/* 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/. */

/*
 * prtime.c --
 *
 *     NSPR date and time functions
 *
 */

#include "prinit.h"
#include "prtime.h"
#include "prlock.h"
#include "prprf.h"
#include "prlog.h"

#include <string.h>
#include <ctype.h>
#include <errno.h> /* for EINVAL */
#include <time.h>

/*
 * The COUNT_LEAPS macro counts the number of leap years passed by
 * till the start of the given year Y.  At the start of the year 4
 * A.D. the number of leap years passed by is 0, while at the start of
 * the year 5 A.D. this count is 1. The number of years divisible by
 * 100 but not divisible by 400 (the non-leap years) is deducted from
 * the count to get the correct number of leap years.
 *
 * The COUNT_DAYS macro counts the number of days since 01/01/01 till the
 * start of the given year Y. The number of days at the start of the year
 * 1 is 0 while the number of days at the start of the year 2 is 365
 * (which is ((2)-1) * 365) and so on. The reference point is 01/01/01
 * midnight 00:00:00.
 */

#define COUNT_LEAPS(Y) (((Y) - 1) / 4 - ((Y) - 1) / 100 + ((Y) - 1) / 400)
#define COUNT_DAYS(Y) (((Y) - 1) * 365 + COUNT_LEAPS(Y))
#define DAYS_BETWEEN_YEARS(A, B) (COUNT_DAYS(B) - COUNT_DAYS(A))

/*
 * Static variables used by functions in this file
 */

/*
 * The following array contains the day of year for the last day of
 * each month, where index 1 is January, and day 0 is January 1.
 */

static const PRInt16 lastDayOfMonth[2][13] = {
    { -1, 30, 58, 89, 119, 150, 180, 211, 242, 272, 303, 333, 364 },
    { -1, 30, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 }
};

/*
 * The number of days in a month
 */

static const PRInt8 nDays[2][12] = {
    { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 },
    { 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }
};

/*
 * Declarations for internal functions defined later in this file.
 */

static void ComputeGMT(PRTime time, PRExplodedTime* gmt);
static int IsLeapYear(PRInt16 year);
static void ApplySecOffset(PRExplodedTime* time, PRInt32 secOffset);

/*
 *------------------------------------------------------------------------
 *
 * ComputeGMT --
 *
 *     Caveats:
 *     - we ignore leap seconds
 *
 *------------------------------------------------------------------------
 */

static void
ComputeGMT(PRTime time, PRExplodedTime* gmt)
{
    PRInt32 tmp, rem;
    PRInt32 numDays;
    PRInt64 numDays64, rem64;
    int isLeap;
    PRInt64 sec;
    PRInt64 usec;
    PRInt64 usecPerSec;
    PRInt64 secPerDay;

    /*
     * We first do the usec, sec, min, hour thing so that we do not
     * have to do LL arithmetic.
     */

    LL_I2L(usecPerSec, 1000000L);
    LL_DIV(sec, time, usecPerSec);
    LL_MOD(usec, time, usecPerSec);
    LL_L2I(gmt->tm_usec, usec);
    /* Correct for weird mod semantics so the remainder is always positive */
    if (gmt->tm_usec < 0) {
        PRInt64 one;

        LL_I2L(one, 1L);
        LL_SUB(sec, sec, one);
        gmt->tm_usec += 1000000L;
    }

    LL_I2L(secPerDay, 86400L);
    LL_DIV(numDays64, sec, secPerDay);
    LL_MOD(rem64, sec, secPerDay);
    /* We are sure both of these numbers can fit into PRInt32 */
    LL_L2I(numDays, numDays64);
    LL_L2I(rem, rem64);
    if (rem < 0) {
        numDays--;
        rem += 86400L;
    }

    /* Compute day of week.  Epoch started on a Thursday. */

    gmt->tm_wday = (numDays + 4) % 7;
    if (gmt->tm_wday < 0) {
        gmt->tm_wday += 7;
    }

    /* Compute the time of day. */

    gmt->tm_hour = rem / 3600;
    rem %= 3600;
    gmt->tm_min = rem / 60;
    gmt->tm_sec = rem % 60;

    /*
     * Compute the year by finding the 400 year period, then working
     * down from there.
     *
     * Since numDays is originally the number of days since January 1, 1970,
     * we must change it to be the number of days from January 1, 0001.
     */

    numDays += 719162;      /* 719162 = days from year 1 up to 1970 */
    tmp = numDays / 146097; /* 146097 = days in 400 years */
    rem = numDays % 146097;
    gmt->tm_year = tmp * 400 + 1;

    /* Compute the 100 year period. */

    tmp = rem / 36524; /* 36524 = days in 100 years */
    rem %= 36524;
    if (tmp == 4) { /* the 400th year is a leap year */
        tmp = 3;
        rem = 36524;
    }
    gmt->tm_year += tmp * 100;

    /* Compute the 4 year period. */

    tmp = rem / 1461; /* 1461 = days in 4 years */
    rem %= 1461;
    gmt->tm_year += tmp * 4;

    /* Compute which year in the 4. */

    tmp = rem / 365;
    rem %= 365;
    if (tmp == 4) { /* the 4th year is a leap year */
        tmp = 3;
        rem = 365;
    }

    gmt->tm_year += tmp;
    gmt->tm_yday = rem;
    isLeap = IsLeapYear(gmt->tm_year);

    /* Compute the month and day of month. */

    for (tmp = 1; lastDayOfMonth[isLeap][tmp] < gmt->tm_yday; tmp++) {
    }
    gmt->tm_month = --tmp;
    gmt->tm_mday = gmt->tm_yday - lastDayOfMonth[isLeap][tmp];

    gmt->tm_params.tp_gmt_offset = 0;
    gmt->tm_params.tp_dst_offset = 0;
}

/*
 *------------------------------------------------------------------------
 *
 * PR_ExplodeTime --
 *
 *     Cf. struct tm *gmtime(const time_t *tp) and
 *         struct tm *localtime(const time_t *tp)
 *
 *------------------------------------------------------------------------
 */

PR_IMPLEMENT(void)
PR_ExplodeTime(PRTime usecs, PRTimeParamFn params, PRExplodedTime* exploded)
{
    ComputeGMT(usecs, exploded);
    exploded->tm_params = params(exploded);
    ApplySecOffset(exploded, exploded->tm_params.tp_gmt_offset +
                                 exploded->tm_params.tp_dst_offset);
}

/*
 *------------------------------------------------------------------------
 *
 * PR_ImplodeTime --
 *
 *     Cf. time_t mktime(struct tm *tp)
 *     Note that 1 year has < 2^25 seconds.  So an PRInt32 is large enough.
 *
 *------------------------------------------------------------------------
 */
PR_IMPLEMENT(PRTime)
PR_ImplodeTime(const PRExplodedTime* exploded)
{
    PRExplodedTime copy;
    PRTime retVal;
    PRInt64 secPerDay, usecPerSec;
    PRInt64 temp;
    PRInt64 numSecs64;
    PRInt32 numDays;
    PRInt32 numSecs;

    /* Normalize first.  Do this on our copy */
    copy = *exploded;
    PR_NormalizeTime(&copy, PR_GMTParameters);

    numDays = DAYS_BETWEEN_YEARS(1970, copy.tm_year);

    numSecs = copy.tm_yday * 86400 + copy.tm_hour * 3600 + copy.tm_min * 60 +
              copy.tm_sec;

    LL_I2L(temp, numDays);
    LL_I2L(secPerDay, 86400);
    LL_MUL(temp, temp, secPerDay);
    LL_I2L(numSecs64, numSecs);
    LL_ADD(numSecs64, numSecs64, temp);

    /* apply the GMT and DST offsets */
    LL_I2L(temp, copy.tm_params.tp_gmt_offset);
    LL_SUB(numSecs64, numSecs64, temp);
    LL_I2L(temp, copy.tm_params.tp_dst_offset);
    LL_SUB(numSecs64, numSecs64, temp);

    LL_I2L(usecPerSec, 1000000L);
    LL_MUL(temp, numSecs64, usecPerSec);
    LL_I2L(retVal, copy.tm_usec);
    LL_ADD(retVal, retVal, temp);

    return retVal;
}

/*
 *-------------------------------------------------------------------------
 *
 * IsLeapYear --
 *
 *     Returns 1 if the year is a leap year, 0 otherwise.
 *
 *-------------------------------------------------------------------------
 */

static int
IsLeapYear(PRInt16 year)
{
    if ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0) {
        return 1;
    }
    return 0;
}

/*
 * 'secOffset' should be less than 86400 (i.e., a day).
 * 'time' should point to a normalized PRExplodedTime.
 */

static void
ApplySecOffset(PRExplodedTime* time, PRInt32 secOffset)
{
    time->tm_sec += secOffset;

