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// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/time/time.h"
namespace base {
// static
TimeTicks TimeTicks::FromUptimeMillis(int64_t uptime_millis_value) {
// The implementation of the SystemClock.uptimeMillis() in AOSP uses the same
// clock as base::TimeTicks::Now(): clock_gettime(CLOCK_MONOTONIC), see in
// platform/system/code:
// 1. libutils/SystemClock.cpp
// 2. libutils/Timers.cpp
//
// We are not aware of any motivations for Android OEMs to modify the AOSP
// implementation of either uptimeMillis() or clock_gettime(CLOCK_MONOTONIC),
// so we assume that there are no such customizations.
//
// Under these assumptions the conversion is as safe as copying the value of
// base::TimeTicks::Now() with a loss of sub-millisecond precision.
return TimeTicks(uptime_millis_value * Time::kMicrosecondsPerMillisecond);
}
// This file is included on chromeos_ash because it needs to interpret
// UptimeMillis values from the Android container.
#if BUILDFLAG(IS_ANDROID)
// static
TimeTicks TimeTicks::FromJavaNanoTime(int64_t nano_time_value) {
// The implementation of the System.nanoTime() in AOSP uses the same
// clock as UptimeMillis() and base::TimeTicks::Now():
// clock_gettime(CLOCK_MONOTONIC), see ojluni/src/main/native/System.c in
// AOSP.
//
// From Android documentation on android.os.SystemClock:
// [uptimeMillis()] is the basis for most interval timing such as
// Thread.sleep(millls), Object.wait(millis), and System.nanoTime().
//
// We are not aware of any motivations for Android OEMs to modify the AOSP
// implementation of either uptimeMillis(), nanoTime, or
// clock_gettime(CLOCK_MONOTONIC), so we assume that there are no such
// customizations.
//
// Under these assumptions the conversion is as safe as copying the value of
// base::TimeTicks::Now() without the (theoretical) sub-microsecond
// resolution.
return TimeTicks(nano_time_value / Time::kNanosecondsPerMicrosecond);
}
jlong TimeTicks::ToUptimeMillis() const {
// See FromUptimeMillis. UptimeMillis and TimeTicks use the same clock source,
// and only differ in resolution.
return us_ / Time::kMicrosecondsPerMillisecond;
}
jlong TimeTicks::ToUptimeMicros() const {
// Same as ToUptimeMillis but maintains sub-millisecond precision.
return us_;
}
#endif // BUILDFLAG(IS_ANDROID)
} // namespace base
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