| 1 | /* Convert a `struct tm' to a time_t value. |
| 2 | Copyright (C) 1993-1999, 2002-2007, 2009-2011 Free Software Foundation, Inc. |
| 3 | This file is part of the GNU C Library. |
| 4 | Contributed by Paul Eggert <eggert@twinsun.com>. |
| 5 | |
| 6 | This program is free software; you can redistribute it and/or modify |
| 7 | it under the terms of the GNU General Public License as published by |
| 8 | the Free Software Foundation; either version 3, or (at your option) |
| 9 | any later version. |
| 10 | |
| 11 | This program is distributed in the hope that it will be useful, |
| 12 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 14 | GNU General Public License for more details. |
| 15 | |
| 16 | You should have received a copy of the GNU General Public License along |
| 17 | with this program; if not, write to the Free Software Foundation, |
| 18 | Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ |
| 19 | |
| 20 | /* Define this to have a standalone program to test this implementation of |
| 21 | mktime. */ |
| 22 | /* #define DEBUG 1 */ |
| 23 | |
| 24 | #ifndef _LIBC |
| 25 | # include <config.h> |
| 26 | #endif |
| 27 | |
| 28 | /* Some of the code in this file assumes that signed integer overflow |
| 29 | silently wraps around. This assumption can't easily be programmed |
| 30 | around, nor can it be checked for portably at compile-time or |
| 31 | easily eliminated at run-time. |
| 32 | |
| 33 | Define WRAPV to 1 if the assumption is valid. Otherwise, define it |
| 34 | to 0; this forces the use of slower code that, while not guaranteed |
| 35 | by the C Standard, works on all production platforms that we know |
| 36 | about. */ |
| 37 | #ifndef WRAPV |
| 38 | # if (__GNUC__ == 4 && 4 <= __GNUC_MINOR__) || 4 < __GNUC__ |
| 39 | # pragma GCC optimize ("wrapv") |
| 40 | # define WRAPV 1 |
| 41 | # else |
| 42 | # define WRAPV 0 |
| 43 | # endif |
| 44 | #endif |
| 45 | |
| 46 | /* Assume that leap seconds are possible, unless told otherwise. |
| 47 | If the host has a `zic' command with a `-L leapsecondfilename' option, |
| 48 | then it supports leap seconds; otherwise it probably doesn't. */ |
| 49 | #ifndef LEAP_SECONDS_POSSIBLE |
| 50 | # define LEAP_SECONDS_POSSIBLE 1 |
| 51 | #endif |
| 52 | |
| 53 | #include <time.h> |
| 54 | |
| 55 | #include <limits.h> |
| 56 | |
| 57 | #include <string.h> /* For the real memcpy prototype. */ |
| 58 | |
| 59 | #if DEBUG |
| 60 | # include <stdio.h> |
| 61 | # include <stdlib.h> |
| 62 | /* Make it work even if the system's libc has its own mktime routine. */ |
| 63 | # undef mktime |
| 64 | # define mktime my_mktime |
| 65 | #endif /* DEBUG */ |
| 66 | |
| 67 | /* Verify a requirement at compile-time (unlike assert, which is runtime). */ |
| 68 | #define verify(name, assertion) struct name { char a[(assertion) ? 1 : -1]; } |
| 69 | |
| 70 | /* A signed type that is at least one bit wider than int. */ |
| 71 | #if INT_MAX <= LONG_MAX / 2 |
| 72 | typedef long int long_int; |
| 73 | #else |
| 74 | typedef long long int long_int; |
| 75 | #endif |
| 76 | verify (long_int_is_wide_enough, INT_MAX == INT_MAX * (long_int) 2 / 2); |
| 77 | |
| 78 | /* Shift A right by B bits portably, by dividing A by 2**B and |
| 79 | truncating towards minus infinity. A and B should be free of side |
| 80 | effects, and B should be in the range 0 <= B <= INT_BITS - 2, where |
| 81 | INT_BITS is the number of useful bits in an int. GNU code can |
| 82 | assume that INT_BITS is at least 32. |
| 83 | |
| 84 | ISO C99 says that A >> B is implementation-defined if A < 0. Some |
