_t>::max()>
class counting_semaphore {
 public:
  static constexpr std::ptrdiff_t max() noexcept {
    static_assert(least_max_value >= 0, "least_max_value shall be non-negative");
    return least_max_value;
  }

  explicit counting_semaphore(std::ptrdiff_t desired) : counter_(desired) { assert(desired >= 0 && desired <= max()); }

  ~counting_semaphore() = default;

  counting_semaphore(const counting_semaphore&) = delete;
  counting_semaphore& operator=(const counting_semaphore&) = delete;

  void release(std::ptrdiff_t update = 1) {
    {
      std::lock_guard<decltype(mutex_)> lock{mutex_};
      assert(update >= 0 && update <= max() - counter_);
      counter_ += update;
      if (counter_ <= 0) {
        return;
      }
    }  // avoid hurry up and wait
    cv_.notify_all();
  }

  void acquire() {
    std::unique_lock<decltype(mutex_)> lock{mutex_};
    cv_.wait(lock, [&]() { return counter_ > 0; });
    --counter_;
  }

  bool try_acquire() noexcept {
    std::unique_lock<decltype(mutex_)> lock{mutex_};
    if (counter_ <= 0) {
      return false;
    }
    --counter_;
    return true;
  }

  template <class Rep, class Period>
  bool try_acquire_for(const std::chrono::duration<Rep, Period>& rel_time) {
    const auto timeout_time = std::chrono::steady_clock::now() + rel_time;
    return do_try_acquire_wait(timeout_time);
  }

  template <class Clock, class Duration>
  bool try_acquire_until(const std::chrono::time_point<Clock, Duration>& abs_time) {
    return do_try_acquire_wait(abs_time);
  }

 private:
  template <typename Clock, typename Duration>
  bool do_try_acquire_wait(const std::chrono::time_point<Clock, Duration>& timeout_time) {
    std::unique_lock<decltype(mutex_)> lock{mutex_};
    if (!cv_.wait_until(lock, timeout_time, [&]() { return counter_ > 0; })) {
      return false;
    }
    --counter_;
    return true;
  }

 private:
  std::ptrdiff_t counter_{0};
  std::condition_variable cv_;
  std::mutex mutex_;
};

using binary_semaphore = counting_semaphore<1>;

}  // namespace cyan