base/time_posix.cc

   1 // Copyright (c) 2010 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.h"
   6
   7 #include <sys/time.h>
   8 #include <time.h>
   9
  10 #include <limits>
  11
  12 #include "base/basictypes.h"
  13 #include "base/logging.h"
  14
  15 namespace base {
  16
  17 struct timespec TimeDelta::ToTimeSpec() const {
  18   int64 microseconds = InMicroseconds();
  19   time_t seconds = 0;
  20   if (microseconds >= Time::kMicrosecondsPerSecond) {
  21     seconds = InSeconds();
  22     microseconds -= seconds * Time::kMicrosecondsPerSecond;
  23   }
  24   struct timespec result =
  25       {seconds,
  26        microseconds * Time::kNanosecondsPerMicrosecond};
  27   return result;
  28 }
  29
  30 #if !defined(OS_MACOSX)
  31 // The Time routines in this file use standard POSIX routines, or almost-
  32 // standard routines in the case of timegm.  We need to use a Mach-specific
  33 // function for TimeTicks::Now() on Mac OS X.
  34
  35 // Time -----------------------------------------------------------------------
  36
  37 // Windows uses a Gregorian epoch of 1601.  We need to match this internally
  38 // so that our time representations match across all platforms.  See bug 14734.
  39 //   irb(main):010:0> Time.at(0).getutc()
  40 //   => Thu Jan 01 00:00:00 UTC 1970
  41 //   irb(main):011:0> Time.at(-11644473600).getutc()
  42 //   => Mon Jan 01 00:00:00 UTC 1601
  43 static const int64 kWindowsEpochDeltaSeconds = GG_INT64_C(11644473600);
  44 static const int64 kWindowsEpochDeltaMilliseconds =
  45     kWindowsEpochDeltaSeconds * Time::kMillisecondsPerSecond;
  46
  47 // static
  48 const int64 Time::kWindowsEpochDeltaMicroseconds =
  49     kWindowsEpochDeltaSeconds * Time::kMicrosecondsPerSecond;
  50
  51 // Some functions in time.cc use time_t directly, so we provide an offset
  52 // to convert from time_t (Unix epoch) and internal (Windows epoch).
  53 // static
  54 const int64 Time::kTimeTToMicrosecondsOffset = kWindowsEpochDeltaMicroseconds;
  55
  56 // static
  57 Time Time::Now() {
  58   struct timeval tv;
  59   struct timezone tz = { 0, 0 };  // UTC
  60   if (gettimeofday(&tv, &tz) != 0) {
  61     DCHECK(0) << "Could not determine time of day";
  62   }
  63   // Combine seconds and microseconds in a 64-bit field containing microseconds
  64   // since the epoch.  That's enough for nearly 600 centuries.  Adjust from
  65   // Unix (1970) to Windows (1601) epoch.
  66   return Time((tv.tv_sec * kMicrosecondsPerSecond + tv.tv_usec) +
  67       kWindowsEpochDeltaMicroseconds);
  68 }
  69
  70 // static
  71 Time Time::NowFromSystemTime() {
  72   // Just use Now() because Now() returns the system time.
  73   return Now();
  74 }
  75
  76 void Time::Explode(bool is_local, Exploded* exploded) const {
  77   // Time stores times with microsecond resolution, but Exploded only carries
  78   // millisecond resolution, so begin by being lossy.  Adjust from Windows
  79   // epoch (1601) to Unix epoch (1970);
  80   int64 milliseconds = (us_ - kWindowsEpochDeltaMicroseconds) /
  81       kMicrosecondsPerMillisecond;
  82   time_t seconds = milliseconds / kMillisecondsPerSecond;
  83
  84   struct tm timestruct;
  85   if (is_local)
  86     localtime_r(&seconds, &timestruct);
  87   else
  88     gmtime_r(&seconds, &timestruct);
  89
  90   exploded->year         = timestruct.tm_year + 1900;
  91   exploded->month        = timestruct.tm_mon + 1;
  92   exploded->day_of_week  = timestruct.tm_wday;
  93   exploded->day_of_month = timestruct.tm_mday;
  94   exploded->hour         = timestruct.tm_hour;
  95   exploded->minute       = timestruct.tm_min;
  96   exploded->second       = timestruct.tm_sec;
  97   exploded->millisecond  = milliseconds % kMillisecondsPerSecond;
  98 }
  99
 100 // static
 101 Time Time::FromExploded(bool is_local, const Exploded& exploded) {
 102   struct tm timestruct;
 103   timestruct.tm_sec    = exploded.second;
 104   timestruct.tm_min    = exploded.minute;
 105   timestruct.tm_hour   = exploded.hour;
 106   timestruct.tm_mday   = exploded.day_of_month;
 107   timestruct.tm_mon    = exploded.month - 1;
 108   timestruct.tm_year   = exploded.year - 1900;
 109   timestruct.tm_wday   = exploded.day_of_week;  // mktime/timegm ignore this
 110   timestruct.tm_yday   = 0;     // mktime/timegm ignore this
 111   timestruct.tm_isdst  = -1;    // attempt to figure it out
 112 #if !defined(OS_NACL)
 113   timestruct.tm_gmtoff = 0;     // not a POSIX field, so mktime/timegm ignore
 114   timestruct.tm_zone   = NULL;  // not a POSIX field, so mktime/timegm ignore
 115 #endif
 116
 117   time_t seconds;
 118   if (is_local)
 119     seconds = mktime(&timestruct);
 120   else
 121     seconds = timegm(&timestruct);
 122
 123   int64 milliseconds;
 124   // Handle overflow.  Clamping the range to what mktime and timegm might
 125   // return is the best that can be done here.  It's not ideal, but it's better
 126   // than failing here or ignoring the overflow case and treating each time
 127   // overflow as one second prior to the epoch.
