timestamp.c

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/*
 * src/interfaces/ecpg/pgtypeslib/timestamp.c
 */
#include "postgres_fe.h"
 
#include <time.h>
#include <limits.h>
#include <math.h>
 
#include "common/int.h"
#include "dt.h"
#include "pgtypes_date.h"
#include "pgtypes_timestamp.h"
#include "pgtypeslib_extern.h"
 
static int64
time2t(const int hour, const int min, const int sec, const fsec_t fsec)
{
    return (((((hour * MINS_PER_HOUR) + min) * SECS_PER_MINUTE) + sec) * USECS_PER_SEC) + fsec;
}                               /* time2t() */
 
static timestamp
dt2local(timestamp dt, int tz)
{
    dt -= (tz * USECS_PER_SEC);
    return dt;
}                               /* dt2local() */
 
/* tm2timestamp()
 * Convert a tm structure to a timestamp data type.
 * Note that year is _not_ 1900-based, but is an explicit full value.
 * Also, month is one-based, _not_ zero-based.
 *
 * Returns -1 on failure (overflow).
 */
int
tm2timestamp(struct tm *tm, fsec_t fsec, int *tzp, timestamp * result)
{
    int         dDate;
    int64       time;
 
    /* Prevent overflow in Julian-day routines */
    if (!IS_VALID_JULIAN(tm->tm_year, tm->tm_mon, tm->tm_mday))
        return -1;
 
    dDate = date2j(tm->tm_year, tm->tm_mon, tm->tm_mday) - date2j(2000, 1, 1);
    time = time2t(tm->tm_hour, tm->tm_min, tm->tm_sec, fsec);
    if (unlikely(pg_mul_s64_overflow(dDate, USECS_PER_DAY, result) ||
                 pg_add_s64_overflow(*result, time, result)))
        return -1;
    if (tzp != NULL)
        *result = dt2local(*result, -(*tzp));
 
    /* final range check catches just-out-of-range timestamps */
    if (!IS_VALID_TIMESTAMP(*result))
        return -1;
 
    return 0;
}                               /* tm2timestamp() */
 
static timestamp
SetEpochTimestamp(void)
{
    int64       noresult = 0;
    timestamp   dt;
    struct tm   tt,
               *tm = &tt;
 
    if (GetEpochTime(tm) < 0)
        return noresult;
 
    tm2timestamp(tm, 0, NULL, &dt);
    return dt;
}                               /* SetEpochTimestamp() */
 
/* timestamp2tm()
 * Convert timestamp data type to POSIX time structure.
 * Note that year is _not_ 1900-based, but is an explicit full value.
 * Also, month is one-based, _not_ zero-based.
 * Returns:
 *   0 on success
 *  -1 on out of range
 *
 * For dates within the system-supported time_t range, convert to the
 *  local time zone. If out of this range, leave as GMT. - tgl 97/05/27
 */
static int
timestamp2tm(timestamp dt, int *tzp, struct tm *tm, fsec_t *fsec, const char **tzn)
{
    int64       dDate,
                date0;
    int64       time;
#if defined(HAVE_STRUCT_TM_TM_ZONE) || defined(HAVE_INT_TIMEZONE)
    time_t      utime;
    struct tm  *tx;
#endif
 
    date0 = date2j(2000, 1, 1);
 
    time = dt;
    TMODULO(time, dDate, USECS_PER_DAY);
 
    if (time < INT64CONST(0))
    {
        time += USECS_PER_DAY;
        dDate -= 1;
    }
 
    /* add offset to go from J2000 back to standard Julian date */
    dDate += date0;
 
