Imported WebKit commit 2ea9d364d0f6efa8fa64acf19f451504c59be0e4 (http://svn.webkit.org/repository/webkit/trunk@104285)

1 files changed, 1062 insertions, 0 deletions

diff --git a/Source/JavaScriptCore/wtf/DateMath.cpp b/Source/JavaScriptCore/wtf/DateMath.cpp
new file mode 100644
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--- /dev/null
+++ b/Source/JavaScriptCore/wtf/DateMath.cpp
@@ -0,0 +1,1062 @@
+/*
+ * Copyright (C) 1999-2000 Harri Porten (porten@kde.org)
+ * Copyright (C) 2006, 2007 Apple Inc. All rights reserved.
+ * Copyright (C) 2009 Google Inc. All rights reserved.
+ * Copyright (C) 2007-2009 Torch Mobile, Inc.
+ * Copyright (C) 2010 &yet, LLC. (nate@andyet.net)
+ *
+ * The Original Code is Mozilla Communicator client code, released
+ * March 31, 1998.
+ *
+ * The Initial Developer of the Original Code is
+ * Netscape Communications Corporation.
+ * Portions created by the Initial Developer are Copyright (C) 1998
+ * the Initial Developer. All Rights Reserved.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * Alternatively, the contents of this file may be used under the terms
+ * of either the Mozilla Public License Version 1.1, found at
+ * http://www.mozilla.org/MPL/ (the "MPL") or the GNU General Public
+ * License Version 2.0, found at http://www.fsf.org/copyleft/gpl.html
+ * (the "GPL"), in which case the provisions of the MPL or the GPL are
+ * applicable instead of those above.  If you wish to allow use of your
+ * version of this file only under the terms of one of those two
+ * licenses (the MPL or the GPL) and not to allow others to use your
+ * version of this file under the LGPL, indicate your decision by
+ * deletingthe provisions above and replace them with the notice and
+ * other provisions required by the MPL or the GPL, as the case may be.
+ * If you do not delete the provisions above, a recipient may use your
+ * version of this file under any of the LGPL, the MPL or the GPL.
+
+ * Copyright 2006-2008 the V8 project authors. All rights reserved.
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ *       copyright notice, this list of conditions and the following
+ *       disclaimer in the documentation and/or other materials provided
+ *       with the distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ *       contributors may be used to endorse or promote products derived
+ *       from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "config.h"
+#include "DateMath.h"
+
+#include "Assertions.h"
+#include "ASCIICType.h"
+#include "CurrentTime.h"
+#include "MathExtras.h"
+#include "StdLibExtras.h"
+#include "StringExtras.h"
+
+#include <algorithm>
+#include <limits.h>
+#include <limits>
+#include <stdint.h>
+#include <time.h>
+#include <wtf/text/StringBuilder.h>
+
+#if HAVE(ERRNO_H)
+#include <errno.h>
+#endif
+
+#if OS(WINCE)
+extern "C" size_t strftime(char * const s, const size_t maxsize, const char * const format, const struct tm * const t);
+extern "C" struct tm * localtime(const time_t *timer);
+#endif
+
+#if HAVE(SYS_TIME_H)
+#include <sys/time.h>
+#endif
+
+#if HAVE(SYS_TIMEB_H)
+#include <sys/timeb.h>
+#endif
+
+using namespace WTF;
+
+namespace WTF {
+
+/* Constants */
+
+static const double minutesPerDay = 24.0 * 60.0;
+static const double secondsPerDay = 24.0 * 60.0 * 60.0;
+static const double secondsPerYear = 24.0 * 60.0 * 60.0 * 365.0;
+
+static const double usecPerSec = 1000000.0;
+
+static const double maxUnixTime = 2145859200.0; // 12/31/2037
+// ECMAScript asks not to support for a date of which total
+// millisecond value is larger than the following value.
+// See 15.9.1.14 of ECMA-262 5th edition.
+static const double maxECMAScriptTime = 8.64E15;
+
+// Day of year for the first day of each month, where index 0 is January, and day 0 is January 1.
+// First for non-leap years, then for leap years.
+static const int firstDayOfMonth[2][12] = {
+    {0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334},
+    {0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335}
+};
+
+bool isLeapYear(int year)
+{
+    if (year % 4 != 0)
+        return false;
+    if (year % 400 == 0)
+        return true;
+    if (year % 100 == 0)
+        return false;
+    return true;
+}
+
+static inline int daysInYear(int year)
+{
+    return 365 + isLeapYear(year);
+}
+
+static inline double daysFrom1970ToYear(int year)
+{
+    // The Gregorian Calendar rules for leap years:
+    // Every fourth year is a leap year.  2004, 2008, and 2012 are leap years.
+    // However, every hundredth year is not a leap year.  1900 and 2100 are not leap years.
+    // Every four hundred years, there's a leap year after all.  2000 and 2400 are leap years.
