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110 lines
3.6 KiB
C++
110 lines
3.6 KiB
C++
// Copyright 2026 The Abseil 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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// https://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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// -----------------------------------------------------------------------------
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// File: simulated_clock.h
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// -----------------------------------------------------------------------------
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#ifndef ABSL_TIME_SIMULATED_CLOCK_H_
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#define ABSL_TIME_SIMULATED_CLOCK_H_
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#include <cstdint>
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#include <map>
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#include <memory>
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#include <optional>
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#include "absl/base/config.h"
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#include "absl/base/macros.h"
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#include "absl/base/nullability.h"
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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/clock.h"
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#include "absl/time/clock_interface.h"
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#include "absl/time/time.h"
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namespace absl {
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ABSL_NAMESPACE_BEGIN
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// A simulated clock is a concrete Clock implementation that does not "tick"
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// on its own. Time is advanced by explicit calls to the AdvanceTime() or
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// SetTime() functions.
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//
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// Example:
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// absl::SimulatedClock sim_clock;
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// absl::Time now = sim_clock.TimeNow();
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// // now == absl::UnixEpoch()
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//
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// now = sim_clock.TimeNow();
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// // now == absl::UnixEpoch() (still)
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//
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// sim_clock.AdvanceTime(absl::Seconds(3));
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// now = sim_clock.TimeNow();
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// // now == absl::UnixEpoch() + absl::Seconds(3)
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//
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// This class is thread-safe.
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class SimulatedClock : public Clock {
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public:
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explicit SimulatedClock(absl::Time t);
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SimulatedClock() : SimulatedClock(absl::UnixEpoch()) {}
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// The destructor should be called only if all Sleep(), etc. and
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// AdvanceTime() calls have completed. The code does its best to let
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// any pending calls finish gracefully, but there are no guarantees.
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~SimulatedClock() 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 specified wakeup_time.
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void SleepUntil(absl::Time wakeup_time) override;
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// Sets the simulated time to the argument. Wakes up any threads whose
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// sleeps have now expired. Returns the number of woken threads.
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int64_t SetTime(absl::Time t);
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// Advances the simulated time by the specified duration. Wakes up any
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// threads whose sleeps have now expired. Returns the number of woken threads.
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int64_t AdvanceTime(absl::Duration d);
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// Blocks until the condition is true or until the simulated clock is
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// advanced to or beyond the wakeup time (or both).
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bool AwaitWithDeadline(absl::Mutex* absl_nonnull mu,
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const absl::Condition& cond,
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absl::Time deadline) override
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ABSL_SHARED_LOCKS_REQUIRED(mu);
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// Returns the earliest wakeup time.
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std::optional<absl::Time> GetEarliestWakeupTime() const;
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private:
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template <class T>
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int64_t UpdateTime(const T& now_updater) ABSL_LOCKS_EXCLUDED(lock_);
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class WakeUpInfo;
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using WaiterList = std::multimap<absl::Time, std::shared_ptr<WakeUpInfo>>;
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mutable absl::Mutex lock_;
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absl::Time now_ ABSL_GUARDED_BY(lock_);
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WaiterList waiters_ ABSL_GUARDED_BY(lock_);
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int64_t num_await_calls_ ABSL_GUARDED_BY(lock_) = 0;
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};
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ABSL_NAMESPACE_END
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} // namespace absl
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#endif // ABSL_TIME_SIMULATED_CLOCK_H_
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