wtf/CurrentTime.cpp

   1 /*
   2  * Copyright (C) 2006 Apple Computer, Inc.  All rights reserved.
   3  * Copyright (C) 2008 Google Inc. All rights reserved.
   4  * Copyright (C) 2007-2009 Torch Mobile, Inc.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions are
   8  * met:
   9  *
  10  *     * Redistributions of source code must retain the above copyright
  11  * notice, this list of conditions and the following disclaimer.
  12  *     * Redistributions in binary form must reproduce the above
  13  * copyright notice, this list of conditions and the following disclaimer
  14  * in the documentation and/or other materials provided with the
  15  * distribution.
  16  *     * Neither the name of Google Inc. nor the names of its
  17  * contributors may be used to endorse or promote products derived from
  18  * this software without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  21  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  22  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  23  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  24  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  25  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  26  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  27  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  28  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  29  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  30  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  31  */
  32
  33 #include "config.h"
  34 #include "CurrentTime.h"
  35
  36 #if OS(WINDOWS)
  37
  38 // Windows is first since we want to use hires timers, despite PLATFORM(CF)
  39 // being defined.
  40 // If defined, WIN32_LEAN_AND_MEAN disables timeBeginPeriod/timeEndPeriod.
  41 #undef WIN32_LEAN_AND_MEAN
  42 #include <windows.h>
  43 #include <math.h>
  44 #include <stdint.h>
  45 #include <time.h>
  46
  47 #if USE(QUERY_PERFORMANCE_COUNTER)
  48 #if OS(WINCE)
  49 extern "C" time_t mktime(struct tm *t);
  50 #else
  51 #include <sys/timeb.h>
  52 #include <sys/types.h>
  53 #endif
  54 #endif
  55
  56 #elif PLATFORM(CF)
  57 #include <CoreFoundation/CFDate.h>
  58 #elif PLATFORM(GTK)
  59 #include <glib.h>
  60 #elif PLATFORM(WX)
  61 #include <wx/datetime.h>
  62 #else // Posix systems relying on the gettimeofday()
  63 #include <sys/time.h>
  64 #endif
  65
  66 #if PLATFORM(CHROMIUM)
  67 #error Chromium uses a different timer implementation
  68 #endif
  69
  70 namespace WTF {
  71
  72 const double msPerSecond = 1000.0;
  73
  74 #if OS(WINDOWS)
  75
  76 #if USE(QUERY_PERFORMANCE_COUNTER)
  77
  78 static LARGE_INTEGER qpcFrequency;
  79 static bool syncedTime;
  80
  81 static double highResUpTime()
  82 {
  83     // We use QPC, but only after sanity checking its result, due to bugs:
  84     // http://support.microsoft.com/kb/274323
  85     // http://support.microsoft.com/kb/895980
  86     // http://msdn.microsoft.com/en-us/library/ms644904.aspx ("...you can get different results on different processors due to bugs in the basic input/output system (BIOS) or the hardware abstraction layer (HAL)."
  87
  88     static LARGE_INTEGER qpcLast;
  89     static DWORD tickCountLast;
  90     static bool inited;
  91
  92     LARGE_INTEGER qpc;
  93     QueryPerformanceCounter(&qpc);
  94     DWORD tickCount = GetTickCount();
  95
  96     if (inited) {
  97         __int64 qpcElapsed = ((qpc.QuadPart - qpcLast.QuadPart) * 1000) / qpcFrequency.QuadPart;
  98         __int64 tickCountElapsed;
  99         if (tickCount >= tickCountLast)
 100             tickCountElapsed = (tickCount - tickCountLast);
 101         else {
 102 #if COMPILER(MINGW)
 103             __int64 tickCountLarge = tickCount + 0x100000000ULL;
 104 #else
 105             __int64 tickCountLarge = tickCount + 0x100000000I64;
 106 #endif
 107             tickCountElapsed = tickCountLarge - tickCountLast;
 108         }
 109
 110         // force a re-sync if QueryPerformanceCounter differs from GetTickCount by more than 500ms.
 111         // (500ms value is from http://support.microsoft.com/kb/274323)
 112         __int64 diff = tickCountElapsed - qpcElapsed;
 113         if (diff > 500 || diff < -500)
 114             syncedTime = false;
 115     } else
 116         inited = true;
 117
 118     qpcLast = qpc;
 119     tickCountLast = tickCount;
 120
 121     return (1000.0 * qpc.QuadPart) / static_cast<double>(qpcFrequency.QuadPart);
 122 }
 123
 124 static double lowResUTCTime()
 125 {
 126 #if OS(WINCE)
 127     SYSTEMTIME systemTime;
 128     GetSystemTime(&systemTime);
 129     struct tm tmtime;
 130     tmtime.tm_year = systemTime.wYear - 1900;
 131     tmtime.tm_mon = systemTime.wMonth - 1;
 132     tmtime.tm_mday = systemTime.wDay;
 133     tmtime.tm_wday = systemTime.wDayOfWeek;
 134     tmtime.tm_hour = systemTime.wHour;
 135     tmtime.tm_min = systemTime.wMinute;
 136     tmtime.tm_sec = systemTime.wSecond;
 137     time_t timet = mktime(&tmtime);
 138     return timet * msPerSecond + systemTime.wMilliseconds;
 139 #else
 140     struct _timeb timebuffer;
 141     _ftime(&timebuffer);
 142     return timebuffer.time * msPerSecond + timebuffer.millitm;
 143 #endif
 144 }
 145
 146 static bool qpcAvailable()
 147 {
 148     static bool available;
 149     static bool checked;
 150
 151     if (checked)
 152         return available;
 153
 154     available = QueryPerformanceFrequency(&qpcFrequency);
 155     checked = true;
 156     return available;
 157 }
 158
 159 double currentTime()
 160 {
 161     // Use a combination of ftime and QueryPerformanceCounter.