    /* Note that in this implementation we do not count leap seconds */
    if (time->tm_sec < 0 || time->tm_sec >= 60) {
        time->tm_min += time->tm_sec / 60;
        time->tm_sec %= 60;
        if (time->tm_sec < 0) {
            time->tm_sec += 60;
            time->tm_min--;
        }
    }

    if (time->tm_min < 0 || time->tm_min >= 60) {
        time->tm_hour += time->tm_min / 60;
        time->tm_min %= 60;
        if (time->tm_min < 0) {
            time->tm_min += 60;
            time->tm_hour--;
        }
    }

    if (time->tm_hour < 0) {
        /* Decrement mday, yday, and wday */
        time->tm_hour += 24;
        time->tm_mday--;
        time->tm_yday--;
        if (time->tm_mday < 1) {
            time->tm_month--;
            if (time->tm_month < 0) {
                time->tm_month = 11;
                time->tm_year--;
                if (IsLeapYear(time->tm_year)) {
                    time->tm_yday = 365;
                } else {
                    time->tm_yday = 364;
                }
            }
            time->tm_mday = nDays[IsLeapYear(time->tm_year)][time->tm_month];
        }
        time->tm_wday--;
        if (time->tm_wday < 0) {
            time->tm_wday = 6;
        }
    } else if (time->tm_hour > 23) {
        /* Increment mday, yday, and wday */
        time->tm_hour -= 24;
        time->tm_mday++;
        time->tm_yday++;
        if (time->tm_mday > nDays[IsLeapYear(time->tm_year)][time->tm_month]) {
            time->tm_mday = 1;
            time->tm_month++;
            if (time->tm_month > 11) {
                time->tm_month = 0;
                time->tm_year++;
                time->tm_yday = 0;
            }
        }
        time->tm_wday++;
        if (time->tm_wday > 6) {
            time->tm_wday = 0;
        }
    }
}

PR_IMPLEMENT(void)
PR_NormalizeTime(PRExplodedTime* time, PRTimeParamFn params)
{
    int daysInMonth;
    PRInt32 numDays;

    /* Get back to GMT */
    time->tm_sec -= time->tm_params.tp_gmt_offset + time->tm_params.tp_dst_offset;
    time->tm_params.tp_gmt_offset = 0;
    time->tm_params.tp_dst_offset = 0;

    /* Now normalize GMT */

    if (time->tm_usec < 0 || time->tm_usec >= 1000000) {
        time->tm_sec += time->tm_usec / 1000000;
        time->tm_usec %= 1000000;
        if (time->tm_usec < 0) {
            time->tm_usec += 1000000;
            time->tm_sec--;
        }
    }

    /* Note that we do not count leap seconds in this implementation */
    if (time->tm_sec < 0 || time->tm_sec >= 60) {
        time->tm_min += time->tm_sec / 60;
        time->tm_sec %= 60;
        if (time->tm_sec < 0) {
            time->tm_sec += 60;
            time->tm_min--;
        }
    }

    if (time->tm_min < 0 || time->tm_min >= 60) {
        time->tm_hour += time->tm_min / 60;
        time->tm_min %= 60;
        if (time->tm_min < 0) {
            time->tm_min += 60;
            time->tm_hour--;
        }
    }

    if (time->tm_hour < 0 || time->tm_hour >= 24) {
        time->tm_mday += time->tm_hour / 24;
        time->tm_hour %= 24;
        if (time->tm_hour < 0) {
            time->tm_hour += 24;
            time->tm_mday--;
        }
    }

    /* Normalize month and year before mday */
    if (time->tm_month < 0 || time->tm_month >= 12) {
        time->tm_year += time->tm_month / 12;
        time->tm_month %= 12;
        if (time->tm_month < 0) {
            time->tm_month += 12;
            time->tm_year--;
        }
    }

    /* Now that month and year are in proper range, normalize mday */

    if (time->tm_mday < 1) {
        /* mday too small */
        do {
            /* the previous month */
            time->tm_month--;
            if (time->tm_month < 0) {
                time->tm_month = 11;
                time->tm_year--;
            }
            time->tm_mday += nDays[IsLeapYear(time->tm_year)][time->tm_month];
        } while (time->tm_mday < 1);
    } else {
        daysInMonth = nDays[IsLeapYear(time->tm_year)][time->tm_month];
        while (time->tm_mday > daysInMonth) {
            /* mday too large */
            time->tm_mday -= daysInMonth;
            time->tm_month++;
            if (time->tm_month > 11) {
                time->tm_month = 0;
                time->tm_year++;
            }
            daysInMonth = nDays[IsLeapYear(time->tm_year)][time->tm_month];
        }
    }

    /* Recompute yday and wday */
    time->tm_yday = (PRInt16)time->tm_mday +
                    lastDayOfMonth[IsLeapYear(time->tm_year)][time->tm_month];

    numDays = DAYS_BETWEEN_YEARS(1970, time->tm_year) + time->tm_yday;
    time->tm_wday = (numDays + 4) % 7;
    if (time->tm_wday < 0) {
        time->tm_wday += 7;
    }

    /* Recompute time parameters */

    time->tm_params = params(time);

    ApplySecOffset(time,
                   time->tm_params.tp_gmt_offset + time->tm_params.tp_dst_offset);
}

/*
 *-------------------------------------------------------------------------
 *
 * PR_LocalTimeParameters --
 *
 *     returns the time parameters for the local time zone
 *
 *     The following uses localtime() from the standard C library.
 *     (time.h)  This is our fallback implementation.  Unix, PC, and BeOS
 *     use this version.  A platform may have its own machine-dependent
 *     implementation of this function.
 *
 *-------------------------------------------------------------------------
 */

#if defined(HAVE_INT_LOCALTIME_R)

/*
 * In this case we could define the macro as
 *     #define MT_safe_localtime(timer, result) \
 *             (localtime_r(timer, result) == 0 ? result : NULL)
 * I chose to compare the return value of localtime_r with -1 so
 * that I can catch the cases where localtime_r returns a pointer
 * to struct tm.  The macro definition above would not be able to
 * detect such mistakes because it is legal to compare a pointer
 * with 0.
 */

#define MT_safe_localtime(timer, result) \
    (localtime_r(timer, result) == -1 ? NULL : result)

#elif defined(HAVE_POINTER_LOCALTIME_R)

#define MT_safe_localtime localtime_r

#elif defined(_MSC_VER)

/* Visual C++ has had localtime_s() since Visual C++ 2005. */

static struct tm*
MT_safe_localtime(const time_t* clock, struct tm* result)
{
    errno_t err = localtime_s(result, clock);
    if (err != 0) {
        errno = err;
        return NULL;
    }
    return result;
}

#else

#define HAVE_LOCALTIME_MONITOR                   \
    1 /* We use 'monitor' to serialize our calls \
       * to localtime(). */
static PRLock* monitor = NULL;

static struct tm*
MT_safe_localtime(const time_t* clock, struct tm* result)
{
    struct tm* tmPtr;
    int needLock = PR_Initialized(); /* We need to use a lock to protect
                                      * against NSPR threads only when the
                                      * NSPR thread system is activated. */

    if (needLock) {
        PR_Lock(monitor);
    }

    /*
     * Microsoft (all flavors) localtime() returns a NULL pointer if 'clock'
     * represents a time before midnight January 1, 1970.  In
     * that case, we also return a NULL pointer and the struct tm
     * object pointed to by 'result' is not modified.
     *
     */

    tmPtr = localtime(clock);

    if (tmPtr) {
        *result = *tmPtr;
    } else {
        result = NULL;
    }

    if (needLock) {
        PR_Unlock(monitor);
    }

    return result;
}

#endif /* definition of MT_safe_localtime() */

void
_PR_InitTime(void)
{
#ifdef HAVE_LOCALTIME_MONITOR
    monitor = PR_NewLock();
#endif
#ifdef WINCE
    _MD_InitTime();
#endif
}

void
_PR_CleanupTime(void)
{
#ifdef HAVE_LOCALTIME_MONITOR
    if (monitor) {
        PR_DestroyLock(monitor);
        monitor = NULL;
    }
#endif
#ifdef WINCE
    _MD_CleanupTime();
#endif
}

#if defined(XP_UNIX) || defined(XP_PC)

PR_IMPLEMENT(PRTimeParameters)
PR_LocalTimeParameters(const PRExplodedTime* gmt)
{
    PRTimeParameters retVal;
    struct tm localTime;
    struct tm* localTimeResult;
    time_t secs;
    PRTime secs64;
    PRInt64 usecPerSec;
    PRInt64 usecPerSec_1;
    PRInt64 maxInt32;
    PRInt64 minInt32;
    PRInt32 dayOffset;
    PRInt32 offset2Jan1970;
    PRInt32 offsetNew;
    int isdst2Jan1970;

