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localtime.c
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/* Convert timestamp from pg_time_t to struct pg_tm. */
/*
* This file is in the public domain, so clarified as of
* 1996-06-05 by Arthur David Olson.
*
* IDENTIFICATION
* src/timezone/localtime.c
*/
/*
* Leap second handling from Bradley White.
* POSIX-style TZ environment variable handling from Guy Harris.
*/
/* this file needs to build in both frontend and backend contexts */
#include "c.h"
#include <fcntl.h>
#include "datatype/timestamp.h"
#include "pgtz.h"
#include "private.h"
#include "tzfile.h"
#ifndef WILDABBR
/*
* Someone might make incorrect use of a time zone abbreviation:
* 1. They might reference tzname[0] before calling tzset (explicitly
* or implicitly).
* 2. They might reference tzname[1] before calling tzset (explicitly
* or implicitly).
* 3. They might reference tzname[1] after setting to a time zone
* in which Daylight Saving Time is never observed.
* 4. They might reference tzname[0] after setting to a time zone
* in which Standard Time is never observed.
* 5. They might reference tm.tm_zone after calling offtime.
* What's best to do in the above cases is open to debate;
* for now, we just set things up so that in any of the five cases
* WILDABBR is used. Another possibility: initialize tzname[0] to the
* string "tzname[0] used before set", and similarly for the other cases.
* And another: initialize tzname[0] to "ERA", with an explanation in the
* manual page of what this "time zone abbreviation" means (doing this so
* that tzname[0] has the "normal" length of three characters).
*/
#define WILDABBR " "
#endif /* !defined WILDABBR */
static const char wildabbr[] = WILDABBR;
static const char gmt[] = "GMT";
/*
* PG: We cache the result of trying to load the TZDEFRULES zone here.
* tzdefrules_loaded is 0 if not tried yet, +1 if good, -1 if failed.
*/
static struct state *tzdefrules_s = NULL;
static int tzdefrules_loaded = 0;
/*
* The DST rules to use if TZ has no rules and we can't load TZDEFRULES.
* Default to US rules as of 2017-05-07.
* POSIX does not specify the default DST rules;
* for historical reasons, US rules are a common default.
*/
#define TZDEFRULESTRING ",M3.2.0,M11.1.0"
/* structs ttinfo, lsinfo, state have been moved to pgtz.h */
enum r_type
{
JULIAN_DAY, /* Jn = Julian day */
DAY_OF_YEAR, /* n = day of year */
MONTH_NTH_DAY_OF_WEEK /* Mm.n.d = month, week, day of week */
};
struct rule
{
enum r_type r_type; /* type of rule */
int r_day; /* day number of rule */
int r_week; /* week number of rule */
int r_mon; /* month number of rule */
int32 r_time; /* transition time of rule */
};
/*
* Prototypes for static functions.
*/
static struct pg_tm *gmtsub(pg_time_t const *, int32, struct pg_tm *);
static bool increment_overflow(int *, int);
static bool increment_overflow_time(pg_time_t *, int32);
static struct pg_tm *timesub(pg_time_t const *, int32, struct state const *,
struct pg_tm *);
static bool typesequiv(struct state const *, int, int);
/*
* Section 4.12.3 of X3.159-1989 requires that
* Except for the strftime function, these functions [asctime,
* ctime, gmtime, localtime] return values in one of two static
* objects: a broken-down time structure and an array of char.
* Thanks to Paul Eggert for noting this.
*/
static struct pg_tm tm;
/* Initialize *S to a value based on UTOFF, ISDST, and DESIGIDX. */
static void
init_ttinfo(struct ttinfo *s, int32 utoff, bool isdst, int desigidx)
{
s->tt_utoff = utoff;
s->tt_isdst = isdst;
s->tt_desigidx = desigidx;
s->tt_ttisstd = false;
s->tt_ttisut = false;
}
static int32
detzcode(const char *const codep)
{
int32 result;
int i;
int32 one = 1;
int32 halfmaxval = one << (32 - 2);
int32 maxval = halfmaxval - 1 + halfmaxval;
int32 minval = -1 - maxval;
result = codep[0] & 0x7f;
for (i = 1; i < 4; ++i)
result = (result << 8) | (codep[i] & 0xff);
if (codep[0] & 0x80)
{
/*
* Do two's-complement negation even on non-two's-complement machines.
