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// Copyright 2022 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef THIRD_PARTY_WEBRTC_OVERRIDES_COALESCED_TASKS_H_
#define THIRD_PARTY_WEBRTC_OVERRIDES_COALESCED_TASKS_H_
#include <cstdint>
#include <map>
#include <optional>
#include <set>
#include "base/functional/callback.h"
#include "base/synchronization/lock.h"
#include "base/thread_annotations.h"
#include "base/time/time.h"
#include "third_party/abseil-cpp/absl/functional/any_invocable.h"
#include "third_party/webrtc/rtc_base/system/rtc_export.h"
namespace blink {
// A thread-safe class for storing queued tasks until they are scheduled to run.
// This is useful for implementing metronome-like task queues where tasks are
// coalesced onto metronome ticks but the tasks still need to execute in order.
class RTC_EXPORT CoalescedTasks {
public:
typedef base::RepeatingCallback<std::optional<base::TimeTicks>()>
PrepareRunTaskCallback;
typedef base::RepeatingCallback<void(std::optional<base::TimeTicks>)>
FinalizeRunTaskCallback;
~CoalescedTasks();
// Queue a delayed tasks that can later be run with RunScheduledTasks().
// `task_time` is the original run time of `task` and `scheduled_time` is the
// `task_time` but snapped to the next time that scheduled tasks may run.
// If true is returned, this is the first task that has been queued to run on
// `scheduled_time`. In this case, the caller is responsible for scheduling a
// call to RunScheduledTasks() at `scheduled_time`.
bool QueueDelayedTask(base::TimeTicks task_time,
absl::AnyInvocable<void() &&> task,
base::TimeTicks scheduled_time);
// Run all queued tasks up to and including `scheduled_time`. If multiple
// tasks were queued onto the same `scheduled_time` they will execute in order
// of their `task_time`. Optionally, the prepare/finalize callbacks can be
// used to sample task run times by being called before/after each task.
void RunScheduledTasks(base::TimeTicks scheduled_time,
PrepareRunTaskCallback prepare_run_task_callback =
PrepareRunTaskCallback(),
FinalizeRunTaskCallback finalize_run_task_callback =
FinalizeRunTaskCallback());
// Clear the queue, deleting all tasks on the calling sequence without running
// them.
void Clear();
// Returns true if there are no stored tasks.
bool Empty() const {
base::AutoLock lock(lock_);
return delayed_tasks_.empty();
}
private:
// The (time_ticks, unique_id) pair allows multiple tasks to be scheduled on
// the same `time_ticks`.
struct RTC_EXPORT UniqueTimeTicks {
UniqueTimeTicks(base::TimeTicks time_ticks, uint64_t unique_id);
// Used for std::map<> ordering.
bool operator<(const UniqueTimeTicks& other) const;
base::TimeTicks time_ticks;
uint64_t unique_id;
};
mutable base::Lock lock_;
std::set<base::TimeTicks> scheduled_ticks_ GUARDED_BY(lock_);
uint64_t next_unique_id_ GUARDED_BY(lock_) = 0;
std::map<UniqueTimeTicks, absl::AnyInvocable<void() &&>> delayed_tasks_
GUARDED_BY(lock_);
};
} // namespace blink
#endif // THIRD_PARTY_WEBRTC_OVERRIDES_COALESCED_TASKS_H_
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