    /*
     * Calculate the GMT offset.  First, figure out what is
     * 00:00:00 Jan. 2, 1970 GMT (which is exactly a day, or 86400
     * seconds, since the epoch) in local time.  Then we calculate
     * the difference between local time and GMT in seconds:
     *     gmt_offset = local_time - GMT
     *
     * Caveat: the validity of this calculation depends on two
     * assumptions:
     * 1. Daylight saving time was not in effect on Jan. 2, 1970.
     * 2. The time zone of the geographic location has not changed
     *    since Jan. 2, 1970.
     */

    secs = 86400L;
    localTimeResult = MT_safe_localtime(&secs, &localTime);
    PR_ASSERT(localTimeResult != NULL);
    if (localTimeResult == NULL) {
        /* Shouldn't happen. Use safe fallback for optimized builds. */
        return PR_GMTParameters(gmt);
    }

    /* GMT is 00:00:00, 2nd of Jan. */

    offset2Jan1970 = (PRInt32)localTime.tm_sec + 60L * (PRInt32)localTime.tm_min +
                     3600L * (PRInt32)localTime.tm_hour +
                     86400L * (PRInt32)((PRInt32)localTime.tm_mday - 2L);

    isdst2Jan1970 = localTime.tm_isdst;

    /*
     * Now compute DST offset.  We calculate the overall offset
     * of local time from GMT, similar to above.  The overall
     * offset has two components: gmt offset and dst offset.
     * We subtract gmt offset from the overall offset to get
     * the dst offset.
     *     overall_offset = local_time - GMT
     *     overall_offset = gmt_offset + dst_offset
     * ==> dst_offset = local_time - GMT - gmt_offset
     */

    secs64 = PR_ImplodeTime(gmt); /* This is still in microseconds */
    LL_I2L(usecPerSec, PR_USEC_PER_SEC);
    LL_I2L(usecPerSec_1, PR_USEC_PER_SEC - 1);
    /* Convert to seconds, truncating down (3.1 -> 3 and -3.1 -> -4) */
    if (LL_GE_ZERO(secs64)) {
        LL_DIV(secs64, secs64, usecPerSec);
    } else {
        LL_NEG(secs64, secs64);
        LL_ADD(secs64, secs64, usecPerSec_1);
        LL_DIV(secs64, secs64, usecPerSec);
        LL_NEG(secs64, secs64);
    }
    LL_I2L(maxInt32, PR_INT32_MAX);
    LL_I2L(minInt32, PR_INT32_MIN);
    if (LL_CMP(secs64, >, maxInt32) || LL_CMP(secs64, <, minInt32)) {
        /* secs64 is too large or too small for time_t (32-bit integer) */
        retVal.tp_gmt_offset = offset2Jan1970;
        retVal.tp_dst_offset = 0;
        return retVal;
    }
    LL_L2I(secs, secs64);

    /*
     * On Windows, localtime() (and our MT_safe_localtime() too)
     * returns a NULL pointer for time before midnight January 1,
     * 1970 GMT.  In that case, we just use the GMT offset for
     * Jan 2, 1970 and assume that DST was not in effect.
     */

    if (MT_safe_localtime(&secs, &localTime) == NULL) {
        retVal.tp_gmt_offset = offset2Jan1970;
        retVal.tp_dst_offset = 0;
        return retVal;
    }

    /*
     * dayOffset is the offset between local time and GMT in
     * the day component, which can only be -1, 0, or 1.  We
     * use the day of the week to compute dayOffset.
     */

    dayOffset = (PRInt32)localTime.tm_wday - gmt->tm_wday;

    /*
     * Need to adjust for wrapping around of day of the week from
     * 6 back to 0.
     */

    if (dayOffset == -6) {
        /* Local time is Sunday (0) and GMT is Saturday (6) */
        dayOffset = 1;
    } else if (dayOffset == 6) {
        /* Local time is Saturday (6) and GMT is Sunday (0) */
        dayOffset = -1;
    }

    offsetNew = (PRInt32)localTime.tm_sec - gmt->tm_sec +
                60L * ((PRInt32)localTime.tm_min - gmt->tm_min) +
                3600L * ((PRInt32)localTime.tm_hour - gmt->tm_hour) +
                86400L * (PRInt32)dayOffset;

    if (localTime.tm_isdst <= 0) {
        /* DST is not in effect */
        retVal.tp_gmt_offset = offsetNew;
        retVal.tp_dst_offset = 0;
    } else {
        /* DST is in effect */
        if (isdst2Jan1970 <= 0) {
            /*
             * DST was not in effect back in 2 Jan. 1970.
             * Use the offset back then as the GMT offset,
             * assuming the time zone has not changed since then.
             */
            retVal.tp_gmt_offset = offset2Jan1970;
            retVal.tp_dst_offset = offsetNew - offset2Jan1970;
        } else {
            /*
             * DST was also in effect back in 2 Jan. 1970.
             * Then our clever trick (or rather, ugly hack) fails.
             * We will just assume DST offset is an hour.
             */
            retVal.tp_gmt_offset = offsetNew - 3600;
            retVal.tp_dst_offset = 3600;
        }
    }

    return retVal;
}

#endif /* defined(XP_UNIX) || defined(XP_PC) */

/*
 *------------------------------------------------------------------------
 *
 * PR_USPacificTimeParameters --
 *
 *     The time parameters function for the US Pacific Time Zone.
 *
 *------------------------------------------------------------------------
 */

/*
 * Returns the mday of the first sunday of the month, where
 * mday and wday are for a given day in the month.
 * mdays start with 1 (e.g. 1..31).
 * wdays start with 0 and are in the range 0..6.  0 = Sunday.
 */
#define firstSunday(mday, wday) (((mday - wday + 7 - 1) % 7) + 1)

/*
 * Returns the mday for the N'th Sunday of the month, where
 * mday and wday are for a given day in the month.
 * mdays start with 1 (e.g. 1..31).
 * wdays start with 0 and are in the range 0..6.  0 = Sunday.
 * N has the following values: 0 = first, 1 = second (etc), -1 = last.
 * ndays is the number of days in that month, the same value as the
 * mday of the last day of the month.
 */
static PRInt32
NthSunday(PRInt32 mday, PRInt32 wday, PRInt32 N, PRInt32 ndays)
{
    PRInt32 firstSun = firstSunday(mday, wday);

    if (N < 0) {
        N = (ndays - firstSun) / 7;
    }
    return firstSun + (7 * N);
}

typedef struct DSTParams {
    PRInt8 dst_start_month;       /* 0 = January */
    PRInt8 dst_start_Nth_Sunday;  /* N as defined above */
    PRInt8 dst_start_month_ndays; /* ndays as defined above */
    PRInt8 dst_end_month;         /* 0 = January */
    PRInt8 dst_end_Nth_Sunday;    /* N as defined above */
    PRInt8 dst_end_month_ndays;   /* ndays as defined above */
} DSTParams;

static const DSTParams dstParams[2] = {
    /* year < 2007:  First April Sunday - Last October Sunday */
    { 3, 0, 30, 9, -1, 31 },
    /* year >= 2007: Second March Sunday - First November Sunday */
    { 2, 1, 31, 10, 0, 30 }
};

PR_IMPLEMENT(PRTimeParameters)
PR_USPacificTimeParameters(const PRExplodedTime* gmt)
{
    const DSTParams* dst;
    PRTimeParameters retVal;
    PRExplodedTime st;

    /*
     * Based on geographic location and GMT, figure out offset of
     * standard time from GMT.  In this example implementation, we
     * assume the local time zone is US Pacific Time.
     */

    retVal.tp_gmt_offset = -8L * 3600L;

    /*
     * Make a copy of GMT.  Note that the tm_params field of this copy
     * is ignored.
     */

    st.tm_usec = gmt->tm_usec;
    st.tm_sec = gmt->tm_sec;
    st.tm_min = gmt->tm_min;
    st.tm_hour = gmt->tm_hour;
    st.tm_mday = gmt->tm_mday;
    st.tm_month = gmt->tm_month;
    st.tm_year = gmt->tm_year;
    st.tm_wday = gmt->tm_wday;
    st.tm_yday = gmt->tm_yday;

    /* Apply the offset to GMT to obtain the local standard time */
    ApplySecOffset(&st, retVal.tp_gmt_offset);

    if (st.tm_year < 2007) { /* first April Sunday - Last October Sunday */
        dst = &dstParams[0];
    } else { /* Second March Sunday - First November Sunday */
        dst = &dstParams[1];
    }

