111 lines
3.7 KiB
C++
111 lines
3.7 KiB
C++
/*
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* Copyright (c) Facebook, Inc. and its affiliates.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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#include <chrono>
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#include <folly/concurrency/UnboundedQueue.h>
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#include <folly/executors/DrivableExecutor.h>
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namespace folly {
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/*
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* A DrivableExecutor can be driven via its drive() method or its driveUntil()
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* that drives until some time point.
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*/
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class TimedDrivableExecutor : public DrivableExecutor {
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public:
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~TimedDrivableExecutor() noexcept {
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// Drain on destruction so that if work is added here during the collapse
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// of a future train, it will propagate.
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drain();
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}
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/// Implements DrivableExecutor
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void drive() noexcept override;
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// Make progress if there is work to do and return true. Otherwise return
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// false.
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bool try_drive() noexcept {
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return try_wait() && run() > 0;
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}
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// Make progress on this Executor's work. Acts as drive, except it will only
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// wait for a period of timeout for work to be enqueued. If no work is
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// enqueued by that point, it will return.
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template <typename Rep, typename Period>
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bool try_drive_for(
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const std::chrono::duration<Rep, Period>& timeout) noexcept {
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return try_wait_for(timeout) && run() > 0;
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}
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// Make progress on this Executor's work. Acts as drive, except it will only
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// wait until deadline for work to be enqueued. If no work is enqueued by
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// that point, it will return.
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template <typename Clock, typename Duration>
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bool try_drive_until(
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const std::chrono::time_point<Clock, Duration>& deadline) noexcept {
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return try_wait_until(deadline) && run() > 0;
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}
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void add(Func) override;
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/// Do work. Returns the number of functions that were executed (maybe 0).
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/// Non-blocking, in the sense that we don't wait for work (we can't
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/// control whether one of the functions blocks).
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/// This is stable, it will not chase an ever-increasing tail of work.
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/// This also means, there may be more work available to perform at the
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/// moment that this returns.
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size_t run() noexcept;
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// Do work until there is no more work to do.
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// Returns the number of functions that were executed (maybe 0).
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// Unlike run, this method is not stable. It will chase an infinite tail of
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// work so should be used with care.
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// There will be no work available to perform at the moment that this
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// returns.
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size_t drain() noexcept;
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/// Wait for work to do.
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void wait() noexcept;
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// Return true if there is work to do, false otherwise
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bool try_wait() noexcept {
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return func_ || queue_.try_dequeue(func_);
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}
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/// Wait for work to do or for a period of timeout, whichever is sooner.
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template <typename Rep, typename Period>
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bool try_wait_for(
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const std::chrono::duration<Rep, Period>& timeout) noexcept {
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return func_ || queue_.try_dequeue_for(func_, timeout);
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}
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/// Wait for work to do or until deadline passes, whichever is sooner.
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template <typename Clock, typename Duration>
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bool try_wait_until(
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const std::chrono::time_point<Clock, Duration>& deadline) noexcept {
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return func_ || queue_.try_dequeue_until(func_, deadline);
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}
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private:
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UMPSCQueue<Func, true> queue_;
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Func func_;
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};
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} // namespace folly
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