    /* Julian day routine does not work for negative Julian days */
    if (dDate < 0 || dDate > (timestamp) INT_MAX)
        return -1;
 
    j2date((int) dDate, &tm->tm_year, &tm->tm_mon, &tm->tm_mday);
    dt2time(time, &tm->tm_hour, &tm->tm_min, &tm->tm_sec, fsec);
 
    if (tzp != NULL)
    {
        /*
         * Does this fall within the capabilities of the localtime()
         * interface? Then use this to rotate to the local time zone.
         */
        if (IS_VALID_UTIME(tm->tm_year, tm->tm_mon, tm->tm_mday))
        {
#if defined(HAVE_STRUCT_TM_TM_ZONE) || defined(HAVE_INT_TIMEZONE)
            struct tm   tmbuf;
 
            utime = dt / USECS_PER_SEC +
                ((date0 - date2j(1970, 1, 1)) * INT64CONST(86400));
 
            tx = localtime_r(&utime, &tmbuf);
            tm->tm_year = tx->tm_year + 1900;
            tm->tm_mon = tx->tm_mon + 1;
            tm->tm_mday = tx->tm_mday;
            tm->tm_hour = tx->tm_hour;
            tm->tm_min = tx->tm_min;
            tm->tm_isdst = tx->tm_isdst;
 
#if defined(HAVE_STRUCT_TM_TM_ZONE)
            tm->tm_gmtoff = tx->tm_gmtoff;
            tm->tm_zone = tx->tm_zone;
 
            *tzp = -tm->tm_gmtoff;  /* tm_gmtoff is Sun/DEC-ism */
            if (tzn != NULL)
                *tzn = tm->tm_zone;
#elif defined(HAVE_INT_TIMEZONE)
            *tzp = (tm->tm_isdst > 0) ? TIMEZONE_GLOBAL - SECS_PER_HOUR : TIMEZONE_GLOBAL;
            if (tzn != NULL)
                *tzn = TZNAME_GLOBAL[(tm->tm_isdst > 0)];
#endif
#else                           /* not (HAVE_STRUCT_TM_TM_ZONE ||
                                 * HAVE_INT_TIMEZONE) */
            *tzp = 0;
            /* Mark this as *no* time zone available */
            tm->tm_isdst = -1;
            if (tzn != NULL)
                *tzn = NULL;
#endif
        }
        else
        {
            *tzp = 0;
            /* Mark this as *no* time zone available */
            tm->tm_isdst = -1;
            if (tzn != NULL)
                *tzn = NULL;
        }
    }
    else
    {
        tm->tm_isdst = -1;
        if (tzn != NULL)
            *tzn = NULL;
    }
 
    tm->tm_yday = dDate - date2j(tm->tm_year, 1, 1) + 1;
 
    return 0;
}                               /* timestamp2tm() */
 
/* EncodeSpecialTimestamp()
 *  * Convert reserved timestamp data type to string.
 *   */
static void
EncodeSpecialTimestamp(timestamp dt, char *str)
{
    if (TIMESTAMP_IS_NOBEGIN(dt))
        strcpy(str, EARLY);
    else if (TIMESTAMP_IS_NOEND(dt))
        strcpy(str, LATE);
    else
        abort();                /* shouldn't happen */
}
 
timestamp
PGTYPEStimestamp_from_asc(char *str, char **endptr)
{
    timestamp   result;
    int64       noresult = 0;
    fsec_t      fsec;
    struct tm   tt,
               *tm = &tt;
    int         dtype;
    int         nf;
    char       *field[MAXDATEFIELDS];
    int         ftype[MAXDATEFIELDS];
    char        lowstr[MAXDATELEN + MAXDATEFIELDS];
    char       *realptr;
    char      **ptr = (endptr != NULL) ? endptr : &realptr;
 
    if (strlen(str) > MAXDATELEN)
    {
        errno = PGTYPES_TS_BAD_TIMESTAMP;
        return noresult;
    }
 
    if (ParseDateTime(str, lowstr, field, ftype, &nf, ptr) != 0 ||
        DecodeDateTime(field, ftype, nf, &dtype, tm, &fsec, 0) != 0)
    {
        errno = PGTYPES_TS_BAD_TIMESTAMP;
        return noresult;
    }
 
    switch (dtype)
    {
        case DTK_DATE:
            if (tm2timestamp(tm, fsec, NULL, &result) != 0)
            {
                errno = PGTYPES_TS_BAD_TIMESTAMP;
                return noresult;
            }
            break;
 
        case DTK_EPOCH:
            result = SetEpochTimestamp();
            break;
 
        case DTK_LATE:
            TIMESTAMP_NOEND(result);
            break;
 
        case DTK_EARLY:
            TIMESTAMP_NOBEGIN(result);
            break;
 
        default:
            errno = PGTYPES_TS_BAD_TIMESTAMP;
            return noresult;
    }
 