* If the result would be minval - 1, return minval.
*/
result -= !TWOS_COMPLEMENT(int32) && result != 0;
result += minval;
}
return result;
}
static int64
detzcode64(const char *const codep)
{
uint64 result;
int i;
int64 one = 1;
int64 halfmaxval = one << (64 - 2);
int64 maxval = halfmaxval - 1 + halfmaxval;
int64 minval = -TWOS_COMPLEMENT(int64) - maxval;
result = codep[0] & 0x7f;
for (i = 1; i < 8; ++i)
result = (result << 8) | (codep[i] & 0xff);
if (codep[0] & 0x80)
{
/*
* Do two's-complement negation even on non-two's-complement machines.
* If the result would be minval - 1, return minval.
*/
result -= !TWOS_COMPLEMENT(int64) && result != 0;
result += minval;
}
return result;
}
static bool
differ_by_repeat(const pg_time_t t1, const pg_time_t t0)
{
if (TYPE_BIT(pg_time_t) - TYPE_SIGNED(pg_time_t) < SECSPERREPEAT_BITS)
return 0;
return t1 - t0 == SECSPERREPEAT;
}
/* Input buffer for data read from a compiled tz file. */
union input_buffer
{
/* The first part of the buffer, interpreted as a header. */
struct tzhead tzhead;
/* The entire buffer. */
char buf[2 * sizeof(struct tzhead) + 2 * sizeof(struct state)
+ 4 * TZ_MAX_TIMES];
};
/* Local storage needed for 'tzloadbody'. */
union local_storage
{
/* The results of analyzing the file's contents after it is opened. */
struct file_analysis
{
/* The input buffer. */
union input_buffer u;
/* A temporary state used for parsing a TZ string in the file. */
struct state st;
} u;
/* We don't need the "fullname" member */
};
/* Load tz data from the file named NAME into *SP. Read extended
* format if DOEXTEND. Use *LSP for temporary storage. Return 0 on
* success, an errno value on failure.
* PG: If "canonname" is not NULL, then on success the canonical spelling of
* given name is stored there (the buffer must be > TZ_STRLEN_MAX bytes!).
*/
static int
tzloadbody(char const *name, char *canonname, struct state *sp, bool doextend,
union local_storage *lsp)
{
int i;
int fid;
int stored;
ssize_t nread;
union input_buffer *up = &lsp->u.u;
int tzheadsize = sizeof(struct tzhead);
sp->goback = sp->goahead = false;
if (!name)
{
name = TZDEFAULT;
if (!name)
return EINVAL;
}
if (name[0] == ':')
++name;
fid = pg_open_tzfile(name, canonname);
if (fid < 0)
return ENOENT; /* pg_open_tzfile may not set errno */
nread = read(fid, up->buf, sizeof up->buf);
if (nread < tzheadsize)
{
int err = nread < 0 ? errno : EINVAL;
close(fid);
return err;
}
if (close(fid) < 0)
return errno;
for (stored = 4; stored <= 8; stored *= 2)
{
int32 ttisstdcnt = detzcode(up->tzhead.tzh_ttisstdcnt);
int32 ttisutcnt = detzcode(up->tzhead.tzh_ttisutcnt);
int64 prevtr = 0;
int32 prevcorr = 0;
int32 leapcnt = detzcode(up->tzhead.tzh_leapcnt);
int32 timecnt = detzcode(up->tzhead.tzh_timecnt);
int32 typecnt = detzcode(up->tzhead.tzh_typecnt);
int32 charcnt = detzcode(up->tzhead.tzh_charcnt);
char const *p = up->buf + tzheadsize;
/*
* Although tzfile(5) currently requires typecnt to be nonzero,
* support future formats that may allow zero typecnt in files that
* have a TZ string and no transitions.