    /*
     * Apply the rules on standard time or GMT to obtain daylight saving
     * time offset.  In this implementation, we use the US DST rule.
     */
    if (st.tm_month < dst->dst_start_month) {
        retVal.tp_dst_offset = 0L;
    } else if (st.tm_month == dst->dst_start_month) {
        int NthSun = NthSunday(st.tm_mday, st.tm_wday, dst->dst_start_Nth_Sunday,
                               dst->dst_start_month_ndays);
        if (st.tm_mday < NthSun) { /* Before starting Sunday */
            retVal.tp_dst_offset = 0L;
        } else if (st.tm_mday == NthSun) { /* Starting Sunday */
            /* 01:59:59 PST -> 03:00:00 PDT */
            if (st.tm_hour < 2) {
                retVal.tp_dst_offset = 0L;
            } else {
                retVal.tp_dst_offset = 3600L;
            }
        } else { /* After starting Sunday */
            retVal.tp_dst_offset = 3600L;
        }
    } else if (st.tm_month < dst->dst_end_month) {
        retVal.tp_dst_offset = 3600L;
    } else if (st.tm_month == dst->dst_end_month) {
        int NthSun = NthSunday(st.tm_mday, st.tm_wday, dst->dst_end_Nth_Sunday,
                               dst->dst_end_month_ndays);
        if (st.tm_mday < NthSun) { /* Before ending Sunday */
            retVal.tp_dst_offset = 3600L;
        } else if (st.tm_mday == NthSun) { /* Ending Sunday */
            /* 01:59:59 PDT -> 01:00:00 PST */
            if (st.tm_hour < 1) {
                retVal.tp_dst_offset = 3600L;
            } else {
                retVal.tp_dst_offset = 0L;
            }
        } else { /* After ending Sunday */
            retVal.tp_dst_offset = 0L;
        }
    } else {
        retVal.tp_dst_offset = 0L;
    }
    return retVal;
}

/*
 *------------------------------------------------------------------------
 *
 * PR_GMTParameters --
 *
 *     Returns the PRTimeParameters for Greenwich Mean Time.
 *     Trivially, both the tp_gmt_offset and tp_dst_offset fields are 0.
 *
 *------------------------------------------------------------------------
 */

PR_IMPLEMENT(PRTimeParameters)
PR_GMTParameters(const PRExplodedTime* gmt)
{
    PRTimeParameters retVal = { 0, 0 };
    return retVal;
}

/*
 * The following code implements PR_ParseTimeString().  It is based on
 * ns/lib/xp/xp_time.c, revision 1.25, by Jamie Zawinski <jwz@netscape.com>.
 */

/*
 * We only recognize the abbreviations of a small subset of time zones
 * in North America, Europe, and Japan.
 *
 * PST/PDT: Pacific Standard/Daylight Time
 * MST/MDT: Mountain Standard/Daylight Time
 * CST/CDT: Central Standard/Daylight Time
 * EST/EDT: Eastern Standard/Daylight Time
 * AST: Atlantic Standard Time
 * NST: Newfoundland Standard Time
 * GMT: Greenwich Mean Time
 * BST: British Summer Time
 * MET: Middle Europe Time
 * EET: Eastern Europe Time
 * JST: Japan Standard Time
 */

typedef enum {
    TT_UNKNOWN,

    TT_SUN,
    TT_MON,
    TT_TUE,
    TT_WED,
    TT_THU,
    TT_FRI,
    TT_SAT,

    TT_JAN,
    TT_FEB,
    TT_MAR,
    TT_APR,
    TT_MAY,
    TT_JUN,
    TT_JUL,
    TT_AUG,
    TT_SEP,
    TT_OCT,
    TT_NOV,
    TT_DEC,

    TT_PST,
    TT_PDT,
    TT_MST,
    TT_MDT,
    TT_CST,
    TT_CDT,
    TT_EST,
    TT_EDT,
    TT_AST,
    TT_NST,
    TT_GMT,
    TT_BST,
    TT_MET,
    TT_EET,
    TT_JST
} TIME_TOKEN;

/*
 * This parses a time/date string into a PRTime
 * (microseconds after "1-Jan-1970 00:00:00 GMT").
 * It returns PR_SUCCESS on success, and PR_FAILURE
 * if the time/date string can't be parsed.
 *
 * Many formats are handled, including:
 *
 *   14 Apr 89 03:20:12
 *   14 Apr 89 03:20 GMT
 *   Fri, 17 Mar 89 4:01:33
 *   Fri, 17 Mar 89 4:01 GMT
 *   Mon Jan 16 16:12 PDT 1989
 *   Mon Jan 16 16:12 +0130 1989
 *   6 May 1992 16:41-JST (Wednesday)
 *   22-AUG-1993 10:59:12.82
 *   22-AUG-1993 10:59pm
 *   22-AUG-1993 12:59am
 *   22-AUG-1993 12:59 PM
 *   Friday, August 04, 1995 3:54 PM
 *   06/21/95 04:24:34 PM
 *   20/06/95 21:07
 *   95-06-08 19:32:48 EDT
 *
 * If the input string doesn't contain a description of the timezone,
 * we consult the `default_to_gmt' to decide whether the string should
 * be interpreted relative to the local time zone (PR_FALSE) or GMT (PR_TRUE).
 * The correct value for this argument depends on what standard specified
 * the time string which you are parsing.
 */

PR_IMPLEMENT(PRStatus)
PR_ParseTimeStringToExplodedTime(const char* string, PRBool default_to_gmt,
                                 PRExplodedTime* result)
{
    TIME_TOKEN dotw = TT_UNKNOWN;
    TIME_TOKEN month = TT_UNKNOWN;
    TIME_TOKEN zone = TT_UNKNOWN;
    int zone_offset = -1;
    int dst_offset = 0;
    int date = -1;
    PRInt32 year = -1;
    int hour = -1;
    int min = -1;
    int sec = -1;
    struct tm* localTimeResult;

    const char* rest = string;

    int iterations = 0;

    PR_ASSERT(string && result);
    if (!string || !result) {
        return PR_FAILURE;
    }

    while (*rest) {
        if (iterations++ > 1000) {
            return PR_FAILURE;
        }