    /* AdjustTimestampForTypmod(&result, typmod); */
 
    /*
     * Since it's difficult to test for noresult, make sure errno is 0 if no
     * error occurred.
     */
    errno = 0;
    return result;
}
 
char *
PGTYPEStimestamp_to_asc(timestamp tstamp)
{
    struct tm   tt,
               *tm = &tt;
    char        buf[MAXDATELEN + 1];
    fsec_t      fsec;
    int         DateStyle = 1;  /* this defaults to USE_ISO_DATES, shall we
                                 * make it an option? */
 
    if (TIMESTAMP_NOT_FINITE(tstamp))
        EncodeSpecialTimestamp(tstamp, buf);
    else if (timestamp2tm(tstamp, NULL, tm, &fsec, NULL) == 0)
        EncodeDateTime(tm, fsec, false, 0, NULL, DateStyle, buf, 0);
    else
    {
        errno = PGTYPES_TS_BAD_TIMESTAMP;
        return NULL;
    }
    return pgtypes_strdup(buf);
}
 
void
PGTYPEStimestamp_current(timestamp * ts)
{
    struct tm   tm;
 
    GetCurrentDateTime(&tm);
    if (errno == 0)
        tm2timestamp(&tm, 0, NULL, ts);
}
 
static int
dttofmtasc_replace(timestamp * ts, date dDate, int dow, struct tm *tm,
                   char *output, int *pstr_len, const char *fmtstr)
{
    union un_fmt_comb replace_val;
    int         replace_type;
    int         i;
    const char *p = fmtstr;
    char       *q = output;
 
    while (*p)
    {
        if (*p == '%')
        {
            p++;
            /* fix compiler warning */
            replace_type = PGTYPES_TYPE_NOTHING;
            switch (*p)
            {
                    /* the abbreviated name of the day in the week */
                    /* XXX should be locale aware */
                case 'a':
                    replace_val.str_val = pgtypes_date_weekdays_short[dow];
                    replace_type = PGTYPES_TYPE_STRING_CONSTANT;
                    break;
                    /* the full name of the day in the week */
                    /* XXX should be locale aware */
                case 'A':
                    replace_val.str_val = days[dow];
                    replace_type = PGTYPES_TYPE_STRING_CONSTANT;
                    break;
                    /* the abbreviated name of the month */
                    /* XXX should be locale aware */
                case 'b':
                case 'h':
                    replace_val.str_val = months[tm->tm_mon - 1];
                    replace_type = PGTYPES_TYPE_STRING_CONSTANT;
                    break;
                    /* the full name of the month */
                    /* XXX should be locale aware */
                case 'B':
                    replace_val.str_val = pgtypes_date_months[tm->tm_mon - 1];
                    replace_type = PGTYPES_TYPE_STRING_CONSTANT;
                    break;
 
                    /*
                     * The preferred date and time representation for the
                     * current locale.
                     */
                case 'c':
                    /* XXX */
                    break;
                    /* the century number with leading zeroes */
                case 'C':
                    replace_val.uint_val = tm->tm_year / 100;
                    replace_type = PGTYPES_TYPE_UINT_2_LZ;
                    break;
                    /* day with leading zeroes (01 - 31) */
                case 'd':
                    replace_val.uint_val = tm->tm_mday;
                    replace_type = PGTYPES_TYPE_UINT_2_LZ;
                    break;
                    /* the date in the format mm/dd/yy */
                case 'D':
 