*/
if (!(0 <= leapcnt && leapcnt < TZ_MAX_LEAPS
&& 0 <= typecnt && typecnt < TZ_MAX_TYPES
&& 0 <= timecnt && timecnt < TZ_MAX_TIMES
&& 0 <= charcnt && charcnt < TZ_MAX_CHARS
&& (ttisstdcnt == typecnt || ttisstdcnt == 0)
&& (ttisutcnt == typecnt || ttisutcnt == 0)))
return EINVAL;
if (nread
< (tzheadsize /* struct tzhead */
+ timecnt * stored /* ats */
+ timecnt /* types */
+ typecnt * 6 /* ttinfos */
+ charcnt /* chars */
+ leapcnt * (stored + 4) /* lsinfos */
+ ttisstdcnt /* ttisstds */
+ ttisutcnt)) /* ttisuts */
return EINVAL;
sp->leapcnt = leapcnt;
sp->timecnt = timecnt;
sp->typecnt = typecnt;
sp->charcnt = charcnt;
/*
* Read transitions, discarding those out of pg_time_t range. But
* pretend the last transition before TIME_T_MIN occurred at
* TIME_T_MIN.
*/
timecnt = 0;
for (i = 0; i < sp->timecnt; ++i)
{
int64 at
= stored == 4 ? detzcode(p) : detzcode64(p);
sp->types[i] = at <= TIME_T_MAX;
if (sp->types[i])
{
pg_time_t attime
= ((TYPE_SIGNED(pg_time_t) ? at < TIME_T_MIN : at < 0)
? TIME_T_MIN : at);
if (timecnt && attime <= sp->ats[timecnt - 1])
{
if (attime < sp->ats[timecnt - 1])
return EINVAL;
sp->types[i - 1] = 0;
timecnt--;
}
sp->ats[timecnt++] = attime;
}
p += stored;
}
timecnt = 0;
for (i = 0; i < sp->timecnt; ++i)
{
unsigned char typ = *p++;
if (sp->typecnt <= typ)
return EINVAL;
if (sp->types[i])
sp->types[timecnt++] = typ;
}
sp->timecnt = timecnt;
for (i = 0; i < sp->typecnt; ++i)
{
struct ttinfo *ttisp;
unsigned char isdst,
desigidx;
ttisp = &sp->ttis[i];
ttisp->tt_utoff = detzcode(p);
p += 4;
isdst = *p++;
if (!(isdst < 2))
return EINVAL;
ttisp->tt_isdst = isdst;
desigidx = *p++;
if (!(desigidx < sp->charcnt))
return EINVAL;
ttisp->tt_desigidx = desigidx;
}
for (i = 0; i < sp->charcnt; ++i)
sp->chars[i] = *p++;
sp->chars[i] = '\0'; /* ensure '\0' at end */
/* Read leap seconds, discarding those out of pg_time_t range. */
leapcnt = 0;
for (i = 0; i < sp->leapcnt; ++i)
{
int64 tr = stored == 4 ? detzcode(p) : detzcode64(p);
int32 corr = detzcode(p + stored);
p += stored + 4;
/* Leap seconds cannot occur before the Epoch. */
if (tr < 0)
return EINVAL;
if (tr <= TIME_T_MAX)
{
/*
* Leap seconds cannot occur more than once per UTC month, and
* UTC months are at least 28 days long (minus 1 second for a
* negative leap second). Each leap second's correction must
* differ from the previous one's by 1 second.
*/
if (tr - prevtr < 28 * SECSPERDAY - 1
|| (corr != prevcorr - 1 && corr != prevcorr + 1))
return EINVAL;
sp->lsis[leapcnt].ls_trans = prevtr = tr;
sp->lsis[leapcnt].ls_corr = prevcorr = corr;
leapcnt++;
}
}
sp->leapcnt = leapcnt;
for (i = 0; i < sp->typecnt; ++i)
{
struct ttinfo *ttisp;
ttisp = &sp->ttis[i];
if (ttisstdcnt == 0)
ttisp->tt_ttisstd = false;
else
{
if (*p != true && *p != false)
return EINVAL;
ttisp->tt_ttisstd = *p++;
}
}
for (i = 0; i < sp->typecnt; ++i)
{
struct ttinfo *ttisp;
ttisp = &sp->ttis[i];
if (ttisutcnt == 0)
ttisp->tt_ttisut = false;
else
{
if (*p != true && *p != false)
return EINVAL;
ttisp->tt_ttisut = *p++;
}
}
/*
* If this is an old file, we're done.