+
+    static const int leapDaysBefore1971By4Rule = 1970 / 4;
+    static const int excludedLeapDaysBefore1971By100Rule = 1970 / 100;
+    static const int leapDaysBefore1971By400Rule = 1970 / 400;
+
+    const double yearMinusOne = year - 1;
+    const double yearsToAddBy4Rule = floor(yearMinusOne / 4.0) - leapDaysBefore1971By4Rule;
+    const double yearsToExcludeBy100Rule = floor(yearMinusOne / 100.0) - excludedLeapDaysBefore1971By100Rule;
+    const double yearsToAddBy400Rule = floor(yearMinusOne / 400.0) - leapDaysBefore1971By400Rule;
+
+    return 365.0 * (year - 1970) + yearsToAddBy4Rule - yearsToExcludeBy100Rule + yearsToAddBy400Rule;
+}
+
+double msToDays(double ms)
+{
+    return floor(ms / msPerDay);
+}
+
+static String twoDigitStringFromNumber(int number)
+{
+    ASSERT(number >= 0 && number < 100);
+    if (number > 9)
+        return String::number(number);
+    return makeString("0", String::number(number));
+}
+
+int msToYear(double ms)
+{
+    int approxYear = static_cast<int>(floor(ms / (msPerDay * 365.2425)) + 1970);
+    double msFromApproxYearTo1970 = msPerDay * daysFrom1970ToYear(approxYear);
+    if (msFromApproxYearTo1970 > ms)
+        return approxYear - 1;
+    if (msFromApproxYearTo1970 + msPerDay * daysInYear(approxYear) <= ms)
+        return approxYear + 1;
+    return approxYear;
+}
+
+int dayInYear(double ms, int year)
+{
+    return static_cast<int>(msToDays(ms) - daysFrom1970ToYear(year));
+}
+
+static inline double msToMilliseconds(double ms)
+{
+    double result = fmod(ms, msPerDay);
+    if (result < 0)
+        result += msPerDay;
+    return result;
+}
+
+int msToMinutes(double ms)
+{
+    double result = fmod(floor(ms / msPerMinute), minutesPerHour);
+    if (result < 0)
+        result += minutesPerHour;
+    return static_cast<int>(result);
+}
+
+int msToHours(double ms)
+{
+    double result = fmod(floor(ms/msPerHour), hoursPerDay);
+    if (result < 0)
+        result += hoursPerDay;
+    return static_cast<int>(result);
+}
+
+int monthFromDayInYear(int dayInYear, bool leapYear)
+{
+    const int d = dayInYear;
+    int step;
+
+    if (d < (step = 31))
+        return 0;
+    step += (leapYear ? 29 : 28);
+    if (d < step)
+        return 1;
+    if (d < (step += 31))
+        return 2;
+    if (d < (step += 30))
+        return 3;
+    if (d < (step += 31))
+        return 4;
+    if (d < (step += 30))
+        return 5;
+    if (d < (step += 31))
+        return 6;
+    if (d < (step += 31))
+        return 7;
+    if (d < (step += 30))
+        return 8;
+    if (d < (step += 31))
+        return 9;
+    if (d < (step += 30))
+        return 10;
+    return 11;
+}
+
+static inline bool checkMonth(int dayInYear, int& startDayOfThisMonth, int& startDayOfNextMonth, int daysInThisMonth)
+{
+    startDayOfThisMonth = startDayOfNextMonth;
+    startDayOfNextMonth += daysInThisMonth;
+    return (dayInYear <= startDayOfNextMonth);
+}
+
+int dayInMonthFromDayInYear(int dayInYear, bool leapYear)
+{
+    const int d = dayInYear;
+    int step;
+    int next = 30;
+
+    if (d <= next)
+        return d + 1;
+    const int daysInFeb = (leapYear ? 29 : 28);
+    if (checkMonth(d, step, next, daysInFeb))
+        return d - step;
+    if (checkMonth(d, step, next, 31))
+        return d - step;
+    if (checkMonth(d, step, next, 30))
+        return d - step;
+    if (checkMonth(d, step, next, 31))
+        return d - step;
+    if (checkMonth(d, step, next, 30))
+        return d - step;
+    if (checkMonth(d, step, next, 31))
+        return d - step;
+    if (checkMonth(d, step, next, 31))
+        return d - step;
+    if (checkMonth(d, step, next, 30))
+        return d - step;
+    if (checkMonth(d, step, next, 31))
+        return d - step;
+    if (checkMonth(d, step, next, 30))
+        return d - step;
+    step = next;
+    return d - step;
+}
+
+static inline int monthToDayInYear(int month, bool isLeapYear)
+{
+    return firstDayOfMonth[isLeapYear][month];
+}
+
+double dateToDaysFrom1970(int year, int month, int day)
+{
+    year += month / 12;
+
+    month %= 12;
+    if (month < 0) {
+        month += 12;
+        --year;
+    }
+
+    double yearday = floor(daysFrom1970ToYear(year));
+    ASSERT((year >= 1970 && yearday >= 0) || (year < 1970 && yearday < 0));
+    int monthday = monthToDayInYear(month, isLeapYear(year));
+
+    return yearday + monthday + day - 1;
+}
+
+// There is a hard limit at 2038 that we currently do not have a workaround
+// for (rdar://problem/5052975).
