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// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <stddef.h>
#include <memory>
#include <queue>
#include <vector>
#include "base/macros.h"
#include "base/single_thread_task_runner.h"
#include "base/synchronization/lock.h"
#include "base/test/test_pending_task.h"
#include "base/threading/thread_checker.h"
#include "base/time/time.h"
namespace base {
class Clock;
class TickClock;
// Runs pending tasks in the order of the tasks' post time + delay, and keeps
// track of a mock (virtual) tick clock time that can be fast-forwarded.
// TestMockTimeTaskRunner has the following properties:
// - Methods RunsTasksOnCurrentThread() and Post[Delayed]Task() can be called
// from any thread, but the rest of the methods must be called on the same
// thread the TaskRunner was created on.
// - It allows for reentrancy, in that it handles the running of tasks that in
// turn call back into it (e.g., to post more tasks).
// - Tasks are stored in a priority queue, and executed in the increasing
// order of post time + delay, but ignoring nestability.
// - It does not check for overflow when doing time arithmetic. A sufficient
// condition for preventing overflows is to make sure that the sum of all
// posted task delays and fast-forward increments is still representable by
// a TimeDelta, and that adding this delta to the starting values of Time
// and TickTime is still within their respective range.
// - Tasks aren't guaranteed to be destroyed immediately after they're run.
// This is a slightly more sophisticated version of TestSimpleTaskRunner, in
// that it supports running delayed tasks in the correct temporal order.
class TestMockTimeTaskRunner : public SingleThreadTaskRunner {
// Constructs an instance whose virtual time will start at the Unix epoch, and
// whose time ticks will start at zero.
// Constructs an instance starting at the given virtual time and time ticks.
TestMockTimeTaskRunner(Time start_time, TimeTicks start_ticks);
// Fast-forwards virtual time by |delta|, causing all tasks with a remaining
// delay less than or equal to |delta| to be executed. |delta| must be
// non-negative.
void FastForwardBy(TimeDelta delta);
// Fast-forwards virtual time just until all tasks are executed.
void FastForwardUntilNoTasksRemain();
// Executes all tasks that have no remaining delay. Tasks with a remaining
// delay greater than zero will remain enqueued, and no virtual time will
// elapse.
void RunUntilIdle();
// Clears the queue of pending tasks without running them.
void ClearPendingTasks();
// Returns the current virtual time (initially starting at the Unix epoch).
Time Now() const;
// Returns the current virtual tick time (initially starting at 0).
TimeTicks NowTicks() const;
// Returns a Clock that uses the virtual time of |this| as its time source.
// The returned Clock will hold a reference to |this|.
std::unique_ptr<Clock> GetMockClock() const;
// Returns a TickClock that uses the virtual time ticks of |this| as its tick
// source. The returned TickClock will hold a reference to |this|.
std::unique_ptr<TickClock> GetMockTickClock() const;
bool HasPendingTask() const;
size_t GetPendingTaskCount() const;
TimeDelta NextPendingTaskDelay() const;
// SingleThreadTaskRunner:
bool RunsTasksOnCurrentThread() const override;
bool PostDelayedTask(const tracked_objects::Location& from_here,
const Closure& task,
TimeDelta delay) override;
bool PostNonNestableDelayedTask(const tracked_objects::Location& from_here,
const Closure& task,
TimeDelta delay) override;
~TestMockTimeTaskRunner() override;
// Whether the elapsing of virtual time is stopped or not. Subclasses can
// override this method to perform early exits from a running task runner.
// Defaults to always return false.
virtual bool IsElapsingStopped();
// Called before the next task to run is selected, so that subclasses have a
// last chance to make sure all tasks are posted.
virtual void OnBeforeSelectingTask();
// Called after the current mock time has been incremented so that subclasses
// can react to the passing of time.
virtual void OnAfterTimePassed();
// Called after each task is run so that subclasses may perform additional
// activities, e.g., pump additional task runners.
virtual void OnAfterTaskRun();
struct TestOrderedPendingTask;
// Predicate that defines a strict weak temporal ordering of tasks.
class TemporalOrder {
bool operator()(const TestOrderedPendingTask& first_task,
const TestOrderedPendingTask& second_task) const;
typedef std::priority_queue<TestOrderedPendingTask,
TemporalOrder> TaskPriorityQueue;
// Core of the implementation for all flavors of fast-forward methods. Given a
// non-negative |max_delta|, runs all tasks with a remaining delay less than
// or equal to |max_delta|, and moves virtual time forward as needed for each
// processed task. Pass in TimeDelta::Max() as |max_delta| to run all tasks.
void ProcessAllTasksNoLaterThan(TimeDelta max_delta);
// Forwards |now_ticks_| until it equals |later_ticks|, and forwards |now_| by
// the same amount. Calls OnAfterTimePassed() if |later_ticks| > |now_ticks_|.
// Does nothing if |later_ticks| <= |now_ticks_|.
void ForwardClocksUntilTickTime(TimeTicks later_ticks);
// Returns the |next_task| to run if there is any with a running time that is
// at most |reference| + |max_delta|. This additional complexity is required
// so that |max_delta| == TimeDelta::Max() can be supported.
bool DequeueNextTask(const TimeTicks& reference,
const TimeDelta& max_delta,
TestPendingTask* next_task);
ThreadChecker thread_checker_;
Time now_;
TimeTicks now_ticks_;
// Temporally ordered heap of pending tasks. Must only be accessed while the
// |tasks_lock_| is held.
TaskPriorityQueue tasks_;
// The ordinal to use for the next task. Must only be accessed while the
// |tasks_lock_| is held.
size_t next_task_ordinal_;
Lock tasks_lock_;
} // namespace base