*/
if (up->tzhead.tzh_version[0] == '\0')
break;
nread -= p - up->buf;
memmove(up->buf, p, nread);
}
if (doextend && nread > 2 &&
up->buf[0] == '\n' && up->buf[nread - 1] == '\n' &&
sp->typecnt + 2 <= TZ_MAX_TYPES)
{
struct state *ts = &lsp->u.st;
up->buf[nread - 1] = '\0';
if (tzparse(&up->buf[1], ts, false))
{
/*
* Attempt to reuse existing abbreviations. Without this,
* America/Anchorage would be right on the edge after 2037 when
* TZ_MAX_CHARS is 50, as sp->charcnt equals 40 (for LMT AST AWT
* APT AHST AHDT YST AKDT AKST) and ts->charcnt equals 10 (for
* AKST AKDT). Reusing means sp->charcnt can stay 40 in this
* example.
*/
int gotabbr = 0;
int charcnt = sp->charcnt;
for (i = 0; i < ts->typecnt; i++)
{
char *tsabbr = ts->chars + ts->ttis[i].tt_desigidx;
int j;
for (j = 0; j < charcnt; j++)
if (strcmp(sp->chars + j, tsabbr) == 0)
{
ts->ttis[i].tt_desigidx = j;
gotabbr++;
break;
}
if (!(j < charcnt))
{
int tsabbrlen = strlen(tsabbr);
if (j + tsabbrlen < TZ_MAX_CHARS)
{
strcpy(sp->chars + j, tsabbr);
charcnt = j + tsabbrlen + 1;
ts->ttis[i].tt_desigidx = j;
gotabbr++;
}
}
}
if (gotabbr == ts->typecnt)
{
sp->charcnt = charcnt;
/*
* Ignore any trailing, no-op transitions generated by zic as
* they don't help here and can run afoul of bugs in zic 2016j
* or earlier.
*/
while (1 < sp->timecnt
&& (sp->types[sp->timecnt - 1]
== sp->types[sp->timecnt - 2]))
sp->timecnt--;
for (i = 0; i < ts->timecnt; i++)
if (sp->timecnt == 0
|| sp->ats[sp->timecnt - 1] < ts->ats[i])
break;
while (i < ts->timecnt
&& sp->timecnt < TZ_MAX_TIMES)
{
sp->ats[sp->timecnt] = ts->ats[i];
sp->types[sp->timecnt] = (sp->typecnt
+ ts->types[i]);
sp->timecnt++;
i++;
}
for (i = 0; i < ts->typecnt; i++)
sp->ttis[sp->typecnt++] = ts->ttis[i];
}
}
}
if (sp->typecnt == 0)
return EINVAL;
if (sp->timecnt > 1)
{
for (i = 1; i < sp->timecnt; ++i)
if (typesequiv(sp, sp->types[i], sp->types[0]) &&
differ_by_repeat(sp->ats[i], sp->ats[0]))
{
sp->goback = true;
break;
}
for (i = sp->timecnt - 2; i >= 0; --i)
if (typesequiv(sp, sp->types[sp->timecnt - 1],
sp->types[i]) &&
differ_by_repeat(sp->ats[sp->timecnt - 1],
sp->ats[i]))
{
sp->goahead = true;
break;
}
}
/*
* Infer sp->defaulttype from the data. Although this default type is
* always zero for data from recent tzdb releases, things are trickier for
* data from tzdb 2018e or earlier.
*
* The first set of heuristics work around bugs in 32-bit data generated
* by tzdb 2013c or earlier. The workaround is for zones like
* Australia/Macquarie where timestamps before the first transition have a
* time type that is not the earliest standard-time type. See:
* https://mm.icann.org/pipermail/tz/2013-May/019368.html
*/
/*
* If type 0 is unused in transitions, it's the type to use for early
* times.