+static inline int maximumYearForDST()
+{
+    return 2037;
+}
+
+static inline int minimumYearForDST()
+{
+    // Because of the 2038 issue (see maximumYearForDST) if the current year is
+    // greater than the max year minus 27 (2010), we want to use the max year
+    // minus 27 instead, to ensure there is a range of 28 years that all years
+    // can map to.
+    return std::min(msToYear(jsCurrentTime()), maximumYearForDST() - 27) ;
+}
+
+/*
+ * Find an equivalent year for the one given, where equivalence is deterined by
+ * the two years having the same leapness and the first day of the year, falling
+ * on the same day of the week.
+ *
+ * This function returns a year between this current year and 2037, however this
+ * function will potentially return incorrect results if the current year is after
+ * 2010, (rdar://problem/5052975), if the year passed in is before 1900 or after
+ * 2100, (rdar://problem/5055038).
+ */
+int equivalentYearForDST(int year)
+{
+    // It is ok if the cached year is not the current year as long as the rules
+    // for DST did not change between the two years; if they did the app would need
+    // to be restarted.
+    static int minYear = minimumYearForDST();
+    int maxYear = maximumYearForDST();
+
+    int difference;
+    if (year > maxYear)
+        difference = minYear - year;
+    else if (year < minYear)
+        difference = maxYear - year;
+    else
+        return year;
+
+    int quotient = difference / 28;
+    int product = (quotient) * 28;
+
+    year += product;
+    ASSERT((year >= minYear && year <= maxYear) || (product - year == static_cast<int>(std::numeric_limits<double>::quiet_NaN())));
+    return year;
+}
+
+int32_t calculateUTCOffset()
+{
+    time_t localTime = time(0);
+    tm localt;
+    getLocalTime(&localTime, &localt);
+
+    // Get the difference between this time zone and UTC on the 1st of January of this year.
+    localt.tm_sec = 0;
+    localt.tm_min = 0;
+    localt.tm_hour = 0;
+    localt.tm_mday = 1;
+    localt.tm_mon = 0;
+    // Not setting localt.tm_year!
+    localt.tm_wday = 0;
+    localt.tm_yday = 0;
+    localt.tm_isdst = 0;
+#if HAVE(TM_GMTOFF)
+    localt.tm_gmtoff = 0;
+#endif
+#if HAVE(TM_ZONE)
+    localt.tm_zone = 0;
+#endif
+    
+#if HAVE(TIMEGM)
+    time_t utcOffset = timegm(&localt) - mktime(&localt);
+#else
+    // Using a canned date of 01/01/2009 on platforms with weaker date-handling foo.
+    localt.tm_year = 109;
+    time_t utcOffset = 1230768000 - mktime(&localt);
+#endif
+
+    return static_cast<int32_t>(utcOffset * 1000);
+}
+
+/*
+ * Get the DST offset for the time passed in.
+ */
+static double calculateDSTOffsetSimple(double localTimeSeconds, double utcOffset)
+{
+    if (localTimeSeconds > maxUnixTime)
+        localTimeSeconds = maxUnixTime;
+    else if (localTimeSeconds < 0) // Go ahead a day to make localtime work (does not work with 0)
+        localTimeSeconds += secondsPerDay;
+
+    //input is UTC so we have to shift back to local time to determine DST thus the + getUTCOffset()
+    double offsetTime = (localTimeSeconds * msPerSecond) + utcOffset;
+
+    // Offset from UTC but doesn't include DST obviously
+    int offsetHour =  msToHours(offsetTime);
+    int offsetMinute =  msToMinutes(offsetTime);
+
+    // FIXME: time_t has a potential problem in 2038
+    time_t localTime = static_cast<time_t>(localTimeSeconds);
+
+    tm localTM;
+    getLocalTime(&localTime, &localTM);
+
+    double diff = ((localTM.tm_hour - offsetHour) * secondsPerHour) + ((localTM.tm_min - offsetMinute) * 60);
+
+    if (diff < 0)
+        diff += secondsPerDay;
+
+    return (diff * msPerSecond);
+}
+
+// Get the DST offset, given a time in UTC
+double calculateDSTOffset(double ms, double utcOffset)
+{
+    // On Mac OS X, the call to localtime (see calculateDSTOffsetSimple) will return historically accurate
+    // DST information (e.g. New Zealand did not have DST from 1946 to 1974) however the JavaScript
+    // standard explicitly dictates that historical information should not be considered when
+    // determining DST. For this reason we shift away from years that localtime can handle but would
+    // return historically accurate information.
