82 lines
2.8 KiB
C++
82 lines
2.8 KiB
C++
// Copyright 2019 The MediaPipe Authors.
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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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#ifndef MEDIAPIPE_FRAMEWORK_TOOL_SIMULATION_CLOCK_H_
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#define MEDIAPIPE_FRAMEWORK_TOOL_SIMULATION_CLOCK_H_
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#include <map>
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#include <set>
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#include "absl/base/thread_annotations.h"
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#include "absl/synchronization/mutex.h"
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#include "absl/time/time.h"
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#include "mediapipe/framework/deps/clock.h"
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namespace mediapipe {
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// A Clock that simulates the passage of time as quickly as possible.
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// Parallel threads can call Sleep() and be woken in the proper order.
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// Simulated time can be advanced by calling SleepUntil for the desired
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// clock time. Clock time does not advance until all woken threads have
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// finished or gone back to sleep.
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//
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// In case multiple threads are scheduled to wake at the same time, they
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// wake in the order in which they called Sleep(). No thread is permitted
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// to continue until all earlier threads have finished or entered Sleep.
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// The result is a single well-defined order of events. Any desired
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// order of events can be defined by adjusting the precise sleep times.
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class SimulationClock : public mediapipe::Clock {
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public:
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SimulationClock() {}
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~SimulationClock() override;
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// Returns the simulated time.
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absl::Time TimeNow() override;
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// Sleeps until the specified duration has elapsed according to this clock.
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void Sleep(absl::Duration d) override;
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// Sleeps until the specifed wakeup_time.
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void SleepUntil(absl::Time wakeup_time) override;
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// Informs this clock that a woken thread has started running.
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void ThreadStart();
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// Informs this clock that a woken thread has finished running.
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void ThreadFinish();
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protected:
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// Queue up wake up waiter.
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void SleepInternal(absl::Time wakeup_time)
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ABSL_EXCLUSIVE_LOCKS_REQUIRED(time_mutex_);
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// Advances to the next wake up time if no related threads are running.
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void TryAdvanceTime() ABSL_EXCLUSIVE_LOCKS_REQUIRED(time_mutex_);
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// Represents a thread blocked in SleepUntil.
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struct Waiter {
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bool sleeping = true;
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absl::CondVar cond;
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};
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protected:
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absl::Mutex time_mutex_;
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absl::Time time_ ABSL_GUARDED_BY(time_mutex_);
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std::multimap<absl::Time, Waiter*> waiters_ ABSL_GUARDED_BY(time_mutex_);
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int num_running_ ABSL_GUARDED_BY(time_mutex_) = 0;
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};
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} // namespace mediapipe
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#endif // MEDIAPIPE_FRAMEWORK_TOOL_SIMULATION_CLOCK_H_
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