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Diffstat (limited to 'time/mktime.c')
| -rw-r--r-- | time/mktime.c | 506 |
1 files changed, 506 insertions, 0 deletions
diff --git a/time/mktime.c b/time/mktime.c new file mode 100644 index 0000000000..f86496a941 --- /dev/null +++ b/time/mktime.c @@ -0,0 +1,506 @@ +/* Copyright (C) 1993, 1994, 1995 Free Software Foundation, Inc. + Contributed by Noel Cragg (noel@cs.oberlin.edu), with fixes by + Michael E. Calwas (calwas@ttd.teradyne.com) and + Wade Hampton (tasi029@tmn.com). + +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 Library General Public License as +published by the Free Software Foundation; either version 2 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 +Library General Public License for more details. + +You should have received a copy of the GNU Library General Public +License along with the GNU C Library; see the file COPYING.LIB. If +not, write to the Free Software Foundation, Inc., 675 Mass Ave, +Cambridge, MA 02139, USA. */ + +/* Define this to have a standalone program to test this implementation of + mktime. */ +/* #define DEBUG */ + +#ifdef HAVE_CONFIG_H +#include <config.h> +#endif + +#include <sys/types.h> /* Some systems define `time_t' here. */ +#include <time.h> + + +#ifndef __isleap +/* Nonzero if YEAR is a leap year (every 4 years, + except every 100th isn't, and every 400th is). */ +#define __isleap(year) \ + ((year) % 4 == 0 && ((year) % 100 != 0 || (year) % 400 == 0)) +#endif + +#ifndef __P +#if defined (__GNUC__) || (defined (__STDC__) && __STDC__) +#define __P(args) args +#else +#define __P(args) () +#endif /* GCC. */ +#endif /* Not __P. */ + +/* How many days are in each month. */ +const unsigned short int __mon_lengths[2][12] = + { + /* Normal years. */ + { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }, + /* Leap years. */ + { 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 } + }; + + +static int times_through_search; /* This library routine should never + hang -- make sure we always return + when we're searching for a value */ + + +#ifdef DEBUG + +#include <stdio.h> +#include <ctype.h> + +int debugging_enabled = 0; + +/* Print the values in a `struct tm'. */ +static void +printtm (it) + struct tm *it; +{ + printf ("%02d/%02d/%04d %02d:%02d:%02d (%s) yday:%03d dst:%d gmtoffset:%ld", + it->tm_mon + 1, + it->tm_mday, + it->tm_year + 1900, + it->tm_hour, + it->tm_min, + it->tm_sec, + it->tm_zone, + it->tm_yday, + it->tm_isdst, + it->tm_gmtoff); +} +#endif + + +static time_t +dist_tm (t1, t2) + struct tm *t1; + struct tm *t2; +{ + time_t distance = 0; + unsigned long int v1, v2; + int diff_flag = 0; + + v1 = v2 = 0; + +#define doit(x, secs) \ + v1 += t1->x * secs; \ + v2 += t2->x * secs; \ + if (!diff_flag) \ + { \ + if (t1->x < t2->x) \ + diff_flag = -1; \ + else if (t1->x > t2->x) \ + diff_flag = 1; \ + } + + doit (tm_year, 31536000); /* Okay, not all years have 365 days. */ + doit (tm_mon, 2592000); /* Okay, not all months have 30 days. */ + doit (tm_mday, 86400); + doit (tm_hour, 3600); + doit (tm_min, 60); + doit (tm_sec, 1); + +#undef doit + + /* We should also make sure that the sign of DISTANCE is correct -- if + DIFF_FLAG is positive, the distance should be positive and vice versa. */ + + distance = (v1 > v2) ? (v1 - v2) : (v2 - v1); + if (diff_flag < 0) + distance = -distance; + + if (times_through_search > 20) /* Arbitrary # of calls, but makes sure we + never hang if there's a problem with + this algorithm. */ + { + distance = diff_flag; + } + + /* We need this DIFF_FLAG business because it is forseeable that the + distance may be zero when, in actuality, the two structures are + different. This is usually the case when the dates are 366 days apart + and one of the years is a leap year. */ + + if (distance == 0 && diff_flag) + distance = 86400 * diff_flag; + + return distance; +} + + +/* MKTIME converts the values in a struct tm to a time_t. The values + in tm_wday and tm_yday are ignored; other values can be put outside + of legal ranges since they will be normalized. This routine takes + care of that normalization. */ + +void +do_normalization (tmptr) + struct tm *tmptr; +{ + +#define normalize(foo,x,y,bar); \ + while (tmptr->foo < x) \ + { \ + tmptr->bar--; \ + tmptr->foo = (y - (x - tmptr->foo) + 1); \ + } \ + while (tmptr->foo > y) \ + { \ + tmptr->foo = (x + (tmptr->foo - y) - 1); \ + tmptr->bar++; \ + } + + normalize (tm_sec, 0, 59, tm_min); + normalize (tm_min, 0, 59, tm_hour); + normalize (tm_hour, 0, 23, tm_mday); + + /* Do the month first, so day range can be found. */ + normalize (tm_mon, 0, 11, tm_year); + + /* Since the day range modifies the month, we should be careful how + we reference the array of month lengths -- it is possible that + the month will go negative, hence the modulo... + + Also, tm_year is the year - 1900, so we have to 1900 to have it + work correctly. */ + + normalize (tm_mday, 1, + __mon_lengths[__isleap (tmptr->tm_year + 1900)] + [((tmptr->tm_mon < 0) + ? (12 + (tmptr->tm_mon % 12)) + : (tmptr->tm_mon % 12)) ], + tm_mon); + + /* Do the month again, because the day may have pushed it out of range. */ + normalize (tm_mon, 0, 11, tm_year); + + /* Do the day again, because the month may have changed the range. */ + normalize (tm_mday, 1, + __mon_lengths[__isleap (tmptr->tm_year + 1900)] + [((tmptr->tm_mon < 0) + ? (12 + (tmptr->tm_mon % 12)) + : (tmptr->tm_mon % 12)) ], + tm_mon); + +#ifdef DEBUG + if (debugging_enabled) + { + printf (" After normalizing:\n "); + printtm (tmptr); + putchar ('\n'); + } +#endif + +} + + +/* Here's where the work gets done. */ + +#define BAD_STRUCT_TM ((time_t) -1) + +time_t +_mktime_internal (timeptr, producer) + struct tm *timeptr; + struct tm *(*producer) __P ((const time_t *)); +{ + struct tm our_tm; /* our working space */ + struct tm *me = &our_tm; /* a pointer to the above */ + time_t result; /* the value we return */ + + *me = *timeptr; /* copy the struct tm that was passed + in by the caller */ + + + /***************************/ + /* Normalize the structure */ + /***************************/ + + /* This routine assumes that the value of TM_ISDST is -1, 0, or 1. + If the user didn't pass it in that way, fix it. */ + + if (me->tm_isdst > 0) + me->tm_isdst = 1; + else if (me->tm_isdst < 0) + me->tm_isdst = -1; + + do_normalization (me); + + /* Get out of here if it's not possible to represent this struct. + If any of the values in the normalized struct tm are negative, + our algorithms won't work. Luckily, we only need to check the + year at this point; normalization guarantees that all values will + be in correct ranges EXCEPT the year. */ + + if (me->tm_year < 0) + return BAD_STRUCT_TM; + + /*************************************************/ + /* Find the appropriate time_t for the structure */ + /*************************************************/ + + /* Modified b-search -- make intelligent guesses as to where the + time might lie along the timeline, assuming that our target time + lies a linear distance (w/o considering time jumps of a + particular region). + + Assume that time does not fluctuate at all along the timeline -- + e.g., assume that a day will always take 86400 seconds, etc. -- + and come up with a hypothetical value for the time_t + representation of the struct tm TARGET, in relation to the guess + variable -- it should be pretty close! + + After testing this, the maximum number of iterations that I had + on any number that I tried was 3! Not bad. + + The reason this is not a subroutine is that we will modify some + fields in the struct tm (yday and mday). I've never felt good + about side-effects when writing structured code... */ + + { + struct tm *guess_tm; + time_t guess = 0; + time_t distance = 0; + time_t last_distance = 0; + + times_through_search = 0; + + do + { + guess += distance; + + times_through_search++; + + guess_tm = (*producer) (&guess); + +#ifdef DEBUG + if (debugging_enabled) + { + printf (" Guessing time_t == %d\n ", (int) guess); + printtm (guess_tm); + putchar ('\n'); + } +#endif + + /* How far is our guess from the desired struct tm? */ + distance = dist_tm (me, guess_tm); + + /* Handle periods of time where a period of time is skipped. + For example, 2:15 3 April 1994 does not exist, because DST + is in effect. The distance function will alternately + return values of 3600 and -3600, because it doesn't know + that the requested time doesn't exist. In these situations + (even if the skip is not exactly an hour) the distances + returned will be the same, but alternating in sign. We + want the later time, so check to see that the distance is + oscillating and we've chosen the correct of the two + possibilities. + + Useful: 3 Apr 94 765356300, 30 Oct 94 783496000 */ + + if ((distance == -last_distance) && (distance < last_distance)) + { + /* If the caller specified that the DST flag was off, it's + not possible to represent this time. */ + if (me->tm_isdst == 0) + { +#ifdef DEBUG + printf (" Distance is oscillating -- dst flag nixes struct!