*/
for (i = 0; i < sp->timecnt; ++i)
if (sp->types[i] == 0)
break;
i = i < sp->timecnt ? -1 : 0;
/*
* Absent the above, if there are transition times and the first
* transition is to a daylight time find the standard type less than and
* closest to the type of the first transition.
*/
if (i < 0 && sp->timecnt > 0 && sp->ttis[sp->types[0]].tt_isdst)
{
i = sp->types[0];
while (--i >= 0)
if (!sp->ttis[i].tt_isdst)
break;
}
/*
* The next heuristics are for data generated by tzdb 2018e or earlier,
* for zones like EST5EDT where the first transition is to DST.
*/
/*
* If no result yet, find the first standard type. If there is none, punt
* to type zero.
*/
if (i < 0)
{
i = 0;
while (sp->ttis[i].tt_isdst)
if (++i >= sp->typecnt)
{
i = 0;
break;
}
}
/*
* A simple 'sp->defaulttype = 0;' would suffice here if we didn't have to
* worry about 2018e-or-earlier data. Even simpler would be to remove the
* defaulttype member and just use 0 in its place.
*/
sp->defaulttype = i;
return 0;
}
/* Load tz data from the file named NAME into *SP. Read extended
* format if DOEXTEND. Return 0 on success, an errno value on failure.
* PG: If "canonname" is not NULL, then on success the canonical spelling of
* given name is stored there (the buffer must be > TZ_STRLEN_MAX bytes!).
*/
int
tzload(const char *name, char *canonname, struct state *sp, bool doextend)
{
union local_storage *lsp = malloc(sizeof *lsp);
if (!lsp)
return errno;
else
{
int err = tzloadbody(name, canonname, sp, doextend, lsp);
free(lsp);
return err;
}
}
static bool
typesequiv(const struct state *sp, int a, int b)
{
bool result;
if (sp == NULL ||
a < 0 || a >= sp->typecnt ||
b < 0 || b >= sp->typecnt)
result = false;
else
{
const struct ttinfo *ap = &sp->ttis[a];
const struct ttinfo *bp = &sp->ttis[b];
result = (ap->tt_utoff == bp->tt_utoff
&& ap->tt_isdst == bp->tt_isdst
&& ap->tt_ttisstd == bp->tt_ttisstd
&& ap->tt_ttisut == bp->tt_ttisut
&& (strcmp(&sp->chars[ap->tt_desigidx],
&sp->chars[bp->tt_desigidx])
== 0));
}
return result;
}
static const int mon_lengths[2][MONSPERYEAR] = {
{31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
{31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}
};
static const int year_lengths[2] = {
DAYSPERNYEAR, DAYSPERLYEAR
};
/*
* Given a pointer into a timezone string, scan until a character that is not
* a valid character in a time zone abbreviation is found.
* Return a pointer to that character.
*/
static const char *
getzname(const char *strp)
{
char c;
while ((c = *strp) != '\0' && !is_digit(c) && c != ',' && c != '-' &&
c != '+')
++strp;
return strp;
}
/*
* Given a pointer into an extended timezone string, scan until the ending
* delimiter of the time zone abbreviation is located.
* Return a pointer to the delimiter.
*
* As with getzname above, the legal character set is actually quite
* restricted, with other characters producing undefined results.
* We don't do any checking here; checking is done later in common-case code.
*/
static const char *
getqzname(const char *strp, const int delim)
{
int c;
while ((c = *strp) != '\0' && c != delim)
++strp;
return strp;
}
/*
* Given a pointer into a timezone string, extract a number from that string.
* Check that the number is within a specified range; if it is not, return
* NULL.
* Otherwise, return a pointer to the first character not part of the number.
