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// Copyright (c) 2012 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 "quic/core/quic_time.h"
#include "quic/platform/api/quic_export.h"
QuicClock is used by QUIC core to get current time. Its instance is created by
applications and passed into QuicDispatcher and QuicConnectionHelperInterface.
namespace quic {
// Interface for retrieving the current time.
virtual ~QuicClock();
QuicClock(const QuicClock&) = delete;
QuicClock& operator=(const QuicClock&) = delete;
// Compute the offset between this clock with the Unix Epoch clock.
// Return the calibrated offset between WallNow() and Now(), in the form of
// (wallnow_in_us - now_in_us).
// The return value can be used by SetCalibrationOffset() to actually
// calibrate the clock, or all instances of this clock type.
QuicTime::Delta ComputeCalibrationOffset() const;
// Calibrate this clock. A calibrated clock guarantees that the
// ConvertWallTimeToQuicTime() function always return the same result for the
// same walltime.
// Should not be called more than once for each QuicClock.
void SetCalibrationOffset(QuicTime::Delta offset);
// Returns the approximate current time as a QuicTime object.
virtual QuicTime ApproximateNow() const = 0;
// Returns the current time as a QuicTime object.
// Note: this use significant resources please use only if needed.
virtual QuicTime Now() const = 0;
// WallNow returns the current wall-time - a time that is consistent across
// different clocks.
virtual QuicWallTime WallNow() const = 0;
// Converts |walltime| to a QuicTime relative to this clock's epoch.
virtual QuicTime ConvertWallTimeToQuicTime(
const QuicWallTime& walltime) const;
// Creates a new QuicTime using |time_us| as the internal value.
QuicTime CreateTimeFromMicroseconds(uint64_t time_us) const {
return QuicTime(time_us);
// True if |calibration_offset_| is valid.
bool is_calibrated_;
// If |is_calibrated_|, |calibration_offset_| is the (fixed) offset between
// the Unix Epoch clock and this clock.
// In other words, the offset between WallNow() and Now().
QuicTime::Delta calibration_offset_;
} // namespace quic