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/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include <algorithm>
#include <cstdint>
namespace mongo {
/**
* Interface for objects generating ticks that roughly represents the passage of time.
*/
class TickSource {
public:
using Tick = int64_t;
virtual ~TickSource() = default;
/**
* Returns the current tick count from this source.
*/
virtual Tick getTicks() = 0;
/**
* Returns the conversion ratio from ticks to seconds.
*/
virtual Tick getTicksPerSecond() = 0;
/**
* Convert the given tick count into a duration, specified by the type parameter.
*
* e.g. tickSource->ticksTo<Milliseconds>(ticks);
*/
template <typename D>
D ticksTo(Tick ticks) {
// The number of ticks per 1 duration unit.
double ticksPerD =
static_cast<double>(getTicksPerSecond()) * D::period::num / D::period::den;
return D(static_cast<int64_t>(ticks / ticksPerD));
}
/**
* Measures the length of the span from the start tick to the end tick and returns the result
* using duration type D.
* If the start tick is after (greater than) the end tick, returns a duration equivalent to 0
* ticks.
*
* e.g. tickSource->spanTo<Milliseconds>(start, end);
*/
template <typename D>
D spanTo(Tick start, Tick end) {
return ticksTo<D>(std::max((end - start), Tick{0}));
}
};
} // namespace mongo
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