*/
static const char *
getnum(const char *strp, int *const nump, const int min, const int max)
{
char c;
int num;
if (strp == NULL || !is_digit(c = *strp))
return NULL;
num = 0;
do
{
num = num * 10 + (c - '0');
if (num > max)
return NULL; /* illegal value */
c = *++strp;
} while (is_digit(c));
if (num < min)
return NULL; /* illegal value */
*nump = num;
return strp;
}
/*
* Given a pointer into a timezone string, extract a number of seconds,
* in hh[:mm[:ss]] form, from the string.
* If any error occurs, return NULL.
* Otherwise, return a pointer to the first character not part of the number
* of seconds.
*/
static const char *
getsecs(const char *strp, int32 *const secsp)
{
int num;
/*
* 'HOURSPERDAY * DAYSPERWEEK - 1' allows quasi-Posix rules like
* "M10.4.6/26", which does not conform to Posix, but which specifies the
* equivalent of "02:00 on the first Sunday on or after 23 Oct".
*/
strp = getnum(strp, &num, 0, HOURSPERDAY * DAYSPERWEEK - 1);
if (strp == NULL)
return NULL;
*secsp = num * (int32) SECSPERHOUR;
if (*strp == ':')
{
++strp;
strp = getnum(strp, &num, 0, MINSPERHOUR - 1);
if (strp == NULL)
return NULL;
*secsp += num * SECSPERMIN;
if (*strp == ':')
{
++strp;
/* 'SECSPERMIN' allows for leap seconds. */
strp = getnum(strp, &num, 0, SECSPERMIN);
if (strp == NULL)
return NULL;
*secsp += num;
}
}
return strp;
}
/*
* Given a pointer into a timezone string, extract an offset, in
* [+-]hh[:mm[:ss]] form, from the string.
* If any error occurs, return NULL.
* Otherwise, return a pointer to the first character not part of the time.
*/
static const char *
getoffset(const char *strp, int32 *const offsetp)
{
bool neg = false;
if (*strp == '-')
{
neg = true;
++strp;
}
else if (*strp == '+')
++strp;
strp = getsecs(strp, offsetp);
if (strp == NULL)
return NULL; /* illegal time */
if (neg)
*offsetp = -*offsetp;
return strp;
}
/*
* Given a pointer into a timezone string, extract a rule in the form
* date[/time]. See POSIX section 8 for the format of "date" and "time".
* If a valid rule is not found, return NULL.
* Otherwise, return a pointer to the first character not part of the rule.
*/
static const char *
getrule(const char *strp, struct rule *const rulep)
{
if (*strp == 'J')
{
/*
* Julian day.
*/
rulep->r_type = JULIAN_DAY;
++strp;
strp = getnum(strp, &rulep->r_day, 1, DAYSPERNYEAR);
}
else if (*strp == 'M')
{
/*
* Month, week, day.
*/
rulep->r_type = MONTH_NTH_DAY_OF_WEEK;
++strp;
strp = getnum(strp, &rulep->r_mon, 1, MONSPERYEAR);
if (strp == NULL)
return NULL;
if (*strp++ != '.')
return NULL;
strp = getnum(strp, &rulep->r_week, 1, 5);
if (strp == NULL)
return NULL;
if (*strp++ != '.')
return NULL;
strp = getnum(strp, &rulep->r_day, 0, DAYSPERWEEK - 1);
}
else if (is_digit(*strp))
{
/*
* Day of year.
*/
rulep->r_type = DAY_OF_YEAR;
strp = getnum(strp, &rulep->r_day, 0, DAYSPERLYEAR - 1);
}
else
return NULL; /* invalid format */
if (strp == NULL)
return NULL;
if (*strp == '/')
{
/*
* Time specified.
*/
++strp;
strp = getoffset(strp, &rulep->r_time);
}
else
rulep->r_time = 2 * SECSPERHOUR; /* default = 2:00:00 */
return strp;
}
/*
* Given a year, a rule, and the offset from UT at the time that rule takes
* effect, calculate the year-relative time that rule takes effect.