                    /*
                     * ts, dDate, dow, tm is information about the timestamp
                     *
                     * q is the start of the current output buffer
                     *
                     * pstr_len is a pointer to the remaining size of output,
                     * i.e. the size of q
                     */
                    i = dttofmtasc_replace(ts, dDate, dow, tm,
                                           q, pstr_len,
                                           "%m/%d/%y");
                    if (i)
                        return i;
                    break;
                    /* day with leading spaces (01 - 31) */
                case 'e':
                    replace_val.uint_val = tm->tm_mday;
                    replace_type = PGTYPES_TYPE_UINT_2_LS;
                    break;
 
                    /*
                     * alternative format modifier
                     */
                case 'E':
                    {
                        char        tmp[4] = "%Ex";
 
                        p++;
                        if (*p == '\0')
                            return -1;
                        tmp[2] = *p;
 
                        /*
                         * strftime's month is 0 based, ours is 1 based
                         */
                        tm->tm_mon -= 1;
                        i = strftime(q, *pstr_len, tmp, tm);
                        if (i == 0)
                            return -1;
                        while (*q)
                        {
                            q++;
                            (*pstr_len)--;
                        }
                        tm->tm_mon += 1;
                        replace_type = PGTYPES_TYPE_NOTHING;
                        break;
                    }
 
                    /*
                     * The ISO 8601 year with century as a decimal number. The
                     * 4-digit year corresponding to the ISO week number.
                     */
                case 'G':
                    {
                        /* Keep compiler quiet - Don't use a literal format */
                        const char *fmt = "%G";
 
                        tm->tm_mon -= 1;
                        i = strftime(q, *pstr_len, fmt, tm);
                        if (i == 0)
                            return -1;
                        while (*q)
                        {
                            q++;
                            (*pstr_len)--;
                        }
                        tm->tm_mon += 1;
                        replace_type = PGTYPES_TYPE_NOTHING;
                    }
                    break;
 
                    /*
                     * Like %G, but without century, i.e., with a 2-digit year
                     * (00-99).
                     */
                case 'g':
                    {
                        const char *fmt = "%g"; /* Keep compiler quiet about
                                                 * 2-digit year */
 
                        tm->tm_mon -= 1;
                        i = strftime(q, *pstr_len, fmt, tm);
                        if (i == 0)
                            return -1;
                        while (*q)
                        {
                            q++;
                            (*pstr_len)--;
                        }
                        tm->tm_mon += 1;
                        replace_type = PGTYPES_TYPE_NOTHING;
                    }
                    break;
                    /* hour (24 hour clock) with leading zeroes */
                case 'H':
                    replace_val.uint_val = tm->tm_hour;
                    replace_type = PGTYPES_TYPE_UINT_2_LZ;
                    break;
                    /* hour (12 hour clock) with leading zeroes */
                case 'I':
                    replace_val.uint_val = tm->tm_hour % 12;
                    replace_type = PGTYPES_TYPE_UINT_2_LZ;
                    break;
 
                    /*
                     * The day of the year as a decimal number with leading
                     * zeroes. It ranges from 001 to 366.
                     */
                case 'j':
                    replace_val.uint_val = tm->tm_yday;
                    replace_type = PGTYPES_TYPE_UINT_3_LZ;
                    break;
 
                    /*
                     * The hour (24 hour clock). Leading zeroes will be turned
                     * into spaces.
                     */
                case 'k':
                    replace_val.uint_val = tm->tm_hour;
                    replace_type = PGTYPES_TYPE_UINT_2_LS;
                    break;
 
