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      1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #include "base/time/time.h"
      6 
      7 #include <CoreFoundation/CFDate.h>
      8 #include <CoreFoundation/CFTimeZone.h>
      9 #include <mach/mach.h>
     10 #include <mach/mach_time.h>
     11 #include <stddef.h>
     12 #include <stdint.h>
     13 #include <sys/sysctl.h>
     14 #include <sys/time.h>
     15 #include <sys/types.h>
     16 #include <time.h>
     17 
     18 #include "base/logging.h"
     19 #include "base/mac/mach_logging.h"
     20 #include "base/mac/scoped_cftyperef.h"
     21 #include "base/mac/scoped_mach_port.h"
     22 #include "base/macros.h"
     23 #include "base/numerics/safe_conversions.h"
     24 #include "build/build_config.h"
     25 
     26 namespace {
     27 
     28 int64_t ComputeCurrentTicks() {
     29 #if defined(OS_IOS)
     30   // On iOS mach_absolute_time stops while the device is sleeping. Instead use
     31   // now - KERN_BOOTTIME to get a time difference that is not impacted by clock
     32   // changes. KERN_BOOTTIME will be updated by the system whenever the system
     33   // clock change.
     34   struct timeval boottime;
     35   int mib[2] = {CTL_KERN, KERN_BOOTTIME};
     36   size_t size = sizeof(boottime);
     37   int kr = sysctl(mib, arraysize(mib), &boottime, &size, NULL, 0);
     38   DCHECK_EQ(KERN_SUCCESS, kr);
     39   base::TimeDelta time_difference = base::Time::Now() -
     40       (base::Time::FromTimeT(boottime.tv_sec) +
     41        base::TimeDelta::FromMicroseconds(boottime.tv_usec));
     42   return time_difference.InMicroseconds();
     43 #else
     44   static mach_timebase_info_data_t timebase_info;
     45   if (timebase_info.denom == 0) {
     46     // Zero-initialization of statics guarantees that denom will be 0 before
     47     // calling mach_timebase_info.  mach_timebase_info will never set denom to
     48     // 0 as that would be invalid, so the zero-check can be used to determine
     49     // whether mach_timebase_info has already been called.  This is
     50     // recommended by Apple's QA1398.
     51     kern_return_t kr = mach_timebase_info(&timebase_info);
     52     MACH_DCHECK(kr == KERN_SUCCESS, kr) << "mach_timebase_info";
     53   }
     54 
     55   // mach_absolute_time is it when it comes to ticks on the Mac.  Other calls
     56   // with less precision (such as TickCount) just call through to
     57   // mach_absolute_time.
     58 
     59   // timebase_info converts absolute time tick units into nanoseconds.  Convert
     60   // to microseconds up front to stave off overflows.
     61   base::CheckedNumeric<uint64_t> result(
     62       mach_absolute_time() / base::Time::kNanosecondsPerMicrosecond);
     63   result *= timebase_info.numer;
     64   result /= timebase_info.denom;
     65 
     66   // Don't bother with the rollover handling that the Windows version does.
     67   // With numer and denom = 1 (the expected case), the 64-bit absolute time
     68   // reported in nanoseconds is enough to last nearly 585 years.
     69   return base::checked_cast<int64_t>(result.ValueOrDie());
     70 #endif  // defined(OS_IOS)
     71 }
     72 
     73 int64_t ComputeThreadTicks() {
     74 #if defined(OS_IOS)
     75   NOTREACHED();
     76   return 0;
     77 #else
     78   base::mac::ScopedMachSendRight thread(mach_thread_self());
     79   mach_msg_type_number_t thread_info_count = THREAD_BASIC_INFO_COUNT;
     80   thread_basic_info_data_t thread_info_data;
     81 
     82   if (thread.get() == MACH_PORT_NULL) {
     83     DLOG(ERROR) << "Failed to get mach_thread_self()";
     84     return 0;
     85   }
     86 
     87   kern_return_t kr = thread_info(
     88       thread.get(),
     89       THREAD_BASIC_INFO,
     90       reinterpret_cast<thread_info_t>(&thread_info_data),
     91       &thread_info_count);
     92   MACH_DCHECK(kr == KERN_SUCCESS, kr) << "thread_info";
     93 
     94   base::CheckedNumeric<int64_t> absolute_micros(
     95       thread_info_data.user_time.seconds);
     96   absolute_micros *= base::Time::kMicrosecondsPerSecond;
     97   absolute_micros += thread_info_data.user_time.microseconds;
     98   return absolute_micros.ValueOrDie();
     99 #endif  // defined(OS_IOS)
    100 }
    101 
    102 }  // namespace
    103 
    104 namespace base {
    105 
    106 // The Time routines in this file use Mach and CoreFoundation APIs, since the
    107 // POSIX definition of time_t in Mac OS X wraps around after 2038--and
    108 // there are already cookie expiration dates, etc., past that time out in
    109 // the field.  Using CFDate prevents that problem, and using mach_absolute_time
    110 // for TimeTicks gives us nice high-resolution interval timing.
    111 
    112 // Time -----------------------------------------------------------------------
    113 
    114 // Core Foundation uses a double second count since 2001-01-01 00:00:00 UTC.
    115 // The UNIX epoch is 1970-01-01 00:00:00 UTC.
    116 // Windows uses a Gregorian epoch of 1601.  We need to match this internally
    117 // so that our time representations match across all platforms.  See bug 14734.