 128   if (seconds == -1 &&
 129       (exploded.year < 1969 || exploded.year > 1970)) {
 130     // If exploded.year is 1969 or 1970, take -1 as correct, with the
 131     // time indicating 1 second prior to the epoch.  (1970 is allowed to handle
 132     // time zone and DST offsets.)  Otherwise, return the most future or past
 133     // time representable.  Assumes the time_t epoch is 1970-01-01 00:00:00 UTC.
 134     //
 135     // The minimum and maximum representible times that mktime and timegm could
 136     // return are used here instead of values outside that range to allow for
 137     // proper round-tripping between exploded and counter-type time
 138     // representations in the presence of possible truncation to time_t by
 139     // division and use with other functions that accept time_t.
 140     //
 141     // When representing the most distant time in the future, add in an extra
 142     // 999ms to avoid the time being less than any other possible value that
 143     // this function can return.
 144     if (exploded.year < 1969) {
 145       milliseconds = std::numeric_limits<time_t>::min() *
 146                      kMillisecondsPerSecond;
 147     } else {
 148       milliseconds = (std::numeric_limits<time_t>::max() *
 149                       kMillisecondsPerSecond) +
 150                      kMillisecondsPerSecond - 1;
 151     }
 152   } else {
 153     milliseconds = seconds * kMillisecondsPerSecond + exploded.millisecond;
 154   }
 155
 156   // Adjust from Unix (1970) to Windows (1601) epoch.
 157   return Time((milliseconds * kMicrosecondsPerMillisecond) +
 158       kWindowsEpochDeltaMicroseconds);
 159 }
 160
 161 // TimeTicks ------------------------------------------------------------------
 162 // FreeBSD 6 has CLOCK_MONOLITHIC but defines _POSIX_MONOTONIC_CLOCK to -1.
 163 #if (defined(OS_POSIX) &&                                               \
 164      defined(_POSIX_MONOTONIC_CLOCK) && _POSIX_MONOTONIC_CLOCK >= 0) || \
 165      defined(OS_FREEBSD) || defined(OS_OPENBSD)
 166
 167 // static
 168 TimeTicks TimeTicks::Now() {
 169   uint64_t absolute_micro;
 170
 171   struct timespec ts;
 172   if (clock_gettime(CLOCK_MONOTONIC, &ts) != 0) {
 173     NOTREACHED() << "clock_gettime(CLOCK_MONOTONIC) failed.";
 174     return TimeTicks();
 175   }
 176
 177   absolute_micro =
 178       (static_cast<int64>(ts.tv_sec) * Time::kMicrosecondsPerSecond) +
 179       (static_cast<int64>(ts.tv_nsec) / Time::kNanosecondsPerMicrosecond);
 180
 181   return TimeTicks(absolute_micro);
 182 }
 183
 184 #elif defined(OS_NACL)
 185
 186 TimeTicks TimeTicks::Now() {
 187   // Sadly, Native Client does not have _POSIX_TIMERS enabled in sys/features.h
 188   // Apparently NaCl only has CLOCK_REALTIME:
 189   // http://code.google.com/p/nativeclient/issues/detail?id=1159
 190   return TimeTicks(clock());
 191 }
 192
 193 #else  // _POSIX_MONOTONIC_CLOCK
 194 #error No usable tick clock function on this platform.
 195 #endif  // _POSIX_MONOTONIC_CLOCK
 196
 197 // static
 198 TimeTicks TimeTicks::HighResNow() {
 199   return Now();
 200 }
 201
 202 #endif  // !OS_MACOSX
 203
 204 struct timeval Time::ToTimeVal() const {
 205   struct timeval result;
 206   int64 us = us_ - kTimeTToMicrosecondsOffset;
 207   result.tv_sec = us / Time::kMicrosecondsPerSecond;
 208   result.tv_usec = us % Time::kMicrosecondsPerSecond;
 209   return result;
 210 }
 211
 212 }  // namespace base