/* Copyright (C) 1991-2024 Free Software Foundation, Inc. This file is part of the GNU C Library. The GNU C Library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. The GNU C Library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with the GNU C Library; if not, see . */ #include #include #include #include #include #include #include #include #include #define SECSPERDAY ((__time64_t) 86400) char *__tzname[2] = { (char *) "GMT", (char *) "GMT" }; int __daylight = 0; long int __timezone = 0L; weak_alias (__tzname, tzname) weak_alias (__daylight, daylight) weak_alias (__timezone, timezone) /* This locks all the state variables in tzfile.c and this file. */ __libc_lock_define_initialized (static, tzset_lock) /* This structure contains all the information about a timezone given in the POSIX standard TZ envariable. */ typedef struct { const char *name; /* When to change. */ enum { J0, J1, M } type; /* Interpretation of: */ unsigned short int m, n, d; /* Month, week, day. */ int secs; /* Time of day. */ int offset; /* Seconds east of GMT (west if < 0). */ /* We cache the computed time of change for a given year so we don't have to recompute it. */ __time64_t change; /* When to change to this zone. */ int computed_for; /* Year above is computed for. */ } tz_rule; /* tz_rules[0] is standard, tz_rules[1] is daylight. */ static tz_rule tz_rules[2]; static void compute_change (tz_rule *rule, int year) __THROW; static void tzset_internal (int always); /* List of buffers containing time zone strings. */ struct tzstring_l { struct tzstring_l *next; size_t len; /* strlen(data) - doesn't count terminating NUL! */ char data[0]; }; static struct tzstring_l *tzstring_list; /* Allocate a permanent home for the first LEN characters of S. It will never be moved or deallocated, but may share space with other strings. Don't modify the returned string. */ static char * __tzstring_len (const char *s, size_t len) { char *p; struct tzstring_l *t, *u, *new; /* Walk the list and look for a match. If this string is the same as the end of an already-allocated string, it can share space. */ for (u = t = tzstring_list; t; u = t, t = t->next) if (len <= t->len) { p = &t->data[t->len - len]; if (memcmp (s, p, len) == 0) return p; } /* Not found; allocate a new buffer. */ new = malloc (sizeof (struct tzstring_l) + len + 1); if (!new) return NULL; new->next = NULL; new->len = len; memcpy (new->data, s, len); new->data[len] = '\0'; if (u) u->next = new; else tzstring_list = new; return new->data; } /* Allocate a permanent home for S. It will never be moved or deallocated, but may share space with other strings. Don't modify the returned string. */ char * __tzstring (const char *s) { return __tzstring_len (s, strlen (s)); } static char *old_tz; static void update_vars (void) { __daylight = tz_rules[0].offset != tz_rules[1].offset; __timezone = -tz_rules[0].offset; __tzname[0] = (char *) tz_rules[0].name; __tzname[1] = (char *) tz_rules[1].name; } static unsigned int compute_offset (unsigned int ss, unsigned int mm, unsigned int hh) { if (ss > 59) ss = 59; if (mm > 59) mm = 59; if (hh > 24) hh = 24; return ss + mm * 60 + hh * 60 * 60; } /* Parses the time zone abbreviation at *TZP, and writes a pointer to an interned string to tz_rules[WHICHRULE].name. On success, advances *TZP, and returns true. Returns false otherwise. */ static bool parse_tzname (const char **tzp, int