+    int year = msToYear(ms);
+    int equivalentYear = equivalentYearForDST(year);
+    if (year != equivalentYear) {
+        bool leapYear = isLeapYear(year);
+        int dayInYearLocal = dayInYear(ms, year);
+        int dayInMonth = dayInMonthFromDayInYear(dayInYearLocal, leapYear);
+        int month = monthFromDayInYear(dayInYearLocal, leapYear);
+        double day = dateToDaysFrom1970(equivalentYear, month, dayInMonth);
+        ms = (day * msPerDay) + msToMilliseconds(ms);
+    }
+
+    return calculateDSTOffsetSimple(ms / msPerSecond, utcOffset);
+}
+
+void initializeDates()
+{
+#if !ASSERT_DISABLED
+    static bool alreadyInitialized;
+    ASSERT(!alreadyInitialized);
+    alreadyInitialized = true;
+#endif
+
+    equivalentYearForDST(2000); // Need to call once to initialize a static used in this function.
+}
+
+static inline double ymdhmsToSeconds(long year, int mon, int day, int hour, int minute, double second)
+{
+    double days = (day - 32075)
+        + floor(1461 * (year + 4800.0 + (mon - 14) / 12) / 4)
+        + 367 * (mon - 2 - (mon - 14) / 12 * 12) / 12
+        - floor(3 * ((year + 4900.0 + (mon - 14) / 12) / 100) / 4)
+        - 2440588;
+    return ((days * hoursPerDay + hour) * minutesPerHour + minute) * secondsPerMinute + second;
+}
+
+// We follow the recommendation of RFC 2822 to consider all
+// obsolete time zones not listed here equivalent to "-0000".
+static const struct KnownZone {
+#if !OS(WINDOWS)
+    const
+#endif
+        char tzName[4];
+    int tzOffset;
+} known_zones[] = {
+    { "UT", 0 },
+    { "GMT", 0 },
+    { "EST", -300 },
+    { "EDT", -240 },
+    { "CST", -360 },
+    { "CDT", -300 },
+    { "MST", -420 },
+    { "MDT", -360 },
+    { "PST", -480 },
+    { "PDT", -420 }
+};
+
+inline static void skipSpacesAndComments(const char*& s)
+{
+    int nesting = 0;
+    char ch;
+    while ((ch = *s)) {
+        if (!isASCIISpace(ch)) {
+            if (ch == '(')
+                nesting++;
+            else if (ch == ')' && nesting > 0)
+                nesting--;
+            else if (nesting == 0)
+                break;
+        }
+        s++;
+    }
+}
+
+// returns 0-11 (Jan-Dec); -1 on failure
+static int findMonth(const char* monthStr)
+{
+    ASSERT(monthStr);
+    char needle[4];
+    for (int i = 0; i < 3; ++i) {
+        if (!*monthStr)
+            return -1;
+        needle[i] = static_cast<char>(toASCIILower(*monthStr++));
+    }
+    needle[3] = '\0';
+    const char *haystack = "janfebmaraprmayjunjulaugsepoctnovdec";
+    const char *str = strstr(haystack, needle);
+    if (str) {
+        int position = static_cast<int>(str - haystack);
+        if (position % 3 == 0)
+            return position / 3;
+    }
+    return -1;
+}
+
+static bool parseLong(const char* string, char** stopPosition, int base, long* result)
+{
+    *result = strtol(string, stopPosition, base);
+    // Avoid the use of errno as it is not available on Windows CE
+    if (string == *stopPosition || *result == LONG_MIN || *result == LONG_MAX)
+        return false;
+    return true;
+}
+
+// Parses a date with the format YYYY[-MM[-DD]].
+// Year parsing is lenient, allows any number of digits, and +/-.
+// Returns 0 if a parse error occurs, else returns the end of the parsed portion of the string.
+static char* parseES5DatePortion(const char* currentPosition, long& year, long& month, long& day)
+{
+    char* postParsePosition;
+
+    // This is a bit more lenient on the year string than ES5 specifies:
+    // instead of restricting to 4 digits (or 6 digits with mandatory +/-),
+    // it accepts any integer value. Consider this an implementation fallback.
+    if (!parseLong(currentPosition, &postParsePosition, 10, &year))
+        return 0;
+
+    // Check for presence of -MM portion.
+    if (*postParsePosition != '-')
+        return postParsePosition;
+    currentPosition = postParsePosition + 1;
+    
+    if (!isASCIIDigit(*currentPosition))
+        return 0;
+    if (!parseLong(currentPosition, &postParsePosition, 10, &month))
+        return 0;
+    if ((postParsePosition - currentPosition) != 2)
+        return 0;
+
+    // Check for presence of -DD portion.