| 85 | implementations (e.g., UNICOS 9.0 on a Cray Y-MP EL) don't shift |
| 86 | right in the usual way when A < 0, so SHR falls back on division if |
| 87 | ordinary A >> B doesn't seem to be the usual signed shift. */ |
| 88 | #define SHR(a, b) \ |
| 89 | ((-1 >> 1 == -1 \ |
| 90 | && (long_int) -1 >> 1 == -1 \ |
| 91 | && ((time_t) -1 >> 1 == -1 || ! TYPE_SIGNED (time_t))) \ |
| 92 | ? (a) >> (b) \ |
| 93 | : (a) / (1 << (b)) - ((a) % (1 << (b)) < 0)) |
| 94 | |
| 95 | /* The extra casts in the following macros work around compiler bugs, |
| 96 | e.g., in Cray C 5.0.3.0. */ |
| 97 | |
| 98 | /* True if the arithmetic type T is an integer type. bool counts as |
| 99 | an integer. */ |
| 100 | #define TYPE_IS_INTEGER(t) ((t) 1.5 == 1) |
| 101 | |
| 102 | /* True if negative values of the signed integer type T use two's |
| 103 | complement, or if T is an unsigned integer type. */ |
| 104 | #define TYPE_TWOS_COMPLEMENT(t) ((t) ~ (t) 0 == (t) -1) |
| 105 | |
| 106 | /* True if the arithmetic type T is signed. */ |
| 107 | #define TYPE_SIGNED(t) (! ((t) 0 < (t) -1)) |
| 108 | |
| 109 | /* The maximum and minimum values for the integer type T. These |
| 110 | macros have undefined behavior if T is signed and has padding bits. |
| 111 | If this is a problem for you, please let us know how to fix it for |
| 112 | your host. */ |
| 113 | #define TYPE_MINIMUM(t) \ |
| 114 | ((t) (! TYPE_SIGNED (t) \ |
| 115 | ? (t) 0 \ |
| 116 | : ~ TYPE_MAXIMUM (t))) |
| 117 | #define TYPE_MAXIMUM(t) \ |
| 118 | ((t) (! TYPE_SIGNED (t) \ |
| 119 | ? (t) -1 \ |
| 120 | : ((((t) 1 << (sizeof (t) * CHAR_BIT - 2)) - 1) * 2 + 1))) |
| 121 | |
| 122 | #ifndef TIME_T_MIN |
| 123 | # define TIME_T_MIN TYPE_MINIMUM (time_t) |
| 124 | #endif |
| 125 | #ifndef TIME_T_MAX |
| 126 | # define TIME_T_MAX TYPE_MAXIMUM (time_t) |
| 127 | #endif |
| 128 | #define TIME_T_MIDPOINT (SHR (TIME_T_MIN + TIME_T_MAX, 1) + 1) |
| 129 | |
| 130 | verify (time_t_is_integer, TYPE_IS_INTEGER (time_t)); |
| 131 | verify (twos_complement_arithmetic, |
| 132 | (TYPE_TWOS_COMPLEMENT (int) |
| 133 | && TYPE_TWOS_COMPLEMENT (long_int) |
| 134 | && TYPE_TWOS_COMPLEMENT (time_t))); |
| 135 | |
| 136 | #define EPOCH_YEAR 1970 |
| 137 | #define TM_YEAR_BASE 1900 |
| 138 | verify (base_year_is_a_multiple_of_100, TM_YEAR_BASE % 100 == 0); |
| 139 | |
| 140 | /* Return 1 if YEAR + TM_YEAR_BASE is a leap year. */ |
| 141 | static inline int |
| 142 | leapyear (long_int year) |
| 143 | { |
| 144 | /* Don't add YEAR to TM_YEAR_BASE, as that might overflow. |
| 145 | Also, work even if YEAR is negative. */ |
| 146 | return |
| 147 | ((year & 3) == 0 |
| 148 | && (year % 100 != 0 |
| 149 | || ((year / 100) & 3) == (- (TM_YEAR_BASE / 100) & 3))); |
| 150 | } |
| 151 | |
| 152 | /* How many days come before each month (0-12). */ |
| 153 | #ifndef _LIBC |
| 154 | static |
| 155 | #endif |
| 156 | const unsigned short int __mon_yday[2][13] = |
| 157 | { |
| 158 | /* Normal years. */ |
| 159 | { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 }, |
| 160 | /* Leap years. */ |
| 161 | { 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366 } |
| 162 | }; |
| 163 | |
| 164 | |
| 165 | #ifndef _LIBC |
| 166 | /* Portable standalone applications should supply a <time.h> that |
| 167 | declares a POSIX-compliant localtime_r, for the benefit of older |
| 168 | implementations that lack localtime_r or have a nonstandard one. |
| 169 | See the gnulib time_r module for one way to implement this. */ |
| 170 | # undef __localtime_r |
