/*

* Copyright 2016 WebAssembly Community Group participants

*

* 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.

*/

#ifndef wasm_support_timing_h

#define wasm_support_timing_h

#include <chrono>

#include <utility>

namespace wasm {

// A utility for measuring time between readings as well as total elapsed time.

// The timer starts upon construction, but can be restarted.

class Timer {

std::chrono::steady_clock::time_point startTime;

std::chrono::steady_clock::time_point lastTime;

public:

Timer() { restart(); }

// Resets the timer's start and last times.

void restart() {

auto now = std::chrono::steady_clock::now();

lastTime = startTime = now;

}

// The time since the timer was started.

double totalElapsed() {

auto now = std::chrono::steady_clock::now();

auto sinceStart = std::chrono::duration<double>(now - startTime).count();

return sinceStart;

}

// The time since the last `lastElapsed` measurement, if any, or since the

// timer started.

double lastElapsed() {

auto now = std::chrono::steady_clock::now();

auto sinceLast = std::chrono::duration<double>(now - lastTime).count();

lastTime = now;

return sinceLast;

}

// The time elapsed since the last measurement and the total elapsed time.

std::pair<double, double> elapsed() {

auto now = std::chrono::steady_clock::now();

auto sinceLast = std::chrono::duration<double>(now - lastTime).count();

auto sinceStart = std::chrono::duration<double>(now - startTime).count();

lastTime = now;

return {sinceLast, sinceStart};

}

};

} // namespace wasm

#endif // wasm_support_timing_h