+    if (*postParsePosition != '-')
+        return postParsePosition;
+    currentPosition = postParsePosition + 1;
+    
+    if (!isASCIIDigit(*currentPosition))
+        return 0;
+    if (!parseLong(currentPosition, &postParsePosition, 10, &day))
+        return 0;
+    if ((postParsePosition - currentPosition) != 2)
+        return 0;
+    return postParsePosition;
+}
+
+// Parses a time with the format HH:mm[:ss[.sss]][Z|(+|-)00:00].
+// Fractional seconds parsing is lenient, allows any number of digits.
+// Returns 0 if a parse error occurs, else returns the end of the parsed portion of the string.
+static char* parseES5TimePortion(char* currentPosition, long& hours, long& minutes, double& seconds, long& timeZoneSeconds)
+{
+    char* postParsePosition;
+    if (!isASCIIDigit(*currentPosition))
+        return 0;
+    if (!parseLong(currentPosition, &postParsePosition, 10, &hours))
+        return 0;
+    if (*postParsePosition != ':' || (postParsePosition - currentPosition) != 2)
+        return 0;
+    currentPosition = postParsePosition + 1;
+    
+    if (!isASCIIDigit(*currentPosition))
+        return 0;
+    if (!parseLong(currentPosition, &postParsePosition, 10, &minutes))
+        return 0;
+    if ((postParsePosition - currentPosition) != 2)
+        return 0;
+    currentPosition = postParsePosition;
+
+    // Seconds are optional.
+    if (*currentPosition == ':') {
+        ++currentPosition;
+    
+        long intSeconds;
+        if (!isASCIIDigit(*currentPosition))
+            return 0;
+        if (!parseLong(currentPosition, &postParsePosition, 10, &intSeconds))
+            return 0;
+        if ((postParsePosition - currentPosition) != 2)
+            return 0;
+        seconds = intSeconds;
+        if (*postParsePosition == '.') {
+            currentPosition = postParsePosition + 1;
+            
+            // In ECMA-262-5 it's a bit unclear if '.' can be present without milliseconds, but
+            // a reasonable interpretation guided by the given examples and RFC 3339 says "no".
+            // We check the next character to avoid reading +/- timezone hours after an invalid decimal.
+            if (!isASCIIDigit(*currentPosition))
+                return 0;
+            
+            // We are more lenient than ES5 by accepting more or less than 3 fraction digits.
+            long fracSeconds;
+            if (!parseLong(currentPosition, &postParsePosition, 10, &fracSeconds))
+                return 0;
+            
+            long numFracDigits = postParsePosition - currentPosition;
+            seconds += fracSeconds * pow(10.0, static_cast<double>(-numFracDigits));
+        }
+        currentPosition = postParsePosition;
+    }
+
+    if (*currentPosition == 'Z')
+        return currentPosition + 1;
+
+    bool tzNegative;
+    if (*currentPosition == '-')
+        tzNegative = true;
+    else if (*currentPosition == '+')
+        tzNegative = false;
+    else
+        return currentPosition; // no timezone
+    ++currentPosition;
+    
+    long tzHours;
+    long tzHoursAbs;
+    long tzMinutes;
+    
+    if (!isASCIIDigit(*currentPosition))
+        return 0;
+    if (!parseLong(currentPosition, &postParsePosition, 10, &tzHours))
+        return 0;
+    if (*postParsePosition != ':' || (postParsePosition - currentPosition) != 2)
+        return 0;
+    tzHoursAbs = labs(tzHours);
+    currentPosition = postParsePosition + 1;
+    
+    if (!isASCIIDigit(*currentPosition))
+        return 0;
+    if (!parseLong(currentPosition, &postParsePosition, 10, &tzMinutes))
+        return 0;
+    if ((postParsePosition - currentPosition) != 2)
+        return 0;
+    currentPosition = postParsePosition;
+    
+    if (tzHoursAbs > 24)
+        return 0;
+    if (tzMinutes < 0 || tzMinutes > 59)
+        return 0;
+    
+    timeZoneSeconds = 60 * (tzMinutes + (60 * tzHoursAbs));
+    if (tzNegative)
+        timeZoneSeconds = -timeZoneSeconds;
+
+    return currentPosition;
+}
+
+double parseES5DateFromNullTerminatedCharacters(const char* dateString)
+{
+    // This parses a date of the form defined in ECMA-262-5, section 15.9.1.15
+    // (similar to RFC 3339 / ISO 8601: YYYY-MM-DDTHH:mm:ss[.sss]Z).
+    // In most cases it is intentionally strict (e.g. correct field widths, no stray whitespace).
+    
+    static const long daysPerMonth[12] = { 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
+    
+    // The year must be present, but the other fields may be omitted - see ES5.1 15.9.1.15.