| 171 | # define __localtime_r localtime_r |
| 172 | # define __mktime_internal mktime_internal |
| 173 | # include "mktime-internal.h" |
| 174 | #endif |
| 175 | |
| 176 | /* Return 1 if the values A and B differ according to the rules for |
| 177 | tm_isdst: A and B differ if one is zero and the other positive. */ |
| 178 | static int |
| 179 | isdst_differ (int a, int b) |
| 180 | { |
| 181 | return (!a != !b) & (0 <= a) & (0 <= b); |
| 182 | } |
| 183 | |
| 184 | /* Return an integer value measuring (YEAR1-YDAY1 HOUR1:MIN1:SEC1) - |
| 185 | (YEAR0-YDAY0 HOUR0:MIN0:SEC0) in seconds, assuming that the clocks |
| 186 | were not adjusted between the time stamps. |
| 187 | |
| 188 | The YEAR values uses the same numbering as TP->tm_year. Values |
| 189 | need not be in the usual range. However, YEAR1 must not be less |
| 190 | than 2 * INT_MIN or greater than 2 * INT_MAX. |
| 191 | |
| 192 | The result may overflow. It is the caller's responsibility to |
| 193 | detect overflow. */ |
| 194 | |
| 195 | static inline time_t |
| 196 | ydhms_diff (long_int year1, long_int yday1, int hour1, int min1, int sec1, |
| 197 | int year0, int yday0, int hour0, int min0, int sec0) |
| 198 | { |
| 199 | verify (C99_integer_division, -1 / 2 == 0); |
| 200 | |
| 201 | /* Compute intervening leap days correctly even if year is negative. |
| 202 | Take care to avoid integer overflow here. */ |
| 203 | int a4 = SHR (year1, 2) + SHR (TM_YEAR_BASE, 2) - ! (year1 & 3); |
| 204 | int b4 = SHR (year0, 2) + SHR (TM_YEAR_BASE, 2) - ! (year0 & 3); |
| 205 | int a100 = a4 / 25 - (a4 % 25 < 0); |
| 206 | int b100 = b4 / 25 - (b4 % 25 < 0); |
| 207 | int a400 = SHR (a100, 2); |
| 208 | int b400 = SHR (b100, 2); |
| 209 | int intervening_leap_days = (a4 - b4) - (a100 - b100) + (a400 - b400); |
| 210 | |
| 211 | /* Compute the desired time in time_t precision. Overflow might |
| 212 | occur here. */ |
| 213 | time_t tyear1 = year1; |
| 214 | time_t years = tyear1 - year0; |
| 215 | time_t days = 365 * years + yday1 - yday0 + intervening_leap_days; |
| 216 | time_t hours = 24 * days + hour1 - hour0; |
| 217 | time_t minutes = 60 * hours + min1 - min0; |
| 218 | time_t seconds = 60 * minutes + sec1 - sec0; |
| 219 | return seconds; |
| 220 | } |
| 221 | |
| 222 | /* Return the average of A and B, even if A + B would overflow. */ |
| 223 | static time_t |
| 224 | time_t_avg (time_t a, time_t b) |
| 225 | { |
| 226 | return SHR (a, 1) + SHR (b, 1) + (a & b & 1); |
| 227 | } |
| 228 | |
| 229 | /* Return 1 if A + B does not overflow. If time_t is unsigned and if |
| 230 | B's top bit is set, assume that the sum represents A - -B, and |
| 231 | return 1 if the subtraction does not wrap around. */ |
| 232 | static int |
| 233 | time_t_add_ok (time_t a, time_t b) |
| 234 | { |
| 235 | if (! TYPE_SIGNED (time_t)) |
| 236 | { |
| 237 | time_t sum = a + b; |
| 238 | return (sum < a) == (TIME_T_MIDPOINT <= b); |
| 239 | } |
| 240 | else if (WRAPV) |
| 241 | { |
| 242 | time_t sum = a + b; |
| 243 | return (sum < a) == (b < 0); |
| 244 | } |
| 245 | else |
| 246 | { |
| 247 | time_t avg = time_t_avg (a, b); |
| 248 | return TIME_T_MIN / 2 <= avg && avg <= TIME_T_MAX / 2; |
| 249 | } |
| 250 | } |
| 251 | |
| 252 | /* Return 1 if A + B does not overflow. */ |
| 253 | static int |
| 254 | time_t_int_add_ok (time_t a, int b) |
| 255 | { |
| 256 | verify (int_no_wider_than_time_t, INT_MAX <= TIME_T_MAX); |
| 257 | if (WRAPV) |
| 258 | { |
| 259 | time_t sum = a + b; |
| 260 | return (sum < a) == (b < 0); |
| 261 | } |
| 262 | else |
| 263 | { |