                    /*
                     * The hour (12 hour clock). Leading zeroes will be turned
                     * into spaces.
                     */
                case 'l':
                    replace_val.uint_val = tm->tm_hour % 12;
                    replace_type = PGTYPES_TYPE_UINT_2_LS;
                    break;
                    /* The month as a decimal number with a leading zero */
                case 'm':
                    replace_val.uint_val = tm->tm_mon;
                    replace_type = PGTYPES_TYPE_UINT_2_LZ;
                    break;
                    /* The minute as a decimal number with a leading zero */
                case 'M':
                    replace_val.uint_val = tm->tm_min;
                    replace_type = PGTYPES_TYPE_UINT_2_LZ;
                    break;
                    /* A newline character */
                case 'n':
                    replace_val.char_val = '\n';
                    replace_type = PGTYPES_TYPE_CHAR;
                    break;
                    /* the AM/PM specifier (uppercase) */
                    /* XXX should be locale aware */
                case 'p':
                    if (tm->tm_hour < 12)
                        replace_val.str_val = "AM";
                    else
                        replace_val.str_val = "PM";
                    replace_type = PGTYPES_TYPE_STRING_CONSTANT;
                    break;
                    /* the AM/PM specifier (lowercase) */
                    /* XXX should be locale aware */
                case 'P':
                    if (tm->tm_hour < 12)
                        replace_val.str_val = "am";
                    else
                        replace_val.str_val = "pm";
                    replace_type = PGTYPES_TYPE_STRING_CONSTANT;
                    break;
                    /* the time in the format %I:%M:%S %p */
                    /* XXX should be locale aware */
                case 'r':
                    i = dttofmtasc_replace(ts, dDate, dow, tm,
                                           q, pstr_len,
                                           "%I:%M:%S %p");
                    if (i)
                        return i;
                    break;
                    /* The time in 24 hour notation (%H:%M) */
                case 'R':
                    i = dttofmtasc_replace(ts, dDate, dow, tm,
                                           q, pstr_len,
                                           "%H:%M");
                    if (i)
                        return i;
                    break;
                    /* The number of seconds since the Epoch (1970-01-01) */
                case 's':
                    replace_val.int64_val = (*ts - SetEpochTimestamp()) / 1000000.0;
                    replace_type = PGTYPES_TYPE_INT64;
                    break;
                    /* seconds as a decimal number with leading zeroes */
                case 'S':
                    replace_val.uint_val = tm->tm_sec;
                    replace_type = PGTYPES_TYPE_UINT_2_LZ;
                    break;
                    /* A tabulator */
                case 't':
                    replace_val.char_val = '\t';
                    replace_type = PGTYPES_TYPE_CHAR;
                    break;
                    /* The time in 24 hour notation (%H:%M:%S) */
                case 'T':
                    i = dttofmtasc_replace(ts, dDate, dow, tm,
                                           q, pstr_len,
                                           "%H:%M:%S");
                    if (i)
                        return i;
                    break;
 
                    /*
                     * The day of the week as a decimal, Monday = 1, Sunday =
                     * 7
                     */
                case 'u':
                    replace_val.uint_val = dow;
                    if (replace_val.uint_val == 0)
                        replace_val.uint_val = 7;
                    replace_type = PGTYPES_TYPE_UINT;
                    break;
                    /* The week number of the year as a decimal number */
                case 'U':
                    tm->tm_mon -= 1;
                    i = strftime(q, *pstr_len, "%U", tm);
                    if (i == 0)
                        return -1;
                    while (*q)
                    {
                        q++;
                        (*pstr_len)--;
                    }
                    tm->tm_mon += 1;
                    replace_type = PGTYPES_TYPE_NOTHING;
                    break;
 
                    /*
                     * The ISO 8601:1988 week number of the current year as a
                     * decimal number.
                     */
                case 'V':
                    {
                        /* Keep compiler quiet - Don't use a literal format */
                        const char *fmt = "%V";
 
                        i = strftime(q, *pstr_len, fmt, tm);
                        if (i == 0)
                            return -1;
                        while (*q)
                        {
                            q++;
                            (*pstr_len)--;
                        }
                        replace_type = PGTYPES_TYPE_NOTHING;
                    }
                    break;
 