+    long year = 0;
+    long month = 1;
+    long day = 1;
+    long hours = 0;
+    long minutes = 0;
+    double seconds = 0;
+    long timeZoneSeconds = 0;
+
+    // Parse the date YYYY[-MM[-DD]]
+    char* currentPosition = parseES5DatePortion(dateString, year, month, day);
+    if (!currentPosition)
+        return std::numeric_limits<double>::quiet_NaN();
+    // Look for a time portion.
+    if (*currentPosition == 'T') {
+        // Parse the time HH:mm[:ss[.sss]][Z|(+|-)00:00]
+        currentPosition = parseES5TimePortion(currentPosition + 1, hours, minutes, seconds, timeZoneSeconds);
+        if (!currentPosition)
+            return std::numeric_limits<double>::quiet_NaN();
+    }
+    // Check that we have parsed all characters in the string.
+    if (*currentPosition)
+        return std::numeric_limits<double>::quiet_NaN();
+
+    // A few of these checks could be done inline above, but since many of them are interrelated
+    // we would be sacrificing readability to "optimize" the (presumably less common) failure path.
+    if (month < 1 || month > 12)
+        return std::numeric_limits<double>::quiet_NaN();
+    if (day < 1 || day > daysPerMonth[month - 1])
+        return std::numeric_limits<double>::quiet_NaN();
+    if (month == 2 && day > 28 && !isLeapYear(year))
+        return std::numeric_limits<double>::quiet_NaN();
+    if (hours < 0 || hours > 24)
+        return std::numeric_limits<double>::quiet_NaN();
+    if (hours == 24 && (minutes || seconds))
+        return std::numeric_limits<double>::quiet_NaN();
+    if (minutes < 0 || minutes > 59)
+        return std::numeric_limits<double>::quiet_NaN();
+    if (seconds < 0 || seconds >= 61)
+        return std::numeric_limits<double>::quiet_NaN();
+    if (seconds > 60) {
+        // Discard leap seconds by clamping to the end of a minute.
+        seconds = 60;
+    }
+        
+    double dateSeconds = ymdhmsToSeconds(year, month, day, hours, minutes, seconds) - timeZoneSeconds;
+    return dateSeconds * msPerSecond;
+}
+
+// Odd case where 'exec' is allowed to be 0, to accomodate a caller in WebCore.
+double parseDateFromNullTerminatedCharacters(const char* dateString, bool& haveTZ, int& offset)
+{
+    haveTZ = false;
+    offset = 0;
+
+    // This parses a date in the form:
+    //     Tuesday, 09-Nov-99 23:12:40 GMT
+    // or
+    //     Sat, 01-Jan-2000 08:00:00 GMT
+    // or
+    //     Sat, 01 Jan 2000 08:00:00 GMT
+    // or
+    //     01 Jan 99 22:00 +0100    (exceptions in rfc822/rfc2822)
+    // ### non RFC formats, added for Javascript:
+    //     [Wednesday] January 09 1999 23:12:40 GMT
+    //     [Wednesday] January 09 23:12:40 GMT 1999
+    //
+    // We ignore the weekday.
+     
+    // Skip leading space
+    skipSpacesAndComments(dateString);
+
+    long month = -1;
+    const char *wordStart = dateString;
+    // Check contents of first words if not number
+    while (*dateString && !isASCIIDigit(*dateString)) {
+        if (isASCIISpace(*dateString) || *dateString == '(') {
+            if (dateString - wordStart >= 3)
+                month = findMonth(wordStart);
+            skipSpacesAndComments(dateString);
+            wordStart = dateString;
+        } else
+           dateString++;
+    }
+
+    // Missing delimiter between month and day (like "January29")?
+    if (month == -1 && wordStart != dateString)
+        month = findMonth(wordStart);
+
+    skipSpacesAndComments(dateString);
+
+    if (!*dateString)
+        return std::numeric_limits<double>::quiet_NaN();
+
+    // ' 09-Nov-99 23:12:40 GMT'
+    char* newPosStr;
+    long day;
+    if (!parseLong(dateString, &newPosStr, 10, &day))
+        return std::numeric_limits<double>::quiet_NaN();
+    dateString = newPosStr;
+
+    if (!*dateString)
+        return std::numeric_limits<double>::quiet_NaN();
+
+    if (day < 0)
+        return std::numeric_limits<double>::quiet_NaN();
+
+    long year = 0;
+    if (day > 31) {
+        // ### where is the boundary and what happens below?
