Annotation of embedaddon/ntp/libntp/mktime.c, revision 1.1
1.1 ! misho 1: /*
! 2: * Copyright (c) 1987, 1989 Regents of the University of California.
! 3: * All rights reserved.
! 4: *
! 5: * This code is derived from software contributed to Berkeley by
! 6: * Arthur David Olson of the National Cancer Institute.
! 7: *
! 8: * Redistribution and use in source and binary forms, with or without
! 9: * modification, are permitted provided that the following conditions
! 10: * are met:
! 11: * 1. Redistributions of source code must retain the above copyright
! 12: * notice, this list of conditions and the following disclaimer.
! 13: * 2. Redistributions in binary form must reproduce the above copyright
! 14: * notice, this list of conditions and the following disclaimer in the
! 15: * documentation and/or other materials provided with the distribution.
! 16: * 3. All advertising materials mentioning features or use of this software
! 17: * must display the following acknowledgement:
! 18: * This product includes software developed by the University of
! 19: * California, Berkeley and its contributors.
! 20: * 4. Neither the name of the University nor the names of its contributors
! 21: * may be used to endorse or promote products derived from this software
! 22: * without specific prior written permission.
! 23: *
! 24: * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
! 25: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
! 26: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
! 27: * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
! 28: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
! 29: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
! 30: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
! 31: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
! 32: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
! 33: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
! 34: * SUCH DAMAGE. */
! 35:
! 36: /*static char *sccsid = "from: @(#)ctime.c 5.26 (Berkeley) 2/23/91";*/
! 37:
! 38: /*
! 39: * This implementation of mktime is lifted straight from the NetBSD (BSD 4.4)
! 40: * version. I modified it slightly to divorce it from the internals of the
! 41: * ctime library. Thus this version can't use details of the internal
! 42: * timezone state file to figure out strange unnormalized struct tm values,
! 43: * as might result from someone doing date math on the tm struct then passing
! 44: * it to mktime.
! 45: *
! 46: * It just does as well as it can at normalizing the tm input, then does a
! 47: * binary search of the time space using the system's localtime() function.
! 48: *
! 49: * The original binary search was defective in that it didn't consider the
! 50: * setting of tm_isdst when comparing tm values, causing the search to be
! 51: * flubbed for times near the dst/standard time changeover. The original
! 52: * code seems to make up for this by grubbing through the timezone info
! 53: * whenever the binary search barfed. Since I don't have that luxury in
! 54: * portable code, I have to take care of tm_isdst in the comparison routine.
! 55: * This requires knowing how many minutes offset dst is from standard time.
! 56: *
! 57: * So, if you live somewhere in the world where dst is not 60 minutes offset,
! 58: * and your vendor doesn't supply mktime(), you'll have to edit this variable
! 59: * by hand. Sorry about that.
! 60: */
! 61:
! 62: #include "ntp_machine.h"
! 63:
! 64: #if !defined(HAVE_MKTIME) || !defined(HAVE_TIMEGM)
! 65:
! 66: #if SIZEOF_TIME_T >= 8
! 67: #error libntp supplied mktime()/timegm() do not support 64-bit time_t
! 68: #endif
! 69:
! 70: #ifndef DSTMINUTES
! 71: #define DSTMINUTES 60
! 72: #endif
! 73:
! 74: #define FALSE 0
! 75: #define TRUE 1
! 76:
! 77: /* some constants from tzfile.h */
! 78: #define SECSPERMIN 60
! 79: #define MINSPERHOUR 60
! 80: #define HOURSPERDAY 24
! 81: #define DAYSPERWEEK 7
! 82: #define DAYSPERNYEAR 365
! 83: #define DAYSPERLYEAR 366
! 84: #define SECSPERHOUR (SECSPERMIN * MINSPERHOUR)
! 85: #define SECSPERDAY ((long) SECSPERHOUR * HOURSPERDAY)
! 86: #define MONSPERYEAR 12
! 87: #define TM_YEAR_BASE 1900
! 88: #define isleap(y) ((((y) % 4) == 0 && ((y) % 100) != 0) || ((y) % 400) == 0)
! 89:
! 90: static int mon_lengths[2][MONSPERYEAR] = {
! 91: { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 },
! 92: { 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }
! 93: };
! 94:
! 95: static int year_lengths[2] = {
! 96: DAYSPERNYEAR, DAYSPERLYEAR
! 97: };
! 98:
! 99: /*
! 100: ** Adapted from code provided by Robert Elz, who writes:
! 101: ** The "best" way to do mktime I think is based on an idea of Bob
! 102: ** Kridle's (so its said...) from a long time ago. (mtxinu!kridle now).
