зеркало из https://github.com/mozilla/gecko-dev.git
318 строки
11 KiB
C++
318 строки
11 KiB
C++
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
|
|
/* vim:set ts=2 sw=2 sts=2 et cindent: */
|
|
/* ***** BEGIN LICENSE BLOCK *****
|
|
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
|
|
*
|
|
* The contents of this file are subject to the Mozilla Public License Version
|
|
* 1.1 (the "License"); you may not use this file except in compliance with
|
|
* the License. You may obtain a copy of the License at
|
|
* http://www.mozilla.org/MPL/
|
|
*
|
|
* Software distributed under the License is distributed on an "AS IS" basis,
|
|
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
|
|
* for the specific language governing rights and limitations under the
|
|
* License.
|
|
*
|
|
* The Original Code is Mozilla code.
|
|
*
|
|
* The Initial Developer of the Original Code is the Mozilla Corporation.
|
|
* Portions created by the Initial Developer are Copyright (C) 2009
|
|
* the Initial Developer. All Rights Reserved.
|
|
*
|
|
* Contributor(s):
|
|
* Robert O'Callahan <robert@ocallahan.org>
|
|
*
|
|
* Alternatively, the contents of this file may be used under the terms of
|
|
* either the GNU General Public License Version 2 or later (the "GPL"), or
|
|
* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
|
|
* in which case the provisions of the GPL or the LGPL are applicable instead
|
|
* of those above. If you wish to allow use of your version of this file only
|
|
* under the terms of either the GPL or the LGPL, and not to allow others to
|
|
* use your version of this file under the terms of the MPL, indicate your
|
|
* decision by deleting the provisions above and replace them with the notice
|
|
* and other provisions required by the GPL or the LGPL. If you do not delete
|
|
* the provisions above, a recipient may use your version of this file under
|
|
* the terms of any one of the MPL, the GPL or the LGPL.
|
|
*
|
|
* ***** END LICENSE BLOCK ***** */
|
|
|
|
#ifndef mozilla_TimeStamp_h
|
|
#define mozilla_TimeStamp_h
|
|
|
|
#include "mozilla/Assertions.h"
|
|
|
|
#include "prinrval.h"
|
|
#include "nsDebug.h"
|
|
#include "prlong.h"
|
|
|
|
namespace mozilla {
|
|
|
|
class TimeStamp;
|
|
|
|
/**
|
|
* Instances of this class represent the length of an interval of time.
|
|
* Negative durations are allowed, meaning the end is before the start.
|
|
*
|
|
* Internally the duration is stored as a PRInt64 in units of
|
|
* PR_TicksPerSecond() when building with NSPR interval timers, or a
|
|
* system-dependent unit when building with system clocks. The
|
|
* system-dependent unit must be constant, otherwise the semantics of
|
|
* this class would be broken.
|
|
*/
|
|
class TimeDuration
|
|
{
|
|
public:
|
|
// The default duration is 0.
|
|
TimeDuration() : mValue(0) {}
|
|
// Allow construction using '0' as the initial value, for readability,
|
|
// but no other numbers (so we don't have any implicit unit conversions).
|
|
struct _SomethingVeryRandomHere;
|
|
TimeDuration(_SomethingVeryRandomHere* aZero) : mValue(0) {
|
|
MOZ_ASSERT(!aZero, "Who's playing funny games here?");
|
|
}
|
|
// Default copy-constructor and assignment are OK
|
|
|
|
double ToSeconds() const;
|
|
// Return a duration value that includes digits of time we think to
|
|
// be significant. This method should be used when displaying a
|
|
// time to humans.
|
|
double ToSecondsSigDigits() const;
|
|
double ToMilliseconds() const {
|
|
return ToSeconds() * 1000.0;
|
|
}
|
|
double ToMicroseconds() const {
|
|
return ToMilliseconds() * 1000.0;
|
|
}
|
|
|
|
// Using a double here is safe enough; with 53 bits we can represent
|
|
// durations up to over 280,000 years exactly. If the units of
|
|
// mValue do not allow us to represent durations of that length,
|
|
// long durations are clamped to the max/min representable value
|
|
// instead of overflowing.