+        if (*dateString != '/')
+            return std::numeric_limits<double>::quiet_NaN();
+        // looks like a YYYY/MM/DD date
+        if (!*++dateString)
+            return std::numeric_limits<double>::quiet_NaN();
+        year = day;
+        if (!parseLong(dateString, &newPosStr, 10, &month))
+            return std::numeric_limits<double>::quiet_NaN();
+        month -= 1;
+        dateString = newPosStr;
+        if (*dateString++ != '/' || !*dateString)
+            return std::numeric_limits<double>::quiet_NaN();
+        if (!parseLong(dateString, &newPosStr, 10, &day))
+            return std::numeric_limits<double>::quiet_NaN();
+        dateString = newPosStr;
+    } else if (*dateString == '/' && month == -1) {
+        dateString++;
+        // This looks like a MM/DD/YYYY date, not an RFC date.
+        month = day - 1; // 0-based
+        if (!parseLong(dateString, &newPosStr, 10, &day))
+            return std::numeric_limits<double>::quiet_NaN();
+        if (day < 1 || day > 31)
+            return std::numeric_limits<double>::quiet_NaN();
+        dateString = newPosStr;
+        if (*dateString == '/')
+            dateString++;
+        if (!*dateString)
+            return std::numeric_limits<double>::quiet_NaN();
+     } else {
+        if (*dateString == '-')
+            dateString++;
+
+        skipSpacesAndComments(dateString);
+
+        if (*dateString == ',')
+            dateString++;
+
+        if (month == -1) { // not found yet
+            month = findMonth(dateString);
+            if (month == -1)
+                return std::numeric_limits<double>::quiet_NaN();
+
+            while (*dateString && *dateString != '-' && *dateString != ',' && !isASCIISpace(*dateString))
+                dateString++;
+
+            if (!*dateString)
+                return std::numeric_limits<double>::quiet_NaN();
+
+            // '-99 23:12:40 GMT'
+            if (*dateString != '-' && *dateString != '/' && *dateString != ',' && !isASCIISpace(*dateString))
+                return std::numeric_limits<double>::quiet_NaN();
+            dateString++;
+        }
+    }
+
+    if (month < 0 || month > 11)
+        return std::numeric_limits<double>::quiet_NaN();
+
+    // '99 23:12:40 GMT'
+    if (year <= 0 && *dateString) {
+        if (!parseLong(dateString, &newPosStr, 10, &year))
+            return std::numeric_limits<double>::quiet_NaN();
+    }
+
+    // Don't fail if the time is missing.
+    long hour = 0;
+    long minute = 0;
+    long second = 0;
+    if (!*newPosStr)
+        dateString = newPosStr;
+    else {
+        // ' 23:12:40 GMT'
+        if (!(isASCIISpace(*newPosStr) || *newPosStr == ',')) {
+            if (*newPosStr != ':')
+                return std::numeric_limits<double>::quiet_NaN();
+            // There was no year; the number was the hour.
+            year = -1;
+        } else {
+            // in the normal case (we parsed the year), advance to the next number
+            dateString = ++newPosStr;
+            skipSpacesAndComments(dateString);
+        }
+
+        parseLong(dateString, &newPosStr, 10, &hour);
+        // Do not check for errno here since we want to continue
+        // even if errno was set becasue we are still looking
+        // for the timezone!
+
+        // Read a number? If not, this might be a timezone name.
+        if (newPosStr != dateString) {
+            dateString = newPosStr;
+
+            if (hour < 0 || hour > 23)
+                return std::numeric_limits<double>::quiet_NaN();
+
+            if (!*dateString)
+                return std::numeric_limits<double>::quiet_NaN();
+
+            // ':12:40 GMT'
+            if (*dateString++ != ':')
+                return std::numeric_limits<double>::quiet_NaN();
+
+            if (!parseLong(dateString, &newPosStr, 10, &minute))
+                return std::numeric_limits<double>::quiet_NaN();
+            dateString = newPosStr;
+
+            if (minute < 0 || minute > 59)
+                return std::numeric_limits<double>::quiet_NaN();
+
+            // ':40 GMT'
+            if (*dateString && *dateString != ':' && !isASCIISpace(*dateString))
+                return std::numeric_limits<double>::quiet_NaN();
+
+            // seconds are optional in rfc822 + rfc2822
+            if (*dateString ==':') {
+                dateString++;
+
+                if (!parseLong(dateString, &newPosStr, 10, &second))
+                    return std::numeric_limits<double>::quiet_NaN();
+                dateString = newPosStr;
+
+                if (second < 0 || second > 59)
+                    return std::numeric_limits<double>::quiet_NaN();
+            }
+
+            skipSpacesAndComments(dateString);
+
+            if (strncasecmp(dateString, "AM", 2) == 0) {
+                if (hour > 12)
+                    return std::numeric_limits<double>::quiet_NaN();
+                if (hour == 12)
+                    hour = 0;
+                dateString += 2;
+                skipSpacesAndComments(dateString);
+            } else if (strncasecmp(dateString, "PM", 2) == 0) {
+                if (hour > 12)
+                    return std::numeric_limits<double>::quiet_NaN();
+                if (hour != 12)
+                    hour += 12;
+                dateString += 2;
+                skipSpacesAndComments(dateString);
+            }
+        }
+    }
+
+    // Don't fail if the time zone is missing. 