| 264 | int a_odd = a & 1; |
| 265 | time_t avg = SHR (a, 1) + (SHR (b, 1) + (a_odd & b)); |
| 266 | return TIME_T_MIN / 2 <= avg && avg <= TIME_T_MAX / 2; |
| 267 | } |
| 268 | } |
| 269 | |
| 270 | /* Return a time_t value corresponding to (YEAR-YDAY HOUR:MIN:SEC), |
| 271 | assuming that *T corresponds to *TP and that no clock adjustments |
| 272 | occurred between *TP and the desired time. |
| 273 | If TP is null, return a value not equal to *T; this avoids false matches. |
| 274 | If overflow occurs, yield the minimal or maximal value, except do not |
| 275 | yield a value equal to *T. */ |
| 276 | static time_t |
| 277 | guess_time_tm (long_int year, long_int yday, int hour, int min, int sec, |
| 278 | const time_t *t, const struct tm *tp) |
| 279 | { |
| 280 | if (tp) |
| 281 | { |
| 282 | time_t d = ydhms_diff (year, yday, hour, min, sec, |
| 283 | tp->tm_year, tp->tm_yday, |
| 284 | tp->tm_hour, tp->tm_min, tp->tm_sec); |
| 285 | if (time_t_add_ok (*t, d)) |
| 286 | return *t + d; |
| 287 | } |
| 288 | |
| 289 | /* Overflow occurred one way or another. Return the nearest result |
| 290 | that is actually in range, except don't report a zero difference |
| 291 | if the actual difference is nonzero, as that would cause a false |
| 292 | match; and don't oscillate between two values, as that would |
| 293 | confuse the spring-forward gap detector. */ |
| 294 | return (*t < TIME_T_MIDPOINT |
| 295 | ? (*t <= TIME_T_MIN + 1 ? *t + 1 : TIME_T_MIN) |
| 296 | : (TIME_T_MAX - 1 <= *t ? *t - 1 : TIME_T_MAX)); |
| 297 | } |
| 298 | |
| 299 | /* Use CONVERT to convert *T to a broken down time in *TP. |
| 300 | If *T is out of range for conversion, adjust it so that |
| 301 | it is the nearest in-range value and then convert that. */ |
| 302 | static struct tm * |
| 303 | ranged_convert (struct tm *(*convert) (const time_t *, struct tm *), |
| 304 | time_t *t, struct tm *tp) |
| 305 | { |
| 306 | struct tm *r = convert (t, tp); |
| 307 | |
| 308 | if (!r && *t) |
| 309 | { |
| 310 | time_t bad = *t; |
| 311 | time_t ok = 0; |
| 312 | |
| 313 | /* BAD is a known unconvertible time_t, and OK is a known good one. |
| 314 | Use binary search to narrow the range between BAD and OK until |
| 315 | they differ by 1. */ |
| 316 | while (bad != ok + (bad < 0 ? -1 : 1)) |
| 317 | { |
| 318 | time_t mid = *t = time_t_avg (ok, bad); |
| 319 | r = convert (t, tp); |
| 320 | if (r) |
| 321 | ok = mid; |
| 322 | else |
| 323 | bad = mid; |
| 324 | } |
| 325 | |
| 326 | if (!r && ok) |
| 327 | { |
| 328 | /* The last conversion attempt failed; |
| 329 | revert to the most recent successful attempt. */ |
| 330 | *t = ok; |
| 331 | r = convert (t, tp); |
| 332 | } |
| 333 | } |
| 334 | |
| 335 | return r; |
| 336 | } |
| 337 | |
| 338 | |
| 339 | /* Convert *TP to a time_t value, inverting |
| 340 | the monotonic and mostly-unit-linear conversion function CONVERT. |
| 341 | Use *OFFSET to keep track of a guess at the offset of the result, |
| 342 | compared to what the result would be for UTC without leap seconds. |
| 343 | If *OFFSET's guess is correct, only one CONVERT call is needed. |
| 344 | This function is external because it is used also by timegm.c. */ |
| 345 | time_t |
| 346 | __mktime_internal (struct tm *tp, |
| 347 | struct tm *(*convert) (const time_t *, struct tm *), |
| 348 | time_t *offset) |
| 349 | { |
| 350 | time_t t, gt, t0, t1, t2; |
| 351 | struct tm tm; |
| 352 | |
| 353 | /* The maximum number of probes (calls to CONVERT) should be enough |