|
|
static inline TimeDuration FromSeconds(double aSeconds) {
|
|
return FromMilliseconds(aSeconds * 1000.0);
|
|
}
|
|
static TimeDuration FromMilliseconds(double aMilliseconds);
|
|
|
|
TimeDuration operator+(const TimeDuration& aOther) const {
|
|
return TimeDuration::FromTicks(mValue + aOther.mValue);
|
|
}
|
|
TimeDuration operator-(const TimeDuration& aOther) const {
|
|
return TimeDuration::FromTicks(mValue - aOther.mValue);
|
|
}
|
|
TimeDuration& operator+=(const TimeDuration& aOther) {
|
|
mValue += aOther.mValue;
|
|
return *this;
|
|
}
|
|
TimeDuration& operator-=(const TimeDuration& aOther) {
|
|
mValue -= aOther.mValue;
|
|
return *this;
|
|
}
|
|
double operator/(const TimeDuration& aOther) {
|
|
return static_cast<double>(mValue) / aOther.mValue;
|
|
}
|
|
|
|
bool operator<(const TimeDuration& aOther) const {
|
|
return mValue < aOther.mValue;
|
|
}
|
|
bool operator<=(const TimeDuration& aOther) const {
|
|
return mValue <= aOther.mValue;
|
|
}
|
|
bool operator>=(const TimeDuration& aOther) const {
|
|
return mValue >= aOther.mValue;
|
|
}
|
|
bool operator>(const TimeDuration& aOther) const {
|
|
return mValue > aOther.mValue;
|
|
}
|
|
|
|
// Return a best guess at the system's current timing resolution,
|
|
// which might be variable. TimeDurations below this order of
|
|
// magnitude are meaningless, and those at the same order of
|
|
// magnitude or just above are suspect.
|
|
static TimeDuration Resolution();
|
|
|
|
// We could define additional operators here:
|
|
// -- convert to/from other time units
|
|
// -- scale duration by a float
|
|
// but let's do that on demand.
|
|
// Comparing durations for equality will only lead to bugs on
|
|
// platforms with high-resolution timers.
|
|
|
|
private:
|
|
friend class TimeStamp;
|
|
|
|
static TimeDuration FromTicks(PRInt64 aTicks) {
|
|
TimeDuration t;
|
|
t.mValue = aTicks;
|
|
return t;
|
|
}
|
|
|
|
static TimeDuration FromTicks(double aTicks) {
|
|
// NOTE: this MUST be a >= test, because PRInt64(double(LL_MAXINT))
|
|
// overflows and gives LL_MININT.
|
|
if (aTicks >= double(LL_MAXINT))
|
|
return TimeDuration::FromTicks(LL_MAXINT);
|
|
|
|
// This MUST be a <= test.
|
|
if (aTicks <= double(LL_MININT))
|
|
return TimeDuration::FromTicks(LL_MININT);
|
|
|
|
return TimeDuration::FromTicks(PRInt64(aTicks));
|
|
}
|
|
|
|
// Duration in PRIntervalTime units
|
|
PRInt64 mValue;
|
|
};
|
|
|
|
/**
|
|
* Instances of this class represent moments in time, or a special
|
|
* "null" moment. We do not use the non-monotonic system clock or
|
|
* local time, since they can be reset, causing apparent backward
|
|
* travel in time, which can confuse algorithms. Instead we measure
|
|
* elapsed time according to the system. This time can never go
|
|
* backwards (i.e. it never wraps around, at least not in less than
|
|
* five million years of system elapsed time). It might not advance
|
|
* while the system is sleeping. If TimeStamp::SetNow() is not called
|
|
* at all for hours or days, we might not notice the passage of some
|
|
* of that time.
|
|
*
|
|
* We deliberately do not expose a way to convert TimeStamps to some
|
|
* particular unit. All you can do is compute a difference between two
|
|
* TimeStamps to get a TimeDuration. You can also add a TimeDuration
|
|
* to a TimeStamp to get a new TimeStamp. You can't do something
|
|
* meaningless like add two TimeStamps.
|
|
*
|
|
* Internally this is implemented as either a wrapper around
|
|
* - high-resolution, monotonic, system clocks if they exist on this
|
|
* platform
|
|
* - PRIntervalTime otherwise. We detect wraparounds of
|
|
* PRIntervalTime and work around them.
|
|
*
|
|
* This class is similar to C++11's time_point, however it is
|
|
* explicitly nullable and provides an IsNull() method. time_point
|
|
* is initialized to the clock's epoch and provides a
|
|
* time_since_epoch() method that functions similiarly. i.e.
|
|
* t.IsNull() is equivalent to t.time_since_epoch() == decltype(t)::duration::zero();
|
|
*/
|
|
class TimeStamp
|
|
{
|
|
public:
|
|
/**
|
|
* Initialize to the "null" moment
|
|
*/
|
|
TimeStamp() : mValue(0) {}
|
|
// Default copy-constructor and assignment are OK
|
|
|
|
/**
|
|
* Return true if this is the "null" moment
|
|
*/
|
|
bool IsNull() const { return mValue == 0; }
|
|
/**
|
|
* Return a timestamp reflecting the current elapsed system time. This
|
|
* is monotonically increasing (i.e., does not decrease) over the
|
|
* lifetime of this process' XPCOM session.
|
|
*/
|
|
static TimeStamp Now();
|
|
/**
|
|
* Compute the difference between two timestamps. Both must be non-null.