+    // Some websites omit the time zone (4275206).
+    if (*dateString) {
+        if (strncasecmp(dateString, "GMT", 3) == 0 || strncasecmp(dateString, "UTC", 3) == 0) {
+            dateString += 3;
+            haveTZ = true;
+        }
+
+        if (*dateString == '+' || *dateString == '-') {
+            long o;
+            if (!parseLong(dateString, &newPosStr, 10, &o))
+                return std::numeric_limits<double>::quiet_NaN();
+            dateString = newPosStr;
+
+            if (o < -9959 || o > 9959)
+                return std::numeric_limits<double>::quiet_NaN();
+
+            int sgn = (o < 0) ? -1 : 1;
+            o = labs(o);
+            if (*dateString != ':') {
+                if (o >= 24)
+                    offset = ((o / 100) * 60 + (o % 100)) * sgn;
+                else
+                    offset = o * 60 * sgn;
+            } else { // GMT+05:00
+                long o2;
+                if (!parseLong(dateString, &newPosStr, 10, &o2))
+                    return std::numeric_limits<double>::quiet_NaN();
+                dateString = newPosStr;
+                offset = (o * 60 + o2) * sgn;
+            }
+            haveTZ = true;
+        } else {
+            for (size_t i = 0; i < WTF_ARRAY_LENGTH(known_zones); ++i) {
+                if (0 == strncasecmp(dateString, known_zones[i].tzName, strlen(known_zones[i].tzName))) {
+                    offset = known_zones[i].tzOffset;
+                    dateString += strlen(known_zones[i].tzName);
+                    haveTZ = true;
+                    break;
+                }
+            }
+        }
+    }
+
+    skipSpacesAndComments(dateString);
+
+    if (*dateString && year == -1) {
+        if (!parseLong(dateString, &newPosStr, 10, &year))
+            return std::numeric_limits<double>::quiet_NaN();
+        dateString = newPosStr;
+    }
+
+    skipSpacesAndComments(dateString);
+
+    // Trailing garbage
+    if (*dateString)
+        return std::numeric_limits<double>::quiet_NaN();
+
+    // Y2K: Handle 2 digit years.
+    if (year >= 0 && year < 100) {
+        if (year < 50)
+            year += 2000;
+        else
+            year += 1900;
+    }
+    
+    return ymdhmsToSeconds(year, month + 1, day, hour, minute, second) * msPerSecond;
+}
+
+double parseDateFromNullTerminatedCharacters(const char* dateString)
+{
+    bool haveTZ;
+    int offset;
+    double ms = parseDateFromNullTerminatedCharacters(dateString, haveTZ, offset);
+    if (isnan(ms))
+        return std::numeric_limits<double>::quiet_NaN();
+
+    // fall back to local timezone
+    if (!haveTZ) {
+        double utcOffset = calculateUTCOffset();
+        double dstOffset = calculateDSTOffset(ms, utcOffset);
+        offset = static_cast<int>((utcOffset + dstOffset) / msPerMinute);
+    }
+    return ms - (offset * msPerMinute);
+}
+
+double timeClip(double t)
+{
+    if (!isfinite(t))
+        return std::numeric_limits<double>::quiet_NaN();
+    if (fabs(t) > maxECMAScriptTime)
+        return std::numeric_limits<double>::quiet_NaN();
+    return trunc(t);
+}
+
+// See http://tools.ietf.org/html/rfc2822#section-3.3 for more information.
+String makeRFC2822DateString(unsigned dayOfWeek, unsigned day, unsigned month, unsigned year, unsigned hours, unsigned minutes, unsigned seconds, int utcOffset)
+{
+    StringBuilder stringBuilder;
+    stringBuilder.append(weekdayName[dayOfWeek]);
+    stringBuilder.append(", ");
+    stringBuilder.append(String::number(day));
+    stringBuilder.append(" ");
+    stringBuilder.append(monthName[month]);
+    stringBuilder.append(" ");
+    stringBuilder.append(String::number(year));
+    stringBuilder.append(" ");
+
+    stringBuilder.append(twoDigitStringFromNumber(hours));
+    stringBuilder.append(':');
+    stringBuilder.append(twoDigitStringFromNumber(minutes));
+    stringBuilder.append(':');
+    stringBuilder.append(twoDigitStringFromNumber(seconds));
+    stringBuilder.append(' ');
+
+    stringBuilder.append(utcOffset > 0 ? "+" : "-");
+    int absoluteUTCOffset = abs(utcOffset);
+    stringBuilder.append(twoDigitStringFromNumber(absoluteUTCOffset / 60));
+    stringBuilder.append(twoDigitStringFromNumber(absoluteUTCOffset % 60));
+
+    return stringBuilder.toString();
+}
+
+} // namespace WTF