        switch (*rest) {
            case 'a':
            case 'A':
                if (month == TT_UNKNOWN && (rest[1] == 'p' || rest[1] == 'P') &&
                    (rest[2] == 'r' || rest[2] == 'R')) {
                    month = TT_APR;
                } else if (zone == TT_UNKNOWN && (rest[1] == 's' || rest[1] == 'S') &&
                           (rest[2] == 't' || rest[2] == 'T')) {
                    zone = TT_AST;
                } else if (month == TT_UNKNOWN && (rest[1] == 'u' || rest[1] == 'U') &&
                           (rest[2] == 'g' || rest[2] == 'G')) {
                    month = TT_AUG;
                }
                break;
            case 'b':
            case 'B':
                if (zone == TT_UNKNOWN && (rest[1] == 's' || rest[1] == 'S') &&
                    (rest[2] == 't' || rest[2] == 'T')) {
                    zone = TT_BST;
                }
                break;
            case 'c':
            case 'C':
                if (zone == TT_UNKNOWN && (rest[1] == 'd' || rest[1] == 'D') &&
                    (rest[2] == 't' || rest[2] == 'T')) {
                    zone = TT_CDT;
                } else if (zone == TT_UNKNOWN && (rest[1] == 's' || rest[1] == 'S') &&
                           (rest[2] == 't' || rest[2] == 'T')) {
                    zone = TT_CST;
                }
                break;
            case 'd':
            case 'D':
                if (month == TT_UNKNOWN && (rest[1] == 'e' || rest[1] == 'E') &&
                    (rest[2] == 'c' || rest[2] == 'C')) {
                    month = TT_DEC;
                }
                break;
            case 'e':
            case 'E':
                if (zone == TT_UNKNOWN && (rest[1] == 'd' || rest[1] == 'D') &&
                    (rest[2] == 't' || rest[2] == 'T')) {
                    zone = TT_EDT;
                } else if (zone == TT_UNKNOWN && (rest[1] == 'e' || rest[1] == 'E') &&
                           (rest[2] == 't' || rest[2] == 'T')) {
                    zone = TT_EET;
                } else if (zone == TT_UNKNOWN && (rest[1] == 's' || rest[1] == 'S') &&
                           (rest[2] == 't' || rest[2] == 'T')) {
                    zone = TT_EST;
                }
                break;
            case 'f':
            case 'F':
                if (month == TT_UNKNOWN && (rest[1] == 'e' || rest[1] == 'E') &&
                    (rest[2] == 'b' || rest[2] == 'B')) {
                    month = TT_FEB;
                } else if (dotw == TT_UNKNOWN && (rest[1] == 'r' || rest[1] == 'R') &&
                           (rest[2] == 'i' || rest[2] == 'I')) {
                    dotw = TT_FRI;
                }
                break;
            case 'g':
            case 'G':
                if (zone == TT_UNKNOWN && (rest[1] == 'm' || rest[1] == 'M') &&
                    (rest[2] == 't' || rest[2] == 'T')) {
                    zone = TT_GMT;
                }
                break;
            case 'j':
            case 'J':
                if (month == TT_UNKNOWN && (rest[1] == 'a' || rest[1] == 'A') &&
                    (rest[2] == 'n' || rest[2] == 'N')) {
                    month = TT_JAN;
                } else if (zone == TT_UNKNOWN && (rest[1] == 's' || rest[1] == 'S') &&
                           (rest[2] == 't' || rest[2] == 'T')) {
                    zone = TT_JST;
                } else if (month == TT_UNKNOWN && (rest[1] == 'u' || rest[1] == 'U') &&
                           (rest[2] == 'l' || rest[2] == 'L')) {
                    month = TT_JUL;
                } else if (month == TT_UNKNOWN && (rest[1] == 'u' || rest[1] == 'U') &&
                           (rest[2] == 'n' || rest[2] == 'N')) {
                    month = TT_JUN;
                }
                break;
            case 'm':
            case 'M':
                if (month == TT_UNKNOWN && (rest[1] == 'a' || rest[1] == 'A') &&
                    (rest[2] == 'r' || rest[2] == 'R')) {
                    month = TT_MAR;
                } else if (month == TT_UNKNOWN && (rest[1] == 'a' || rest[1] == 'A') &&
                           (rest[2] == 'y' || rest[2] == 'Y')) {
                    month = TT_MAY;
                } else if (zone == TT_UNKNOWN && (rest[1] == 'd' || rest[1] == 'D') &&
                           (rest[2] == 't' || rest[2] == 'T')) {
                    zone = TT_MDT;
                } else if (zone == TT_UNKNOWN && (rest[1] == 'e' || rest[1] == 'E') &&
                           (rest[2] == 't' || rest[2] == 'T')) {
                    zone = TT_MET;
                } else if (dotw == TT_UNKNOWN && (rest[1] == 'o' || rest[1] == 'O') &&
                           (rest[2] == 'n' || rest[2] == 'N')) {
                    dotw = TT_MON;
                } else if (zone == TT_UNKNOWN && (rest[1] == 's' || rest[1] == 'S') &&
                           (rest[2] == 't' || rest[2] == 'T')) {
                    zone = TT_MST;
                }
                break;
            case 'n':
            case 'N':
                if (month == TT_UNKNOWN && (rest[1] == 'o' || rest[1] == 'O') &&
                    (rest[2] == 'v' || rest[2] == 'V')) {
                    month = TT_NOV;
                } else if (zone == TT_UNKNOWN && (rest[1] == 's' || rest[1] == 'S') &&
                           (rest[2] == 't' || rest[2] == 'T')) {
                    zone = TT_NST;
                }
                break;
            case 'o':
            case 'O':
                if (month == TT_UNKNOWN && (rest[1] == 'c' || rest[1] == 'C') &&
                    (rest[2] == 't' || rest[2] == 'T')) {
                    month = TT_OCT;
                }
                break;
            case 'p':
            case 'P':
                if (zone == TT_UNKNOWN && (rest[1] == 'd' || rest[1] == 'D') &&
                    (rest[2] == 't' || rest[2] == 'T')) {
                    zone = TT_PDT;
                } else if (zone == TT_UNKNOWN && (rest[1] == 's' || rest[1] == 'S') &&
                           (rest[2] == 't' || rest[2] == 'T')) {
                    zone = TT_PST;
                }
                break;
            case 's':
            case 'S':
                if (dotw == TT_UNKNOWN && (rest[1] == 'a' || rest[1] == 'A') &&
                    (rest[2] == 't' || rest[2] == 'T')) {
                    dotw = TT_SAT;
                } else if (month == TT_UNKNOWN && (rest[1] == 'e' || rest[1] == 'E') &&
                           (rest[2] == 'p' || rest[2] == 'P')) {
                    month = TT_SEP;
                } else if (dotw == TT_UNKNOWN && (rest[1] == 'u' || rest[1] == 'U') &&
                           (rest[2] == 'n' || rest[2] == 'N')) {
                    dotw = TT_SUN;
                }
                break;
            case 't':
            case 'T':
                if (dotw == TT_UNKNOWN && (rest[1] == 'h' || rest[1] == 'H') &&
                    (rest[2] == 'u' || rest[2] == 'U')) {
                    dotw = TT_THU;
                } else if (dotw == TT_UNKNOWN && (rest[1] == 'u' || rest[1] == 'U') &&
                           (rest[2] == 'e' || rest[2] == 'E')) {
                    dotw = TT_TUE;
                }
                break;
            case 'u':
            case 'U':
                if (zone == TT_UNKNOWN && (rest[1] == 't' || rest[1] == 'T') &&
                    !(rest[2] >= 'A' && rest[2] <= 'Z') &&
                    !(rest[2] >= 'a' && rest[2] <= 'z'))
                /* UT is the same as GMT but UTx is not. */
                {
                    zone = TT_GMT;
                }
                break;
            case 'w':
            case 'W':
                if (dotw == TT_UNKNOWN && (rest[1] == 'e' || rest[1] == 'E') &&
                    (rest[2] == 'd' || rest[2] == 'D')) {
                    dotw = TT_WED;
                }
                break;

            case '+':
            case '-': {
                const char* end;
                int sign;
                if (zone_offset != -1) {
                    /* already got one... */
                    rest++;
                    break;
                }
                if (zone != TT_UNKNOWN && zone != TT_GMT) {
                    /* GMT+0300 is legal, but PST+0300 is not. */
                    rest++;
                    break;
                }

                sign = ((*rest == '+') ? 1 : -1);
                rest++; /* move over sign */
                end = rest;
                while (*end >= '0' && *end <= '9') {
                    end++;
                }
                if (rest == end) { /* no digits here */
                    break;
                }

                if ((end - rest) == 4) /* offset in HHMM */
                    zone_offset = (((((rest[0] - '0') * 10) + (rest[1] - '0')) * 60) +
                                   (((rest[2] - '0') * 10) + (rest[3] - '0')));
                else if ((end - rest) == 2)
                /* offset in hours */
                {
                    zone_offset = (((rest[0] - '0') * 10) + (rest[1] - '0')) * 60;
                } else if ((end - rest) == 1)
                /* offset in hours */
                {
                    zone_offset = (rest[0] - '0') * 60;
                } else
                /* 3 or >4 */
                {
                    break;
                }

                zone_offset *= sign;
                zone = TT_GMT;
                break;
            }

            case '0':
            case '1':
            case '2':
            case '3':
            case '4':
            case '5':
            case '6':
            case '7':
            case '8':
            case '9': {
                int tmp_hour = -1;
                int tmp_min = -1;
                int tmp_sec = -1;
                const char* end = rest + 1;
                while (*end >= '0' && *end <= '9') {
                    end++;
                }

                /* end is now the first character after a range of digits. */

                if (*end == ':') {
                    if (hour >= 0 && min >= 0) { /* already got it */
                        break;
                    }

                    /* We have seen "[0-9]+:", so this is probably HH:MM[:SS] */
                    if ((end - rest) > 2)
                    /* it is [0-9][0-9][0-9]+: */
                    {
                        break;
                    }
                    if ((end - rest) == 2)
                        tmp_hour = ((rest[0] - '0') * 10 + (rest[1] - '0'));
                    else {
                        tmp_hour = (rest[0] - '0');
                    }

                    /* move over the colon, and parse minutes */

                    rest = ++end;
                    while (*end >= '0' && *end <= '9') {
                        end++;
                    }

                    if (end == rest)
                    /* no digits after first colon? */
                    {
                        break;
                    }
                    if ((end - rest) > 2)
                    /* it is [0-9][0-9][0-9]+: */
                    {
                        break;
                    }
                    if ((end - rest) == 2)
                        tmp_min = ((rest[0] - '0') * 10 + (rest[1] - '0'));
                    else {
                        tmp_min = (rest[0] - '0');
                    }

                    /* now go for seconds */
                    rest = end;
                    if (*rest == ':') {
                        rest++;
                    }
                    end = rest;
                    while (*end >= '0' && *end <= '9') {
                        end++;
                    }

                    if (end == rest) /* no digits after second colon - that's ok. */
                        ;
                    else if ((end - rest) > 2)
                    /* it is [0-9][0-9][0-9]+: */
                    {
                        break;
                    } else if ((end - rest) == 2)
                        tmp_sec = ((rest[0] - '0') * 10 + (rest[1] - '0'));
                    else {
                        tmp_sec = (rest[0] - '0');
                    }

                    /* If we made it here, we've parsed hour and min,
                       and possibly sec, so it worked as a unit. */