    118 //   irb(main):010:0> Time.at(0).getutc()
    119 //   => Thu Jan 01 00:00:00 UTC 1970
    120 //   irb(main):011:0> Time.at(-11644473600).getutc()
    121 //   => Mon Jan 01 00:00:00 UTC 1601
    122 static const int64_t kWindowsEpochDeltaSeconds = INT64_C(11644473600);
    123 
    124 // static
    125 const int64_t Time::kWindowsEpochDeltaMicroseconds =
    126     kWindowsEpochDeltaSeconds * Time::kMicrosecondsPerSecond;
    127 
    128 // Some functions in time.cc use time_t directly, so we provide an offset
    129 // to convert from time_t (Unix epoch) and internal (Windows epoch).
    130 // static
    131 const int64_t Time::kTimeTToMicrosecondsOffset = kWindowsEpochDeltaMicroseconds;
    132 
    133 // static
    134 Time Time::Now() {
    135   return FromCFAbsoluteTime(CFAbsoluteTimeGetCurrent());
    136 }
    137 
    138 // static
    139 Time Time::FromCFAbsoluteTime(CFAbsoluteTime t) {
    140   static_assert(std::numeric_limits<CFAbsoluteTime>::has_infinity,
    141                 "CFAbsoluteTime must have an infinity value");
    142   if (t == 0)
    143     return Time();  // Consider 0 as a null Time.
    144   if (t == std::numeric_limits<CFAbsoluteTime>::infinity())
    145     return Max();
    146   return Time(static_cast<int64_t>((t + kCFAbsoluteTimeIntervalSince1970) *
    147                                    kMicrosecondsPerSecond) +
    148               kWindowsEpochDeltaMicroseconds);
    149 }
    150 
    151 CFAbsoluteTime Time::ToCFAbsoluteTime() const {
    152   static_assert(std::numeric_limits<CFAbsoluteTime>::has_infinity,
    153                 "CFAbsoluteTime must have an infinity value");
    154   if (is_null())
    155     return 0;  // Consider 0 as a null Time.
    156   if (is_max())
    157     return std::numeric_limits<CFAbsoluteTime>::infinity();
    158   return (static_cast<CFAbsoluteTime>(us_ - kWindowsEpochDeltaMicroseconds) /
    159       kMicrosecondsPerSecond) - kCFAbsoluteTimeIntervalSince1970;
    160 }
    161 
    162 // static
    163 Time Time::NowFromSystemTime() {
    164   // Just use Now() because Now() returns the system time.
    165   return Now();
    166 }
    167 
    168 // static
    169 Time Time::FromExploded(bool is_local, const Exploded& exploded) {
    170   CFGregorianDate date;
    171   date.second = exploded.second +
    172       exploded.millisecond / static_cast<double>(kMillisecondsPerSecond);
    173   date.minute = exploded.minute;
    174   date.hour = exploded.hour;
    175   date.day = exploded.day_of_month;
    176   date.month = exploded.month;
    177   date.year = exploded.year;
    178 
    179   base::ScopedCFTypeRef<CFTimeZoneRef> time_zone(
    180       is_local ? CFTimeZoneCopySystem() : NULL);
    181   CFAbsoluteTime seconds = CFGregorianDateGetAbsoluteTime(date, time_zone) +
    182       kCFAbsoluteTimeIntervalSince1970;
    183   return Time(static_cast<int64_t>(seconds * kMicrosecondsPerSecond) +
    184               kWindowsEpochDeltaMicroseconds);
    185 }
    186 
    187 void Time::Explode(bool is_local, Exploded* exploded) const {
    188   // Avoid rounding issues, by only putting the integral number of seconds
    189   // (rounded towards -infinity) into a |CFAbsoluteTime| (which is a |double|).
    190   int64_t microsecond = us_ % kMicrosecondsPerSecond;
    191   if (microsecond < 0)
    192     microsecond += kMicrosecondsPerSecond;
    193   CFAbsoluteTime seconds = ((us_ - microsecond) / kMicrosecondsPerSecond) -
    194                            kWindowsEpochDeltaSeconds -
    195                            kCFAbsoluteTimeIntervalSince1970;
    196 
    197   base::ScopedCFTypeRef<CFTimeZoneRef> time_zone(
    198       is_local ? CFTimeZoneCopySystem() : NULL);
    199   CFGregorianDate date = CFAbsoluteTimeGetGregorianDate(seconds, time_zone);
    200   // 1 = Monday, ..., 7 = Sunday.
    201   int cf_day_of_week = CFAbsoluteTimeGetDayOfWeek(seconds, time_zone);
    202 
    203   exploded->year = date.year;
    204   exploded->month = date.month;
    205   exploded->day_of_week = cf_day_of_week % 7;
    206   exploded->day_of_month = date.day;
    207   exploded->hour = date.hour;
    208   exploded->minute = date.minute;
    209   // Make sure seconds are rounded down towards -infinity.
    210   exploded->second = floor(date.second);
    211   // Calculate milliseconds ourselves, since we rounded the |seconds|, making
    212   // sure to round towards -infinity.
    213   exploded->millisecond =
    214       (microsecond >= 0) ? microsecond / kMicrosecondsPerMillisecond :
    215                            (microsecond - kMicrosecondsPerMillisecond + 1) /
    216                                kMicrosecondsPerMillisecond;
    217 }
    218 
    219 // TimeTicks ------------------------------------------------------------------
    220 
    221 // static
    222 TimeTicks TimeTicks::Now() {
    223   return TimeTicks(ComputeCurrentTicks());
    224 }
    225 
    226 // static
    227 bool TimeTicks::IsHighResolution() {
    228   return true;
    229 }
    230 
    231 // static
    232 ThreadTicks ThreadTicks::Now() {
    233   return ThreadTicks(ComputeThreadTicks());
    234 }
    235 
    236 }  // namespace base
    237