mozglue/misc/TimeStamp_darwin.cpp
author Michael Comella <michael.l.comella@gmail.com>
Tue, 15 Sep 2015 16:46:58 -0700
changeset 266944 ed8188590f14b1aae2e4f44c8196994f375a99f4
parent 249681 bf2f1318c3c052e9da173c32ed1dab4de2a4a30c
child 443187 b00e84c0233b17a1daf0feccf660580aa5fe2d30
permissions -rw-r--r--
Bug 1201206 - Correct menu button background on 2.3. r=mhaigh One fear is that different devices set different menu colors and text colors. Since we're using the default text color and set an explicit menu color, the text color may not look good on these devices. I was unable to find a way to override the menu text color. It seems the best way to find out if this is a problem is to land it and test though!

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

//
// Implement TimeStamp::Now() with mach_absolute_time
//
// The "tick" unit for mach_absolute_time is defined using mach_timebase_info() which
// gives a conversion ratio to nanoseconds. For more information see Apple's QA1398.
//
// This code is inspired by Chromium's time_mac.cc. The biggest
// differences are that we explicitly initialize using
// TimeStamp::Initialize() instead of lazily in Now() and that
// we store the time value in ticks and convert when needed instead
// of storing the time value in nanoseconds.

#include <mach/mach_time.h>
#include <sys/time.h>
#include <sys/sysctl.h>
#include <time.h>
#include <unistd.h>

#include "mozilla/TimeStamp.h"

// Estimate of the smallest duration of time we can measure.
static uint64_t sResolution;
static uint64_t sResolutionSigDigs;

static const uint64_t kNsPerMs   =    1000000;
static const uint64_t kUsPerSec  =    1000000;
static const double kNsPerMsd    =    1000000.0;
static const double kNsPerSecd   = 1000000000.0;

static bool gInitialized = false;
static double sNsPerTick;

static uint64_t
ClockTime()
{
  // mach_absolute_time is it when it comes to ticks on the Mac.  Other calls
  // with less precision (such as TickCount) just call through to
  // mach_absolute_time.
  //
  // At the time of writing mach_absolute_time returns the number of nanoseconds
  // since boot. This won't overflow 64bits for 500+ years so we aren't going
  // to worry about that possiblity
  return mach_absolute_time();
}

static uint64_t
ClockResolutionNs()
{
  uint64_t start = ClockTime();
  uint64_t end = ClockTime();
  uint64_t minres = (end - start);

  // 10 total trials is arbitrary: what we're trying to avoid by
  // looping is getting unlucky and being interrupted by a context
  // switch or signal, or being bitten by paging/cache effects
  for (int i = 0; i < 9; ++i) {
    start = ClockTime();
    end = ClockTime();

    uint64_t candidate = (start - end);
    if (candidate < minres) {
      minres = candidate;
    }
  }

  if (0 == minres) {
    // measurable resolution is either incredibly low, ~1ns, or very
    // high.  fall back on NSPR's resolution assumption
    minres = 1 * kNsPerMs;
  }

  return minres;
}

namespace mozilla {

double
BaseTimeDurationPlatformUtils::ToSeconds(int64_t aTicks)
{
  MOZ_ASSERT(gInitialized, "calling TimeDuration too early");
  return (aTicks * sNsPerTick) / kNsPerSecd;
}

double
BaseTimeDurationPlatformUtils::ToSecondsSigDigits(int64_t aTicks)
{
  MOZ_ASSERT(gInitialized, "calling TimeDuration too early");
  // don't report a value < mResolution ...
  int64_t valueSigDigs = sResolution * (aTicks / sResolution);
  // and chop off insignificant digits
  valueSigDigs = sResolutionSigDigs * (valueSigDigs / sResolutionSigDigs);
  return (valueSigDigs * sNsPerTick) / kNsPerSecd;
}

int64_t
BaseTimeDurationPlatformUtils::TicksFromMilliseconds(double aMilliseconds)
{
  MOZ_ASSERT(gInitialized, "calling TimeDuration too early");
  double result = (aMilliseconds * kNsPerMsd) / sNsPerTick;
  if (result > INT64_MAX) {
    return INT64_MAX;
  } else if (result < INT64_MIN) {
    return INT64_MIN;
  }

  return result;
}

int64_t
BaseTimeDurationPlatformUtils::ResolutionInTicks()
{
  MOZ_ASSERT(gInitialized, "calling TimeDuration too early");
  return static_cast<int64_t>(sResolution);
}

void
TimeStamp::Startup()
{
  if (gInitialized) {
    return;
  }

  mach_timebase_info_data_t timebaseInfo;
  // Apple's QA1398 suggests that the output from mach_timebase_info
  // will not change while a program is running, so it should be safe
  // to cache the result.
  kern_return_t kr = mach_timebase_info(&timebaseInfo);
  if (kr != KERN_SUCCESS) {
    MOZ_RELEASE_ASSERT(false, "mach_timebase_info failed");
  }

  sNsPerTick = double(timebaseInfo.numer) / timebaseInfo.denom;

  sResolution = ClockResolutionNs();

  // find the number of significant digits in sResolution, for the
  // sake of ToSecondsSigDigits()
  for (sResolutionSigDigs = 1;
       !(sResolutionSigDigs == sResolution ||
         10 * sResolutionSigDigs > sResolution);
       sResolutionSigDigs *= 10);

  gInitialized = true;

  return;
}

void
TimeStamp::Shutdown()
{
}

TimeStamp
TimeStamp::Now(bool aHighResolution)
{
  return TimeStamp(ClockTime());
}

// Computes and returns the process uptime in microseconds.
// Returns 0 if an error was encountered.

uint64_t
TimeStamp::ComputeProcessUptime()
{
  struct timeval tv;
  int rv = gettimeofday(&tv, nullptr);

  if (rv == -1) {
    return 0;
  }

  int mib[] = {
    CTL_KERN,
    KERN_PROC,
    KERN_PROC_PID,
    getpid(),
  };
  u_int mibLen = sizeof(mib) / sizeof(mib[0]);

  struct kinfo_proc proc;
  size_t bufferSize = sizeof(proc);
  rv = sysctl(mib, mibLen, &proc, &bufferSize, nullptr, 0);

  if (rv == -1) {
    return 0;
  }

  uint64_t startTime =
    ((uint64_t)proc.kp_proc.p_un.__p_starttime.tv_sec * kUsPerSec) +
    proc.kp_proc.p_un.__p_starttime.tv_usec;
  uint64_t now = (tv.tv_sec * kUsPerSec) + tv.tv_usec;

  if (startTime > now) {
    return 0;
  }

  return now - startTime;
}

} // namespace mozilla