                    /*
                     * The day of the week as a decimal, Sunday being 0 and
                     * Monday 1.
                     */
                case 'w':
                    replace_val.uint_val = dow;
                    replace_type = PGTYPES_TYPE_UINT;
                    break;
                    /* The week number of the year (another definition) */
                case 'W':
                    tm->tm_mon -= 1;
                    i = strftime(q, *pstr_len, "%U", tm);
                    if (i == 0)
                        return -1;
                    while (*q)
                    {
                        q++;
                        (*pstr_len)--;
                    }
                    tm->tm_mon += 1;
                    replace_type = PGTYPES_TYPE_NOTHING;
                    break;
 
                    /*
                     * The preferred date representation for the current
                     * locale without the time.
                     */
                case 'x':
                    {
                        const char *fmt = "%x"; /* Keep compiler quiet about
                                                 * 2-digit year */
 
                        tm->tm_mon -= 1;
                        i = strftime(q, *pstr_len, fmt, tm);
                        if (i == 0)
                            return -1;
                        while (*q)
                        {
                            q++;
                            (*pstr_len)--;
                        }
                        tm->tm_mon += 1;
                        replace_type = PGTYPES_TYPE_NOTHING;
                    }
                    break;
 
                    /*
                     * The preferred time representation for the current
                     * locale without the date.
                     */
                case 'X':
                    tm->tm_mon -= 1;
                    i = strftime(q, *pstr_len, "%X", tm);
                    if (i == 0)
                        return -1;
                    while (*q)
                    {
                        q++;
                        (*pstr_len)--;
                    }
                    tm->tm_mon += 1;
                    replace_type = PGTYPES_TYPE_NOTHING;
                    break;
                    /* The year without the century (2 digits, leading zeroes) */
                case 'y':
                    replace_val.uint_val = tm->tm_year % 100;
                    replace_type = PGTYPES_TYPE_UINT_2_LZ;
                    break;
                    /* The year with the century (4 digits) */
                case 'Y':
                    replace_val.uint_val = tm->tm_year;
                    replace_type = PGTYPES_TYPE_UINT;
                    break;
                    /* The time zone offset from GMT */
                case 'z':
                    tm->tm_mon -= 1;
                    i = strftime(q, *pstr_len, "%z", tm);
                    if (i == 0)
                        return -1;
                    while (*q)
                    {
                        q++;
                        (*pstr_len)--;
                    }
                    tm->tm_mon += 1;
                    replace_type = PGTYPES_TYPE_NOTHING;
                    break;
                    /* The name or abbreviation of the time zone */
                case 'Z':
                    tm->tm_mon -= 1;
                    i = strftime(q, *pstr_len, "%Z", tm);
                    if (i == 0)
                        return -1;
                    while (*q)
                    {
                        q++;
                        (*pstr_len)--;
                    }
                    tm->tm_mon += 1;
                    replace_type = PGTYPES_TYPE_NOTHING;
                    break;
                    /* A % sign */
                case '%':
                    replace_val.char_val = '%';
                    replace_type = PGTYPES_TYPE_CHAR;
                    break;
                case '\0':
                    /* fmtstr: foo%' - The string ends with a % sign */
 
                    /*
                     * this is not compliant to the specification
                     */
                    return -1;
                default:
 
                    /*
                     * if we don't know the pattern, we just copy it
                     */
                    if (*pstr_len > 1)
                    {
                        *q = '%';
                        q++;
                        (*pstr_len)--;
                        if (*pstr_len > 1)
                        {
                            *q = *p;
                            q++;
                            (*pstr_len)--;
                        }
                        else
                        {
                            *q = '\0';
                            return -1;
                        }
                        *q = '\0';
                    }
                    else
                        return -1;
                    break;
            }
            i = pgtypes_fmt_replace(replace_val, replace_type, &q, pstr_len);
            if (i)
                return i;
        }
        else
        {
            if (*pstr_len > 1)
            {
                *q = *p;
                (*pstr_len)--;
                q++;
                *q = '\0';
            }
            else
                return -1;
        }
        p++;
    }
    return 0;
}
 
