The Tor Browser: js/src/vm/DateTime.cpp@6474c204b198 (annotated)

js/src/vm/DateTime.cpp@6474c204b198 (annotated)

js/src/vm/DateTime.cpp

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
  * vim: set ts=8 sts=4 et sw=4 tw=99:
  * 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/. */
 #include "vm/DateTime.h"
 #include <time.h>
 #include "jsutil.h"
 using mozilla::UnspecifiedNaN;
 static bool
 ComputeLocalTime(time_t local, struct tm *ptm)
 {
 #ifdef HAVE_LOCALTIME_R
     return localtime_r(&local, ptm);
 #else
     struct tm *otm = localtime(&local);
     if (!otm)
         return false;
     *ptm = *otm;
     return true;
 #endif
 }
 static bool
 ComputeUTCTime(time_t t, struct tm *ptm)
 {
 #ifdef HAVE_GMTIME_R
     return gmtime_r(&t, ptm);
 #else
     struct tm *otm = gmtime(&t);
     if (!otm)
         return false;
     *ptm = *otm;
     return true;
 #endif
 }
 /*
  * Compute the offset in seconds from the current UTC time to the current local
  * standard time (i.e. not including any offset due to DST).
  *
  * Examples:
  *
  * Suppose we are in California, USA on January 1, 2013 at 04:00 PST (UTC-8, no
  * DST in effect), corresponding to 12:00 UTC.  This function would then return
  * -8 * SecondsPerHour, or -28800.
  *
  * Or suppose we are in Berlin, Germany on July 1, 2013 at 17:00 CEST (UTC+2,
  * DST in effect), corresponding to 15:00 UTC.  This function would then return
  * +1 * SecondsPerHour, or +3600.
  */
 static int32_t
 UTCToLocalStandardOffsetSeconds()
 {
     using js::SecondsPerDay;
     using js::SecondsPerHour;
     using js::SecondsPerMinute;
 #if defined(XP_WIN)
     // Windows doesn't follow POSIX: updates to the TZ environment variable are
     // not reflected immediately on that platform as they are on other systems
     // without this call.
     _tzset();
 #endif
     // Get the current time.
     time_t currentMaybeWithDST = time(nullptr);
     if (currentMaybeWithDST == time_t(-1))
         return 0;
     // Break down the current time into its (locally-valued, maybe with DST)
     // components.
     struct tm local;
     if (!ComputeLocalTime(currentMaybeWithDST, &local))
         return 0;
     // Compute a |time_t| corresponding to |local| interpreted without DST.
     time_t currentNoDST;
     if (local.tm_isdst == 0) {
         // If |local| wasn't DST, we can use the same time.
         currentNoDST = currentMaybeWithDST;
     } else {
         // If |local| respected DST, we need a time broken down into components
         // ignoring DST.  Turn off DST in the broken-down time.
         local.tm_isdst = 0;
         // Compute a |time_t t| corresponding to the broken-down time with DST
         // off.  This has boundary-condition issues (for about the duration of
         // a DST offset) near the time a location moves to a different time
         // zone.  But 1) errors will be transient; 2) locations rarely change
         // time zone; and 3) in the absence of an API that provides the time
         // zone offset directly, this may be the best we can do.
         currentNoDST = mktime(&local);
         if (currentNoDST == time_t(-1))
             return 0;
     }
     // Break down the time corresponding to the no-DST |local| into UTC-based
     // components.
     struct tm utc;
     if (!ComputeUTCTime(currentNoDST, &utc))
         return 0;
     // Finally, compare the seconds-based components of the local non-DST
     // representation and the UTC representation to determine the actual
     // difference.
     int utc_secs = utc.tm_hour * SecondsPerHour + utc.tm_min * SecondsPerMinute;
     int local_secs = local.tm_hour * SecondsPerHour + local.tm_min * SecondsPerMinute;
     // Same-day?  Just subtract the seconds counts.
     if (utc.tm_mday == local.tm_mday)
         return local_secs - utc_secs;
     // If we have more UTC seconds, move local seconds into the UTC seconds'
     // frame of reference and then subtract.
     if (utc_secs > local_secs)
         return (SecondsPerDay + local_secs) - utc_secs;
     // Otherwise we have more local seconds, so move the UTC seconds into the
     // local seconds' frame of reference and then subtract.
     return local_secs - (utc_secs + SecondsPerDay);
 }
 void
 js::DateTimeInfo::updateTimeZoneAdjustment()
 {
     /*
      * The difference between local standard time and UTC will never change for
      * a given time zone.
      */
     utcToLocalStandardOffsetSeconds = UTCToLocalStandardOffsetSeconds();
     double newTZA = utcToLocalStandardOffsetSeconds * msPerSecond;
     if (newTZA == localTZA_)
         return;
     localTZA_ = newTZA;
     /*
      * The initial range values are carefully chosen to result in a cache miss
      * on first use given the range of possible values.  Be careful to keep
      * these values and the caching algorithm in sync!
      */
     offsetMilliseconds = 0;
     rangeStartSeconds = rangeEndSeconds = INT64_MIN;
