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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 "mongo/stdx/condition_variable.h"
#include "mongo/stdx/mutex.h"
#include "mongo/util/clock_source.h"
#include "mongo/util/time_support.h"
namespace mongo {
/**
* Waitable is a lightweight type that can be used with stdx::condition_variable and can do other
* work while the condvar 'waits'.
*
* It handles this dance by using a special hook that condvar provides to register itself (as a
* notifyable, which it inherits from) during calls to wait. Then, rather than actually waiting on
* the condvar, it invokes its run/run_until methods.
*
* The current implementer of Waitable is the transport layer baton type, which performs delayed IO
* when it would otherwise block.
*/
class Waitable : public Notifyable {
public:
static void wait(Waitable* waitable,
ClockSource* clkSource,
stdx::condition_variable& cv,
stdx::unique_lock<stdx::mutex>& lk) {
if (waitable) {
cv._runWithNotifyable(*waitable, [&]() noexcept {
lk.unlock();
waitable->run(clkSource);
lk.lock();
});
} else {
cv.wait(lk);
}
}
template <typename Predicate>
static void wait(Waitable* waitable,
ClockSource* clkSource,
stdx::condition_variable& cv,
stdx::unique_lock<stdx::mutex>& lk,
Predicate pred) {
while (!pred()) {
wait(waitable, clkSource, cv, lk);
}
}
static stdx::cv_status wait_until(
Waitable* waitable,
ClockSource* clkSource,
stdx::condition_variable& cv,
stdx::unique_lock<stdx::mutex>& lk,
const stdx::chrono::time_point<stdx::chrono::system_clock>& timeout_time) {
if (waitable) {
auto rval = stdx::cv_status::no_timeout;
cv._runWithNotifyable(*waitable, [&]() noexcept {
lk.unlock();
if (waitable->run_until(clkSource, Date_t(timeout_time)) == TimeoutState::Timeout) {
rval = stdx::cv_status::timeout;
}
lk.lock();
});
return rval;
} else {
return cv.wait_until(lk, timeout_time);
}
}
template <typename Predicate>
static bool wait_until(Waitable* waitable,
ClockSource* clkSource,
stdx::condition_variable& cv,
stdx::unique_lock<stdx::mutex>& lk,
const stdx::chrono::time_point<stdx::chrono::system_clock>& timeout_time,
Predicate pred) {
while (!pred()) {
if (wait_until(waitable, clkSource, cv, lk, timeout_time) == stdx::cv_status::timeout) {
return pred();
}
}
return true;
}
protected:
~Waitable() noexcept {}
enum class TimeoutState {
NoTimeout,
Timeout,
};
/**
* Run some amount of work. The intention is that this function perform work until it's
* possible that the surrounding condvar clause could have finished.
*
* Note that like regular condvar.wait, this allows implementers the flexibility to possibly
* return early.
*
* We take a clock source here to allow for synthetic timeouts.
*/
virtual void run(ClockSource* clkSource) noexcept = 0;
/**
* Like run, but only until the passed deadline has passed.
*/
virtual TimeoutState run_until(ClockSource* clkSource, Date_t deadline) noexcept = 0;
};
} // namespace mongo
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