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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 <type_traits>
#include "mongo/stdx/condition_variable.h"
#include "mongo/stdx/functional.h"
#include "mongo/stdx/mutex.h"
#include "mongo/util/time_support.h"
namespace mongo {
class Date_t;
/**
* An interface for getting the current wall clock time.
*/
class ClockSource {
// We need a type trait to differentiate waitable ptr args from predicates.
//
// This returns true for non-pointers and function pointers
template <typename Pred>
struct CouldBePredicate
: public std::integral_constant<bool,
!std::is_pointer<Pred>::value ||
std::is_function<std::remove_pointer_t<Pred>>::value> {
};
public:
virtual ~ClockSource() = default;
/**
* Returns the minimum time change that the clock can describe.
*/
virtual Milliseconds getPrecision() = 0;
/**
* Returns the current wall clock time, as defined by this source.
*/
virtual Date_t now() = 0;
/**
* Schedules "action" to run sometime after this clock source reaches "when".
*
* Returns InternalError if this clock source does not implement setAlarm. May also
* return ShutdownInProgress during shutdown. Other errors are also allowed.
*/
virtual Status setAlarm(Date_t when, stdx::function<void()> action) {
return {ErrorCodes::InternalError, "This clock source does not implement setAlarm."};
}
/**
* Returns true if this clock source (loosely) tracks the OS clock used for things
* like condition_variable::wait_until. Virtualized clocks used for testing return
* false here, and should provide an implementation for setAlarm, above.
*/
bool tracksSystemClock() const {
return _tracksSystemClock;
}
/**
* Like cv.wait_until(m, deadline), but uses this ClockSource instead of
* stdx::chrono::system_clock to measure the passage of time.
*/
stdx::cv_status waitForConditionUntil(stdx::condition_variable& cv,
stdx::unique_lock<stdx::mutex>& m,
Date_t deadline,
Waitable* waitable = nullptr);
/**
* Like cv.wait_until(m, deadline, pred), but uses this ClockSource instead of
* stdx::chrono::system_clock to measure the passage of time.
*/
template <typename Pred, std::enable_if_t<CouldBePredicate<Pred>::value, int> = 0>
bool waitForConditionUntil(stdx::condition_variable& cv,
stdx::unique_lock<stdx::mutex>& m,
Date_t deadline,
const Pred& pred,
Waitable* waitable = nullptr) {
while (!pred()) {
if (waitForConditionUntil(cv, m, deadline, waitable) == stdx::cv_status::timeout) {
return pred();
}
}
return true;
}
/**
* Like cv.wait_for(m, duration, pred), but uses this ClockSource instead of
* stdx::chrono::system_clock to measure the passage of time.
*/
template <typename Duration,
typename Pred,
std::enable_if_t<CouldBePredicate<Pred>::value, int> = 0>
bool waitForConditionFor(stdx::condition_variable& cv,
stdx::unique_lock<stdx::mutex>& m,
Duration duration,
const Pred& pred,
Waitable* waitable = nullptr) {
return waitForConditionUntil(cv, m, now() + duration, pred, waitable);
}
protected:
bool _tracksSystemClock = true;
};
} // namespace mongo
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