| 354 | to handle any combinations of time zone rule changes, solar time, |
| 355 | leap seconds, and oscillations around a spring-forward gap. |
| 356 | POSIX.1 prohibits leap seconds, but some hosts have them anyway. */ |
| 357 | int remaining_probes = 6; |
| 358 | |
| 359 | /* Time requested. Copy it in case CONVERT modifies *TP; this can |
| 360 | occur if TP is localtime's returned value and CONVERT is localtime. */ |
| 361 | int sec = tp->tm_sec; |
| 362 | int min = tp->tm_min; |
| 363 | int hour = tp->tm_hour; |
| 364 | int mday = tp->tm_mday; |
| 365 | int mon = tp->tm_mon; |
| 366 | int year_requested = tp->tm_year; |
| 367 | int isdst = tp->tm_isdst; |
| 368 | |
| 369 | /* 1 if the previous probe was DST. */ |
| 370 | int dst2; |
| 371 | |
| 372 | /* Ensure that mon is in range, and set year accordingly. */ |
| 373 | int mon_remainder = mon % 12; |
| 374 | int negative_mon_remainder = mon_remainder < 0; |
| 375 | int mon_years = mon / 12 - negative_mon_remainder; |
| 376 | long_int lyear_requested = year_requested; |
| 377 | long_int year = lyear_requested + mon_years; |
| 378 | |
| 379 | /* The other values need not be in range: |
| 380 | the remaining code handles minor overflows correctly, |
| 381 | assuming int and time_t arithmetic wraps around. |
| 382 | Major overflows are caught at the end. */ |
| 383 | |
| 384 | /* Calculate day of year from year, month, and day of month. |
| 385 | The result need not be in range. */ |
| 386 | int mon_yday = ((__mon_yday[leapyear (year)] |
| 387 | [mon_remainder + 12 * negative_mon_remainder]) |
| 388 | - 1); |
| 389 | long_int lmday = mday; |
| 390 | long_int yday = mon_yday + lmday; |
| 391 | |
| 392 | time_t guessed_offset = *offset; |
| 393 | |
| 394 | int sec_requested = sec; |
| 395 | |
| 396 | if (LEAP_SECONDS_POSSIBLE) |
| 397 | { |
| 398 | /* Handle out-of-range seconds specially, |
| 399 | since ydhms_tm_diff assumes every minute has 60 seconds. */ |
| 400 | if (sec < 0) |
| 401 | sec = 0; |
| 402 | if (59 < sec) |
| 403 | sec = 59; |
| 404 | } |
| 405 | |
| 406 | /* Invert CONVERT by probing. First assume the same offset as last |
| 407 | time. */ |
| 408 | |
| 409 | t0 = ydhms_diff (year, yday, hour, min, sec, |
| 410 | EPOCH_YEAR - TM_YEAR_BASE, 0, 0, 0, - guessed_offset); |
| 411 | |
| 412 | if (TIME_T_MAX / INT_MAX / 366 / 24 / 60 / 60 < 3) |
| 413 | { |
| 414 | /* time_t isn't large enough to rule out overflows, so check |
| 415 | for major overflows. A gross check suffices, since if t0 |
| 416 | has overflowed, it is off by a multiple of TIME_T_MAX - |
| 417 | TIME_T_MIN + 1. So ignore any component of the difference |
| 418 | that is bounded by a small value. */ |
| 419 | |
| 420 | /* Approximate log base 2 of the number of time units per |
| 421 | biennium. A biennium is 2 years; use this unit instead of |
| 422 | years to avoid integer overflow. For example, 2 average |
| 423 | Gregorian years are 2 * 365.2425 * 24 * 60 * 60 seconds, |
| 424 | which is 63113904 seconds, and rint (log2 (63113904)) is |
| 425 | 26. */ |
| 426 | int ALOG2_SECONDS_PER_BIENNIUM = 26; |
| 427 | int ALOG2_MINUTES_PER_BIENNIUM = 20; |
| 428 | int ALOG2_HOURS_PER_BIENNIUM = 14; |
| 429 | int ALOG2_DAYS_PER_BIENNIUM = 10; |
| 430 | int LOG2_YEARS_PER_BIENNIUM = 1; |
| 431 | |
| 432 | int approx_requested_biennia = |
| 433 | (SHR (year_requested, LOG2_YEARS_PER_BIENNIUM) |
| 434 | - SHR (EPOCH_YEAR - TM_YEAR_BASE, LOG2_YEARS_PER_BIENNIUM) |
| 435 | + SHR (mday, ALOG2_DAYS_PER_BIENNIUM) |
| 436 | + SHR (hour, ALOG2_HOURS_PER_BIENNIUM) |
| 437 | + SHR (min, ALOG2_MINUTES_PER_BIENNIUM) |