|
|
*/
|
|
TimeDuration operator-(const TimeStamp& aOther) const {
|
|
MOZ_ASSERT(!IsNull(), "Cannot compute with a null value");
|
|
MOZ_ASSERT(!aOther.IsNull(), "Cannot compute with aOther null value");
|
|
PR_STATIC_ASSERT(-LL_MAXINT > LL_MININT);
|
|
PRInt64 ticks = PRInt64(mValue - aOther.mValue);
|
|
// Check for overflow.
|
|
if (mValue > aOther.mValue) {
|
|
if (ticks < 0) {
|
|
ticks = LL_MAXINT;
|
|
}
|
|
} else {
|
|
if (ticks > 0) {
|
|
ticks = LL_MININT;
|
|
}
|
|
}
|
|
return TimeDuration::FromTicks(ticks);
|
|
}
|
|
|
|
TimeStamp operator+(const TimeDuration& aOther) const {
|
|
MOZ_ASSERT(!IsNull(), "Cannot compute with a null value");
|
|
return TimeStamp(mValue + aOther.mValue);
|
|
}
|
|
TimeStamp operator-(const TimeDuration& aOther) const {
|
|
MOZ_ASSERT(!IsNull(), "Cannot compute with a null value");
|
|
return TimeStamp(mValue - aOther.mValue);
|
|
}
|
|
TimeStamp& operator+=(const TimeDuration& aOther) {
|
|
MOZ_ASSERT(!IsNull(), "Cannot compute with a null value");
|
|
mValue += aOther.mValue;
|
|
return *this;
|
|
}
|
|
TimeStamp& operator-=(const TimeDuration& aOther) {
|
|
MOZ_ASSERT(!IsNull(), "Cannot compute with a null value");
|
|
mValue -= aOther.mValue;
|
|
return *this;
|
|
}
|
|
|
|
bool operator<(const TimeStamp& aOther) const {
|
|
MOZ_ASSERT(!IsNull(), "Cannot compute with a null value");
|
|
MOZ_ASSERT(!aOther.IsNull(), "Cannot compute with aOther null value");
|
|
return mValue < aOther.mValue;
|
|
}
|
|
bool operator<=(const TimeStamp& aOther) const {
|
|
MOZ_ASSERT(!IsNull(), "Cannot compute with a null value");
|
|
MOZ_ASSERT(!aOther.IsNull(), "Cannot compute with aOther null value");
|
|
return mValue <= aOther.mValue;
|
|
}
|
|
bool operator>=(const TimeStamp& aOther) const {
|
|
MOZ_ASSERT(!IsNull(), "Cannot compute with a null value");
|
|
MOZ_ASSERT(!aOther.IsNull(), "Cannot compute with aOther null value");
|
|
return mValue >= aOther.mValue;
|
|
}
|
|
bool operator>(const TimeStamp& aOther) const {
|
|
MOZ_ASSERT(!IsNull(), "Cannot compute with a null value");
|
|
MOZ_ASSERT(!aOther.IsNull(), "Cannot compute with aOther null value");
|
|
return mValue > aOther.mValue;
|
|
}
|
|
bool operator==(const TimeStamp& aOther) const {
|
|
// Maybe it's ok to check == with null timestamps?
|
|
MOZ_ASSERT(!IsNull() && "Cannot compute with a null value");
|
|
MOZ_ASSERT(!aOther.IsNull(), "Cannot compute with aOther null value");
|
|
return mValue == aOther.mValue;
|
|
}
|
|
bool operator!=(const TimeStamp& aOther) const {
|
|
// Maybe it's ok to check != with null timestamps?
|
|
MOZ_ASSERT(!IsNull(), "Cannot compute with a null value");
|
|
MOZ_ASSERT(!aOther.IsNull(), "Cannot compute with aOther null value");
|
|
return mValue != aOther.mValue;
|
|
}
|
|
|
|
// Comparing TimeStamps for equality should be discouraged. Adding
|
|
// two TimeStamps, or scaling TimeStamps, is nonsense and must never
|
|
// be allowed.
|
|
|
|
static NS_HIDDEN_(nsresult) Startup();
|
|
static NS_HIDDEN_(void) Shutdown();
|
|
|
|
private:
|
|
TimeStamp(PRUint64 aValue) : mValue(aValue) {}
|
|
|
|
/**
|
|
* When built with PRIntervalTime, a value of 0 means this instance
|
|
* is "null". Otherwise, the low 32 bits represent a PRIntervalTime,
|
|
* and the high 32 bits represent a counter of the number of
|
|
* rollovers of PRIntervalTime that we've seen. This counter starts
|
|
* at 1 to avoid a real time colliding with the "null" value.
|
|
*
|
|
* PR_INTERVAL_MAX is set at 100,000 ticks per second. So the minimum
|
|
* time to wrap around is about 2^64/100000 seconds, i.e. about
|
|
* 5,849,424 years.
|
|
*
|
|
* When using a system clock, a value is system dependent.
|
|
*/
|
|
PRUint64 mValue;
|
|
};
|
|
|
|
}
|
|
|
|
#endif /* mozilla_TimeStamp_h */
|