 
int
PGTYPEStimestamp_fmt_asc(timestamp * ts, char *output, int str_len, const char *fmtstr)
{
    struct tm   tm;
    fsec_t      fsec;
    date        dDate;
    int         dow;
 
    dDate = PGTYPESdate_from_timestamp(*ts);
    dow = PGTYPESdate_dayofweek(dDate);
    timestamp2tm(*ts, NULL, &tm, &fsec, NULL);
 
    return dttofmtasc_replace(ts, dDate, dow, &tm, output, &str_len, fmtstr);
}
 
int
PGTYPEStimestamp_sub(timestamp * ts1, timestamp * ts2, interval * iv)
{
    if (TIMESTAMP_NOT_FINITE(*ts1) || TIMESTAMP_NOT_FINITE(*ts2))
        return PGTYPES_TS_ERR_EINFTIME;
    else
        iv->time = (*ts1 - *ts2);
 
    iv->month = 0;
 
    return 0;
}
 
int
PGTYPEStimestamp_defmt_asc(const char *str, const char *fmt, timestamp * d)
{
    int         year,
                month,
                day;
    int         hour,
                minute,
                second;
    int         tz;
 
    int         i;
    char       *mstr;
    char       *mfmt;
 
    if (!fmt)
        fmt = "%Y-%m-%d %H:%M:%S";
    if (!fmt[0])
        return 1;
 
    mstr = pgtypes_strdup(str);
    mfmt = pgtypes_strdup(fmt);
 
    /*
     * initialize with impossible values so that we can see if the fields
     * where specified at all
     */
    /* XXX ambiguity with 1 BC for year? */
    year = -1;
    month = -1;
    day = -1;
    hour = 0;
    minute = -1;
    second = -1;
    tz = 0;
 
    i = PGTYPEStimestamp_defmt_scan(&mstr, mfmt, d, &year, &month, &day, &hour, &minute, &second, &tz);
    free(mstr);
    free(mfmt);
    return i;
}
 
/*
* add an interval to a time stamp
*
*   *tout = tin + span
*
*    returns 0 if successful
*    returns -1 if it fails
*
*/
 
int
PGTYPEStimestamp_add_interval(timestamp * tin, interval * span, timestamp * tout)
{
    if (TIMESTAMP_NOT_FINITE(*tin))
        *tout = *tin;
    else
    {
        if (span->month != 0)
        {
            struct tm   tt,
                       *tm = &tt;
            fsec_t      fsec;
 
            if (timestamp2tm(*tin, NULL, tm, &fsec, NULL) != 0)
                return -1;
            tm->tm_mon += span->month;
            if (tm->tm_mon > MONTHS_PER_YEAR)
            {
                tm->tm_year += (tm->tm_mon - 1) / MONTHS_PER_YEAR;
                tm->tm_mon = (tm->tm_mon - 1) % MONTHS_PER_YEAR + 1;
            }
            else if (tm->tm_mon < 1)
            {
                tm->tm_year += tm->tm_mon / MONTHS_PER_YEAR - 1;
                tm->tm_mon = tm->tm_mon % MONTHS_PER_YEAR + MONTHS_PER_YEAR;
            }
 
 
            /* adjust for end of month boundary problems... */
            if (tm->tm_mday > day_tab[isleap(tm->tm_year)][tm->tm_mon - 1])
                tm->tm_mday = (day_tab[isleap(tm->tm_year)][tm->tm_mon - 1]);
 
 
            if (tm2timestamp(tm, fsec, NULL, tin) != 0)
                return -1;
        }
 
        *tin += span->time;
        *tout = *tin;
    }
 
    return 0;
}
 
 
/*
* subtract an interval from a time stamp
*
*   *tout = tin - span
*
*    returns 0 if successful
*    returns -1 if it fails
*
*/
 
int
PGTYPEStimestamp_sub_interval(timestamp * tin, interval * span, timestamp * tout)
{
    interval    tspan;
 
    tspan.month = -span->month;
    tspan.time = -span->time;
 
    return PGTYPEStimestamp_add_interval(tin, &tspan, tout);
}