*/
static int32
transtime(const int year, const struct rule *const rulep,
const int32 offset)
{
bool leapyear;
int32 value;
int i;
int d,
m1,
yy0,
yy1,
yy2,
dow;
INITIALIZE(value);
leapyear = isleap(year);
switch (rulep->r_type)
{
case JULIAN_DAY:
/*
* Jn - Julian day, 1 == January 1, 60 == March 1 even in leap
* years. In non-leap years, or if the day number is 59 or less,
* just add SECSPERDAY times the day number-1 to the time of
* January 1, midnight, to get the day.
*/
value = (rulep->r_day - 1) * SECSPERDAY;
if (leapyear && rulep->r_day >= 60)
value += SECSPERDAY;
break;
case DAY_OF_YEAR:
/*
* n - day of year. Just add SECSPERDAY times the day number to
* the time of January 1, midnight, to get the day.
*/
value = rulep->r_day * SECSPERDAY;
break;
case MONTH_NTH_DAY_OF_WEEK:
/*
* Mm.n.d - nth "dth day" of month m.
*/
/*
* Use Zeller's Congruence to get day-of-week of first day of
* month.
*/
m1 = (rulep->r_mon + 9) % 12 + 1;
yy0 = (rulep->r_mon <= 2) ? (year - 1) : year;
yy1 = yy0 / 100;
yy2 = yy0 % 100;
dow = ((26 * m1 - 2) / 10 +
1 + yy2 + yy2 / 4 + yy1 / 4 - 2 * yy1) % 7;
if (dow < 0)
dow += DAYSPERWEEK;
/*
* "dow" is the day-of-week of the first day of the month. Get the
* day-of-month (zero-origin) of the first "dow" day of the month.
*/
d = rulep->r_day - dow;
if (d < 0)
d += DAYSPERWEEK;
for (i = 1; i < rulep->r_week; ++i)
{
if (d + DAYSPERWEEK >=
mon_lengths[(int) leapyear][rulep->r_mon - 1])
break;
d += DAYSPERWEEK;
}
/*
* "d" is the day-of-month (zero-origin) of the day we want.
*/
value = d * SECSPERDAY;
for (i = 0; i < rulep->r_mon - 1; ++i)
value += mon_lengths[(int) leapyear][i] * SECSPERDAY;
break;
}
/*
* "value" is the year-relative time of 00:00:00 UT on the day in
* question. To get the year-relative time of the specified local time on
* that day, add the transition time and the current offset from UT.
*/
return value + rulep->r_time + offset;
}
/*
* Given a POSIX section 8-style TZ string, fill in the rule tables as
* appropriate.
* Returns true on success, false on failure.
*/
bool
tzparse(const char *name, struct state *sp, bool lastditch)
{
const char *stdname;
const char *dstname = NULL;
size_t stdlen;
size_t dstlen;
size_t charcnt;
int32 stdoffset;
int32 dstoffset;
char *cp;
bool load_ok;
stdname = name;
if (lastditch)
{
/* Unlike IANA, don't assume name is exactly "GMT" */
stdlen = strlen(name); /* length of standard zone name */
name += stdlen;
stdoffset = 0;
}
else
{
if (*name == '<')
{
name++;
stdname = name;
name = getqzname(name, '>');
if (*name != '>')
return false;
stdlen = name - stdname;
name++;
}
else
{
name = getzname(name);
stdlen = name - stdname;
}
if (*name == '\0') /* we allow empty STD abbrev, unlike IANA */
return false;
name = getoffset(name, &stdoffset);
if (name == NULL)
return false;
}
charcnt = stdlen + 1;
if (sizeof sp->chars < charcnt)
return false;
/*
* The IANA code always tries tzload(TZDEFRULES) here. We do not want to
* do that; it would be bad news in the lastditch case, where we can't
* assume pg_open_tzfile() is sane yet. Moreover, the only reason to do
* it unconditionally is to absorb the TZDEFRULES zone's leap second info,
* which we don't want to do anyway. Without that, we only need to load
* TZDEFRULES if the zone name specifies DST but doesn't incorporate a
* POSIX-style transition date rule, which is not a common case.
*/
sp->goback = sp->goahead = false; /* simulate failed tzload() */
sp->leapcnt = 0; /* intentionally assume no leap seconds */
if (*name != '\0')
{
if (*name == '<')
{