                    /* skip over whitespace and see if there's an AM or PM
                       directly following the time.
                     */
                    if (tmp_hour <= 12) {
                        const char* s = end;
                        while (*s && (*s == ' ' || *s == '\t')) {
                            s++;
                        }
                        if ((s[0] == 'p' || s[0] == 'P') && (s[1] == 'm' || s[1] == 'M'))
                        /* 10:05pm == 22:05, and 12:05pm == 12:05 */
                        {
                            tmp_hour = (tmp_hour == 12 ? 12 : tmp_hour + 12);
                        } else if (tmp_hour == 12 && (s[0] == 'a' || s[0] == 'A') &&
                                   (s[1] == 'm' || s[1] == 'M'))
                        /* 12:05am == 00:05 */
                        {
                            tmp_hour = 0;
                        }
                    }

                    hour = tmp_hour;
                    min = tmp_min;
                    sec = tmp_sec;
                    rest = end;
                    break;
                }
                if ((*end == '/' || *end == '-') && end[1] >= '0' && end[1] <= '9') {
                    /* Perhaps this is 6/16/95, 16/6/95, 6-16-95, or 16-6-95
                       or even 95-06-05...
                       #### But it doesn't handle 1995-06-22.
                     */
                    int n1, n2, n3;
                    const char* s;

                    if (month != TT_UNKNOWN)
                    /* if we saw a month name, this can't be. */
                    {
                        break;
                    }

                    s = rest;

                    n1 = (*s++ - '0'); /* first 1 or 2 digits */
                    if (*s >= '0' && *s <= '9') {
                        n1 = n1 * 10 + (*s++ - '0');
                    }

                    if (*s != '/' && *s != '-') { /* slash */
                        break;
                    }
                    s++;

                    if (*s < '0' || *s > '9') { /* second 1 or 2 digits */
                        break;
                    }
                    n2 = (*s++ - '0');
                    if (*s >= '0' && *s <= '9') {
                        n2 = n2 * 10 + (*s++ - '0');
                    }

                    if (*s != '/' && *s != '-') { /* slash */
                        break;
                    }
                    s++;

                    if (*s < '0' || *s > '9') { /* third 1, 2, 4, or 5 digits */
                        break;
                    }
                    n3 = (*s++ - '0');
                    if (*s >= '0' && *s <= '9') {
                        n3 = n3 * 10 + (*s++ - '0');
                    }

                    if (*s >= '0' && *s <= '9') /* optional digits 3, 4, and 5 */
                    {
                        n3 = n3 * 10 + (*s++ - '0');
                        if (*s < '0' || *s > '9') {
                            break;
                        }
                        n3 = n3 * 10 + (*s++ - '0');
                        if (*s >= '0' && *s <= '9') {
                            n3 = n3 * 10 + (*s++ - '0');
                        }
                    }

                    if ((*s >= '0' && *s <= '9') || /* followed by non-alphanum */
                        (*s >= 'A' && *s <= 'Z') || (*s >= 'a' && *s <= 'z')) {
                        break;
                    }

                    /* Ok, we parsed three 1-2 digit numbers, with / or -
                       between them.  Now decide what the hell they are
                       (DD/MM/YY or MM/DD/YY or YY/MM/DD.)
                     */

                    if (n1 > 31 || n1 == 0) /* must be YY/MM/DD */
                    {
                        if (n2 > 12) {
                            break;
                        }
                        if (n3 > 31) {
                            break;
                        }
                        year = n1;
                        if (year < 70) {
                            year += 2000;
                        } else if (year < 100) {
                            year += 1900;
                        }
                        month = (TIME_TOKEN)(n2 + ((int)TT_JAN) - 1);
                        date = n3;
                        rest = s;
                        break;
                    }

                    if (n1 > 12 && n2 > 12) /* illegal */
                    {
                        rest = s;
                        break;
                    }

                    if (n3 < 70) {
                        n3 += 2000;
                    } else if (n3 < 100) {
                        n3 += 1900;
                    }

                    if (n1 > 12) /* must be DD/MM/YY */
                    {
                        date = n1;
                        month = (TIME_TOKEN)(n2 + ((int)TT_JAN) - 1);
                        year = n3;
                    } else /* assume MM/DD/YY */
                    {
                        /* #### In the ambiguous case, should we consult the
                           locale to find out the local default? */
                        month = (TIME_TOKEN)(n1 + ((int)TT_JAN) - 1);
                        date = n2;
                        year = n3;
                    }
                    rest = s;
                } else if ((*end >= 'A' && *end <= 'Z') || (*end >= 'a' && *end <= 'z'))
                    /* Digits followed by non-punctuation - what's that? */
                    ;
                else if ((end - rest) == 5) /* five digits is a year */
                    year = (year < 0 ? ((rest[0] - '0') * 10000L +
                                        (rest[1] - '0') * 1000L + (rest[2] - '0') * 100L +
                                        (rest[3] - '0') * 10L + (rest[4] - '0'))
                                     : year);
                else if ((end - rest) == 4) /* four digits is a year */
                    year = (year < 0 ? ((rest[0] - '0') * 1000L + (rest[1] - '0') * 100L +
                                        (rest[2] - '0') * 10L + (rest[3] - '0'))
                                     : year);
                else if ((end - rest) == 2) /* two digits - date or year */
                {
                    int n = ((rest[0] - '0') * 10 + (rest[1] - '0'));
                    /* If we don't have a date (day of the month) and we see a number
                         less than 32, then assume that is the date.

                             Otherwise, if we have a date and not a year, assume this is
                       the year.  If it is less than 70, then assume it refers to the 21st
                             century.  If it is two digits (>= 70), assume it refers to
                       this century.  Otherwise, assume it refers to an unambiguous year.

                             The world will surely end soon.
                       */
                    if (date < 0 && n < 32) {
                        date = n;
                    } else if (year < 0) {
                        if (n < 70) {
                            year = 2000 + n;
                        } else if (n < 100) {
                            year = 1900 + n;
                        } else {
                            year = n;
                        }
                    }
                    /* else what the hell is this. */
                } else if ((end - rest) == 1) { /* one digit - date */
                    date = (date < 0 ? (rest[0] - '0') : date);
                }
                /* else, three or more than five digits - what's that? */

                break;
            }
        }

        /* Skip to the end of this token, whether we parsed it or not.
               Tokens are delimited by whitespace, or ,;-/
               But explicitly not :+-.
         */
        while (*rest && *rest != ' ' && *rest != '\t' && *rest != ',' &&
               *rest != ';' && *rest != '-' && *rest != '+' && *rest != '/' &&
               *rest != '(' && *rest != ')' && *rest != '[' && *rest != ']') {
            rest++;
        }
        /* skip over uninteresting chars. */
    SKIP_MORE:
        while (*rest && (*rest == ' ' || *rest == '\t' || *rest == ',' ||
                         *rest == ';' || *rest == '/' || *rest == '(' ||
                         *rest == ')' || *rest == '[' || *rest == ']')) {
            rest++;
        }

        /* "-" is ignored at the beginning of a token if we have not yet
               parsed a year (e.g., the second "-" in "30-AUG-1966"), or if
               the character after the dash is not a digit. */
        if (*rest == '-' &&
            ((rest > string && isalpha((unsigned char)rest[-1]) && year < 0) ||
             rest[1] < '0' || rest[1] > '9')) {
            rest++;
            goto SKIP_MORE;
        }
    }

    if (zone != TT_UNKNOWN && zone_offset == -1) {
        switch (zone) {
            case TT_PST:
                zone_offset = -8 * 60;
                break;
            case TT_PDT:
                zone_offset = -8 * 60;
                dst_offset = 1 * 60;
                break;
            case TT_MST:
                zone_offset = -7 * 60;
                break;
            case TT_MDT:
                zone_offset = -7 * 60;
                dst_offset = 1 * 60;
                break;
            case TT_CST:
                zone_offset = -6 * 60;
                break;
            case TT_CDT:
                zone_offset = -6 * 60;
                dst_offset = 1 * 60;
                break;
            case TT_EST:
                zone_offset = -5 * 60;
                break;
            case TT_EDT:
                zone_offset = -5 * 60;
                dst_offset = 1 * 60;
                break;
            case TT_AST:
                zone_offset = -4 * 60;
                break;
            case TT_NST:
                zone_offset = -3 * 60 - 30;
                break;
            case TT_GMT:
                zone_offset = 0 * 60;
                break;
            case TT_BST:
                zone_offset = 0 * 60;
                dst_offset = 1 * 60;
                break;
            case TT_MET:
                zone_offset = 1 * 60;
                break;
            case TT_EET:
                zone_offset = 2 * 60;
                break;
            case TT_JST:
                zone_offset = 9 * 60;
                break;
            default:
                PR_ASSERT(0);
                break;
        }
    }

