stop_watch.h

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/*
 * Copyright 2016-present Facebook, Inc.
 *
 * 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.
 */

#pragma once

#include <chrono>
#include <stdexcept>
#include <utility>

#include <folly/Chrono.h>
#include <folly/portability/Time.h>

namespace folly {

using monotonic_clock = std::chrono::steady_clock;

template <typename Clock, typename Duration = typename Clock::duration>
struct custom_stop_watch {
  using clock_type = Clock;
  using duration = Duration;
  using time_point = std::chrono::time_point<clock_type, duration>;

  static_assert(
      std::ratio_less_equal<
          typename clock_type::duration::period,
          typename duration::period>::value,
      "clock must be at least as precise as the requested duration");

  static_assert(
      Clock::is_steady,
      "only monotonic clocks should be used to track time intervals");

  custom_stop_watch() : checkpoint_(clock_type::now()) {}

  explicit custom_stop_watch(typename clock_type::time_point checkpoint)
      : checkpoint_(std::move(checkpoint)) {}

  void reset() {
    checkpoint_ = clock_type::now();
  }

  duration elapsed() const {
    return std::chrono::duration_cast<duration>(
        clock_type::now() - checkpoint_);
  }

  template <typename UDuration>
  bool elapsed(UDuration&& amount) const {
    return clock_type::now() - checkpoint_ >= amount;
  }

  duration lap() {
    auto lastCheckpoint = checkpoint_;

    checkpoint_ = clock_type::now();

    return std::chrono::duration_cast<duration>(checkpoint_ - lastCheckpoint);
  }

  template <typename UDuration>
  bool lap(UDuration&& amount) {
    auto now = clock_type::now();

    if (now - checkpoint_ < amount) {
      return false;
    }

    checkpoint_ = now;
    return true;
  }

  typename clock_type::time_point getCheckpoint() const {
    return checkpoint_;
  }

 private:
  typename clock_type::time_point checkpoint_;
};

template <typename Duration = folly::chrono::coarse_steady_clock::duration>
using coarse_stop_watch =
    custom_stop_watch<folly::chrono::coarse_steady_clock, Duration>;

template <typename Duration = std::chrono::steady_clock::duration>
using stop_watch = custom_stop_watch<std::chrono::steady_clock, Duration>;
} // namespace folly