     oldOffsetMilliseconds = 0;
     oldRangeStartSeconds = oldRangeEndSeconds = INT64_MIN;
     sanityCheck();
 }
 /*
  * Since getDSTOffsetMilliseconds guarantees that all times seen will be
  * positive, we can initialize the range at construction time with large
  * negative numbers to ensure the first computation is always a cache miss and
  * doesn't return a bogus offset.
  */
 js::DateTimeInfo::DateTimeInfo()
 {
     // Set to a totally impossible TZA so that the comparison above will fail
     // and all fields will be properly initialized.
     localTZA_ = UnspecifiedNaN<double>();
     updateTimeZoneAdjustment();
 }
 int64_t
 js::DateTimeInfo::computeDSTOffsetMilliseconds(int64_t utcSeconds)
 {
     MOZ_ASSERT(utcSeconds >= 0);
     MOZ_ASSERT(utcSeconds <= MaxUnixTimeT);
 #if defined(XP_WIN)
     // Windows does not follow POSIX. Updates to the TZ environment variable
     // are not reflected immediately on that platform as they are on UNIX
     // systems without this call.
     _tzset();
 #endif
     struct tm tm;
     if (!ComputeLocalTime(static_cast<time_t>(utcSeconds), &tm))
         return 0;
     int32_t dayoff = int32_t((utcSeconds + utcToLocalStandardOffsetSeconds) % SecondsPerDay);
     int32_t tmoff = tm.tm_sec + (tm.tm_min * SecondsPerMinute) + (tm.tm_hour * SecondsPerHour);
     int32_t diff = tmoff - dayoff;
     if (diff < 0)
         diff += SecondsPerDay;
     return diff * msPerSecond;
 }
 int64_t
 js::DateTimeInfo::getDSTOffsetMilliseconds(int64_t utcMilliseconds)
 {
     sanityCheck();
     int64_t utcSeconds = utcMilliseconds / msPerSecond;
     if (utcSeconds > MaxUnixTimeT) {
         utcSeconds = MaxUnixTimeT;
     } else if (utcSeconds < 0) {
         /* Go ahead a day to make localtime work (does not work with 0). */
         utcSeconds = SecondsPerDay;
     }
     /*
      * NB: Be aware of the initial range values when making changes to this
      *     code: the first call to this method, with those initial range
      *     values, must result in a cache miss.
      */
     if (rangeStartSeconds <= utcSeconds && utcSeconds <= rangeEndSeconds)
         return offsetMilliseconds;
     if (oldRangeStartSeconds <= utcSeconds && utcSeconds <= oldRangeEndSeconds)
         return oldOffsetMilliseconds;
     oldOffsetMilliseconds = offsetMilliseconds;
     oldRangeStartSeconds = rangeStartSeconds;
     oldRangeEndSeconds = rangeEndSeconds;
     if (rangeStartSeconds <= utcSeconds) {
         int64_t newEndSeconds = Min(rangeEndSeconds + RangeExpansionAmount, MaxUnixTimeT);
         if (newEndSeconds >= utcSeconds) {
             int64_t endOffsetMilliseconds = computeDSTOffsetMilliseconds(newEndSeconds);
             if (endOffsetMilliseconds == offsetMilliseconds) {
                 rangeEndSeconds = newEndSeconds;
                 return offsetMilliseconds;
             }
             offsetMilliseconds = computeDSTOffsetMilliseconds(utcSeconds);
             if (offsetMilliseconds == endOffsetMilliseconds) {
                 rangeStartSeconds = utcSeconds;
                 rangeEndSeconds = newEndSeconds;
             } else {
                 rangeEndSeconds = utcSeconds;
             }
             return offsetMilliseconds;
         }
         offsetMilliseconds = computeDSTOffsetMilliseconds(utcSeconds);
         rangeStartSeconds = rangeEndSeconds = utcSeconds;
         return offsetMilliseconds;
     }
     int64_t newStartSeconds = Max<int64_t>(rangeStartSeconds - RangeExpansionAmount, 0);
     if (newStartSeconds <= utcSeconds) {
         int64_t startOffsetMilliseconds = computeDSTOffsetMilliseconds(newStartSeconds);
         if (startOffsetMilliseconds == offsetMilliseconds) {
             rangeStartSeconds = newStartSeconds;
             return offsetMilliseconds;
         }
         offsetMilliseconds = computeDSTOffsetMilliseconds(utcSeconds);
         if (offsetMilliseconds == startOffsetMilliseconds) {
             rangeStartSeconds = newStartSeconds;
             rangeEndSeconds = utcSeconds;
         } else {
             rangeStartSeconds = utcSeconds;
         }
         return offsetMilliseconds;
     }
     rangeStartSeconds = rangeEndSeconds = utcSeconds;
     offsetMilliseconds = computeDSTOffsetMilliseconds(utcSeconds);
     return offsetMilliseconds;
 }
 void
 js::DateTimeInfo::sanityCheck()
 {
     MOZ_ASSERT(rangeStartSeconds <= rangeEndSeconds);
     MOZ_ASSERT_IF(rangeStartSeconds == INT64_MIN, rangeEndSeconds == INT64_MIN);
     MOZ_ASSERT_IF(rangeEndSeconds == INT64_MIN, rangeStartSeconds == INT64_MIN);
     MOZ_ASSERT_IF(rangeStartSeconds != INT64_MIN,
                   rangeStartSeconds >= 0 && rangeEndSeconds >= 0);
     MOZ_ASSERT_IF(rangeStartSeconds != INT64_MIN,
                   rangeStartSeconds <= MaxUnixTimeT && rangeEndSeconds <= MaxUnixTimeT);
 }

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js/src/vm/DateTime.cpp@6474c204b198 (annotated)

js/src/vm/DateTime.cpp