/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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 int 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 =
      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;
          }
          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 = year;
  }
  if (dotw != TT_UNKNOWN) {
    result->tm_wday = (((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);
}