    /* If we didn't find a year, month, or day-of-the-month, we can't
           possibly parse this, and in fact, mktime() will do something random
           (I'm seeing it return "Tue Feb  5 06:28:16 2036", which is no doubt
           a numerologically significant date... */
    if (month == TT_UNKNOWN || date == -1 || year == -1 || year > PR_INT16_MAX) {
        return PR_FAILURE;
    }

    memset(result, 0, sizeof(*result));
    if (sec != -1) {
        result->tm_sec = sec;
    }
    if (min != -1) {
        result->tm_min = min;
    }
    if (hour != -1) {
        result->tm_hour = hour;
    }
    if (date != -1) {
        result->tm_mday = date;
    }
    if (month != TT_UNKNOWN) {
        result->tm_month = (((int)month) - ((int)TT_JAN));
    }
    if (year != -1) {
        result->tm_year = (PRInt16)year;
    }
    if (dotw != TT_UNKNOWN) {
        result->tm_wday = (PRInt8)(((int)dotw) - ((int)TT_SUN));
    }
    /*
     * Mainly to compute wday and yday, but normalized time is also required
     * by the check below that works around a Visual C++ 2005 mktime problem.
     */
    PR_NormalizeTime(result, PR_GMTParameters);
    /* The remaining work is to set the gmt and dst offsets in tm_params. */

    if (zone == TT_UNKNOWN && default_to_gmt) {
        /* No zone was specified, so pretend the zone was GMT. */
        zone = TT_GMT;
        zone_offset = 0;
    }

    if (zone_offset == -1) {
        /* no zone was specified, and we're to assume that everything
          is local. */
        struct tm localTime;
        time_t secs;

        PR_ASSERT(result->tm_month > -1 && result->tm_mday > 0 &&
                  result->tm_hour > -1 && result->tm_min > -1 &&
                  result->tm_sec > -1);

        /*
         * To obtain time_t from a tm structure representing the local
         * time, we call mktime().  However, we need to see if we are
         * on 1-Jan-1970 or before.  If we are, we can't call mktime()
         * because mktime() will crash on win16. In that case, we
         * calculate zone_offset based on the zone offset at
         * 00:00:00, 2 Jan 1970 GMT, and subtract zone_offset from the
         * date we are parsing to transform the date to GMT.  We also
         * do so if mktime() returns (time_t) -1 (time out of range).
         */

        /* month, day, hours, mins and secs are always non-negative
           so we dont need to worry about them. */
        if (result->tm_year >= 1970) {
            PRInt64 usec_per_sec;

            localTime.tm_sec = result->tm_sec;
            localTime.tm_min = result->tm_min;
            localTime.tm_hour = result->tm_hour;
            localTime.tm_mday = result->tm_mday;
            localTime.tm_mon = result->tm_month;
            localTime.tm_year = result->tm_year - 1900;
            /* Set this to -1 to tell mktime "I don't care".  If you set
               it to 0 or 1, you are making assertions about whether the
               date you are handing it is in daylight savings mode or not;
               and if you're wrong, it will "fix" it for you. */
            localTime.tm_isdst = -1;

#if _MSC_VER == 1400 /* 1400 = Visual C++ 2005 (8.0) */
            /*
             * mktime will return (time_t) -1 if the input is a date
             * after 23:59:59, December 31, 3000, US Pacific Time (not
             * UTC as documented):
             * http://msdn.microsoft.com/en-us/library/d1y53h2a(VS.80).aspx
             * But if the year is 3001, mktime also invokes the invalid
             * parameter handler, causing the application to crash.  This
             * problem has been reported in
             * http://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=266036.
             * We avoid this crash by not calling mktime if the date is
             * out of range.  To use a simple test that works in any time
             * zone, we consider year 3000 out of range as well.  (See
             * bug 480740.)
             */
            if (result->tm_year >= 3000) {
                /* Emulate what mktime would have done. */
                errno = EINVAL;
                secs = (time_t)-1;
            } else {
                secs = mktime(&localTime);
            }
#else
            secs = mktime(&localTime);
#endif
            if (secs != (time_t)-1) {
                PRTime usecs64;
                LL_I2L(usecs64, secs);
                LL_I2L(usec_per_sec, PR_USEC_PER_SEC);
                LL_MUL(usecs64, usecs64, usec_per_sec);
                PR_ExplodeTime(usecs64, PR_LocalTimeParameters, result);
                return PR_SUCCESS;
            }
        }

        /* So mktime() can't handle this case.  We assume the
           zone_offset for the date we are parsing is the same as
           the zone offset on 00:00:00 2 Jan 1970 GMT. */
        secs = 86400;
        localTimeResult = MT_safe_localtime(&secs, &localTime);
        PR_ASSERT(localTimeResult != NULL);
        if (localTimeResult == NULL) {
            return PR_FAILURE;
        }
        zone_offset = localTime.tm_min + 60 * localTime.tm_hour +
                      1440 * (localTime.tm_mday - 2);
    }

    result->tm_params.tp_gmt_offset = zone_offset * 60;
    result->tm_params.tp_dst_offset = dst_offset * 60;

    return PR_SUCCESS;
}

PR_IMPLEMENT(PRStatus)
PR_ParseTimeString(const char* string, PRBool default_to_gmt, PRTime* result)
{
    PRExplodedTime tm;
    PRStatus rv;

    rv = PR_ParseTimeStringToExplodedTime(string, default_to_gmt, &tm);
    if (rv != PR_SUCCESS) {
        return rv;
    }

    *result = PR_ImplodeTime(&tm);

    return PR_SUCCESS;
}

/*
 *******************************************************************
 *******************************************************************
 **
 **    OLD COMPATIBILITY FUNCTIONS
 **
 *******************************************************************
 *******************************************************************
 */

/*
 *-----------------------------------------------------------------------
 *
 * PR_FormatTime --
 *
 *     Format a time value into a buffer. Same semantics as strftime().
 *
 *-----------------------------------------------------------------------
 */

PR_IMPLEMENT(PRUint32)
PR_FormatTime(char* buf, int buflen, const char* fmt,
              const PRExplodedTime* time)
{
    size_t rv;
    struct tm a;
    struct tm* ap;

    if (time) {
        ap = &a;
        a.tm_sec = time->tm_sec;
        a.tm_min = time->tm_min;
        a.tm_hour = time->tm_hour;
        a.tm_mday = time->tm_mday;
        a.tm_mon = time->tm_month;
        a.tm_wday = time->tm_wday;
        a.tm_year = time->tm_year - 1900;
        a.tm_yday = time->tm_yday;
        a.tm_isdst = time->tm_params.tp_dst_offset ? 1 : 0;

        /*
         * On some platforms, for example SunOS 4, struct tm has two
         * additional fields: tm_zone and tm_gmtoff.
         */

#if (__GLIBC__ >= 2) || defined(NETBSD) || defined(OPENBSD) || \
    defined(FREEBSD) || defined(DARWIN) || defined(ANDROID)
        a.tm_zone = NULL;
        a.tm_gmtoff = time->tm_params.tp_gmt_offset + time->tm_params.tp_dst_offset;
#endif
    } else {
        ap = NULL;
    }

    rv = strftime(buf, buflen, fmt, ap);
    if (!rv && buf && buflen > 0) {
        /*
         * When strftime fails, the contents of buf are indeterminate.
         * Some callers don't check the return value from this function,
         * so store an empty string in buf in case they try to print it.
         */
        buf[0] = '\0';
    }
    return rv;
}

/*
 * The following string arrays and macros are used by PR_FormatTimeUSEnglish().
 */

static const char* abbrevDays[] = { "Sun", "Mon", "Tue", "Wed",
                                    "Thu", "Fri", "Sat" };

static const char* days[] = { "Sunday", "Monday", "Tuesday", "Wednesday",
                              "Thursday", "Friday", "Saturday" };

static const char* abbrevMonths[] = { "Jan", "Feb", "Mar", "Apr", "May", "Jun",
                                      "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" };

static const char* months[] = { "January", "February", "March", "April",
                                "May", "June", "July", "August",
                                "September", "October", "November", "December" };

/*
 * Add a single character to the given buffer, incrementing the buffer pointer
 * and decrementing the buffer size. Return 0 on error.
 */
#define ADDCHAR(buf, bufSize, ch) \
    do {                          \
        if (bufSize < 1) {        \
            *(--buf) = '\0';      \
            return 0;             \
        }                         \
        *buf++ = ch;              \
        bufSize--;                \
    } while (0)