| 438 | + (LEAP_SECONDS_POSSIBLE |
| 439 | ? 0 |
| 440 | : SHR (sec, ALOG2_SECONDS_PER_BIENNIUM))); |
| 441 | |
| 442 | int approx_biennia = SHR (t0, ALOG2_SECONDS_PER_BIENNIUM); |
| 443 | int diff = approx_biennia - approx_requested_biennia; |
| 444 | int abs_diff = diff < 0 ? -1 - diff : diff; |
| 445 | |
| 446 | /* IRIX 4.0.5 cc miscalculates TIME_T_MIN / 3: it erroneously |
| 447 | gives a positive value of 715827882. Setting a variable |
| 448 | first then doing math on it seems to work. |
| 449 | (ghazi@caip.rutgers.edu) */ |
| 450 | time_t time_t_max = TIME_T_MAX; |
| 451 | time_t time_t_min = TIME_T_MIN; |
| 452 | time_t overflow_threshold = |
| 453 | (time_t_max / 3 - time_t_min / 3) >> ALOG2_SECONDS_PER_BIENNIUM; |
| 454 | |
| 455 | if (overflow_threshold < abs_diff) |
| 456 | { |
| 457 | /* Overflow occurred. Try repairing it; this might work if |
| 458 | the time zone offset is enough to undo the overflow. */ |
| 459 | time_t repaired_t0 = -1 - t0; |
| 460 | approx_biennia = SHR (repaired_t0, ALOG2_SECONDS_PER_BIENNIUM); |
| 461 | diff = approx_biennia - approx_requested_biennia; |
| 462 | abs_diff = diff < 0 ? -1 - diff : diff; |
| 463 | if (overflow_threshold < abs_diff) |
| 464 | return -1; |
| 465 | guessed_offset += repaired_t0 - t0; |
| 466 | t0 = repaired_t0; |
| 467 | } |
| 468 | } |
| 469 | |
| 470 | /* Repeatedly use the error to improve the guess. */ |
| 471 | |
| 472 | for (t = t1 = t2 = t0, dst2 = 0; |
| 473 | (gt = guess_time_tm (year, yday, hour, min, sec, &t, |
| 474 | ranged_convert (convert, &t, &tm)), |
| 475 | t != gt); |
| 476 | t1 = t2, t2 = t, t = gt, dst2 = tm.tm_isdst != 0) |
| 477 | if (t == t1 && t != t2 |
| 478 | && (tm.tm_isdst < 0 |
| 479 | || (isdst < 0 |
| 480 | ? dst2 <= (tm.tm_isdst != 0) |
| 481 | : (isdst != 0) != (tm.tm_isdst != 0)))) |
| 482 | /* We can't possibly find a match, as we are oscillating |
| 483 | between two values. The requested time probably falls |
| 484 | within a spring-forward gap of size GT - T. Follow the common |
| 485 | practice in this case, which is to return a time that is GT - T |
| 486 | away from the requested time, preferring a time whose |
| 487 | tm_isdst differs from the requested value. (If no tm_isdst |
| 488 | was requested and only one of the two values has a nonzero |
| 489 | tm_isdst, prefer that value.) In practice, this is more |
| 490 | useful than returning -1. */ |
| 491 | goto offset_found; |
| 492 | else if (--remaining_probes == 0) |
| 493 | return -1; |
| 494 | |
| 495 | /* We have a match. Check whether tm.tm_isdst has the requested |
| 496 | value, if any. */ |
| 497 | if (isdst_differ (isdst, tm.tm_isdst)) |
| 498 | { |
| 499 | /* tm.tm_isdst has the wrong value. Look for a neighboring |
| 500 | time with the right value, and use its UTC offset. |
| 501 | |
| 502 | Heuristic: probe the adjacent timestamps in both directions, |
| 503 | looking for the desired isdst. This should work for all real |
| 504 | time zone histories in the tz database. */ |
| 505 | |
| 506 | /* Distance between probes when looking for a DST boundary. In |
| 507 | tzdata2003a, the shortest period of DST is 601200 seconds |
| 508 | (e.g., America/Recife starting 2000-10-08 01:00), and the |
| 509 | shortest period of non-DST surrounded by DST is 694800 |
| 510 | seconds (Africa/Tunis starting 1943-04-17 01:00). Use the |
| 511 | minimum of these two values, so we don't miss these short |
| 512 | periods when probing. */ |
| 513 | int stride = 601200; |
| 514 | |
| 515 | /* The longest period of DST in tzdata2003a is 536454000 seconds |