 162     // ftime returns the information we want, but doesn't have sufficient resolution.
 163     // QueryPerformanceCounter has high resolution, but is only usable to measure time intervals.
 164     // To combine them, we call ftime and QueryPerformanceCounter initially. Later calls will use QueryPerformanceCounter
 165     // by itself, adding the delta to the saved ftime.  We periodically re-sync to correct for drift.
 166     static bool started;
 167     static double syncLowResUTCTime;
 168     static double syncHighResUpTime;
 169     static double lastUTCTime;
 170
 171     double lowResTime = lowResUTCTime();
 172
 173     if (!qpcAvailable())
 174         return lowResTime / 1000.0;
 175
 176     double highResTime = highResUpTime();
 177
 178     if (!syncedTime) {
 179         timeBeginPeriod(1); // increase time resolution around low-res time getter
 180         syncLowResUTCTime = lowResTime = lowResUTCTime();
 181         timeEndPeriod(1); // restore time resolution
 182         syncHighResUpTime = highResTime;
 183         syncedTime = true;
 184     }
 185
 186     double highResElapsed = highResTime - syncHighResUpTime;
 187     double utc = syncLowResUTCTime + highResElapsed;
 188
 189     // force a clock re-sync if we've drifted
 190     double lowResElapsed = lowResTime - syncLowResUTCTime;
 191     const double maximumAllowedDriftMsec = 15.625 * 2.0; // 2x the typical low-res accuracy
 192     if (fabs(highResElapsed - lowResElapsed) > maximumAllowedDriftMsec)
 193         syncedTime = false;
 194
 195     // make sure time doesn't run backwards (only correct if difference is < 2 seconds, since DST or clock changes could occur)
 196     const double backwardTimeLimit = 2000.0;
 197     if (utc < lastUTCTime && (lastUTCTime - utc) < backwardTimeLimit)
 198         return lastUTCTime / 1000.0;
 199     lastUTCTime = utc;
 200     return utc / 1000.0;
 201 }
 202
 203 #else
 204
 205 static double currentSystemTime()
 206 {
 207     FILETIME ft;
 208     GetCurrentFT(&ft);
 209
 210     // As per Windows documentation for FILETIME, copy the resulting FILETIME structure to a
 211     // ULARGE_INTEGER structure using memcpy (using memcpy instead of direct assignment can
 212     // prevent alignment faults on 64-bit Windows).
 213
 214     ULARGE_INTEGER t;
 215     memcpy(&t, &ft, sizeof(t));
 216
 217     // Windows file times are in 100s of nanoseconds.
 218     // To convert to seconds, we have to divide by 10,000,000, which is more quickly
 219     // done by multiplying by 0.0000001.
 220
 221     // Between January 1, 1601 and January 1, 1970, there were 369 complete years,
 222     // of which 89 were leap years (1700, 1800, and 1900 were not leap years).
 223     // That is a total of 134774 days, which is 11644473600 seconds.
 224
 225     return t.QuadPart * 0.0000001 - 11644473600.0;
 226 }
 227
 228 double currentTime()
 229 {
 230     static bool init = false;
 231     static double lastTime;
 232     static DWORD lastTickCount;
 233     if (!init) {
 234         lastTime = currentSystemTime();
 235         lastTickCount = GetTickCount();
 236         init = true;
 237         return lastTime;
 238     }
 239
 240     DWORD tickCountNow = GetTickCount();
 241     DWORD elapsed = tickCountNow - lastTickCount;
 242     double timeNow = lastTime + (double)elapsed / 1000.;
 243     if (elapsed >= 0x7FFFFFFF) {
 244         lastTime = timeNow;
 245         lastTickCount = tickCountNow;
 246     }
 247     return timeNow;
 248 }
 249
 250 #endif // USE(QUERY_PERFORMANCE_COUNTER)
 251
 252 #elif PLATFORM(CF)
 253
 254 double currentTime()
 255 {
 256     return CFAbsoluteTimeGetCurrent() + kCFAbsoluteTimeIntervalSince1970;
 257 }
 258
 259 #elif PLATFORM(GTK)
 260
 261 // Note: GTK on Windows will pick up the PLATFORM(WIN) implementation above which provides
 262 // better accuracy compared with Windows implementation of g_get_current_time:
 263 // (http://www.google.com/codesearch/p?hl=en#HHnNRjks1t0/glib-2.5.2/glib/gmain.c&q=g_get_current_time).
 264 // Non-Windows GTK builds could use gettimeofday() directly but for the sake of consistency lets use GTK function.
 265 double currentTime()
 266 {
 267     GTimeVal now;
 268     g_get_current_time(&now);
 269     return static_cast<double>(now.tv_sec) + static_cast<double>(now.tv_usec / 1000000.0);
 270 }
 271
 272 #elif PLATFORM(WX)
 273
 274 double currentTime()
 275 {
 276     wxDateTime now = wxDateTime::UNow();
 277     return (double)now.GetTicks() + (double)(now.GetMillisecond() / 1000.0);
 278 }
 279
 280 #else // Other Posix systems rely on the gettimeofday().
 281
 282 double currentTime()
 283 {
 284     struct timeval now;
 285     struct timezone zone;
 286
 287     gettimeofday(&now, &zone);
 288     return static_cast<double>(now.tv_sec) + (double)(now.tv_usec / 1000000.0);
 289 }
 290
 291 #endif
 292
 293 } // namespace WTF