whichrule) { const char *start = *tzp; const char *p = start; while (('a' <= *p && *p <= 'z') || ('A' <= *p && *p <= 'Z')) ++p; size_t len = p - start; if (len < 3) { p = *tzp; if (__glibc_unlikely (*p++ != '<')) return false; start = p; while (('a' <= *p && *p <= 'z') || ('A' <= *p && *p <= 'Z') || ('0' <= *p && *p <= '9') || *p == '+' || *p == '-') ++p; len = p - start; if (*p++ != '>' || len < 3) return false; } const char *name = __tzstring_len (start, len); if (name == NULL) return false; tz_rules[whichrule].name = name; *tzp = p; return true; } /* Parses the time zone offset at *TZP, and writes it to tz_rules[WHICHRULE].offset. Returns true if the parse was successful. */ static bool parse_offset (const char **tzp, int whichrule) { const char *tz = *tzp; if (whichrule == 0 && (*tz == '\0' || (*tz != '+' && *tz != '-' && !isdigit (*tz)))) return false; int sign; if (*tz == '-' || *tz == '+') sign = *tz++ == '-' ? 1 : -1; else sign = -1; *tzp = tz; unsigned short int hh; unsigned short mm = 0; unsigned short ss = 0; int consumed = 0; if (sscanf (tz, "%hu%n:%hu%n:%hu%n", &hh, &consumed, &mm, &consumed, &ss, &consumed) > 0) tz_rules[whichrule].offset = sign * compute_offset (ss, mm, hh); else /* Nothing could be parsed. */ if (whichrule == 0) { /* Standard time defaults to offset zero. */ tz_rules[0].offset = 0; return false; } else /* DST defaults to one hour later than standard time. */ tz_rules[1].offset = tz_rules[0].offset + (60 * 60); *tzp = tz + consumed; return true; } /* Parses the standard <-> DST rules at *TZP. Updates tz_rule[WHICHRULE]. On success, advances *TZP and returns true. Otherwise, returns false. */ static bool parse_rule (const char **tzp, int whichrule) { const char *tz = *tzp; tz_rule *tzr = &tz_rules[whichrule]; /* Ignore comma to support string following the incorrect specification in early POSIX.1 printings. */ tz += *tz == ','; /* Get the date of the change. */ if (*tz == 'J' || isdigit (*tz)) { char *end; tzr->type = *tz == 'J' ? J1 : J0; if (tzr->type == J1 && !isdigit (*++tz)) return false; unsigned long int d = strtoul (tz, &end, 10); if (end == tz || d > 365) return false; if (tzr->type == J1 && d == 0) return false; tzr->d = d; tz = end; } else if (*tz == 'M') { tzr->type = M; int consumed; if (sscanf (tz, "M%hu.%hu.%hu%n", &tzr->m, &tzr->n, &tzr->d, &consumed) != 3 || tzr->m < 1 || tzr->m > 12 || tzr->n < 1 || tzr->n > 5 || tzr->d > 6) return false; tz += consumed; } else if (*tz == '\0') { /* Daylight time rules in the U.S. are defined in the U.S. Code, Title 15, Chapter 6, Subchapter IX - Standard Time. These dates were established by Congress in the Energy Policy Act of 2005 [Pub. L. no. 109-58, 119 Stat 594 (2005)]. Below is the equivalent of "M3.2.0,M11.1.0" [/2 not needed since 2:00AM is the default]. */ tzr->type = M; if (tzr == &tz_rules[0]) { tzr->m = 3; tzr->n = 2; tzr->d = 0; } else { tzr->m = 11; tzr->n = 1; tzr->d = 0; } } else return false; if (*tz != '\0' && *tz != '/' && *tz != ',') return false; else if (*tz == '/') { /* Get the time of day of the change. */ int negative; ++tz; if (*tz == '\0') return false; negative = *tz == '-'; tz += negative; /* Default to 2:00 AM. */ unsigned short hh = 2; unsigned short mm = 0; unsigned short ss = 0; int consumed = 0; sscanf (tz, "%hu%n:%hu%n:%hu%n", &hh, &consumed, &mm, &consumed, &ss, &consumed);; tz += consumed; tzr->secs = (negative ? -1 : 1) * ((hh * 60 * 60) + (mm * 60) + ss); } else /* Default to 2:00 AM. */ tzr->secs = 2 * 60 * 60; tzr->computed_for = -1; *tzp = tz; return true; } /* Parse the POSIX TZ-style string. */ void __tzset_parse_tz (const char *tz) { /* Clear out old state and reset to unnamed UTC. */ memset (tz_rules, '\0', sizeof tz_rules); tz_rules[0].name = tz_rules[1].name = ""; /* Get the standard time zone abbreviations. */ if (parse_tzname (&tz, 0) && parse_offset (&tz, 0)) { /* Get the DST time zone abbreviation (if any). */ if (*tz != '\0') { if (parse_tzname (&tz, 1)) { parse_offset (&tz, 1); if (*tz == '\0' || (tz[0] == ',' && tz[1] == '\0')) { /* There is no rule. See if there is a default rule file. */ __tzfile_default (tz_rules[0].name, tz_rules[1].name, tz_rules[0].offset, tz_rules[1].offset); if (__use_tzfile) { free (old_tz); old_tz = NULL; return; } } } /* Figure out the standard <-> DST rules. */ if (parse_rule (&tz, 0)) parse_rule (&tz, 1); } else { /* There is no DST. */ tz_rules[1].name = tz_rules[0].name; tz_rules[1].offset = tz_rules[0].offset; } } update_vars (); } /* Interpret the TZ envariable. */ static void tzset_internal (int always) { static int is_initialized; const char *tz; if (is_initialized && !always) return; is_initialized = 1; /* Examine the TZ environment variable. */ tz = getenv ("TZ"); if (tz && *tz == '\0') /* User specified the empty string; use UTC explicitly. */ tz = "Universal"; /* A leading colon means "implementation defined syntax". We ignore the colon and always use the same algorithm: try a data file, and if none exists parse the 1003.1 syntax. */ if (tz && *tz == ':') ++tz; /* Check whether the value changed since the last run. */ if (old_tz != NULL && tz != NULL && strcmp (tz, old_tz) == 0) /* No change, simply return. */ return; if (tz == NULL) /* No user specification; use the site-wide default. */ tz = TZDEFAULT; tz_rules[0].name = NULL; tz_rules[1].name = NULL; /* Save the value of `tz'. */ free (old_tz); old_tz = tz ? __strdup (tz) : NULL; /* Try to read a data file. */ __tzfile_read (tz, 0, NULL); if (__use_tzfile) return; /* No data file found. Default to UTC if nothing specified. */ if (tz == NULL || *tz == '\0' || (TZDEFAULT != NULL && strcmp (tz, TZDEFAULT) == 0)) { memset (tz_rules, '\0', sizeof tz_rules); tz_rules[0].name = tz_rules[1].name = "UTC"; if (J0 != 0) tz_rules[0].type = tz_rules[1].type = J0; tz_rules[0].change = tz_rules[1].change = -1; update_vars (); return; } __tzset_parse_tz (tz); } /* Figure out the exact time (as a __time64_t) in YEAR when the change described by RULE will occur and put it in RULE->change, saving YEAR in RULE->computed_for. */ static void compute_change (tz_rule *rule, int year) { __time64_t t; if (year != -1 && rule->computed_for == year) /* Operations on times in 2 BC will be slower. Oh well. */ return; /* First set T to January 1st, 0:00:00 GMT in YEAR. */ if (year > 1970) t = ((year - 1970) * 365 + /* Compute the number of leapdays between 1970 and YEAR (exclusive). There is a leapday every 4th year ... */ + ((year - 1) / 4 - 1970 / 4) /* ... except every 100th year ... */ - ((year - 1) / 100 - 1970 / 100) /* ... but still every 400th year. */ + ((year - 1) / 400 - 1970 / 400)) * SECSPERDAY; else t = 0; switch (rule->type) { case J1: /* 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. */ t += (rule->d - 1) * SECSPERDAY; if (rule->d >= 60 && __isleap (year)) t += SECSPERDAY; break; case J0: /* n - Day of year. Just add SECSPERDAY times the day number to the time of Jan 1st. */ t += rule->d * SECSPERDAY; break; case M: /* Mm.n.d - Nth "Dth day" of month M. */ { unsigned int i; int d, m1, yy0, yy1, yy2, dow; const unsigned short int *myday = &__mon_yday[__isleap (year)][rule->m]; /* First add SECSPERDAY for each day in months before M. */ t += myday[-1] * SECSPERDAY; /* Use Zeller's Congruence to get day-of-week of first day of month. */ m1 = (rule->m + 9) % 12 + 1; yy0 = (rule->m <= 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 += 7; /* 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 = rule->d - dow; if (d < 0) d += 7; for (i = 1; i < rule->n; ++i) { if (d + 7 >= (int) myday[0] - myday[-1]) break; d += 7; } /* D is the day-of-month (zero-origin) of the day we want. */ t += d * SECSPERDAY; } break; } /* T is now the Epoch-relative time of 0:00:00 GMT on the day we want. Just add the time of day and local offset from GMT, and we're done. */ rule->change = t - rule->offset + rule->secs; rule->computed_for = year; } /* Figure out the correct timezone for TM and set `__tzname', `__timezone', and `__daylight' accordingly. */ void __tz_compute (__time64_t timer, struct tm *tm, int use_localtime) { compute_change (&tz_rules[0], 1900 + tm->tm_year); compute_change (&tz_rules[1], 1900 + tm->tm_year); if (use_localtime) { int isdst; /* We have to distinguish between northern and southern hemisphere. For the latter the daylight saving time ends in the next year. */ if (__builtin_expect (tz_rules[0].change > tz_rules[1].change, 0)) isdst = (timer < tz_rules[1].change || timer >= tz_rules[0].change); else isdst = (timer >= tz_rules[0].change && timer < tz_rules[1].change); tm->tm_isdst = isdst; tm->tm_zone = __tzname[isdst]; tm->tm_gmtoff = tz_rules[isdst].offset; } } /* Reinterpret the TZ environment variable and set `tzname'. */ #undef tzset void __tzset (void) { __libc_lock_lock (tzset_lock); tzset_internal (1); if (!__use_tzfile) { /* Set `tzname'. */ __tzname[0] = (char *) tz_rules[0].name; __tzname[1] = (char *) tz_rules[1].name; } __libc_lock_unlock (tzset_lock); } weak_alias (__tzset, tzset) /* Return the `struct tm' representation of TIMER in the local timezone. Use local time if USE_LOCALTIME is nonzero, UTC otherwise. */ struct tm * __tz_convert (__time64_t timer, int use_localtime, struct tm *tp) { long int leap_correction; int leap_extra_secs; __libc_lock_lock (tzset_lock); /* Update internal database according to current TZ setting. POSIX.1 8.3.7.2 says that localtime_r is not required to set tzname. This is a good idea since this allows at least a bit more parallelism. */ tzset_internal (tp == &_tmbuf && use_localtime); if (__use_tzfile) __tzfile_compute (timer, use_localtime, &leap_correction, &leap_extra_secs, tp); else { if (! __offtime (timer, 0, tp)) tp = NULL; else __tz_compute (timer, tp, use_localtime); leap_correction = 0L; leap_extra_secs = 0; } __libc_lock_unlock (tzset_lock); if (tp) { if (! use_localtime) { tp->tm_isdst = 0; tp->tm_zone = "GMT"; tp->tm_gmtoff = 0L; } if (__offtime (timer, tp->tm_gmtoff - leap_correction, tp)) tp->tm_sec += leap_extra_secs; else tp = NULL; } return tp; } void __libc_tzset_freemem (void) { while (tzstring_list != NULL) { struct tzstring_l *old = tzstring_list; tzstring_list = tzstring_list->next; free (old); } free (old_tz); old_tz = NULL; }