/*
 * Add a string to the given buffer, incrementing the buffer pointer
 * and decrementing the buffer size appropriately.  Return 0 on error.
 */
#define ADDSTR(buf, bufSize, str)       \
    do {                                \
        PRUint32 strSize = strlen(str); \
        if (strSize > bufSize) {        \
            if (bufSize == 0)           \
                *(--buf) = '\0';        \
            else                        \
                *buf = '\0';            \
            return 0;                   \
        }                               \
        memcpy(buf, str, strSize);      \
        buf += strSize;                 \
        bufSize -= strSize;             \
    } while (0)

/* Needed by PR_FormatTimeUSEnglish() */
static unsigned int pr_WeekOfYear(const PRExplodedTime* time,
                                  unsigned int firstDayOfWeek);

/***********************************************************************************
 *
 * Description:
 *  This is a dumbed down version of strftime that will format the date in US
 *  English regardless of the setting of the global locale.  This functionality
 *is needed to write things like MIME headers which must always be in US
 *English.
 *
 **********************************************************************************/

PR_IMPLEMENT(PRUint32)
PR_FormatTimeUSEnglish(char* buf, PRUint32 bufSize, const char* format,
                       const PRExplodedTime* time)
{
    char* bufPtr = buf;
    const char* fmtPtr;
    char tmpBuf[40];
    const int tmpBufSize = sizeof(tmpBuf);

    for (fmtPtr = format; *fmtPtr != '\0'; fmtPtr++) {
        if (*fmtPtr != '%') {
            ADDCHAR(bufPtr, bufSize, *fmtPtr);
        } else {
            switch (*(++fmtPtr)) {
                case '%':
                    /* escaped '%' character */
                    ADDCHAR(bufPtr, bufSize, '%');
                    break;

                case 'a':
                    /* abbreviated weekday name */
                    ADDSTR(bufPtr, bufSize, abbrevDays[time->tm_wday]);
                    break;

                case 'A':
                    /* full weekday name */
                    ADDSTR(bufPtr, bufSize, days[time->tm_wday]);
                    break;

                case 'b':
                    /* abbreviated month name */
                    ADDSTR(bufPtr, bufSize, abbrevMonths[time->tm_month]);
                    break;

                case 'B':
                    /* full month name */
                    ADDSTR(bufPtr, bufSize, months[time->tm_month]);
                    break;

                case 'c':
                    /* Date and time. */
                    PR_FormatTimeUSEnglish(tmpBuf, tmpBufSize, "%a %b %d %H:%M:%S %Y",
                                           time);
                    ADDSTR(bufPtr, bufSize, tmpBuf);
                    break;

                case 'd':
                    /* day of month ( 01 - 31 ) */
                    PR_snprintf(tmpBuf, tmpBufSize, "%.2ld", time->tm_mday);
                    ADDSTR(bufPtr, bufSize, tmpBuf);
                    break;

                case 'e':
                    /* day of month with space prefix for single digits ( 1 - 31 ) */
                    PR_snprintf(tmpBuf, tmpBufSize, "%2ld", time->tm_mday);
                    ADDSTR(bufPtr, bufSize, tmpBuf);
                    break;

                case 'H':
                    /* hour ( 00 - 23 ) */
                    PR_snprintf(tmpBuf, tmpBufSize, "%.2ld", time->tm_hour);
                    ADDSTR(bufPtr, bufSize, tmpBuf);
                    break;

                case 'I':
                    /* hour ( 01 - 12 ) */
                    PR_snprintf(tmpBuf, tmpBufSize, "%.2ld",
                                (time->tm_hour % 12) ? time->tm_hour % 12 : (PRInt32)12);
                    ADDSTR(bufPtr, bufSize, tmpBuf);
                    break;

                case 'j':
                    /* day number of year ( 001 - 366 ) */
                    PR_snprintf(tmpBuf, tmpBufSize, "%.3d", time->tm_yday + 1);
                    ADDSTR(bufPtr, bufSize, tmpBuf);
                    break;

                case 'm':
                    /* month number ( 01 - 12 ) */
                    PR_snprintf(tmpBuf, tmpBufSize, "%.2ld", time->tm_month + 1);
                    ADDSTR(bufPtr, bufSize, tmpBuf);
                    break;

                case 'M':
                    /* minute ( 00 - 59 ) */
                    PR_snprintf(tmpBuf, tmpBufSize, "%.2ld", time->tm_min);
                    ADDSTR(bufPtr, bufSize, tmpBuf);
                    break;

                case 'p':
                    /* locale's equivalent of either AM or PM */
                    ADDSTR(bufPtr, bufSize, (time->tm_hour < 12) ? "AM" : "PM");
                    break;

                case 'S':
                    /* seconds ( 00 - 61 ), allows for leap seconds */
                    PR_snprintf(tmpBuf, tmpBufSize, "%.2ld", time->tm_sec);
                    ADDSTR(bufPtr, bufSize, tmpBuf);
                    break;

                case 'U':
                    /* week number of year ( 00 - 53  ),  Sunday  is  the first day of
                     * week 1 */
                    PR_snprintf(tmpBuf, tmpBufSize, "%.2d", pr_WeekOfYear(time, 0));
                    ADDSTR(bufPtr, bufSize, tmpBuf);
                    break;

                case 'w':
                    /* weekday number ( 0 - 6 ), Sunday = 0 */
                    PR_snprintf(tmpBuf, tmpBufSize, "%d", time->tm_wday);
                    ADDSTR(bufPtr, bufSize, tmpBuf);
                    break;

                case 'W':
                    /* Week number of year ( 00 - 53  ),  Monday  is  the first day of
                     * week 1 */
                    PR_snprintf(tmpBuf, tmpBufSize, "%.2d", pr_WeekOfYear(time, 1));
                    ADDSTR(bufPtr, bufSize, tmpBuf);
                    break;

                case 'x':
                    /* Date representation */
                    PR_FormatTimeUSEnglish(tmpBuf, tmpBufSize, "%m/%d/%y", time);
                    ADDSTR(bufPtr, bufSize, tmpBuf);
                    break;

                case 'X':
                    /* Time representation. */
                    PR_FormatTimeUSEnglish(tmpBuf, tmpBufSize, "%H:%M:%S", time);
                    ADDSTR(bufPtr, bufSize, tmpBuf);
                    break;

                case 'y':
                    /* year within century ( 00 - 99 ) */
                    PR_snprintf(tmpBuf, tmpBufSize, "%.2d", time->tm_year % 100);
                    ADDSTR(bufPtr, bufSize, tmpBuf);
                    break;

                case 'Y':
                    /* year as ccyy ( for example 1986 ) */
                    PR_snprintf(tmpBuf, tmpBufSize, "%.4d", time->tm_year);
                    ADDSTR(bufPtr, bufSize, tmpBuf);
                    break;

                case 'Z':
                    /* Time zone name or no characters if  no  time  zone exists.
                     * Since time zone name is supposed to be independant of locale, we
                     * defer to PR_FormatTime() for this option.
                     */
                    PR_FormatTime(tmpBuf, tmpBufSize, "%Z", time);
                    ADDSTR(bufPtr, bufSize, tmpBuf);
                    break;

                default:
                    /* Unknown format.  Simply copy format into output buffer. */
                    ADDCHAR(bufPtr, bufSize, '%');
                    ADDCHAR(bufPtr, bufSize, *fmtPtr);
                    break;
            }
        }
    }

    ADDCHAR(bufPtr, bufSize, '\0');
    return (PRUint32)(bufPtr - buf - 1);
}

/***********************************************************************************
 *
 * Description:
 *  Returns the week number of the year (0-53) for the given time.
 *firstDayOfWeek is the day on which the week is considered to start (0=Sun,
 *1=Mon, ...). Week 1 starts the first time firstDayOfWeek occurs in the year.
 *In other words, a partial week at the start of the year is considered week 0.
 *
 **********************************************************************************/

static unsigned int
pr_WeekOfYear(const PRExplodedTime* time,
              unsigned int firstDayOfWeek)
{
    int dayOfWeek;
    int dayOfYear;

    /* Get the day of the year for the given time then adjust it to represent the
     * first day of the week containing the given time.
     */
    dayOfWeek = time->tm_wday - firstDayOfWeek;
    if (dayOfWeek < 0) {
        dayOfWeek += 7;
    }

    dayOfYear = time->tm_yday - dayOfWeek;

    if (dayOfYear <= 0) {
        /* If dayOfYear is <= 0, it is in the first partial week of the year. */
        return 0;
    }

    /* Count the number of full weeks ( dayOfYear / 7 ) then add a week if there
     * are any days left over ( dayOfYear % 7 ).  Because we are only counting to
     * the first day of the week containing the given time, rather than to the
     * actual day representing the given time, any days in week 0 will be
     * "absorbed" as extra days in the given week.
     */
    return (dayOfYear / 7) + ((dayOfYear % 7) == 0 ? 0 : 1);
}