| 516 | (e.g., America/Jujuy starting 1946-10-01 01:00). The longest |
| 517 | period of non-DST is much longer, but it makes no real sense |
| 518 | to search for more than a year of non-DST, so use the DST |
| 519 | max. */ |
| 520 | int duration_max = 536454000; |
| 521 | |
| 522 | /* Search in both directions, so the maximum distance is half |
| 523 | the duration; add the stride to avoid off-by-1 problems. */ |
| 524 | int delta_bound = duration_max / 2 + stride; |
| 525 | |
| 526 | int delta, direction; |
| 527 | |
| 528 | for (delta = stride; delta < delta_bound; delta += stride) |
| 529 | for (direction = -1; direction <= 1; direction += 2) |
| 530 | if (time_t_int_add_ok (t, delta * direction)) |
| 531 | { |
| 532 | time_t ot = t + delta * direction; |
| 533 | struct tm otm; |
| 534 | ranged_convert (convert, &ot, &otm); |
| 535 | if (! isdst_differ (isdst, otm.tm_isdst)) |
| 536 | { |
| 537 | /* We found the desired tm_isdst. |
| 538 | Extrapolate back to the desired time. */ |
| 539 | t = guess_time_tm (year, yday, hour, min, sec, &ot, &otm); |
| 540 | ranged_convert (convert, &t, &tm); |
| 541 | goto offset_found; |
| 542 | } |
| 543 | } |
| 544 | } |
| 545 | |
| 546 | offset_found: |
| 547 | *offset = guessed_offset + t - t0; |
| 548 | |
| 549 | if (LEAP_SECONDS_POSSIBLE && sec_requested != tm.tm_sec) |
| 550 | { |
| 551 | /* Adjust time to reflect the tm_sec requested, not the normalized value. |
| 552 | Also, repair any damage from a false match due to a leap second. */ |
| 553 | int sec_adjustment = (sec == 0 && tm.tm_sec == 60) - sec; |
| 554 | if (! time_t_int_add_ok (t, sec_requested)) |
| 555 | return -1; |
| 556 | t1 = t + sec_requested; |
| 557 | if (! time_t_int_add_ok (t1, sec_adjustment)) |
| 558 | return -1; |
| 559 | t2 = t1 + sec_adjustment; |
| 560 | if (! convert (&t2, &tm)) |
| 561 | return -1; |
| 562 | t = t2; |
| 563 | } |
| 564 | |
| 565 | *tp = tm; |
| 566 | return t; |
| 567 | } |
| 568 | |
| 569 | |
| 570 | /* FIXME: This should use a signed type wide enough to hold any UTC |
| 571 | offset in seconds. 'int' should be good enough for GNU code. We |
| 572 | can't fix this unilaterally though, as other modules invoke |
| 573 | __mktime_internal. */ |
| 574 | static time_t localtime_offset; |
| 575 | |
| 576 | /* Convert *TP to a time_t value. */ |
| 577 | time_t |
| 578 | mktime (struct tm *tp) |
| 579 | { |
| 580 | #ifdef _LIBC |
| 581 | /* POSIX.1 8.1.1 requires that whenever mktime() is called, the |
| 582 | time zone names contained in the external variable `tzname' shall |
| 583 | be set as if the tzset() function had been called. */ |
| 584 | __tzset (); |
| 585 | #endif |
| 586 | |
| 587 | return __mktime_internal (tp, __localtime_r, &localtime_offset); |
| 588 | } |
| 589 | |
| 590 | #ifdef weak_alias |
| 591 | weak_alias (mktime, timelocal) |
| 592 | #endif |
| 593 | |
| 594 | #ifdef _LIBC |
| 595 | libc_hidden_def (mktime) |
| 596 | libc_hidden_weak (timelocal) |
| 597 | #endif |
| 598 | \f |
| 599 | #if DEBUG |
| 600 | |
| 601 | static int |
| 602 | not_equal_tm (const struct tm *a, const struct tm *b) |
| 603 | { |
| 604 | return ((a->tm_sec ^ b->tm_sec) |
| 605 | | (a->tm_min ^ b->tm_min) |
| 606 | | (a->tm_hour ^ b->tm_hour) |
| 607 | | (a->tm_mday ^ b->tm_mday) |
| 608 | | (a->tm_mon ^ b->tm_mon) |
| 609 | | (a->tm_year ^ b->tm_year) |
| 610 | | (a->tm_yday ^ b->tm_yday) |
| 611 | | isdst_differ (a->tm_isdst, b->tm_isdst)); |
| 612 | } |
| 613 | |
| 614 | static void |
| 615 | print_tm (const struct tm *tp) |