\n"); +#endif + return BAD_STRUCT_TM; + } + +#ifdef DEBUG + printf (" Distance is oscillating -- chose the later time.\n"); +#endif + distance = 0; + } + + if ((distance == 0) && (me->tm_isdst != -1) + && (me->tm_isdst != guess_tm->tm_isdst)) + { + /* If we're in this code, we've got the right time but the + wrong daylight savings flag. We need to move away from + the time that we have and approach the other time from + the other direction. That is, if I've requested the + non-DST version of a time and I get the DST version + instead, I want to put us forward in time and search + backwards to get the other time. I checked all of the + configuration files for the tz package -- no entry + saves more than two hours, so I think we'll be safe by + moving 24 hours in one direction. IF THE AMOUNT OF + TIME SAVED IN THE CONFIGURATION FILES CHANGES, THIS + VALUE MAY NEED TO BE ADJUSTED. Luckily, we can never + have more than one level of overlaps, or this would + never work. */ + +#define SKIP_VALUE 86400 + + if (guess_tm->tm_isdst == 0) + /* we got the later one, but want the earlier one */ + distance = -SKIP_VALUE; + else + distance = SKIP_VALUE; + +#ifdef DEBUG + printf (" Got the right time, wrong DST value -- adjusting\n"); +#endif + } + + last_distance = distance; + + } while (distance != 0); + + /* Check to see that the dst flag matches */ + + if (me->tm_isdst != -1) + { + if (me->tm_isdst != guess_tm->tm_isdst) + { +#ifdef DEBUG + printf (" DST flag doesn't match! FIXME?\n"); +#endif + return BAD_STRUCT_TM; + } + } + + result = guess; /* Success! */ + + /* On successful completion, the values of tm_wday and tm_yday + have to be set appropriately. */ + + /* me->tm_yday = guess_tm->tm_yday; + me->tm_mday = guess_tm->tm_mday; */ + + *me = *guess_tm; + } + + /* Update the caller's version of the structure */ + + *timeptr = *me; + + return result; +} + +time_t +#ifdef DEBUG /* make it work even if the system's + libc has it's own mktime routine */ +my_mktime (timeptr) +#else +mktime (timeptr) +#endif + struct tm *timeptr; +{ + return _mktime_internal (timeptr, localtime); +} + +#ifdef weak_alias +weak_alias (mktime, timelocal) +#endif + +#ifdef DEBUG +void +main (argc, argv) + int argc; + char *argv[]; +{ + int time; + int result_time; + struct tm *tmptr; + + if (argc == 1) + { + long q; + + printf ("starting long test...\n"); + + for (q = 10000000; q < 1000000000; q += 599) + { + struct tm *tm = localtime ((time_t *) &q); + if ((q % 10000) == 0) { printf ("%ld\n", q); fflush (stdout); } + if (q != my_mktime (tm)) + { printf ("failed for %ld\n", q); fflush (stdout); } + } + + printf ("test finished\n"); + + exit (0); + } + + if (argc != 2) + { + printf ("wrong # of args\n"); + exit (0); + } + + debugging_enabled = 1; /* We want to see the info */ + + ++argv; + time = atoi (*argv); + + tmptr = localtime ((time_t *) &time); + printf ("Localtime tells us that a time_t of %d represents\n ", time); + printtm (tmptr); + putchar ('\n'); + + printf (" Given localtime's return val, mktime returns %d which is\n ", + (int) my_mktime (tmptr)); + printtm (tmptr); + putchar ('\n'); + +#if 0 + tmptr->tm_sec -= 20; + tmptr->tm_min -= 20; + tmptr->tm_hour -= 20; + tmptr->tm_mday -= 20; + tmptr->tm_mon -= 20; + tmptr->tm_year -= 20; + tmptr->tm_gmtoff -= 20000; /* This has no effect! */ + tmptr->tm_zone = NULL; /* Nor does this! */ + tmptr->tm_isdst = -1; +#endif + + tmptr->tm_hour += 1; + tmptr->tm_isdst = -1; + + printf ("\n\nchanged ranges: "); + printtm (tmptr); + putchar ('\n'); + + result_time = my_mktime (tmptr); + printf ("\nmktime: %d\n", result_time); + + tmptr->tm_isdst = 0; + + printf ("\n\nchanged ranges: "); + printtm (tmptr); + putchar ('\n'); + + result_time = my_mktime (tmptr); + printf ("\nmktime: %d\n", result_time); +} +#endif /* DEBUG */ + + +/* +Local Variables: +compile-command: "gcc -g mktime.c -o mktime -DDEBUG" +End: +*/ |