| 616 | { |
| 617 | if (tp) |
| 618 | printf ("%04d-%02d-%02d %02d:%02d:%02d yday %03d wday %d isdst %d", |
| 619 | tp->tm_year + TM_YEAR_BASE, tp->tm_mon + 1, tp->tm_mday, |
| 620 | tp->tm_hour, tp->tm_min, tp->tm_sec, |
| 621 | tp->tm_yday, tp->tm_wday, tp->tm_isdst); |
| 622 | else |
| 623 | printf ("0"); |
| 624 | } |
| 625 | |
| 626 | static int |
| 627 | check_result (time_t tk, struct tm tmk, time_t tl, const struct tm *lt) |
| 628 | { |
| 629 | if (tk != tl || !lt || not_equal_tm (&tmk, lt)) |
| 630 | { |
| 631 | printf ("mktime ("); |
| 632 | print_tm (lt); |
| 633 | printf (")\nyields ("); |
| 634 | print_tm (&tmk); |
| 635 | printf (") == %ld, should be %ld\n", (long int) tk, (long int) tl); |
| 636 | return 1; |
| 637 | } |
| 638 | |
| 639 | return 0; |
| 640 | } |
| 641 | |
| 642 | int |
| 643 | main (int argc, char **argv) |
| 644 | { |
| 645 | int status = 0; |
| 646 | struct tm tm, tmk, tml; |
| 647 | struct tm *lt; |
| 648 | time_t tk, tl, tl1; |
| 649 | char trailer; |
| 650 | |
| 651 | if ((argc == 3 || argc == 4) |
| 652 | && (sscanf (argv[1], "%d-%d-%d%c", |
| 653 | &tm.tm_year, &tm.tm_mon, &tm.tm_mday, &trailer) |
| 654 | == 3) |
| 655 | && (sscanf (argv[2], "%d:%d:%d%c", |
| 656 | &tm.tm_hour, &tm.tm_min, &tm.tm_sec, &trailer) |
| 657 | == 3)) |
| 658 | { |
| 659 | tm.tm_year -= TM_YEAR_BASE; |
| 660 | tm.tm_mon--; |
| 661 | tm.tm_isdst = argc == 3 ? -1 : atoi (argv[3]); |
| 662 | tmk = tm; |
| 663 | tl = mktime (&tmk); |
| 664 | lt = localtime (&tl); |
| 665 | if (lt) |
| 666 | { |
| 667 | tml = *lt; |
| 668 | lt = &tml; |
| 669 | } |
| 670 | printf ("mktime returns %ld == ", (long int) tl); |
| 671 | print_tm (&tmk); |
| 672 | printf ("\n"); |
| 673 | status = check_result (tl, tmk, tl, lt); |
| 674 | } |
| 675 | else if (argc == 4 || (argc == 5 && strcmp (argv[4], "-") == 0)) |
| 676 | { |
| 677 | time_t from = atol (argv[1]); |
| 678 | time_t by = atol (argv[2]); |
| 679 | time_t to = atol (argv[3]); |
| 680 | |
| 681 | if (argc == 4) |
| 682 | for (tl = from; by < 0 ? to <= tl : tl <= to; tl = tl1) |
| 683 | { |
| 684 | lt = localtime (&tl); |
| 685 | if (lt) |
| 686 | { |
| 687 | tmk = tml = *lt; |
| 688 | tk = mktime (&tmk); |
| 689 | status |= check_result (tk, tmk, tl, &tml); |
| 690 | } |
| 691 | else |
| 692 | { |
| 693 | printf ("localtime (%ld) yields 0\n", (long int) tl); |
| 694 | status = 1; |
| 695 | } |
| 696 | tl1 = tl + by; |
| 697 | if ((tl1 < tl) != (by < 0)) |
| 698 | break; |
| 699 | } |
| 700 | else |
| 701 | for (tl = from; by < 0 ? to <= tl : tl <= to; tl = tl1) |
| 702 | { |
| 703 | /* Null benchmark. */ |
| 704 | lt = localtime (&tl); |
| 705 | if (lt) |
| 706 | { |
| 707 | tmk = tml = *lt; |
| 708 | tk = tl; |
| 709 | status |= check_result (tk, tmk, tl, &tml); |
| 710 | } |
| 711 | else |
| 712 | { |
| 713 | printf ("localtime (%ld) yields 0\n", (long int) tl); |
| 714 | status = 1; |
| 715 | } |
| 716 | tl1 = tl + by; |
| 717 | if ((tl1 < tl) != (by < 0)) |
| 718 | break; |
| 719 | } |
| 720 | } |
| 721 | else |
| 722 | printf ("Usage:\ |
| 723 | \t%s YYYY-MM-DD HH:MM:SS [ISDST] # Test given time.\n\ |
| 724 | \t%s FROM BY TO # Test values FROM, FROM+BY, ..., TO.\n\ |
| 725 | \t%s FROM BY TO - # Do not test those values (for benchmark).\n", |
| 726 | argv[0], argv[0], argv[0]); |
| 727 | |
| 728 | return status; |
| 729 | } |
| 730 | |
| 731 | #endif /* DEBUG */ |
| 732 | \f |
| 733 | /* |
| 734 | Local Variables: |
| 735 | compile-command: "gcc -DDEBUG -I. -Wall -W -O2 -g mktime.c -o mktime" |
| 736 | End: |
| 737 | */ |