! 103: ** It does a binary search of the time_t space. Since time_t's are
! 104: ** just 32 bits, its a max of 32 iterations (even at 64 bits it
! 105: ** would still be very reasonable).
! 106: */
! 107:
! 108: #ifndef WRONG
! 109: #define WRONG (-1)
! 110: #endif /* !defined WRONG */
! 111:
! 112: static void
! 113: normalize(
! 114: int * tensptr,
! 115: int * unitsptr,
! 116: int base
! 117: )
! 118: {
! 119: if (*unitsptr >= base) {
! 120: *tensptr += *unitsptr / base;
! 121: *unitsptr %= base;
! 122: } else if (*unitsptr < 0) {
! 123: --*tensptr;
! 124: *unitsptr += base;
! 125: if (*unitsptr < 0) {
! 126: *tensptr -= 1 + (-*unitsptr) / base;
! 127: *unitsptr = base - (-*unitsptr) % base;
! 128: }
! 129: }
! 130: }
! 131:
! 132: static struct tm *
! 133: mkdst(
! 134: struct tm * tmp
! 135: )
! 136: {
! 137: /* jds */
! 138: static struct tm tmbuf;
! 139:
! 140: tmbuf = *tmp;
! 141: tmbuf.tm_isdst = 1;
! 142: tmbuf.tm_min += DSTMINUTES;
! 143: normalize(&tmbuf.tm_hour, &tmbuf.tm_min, MINSPERHOUR);
! 144: return &tmbuf;
! 145: }
! 146:
! 147: static int
! 148: tmcomp(
! 149: register struct tm * atmp,
! 150: register struct tm * btmp
! 151: )
! 152: {
! 153: register int result;
! 154:
! 155: /* compare down to the same day */
! 156:
! 157: if ((result = (atmp->tm_year - btmp->tm_year)) == 0 &&
! 158: (result = (atmp->tm_mon - btmp->tm_mon)) == 0)
! 159: result = (atmp->tm_mday - btmp->tm_mday);
! 160:
! 161: if(result != 0)
! 162: return result;
! 163:
! 164: /* get rid of one-sided dst bias */
! 165:
! 166: if(atmp->tm_isdst == 1 && !btmp->tm_isdst)
! 167: btmp = mkdst(btmp);
! 168: else if(btmp->tm_isdst == 1 && !atmp->tm_isdst)
! 169: atmp = mkdst(atmp);
! 170:
! 171: /* compare the rest of the way */
! 172:
! 173: if ((result = (atmp->tm_hour - btmp->tm_hour)) == 0 &&
! 174: (result = (atmp->tm_min - btmp->tm_min)) == 0)
! 175: result = atmp->tm_sec - btmp->tm_sec;
! 176: return result;
! 177: }
! 178:
! 179:
! 180: static time_t
! 181: time2(
! 182: struct tm * tmp,
! 183: int * okayp,
! 184: int usezn
! 185: )
! 186: {
! 187: register int dir;
! 188: register int bits;
! 189: register int i;
! 190: register int saved_seconds;
! 191: time_t t;
! 192: struct tm yourtm, mytm;
! 193:
! 194: *okayp = FALSE;
! 195: yourtm = *tmp;
! 196: if (yourtm.tm_sec >= SECSPERMIN + 2 || yourtm.tm_sec < 0)
! 197: normalize(&yourtm.tm_min, &yourtm.tm_sec, SECSPERMIN);
! 198: normalize(&yourtm.tm_hour, &yourtm.tm_min, MINSPERHOUR);
! 199: normalize(&yourtm.tm_mday, &yourtm.tm_hour, HOURSPERDAY);
! 200: normalize(&yourtm.tm_year, &yourtm.tm_mon, MONSPERYEAR);
! 201: while (yourtm.tm_mday <= 0) {
! 202: --yourtm.tm_year;
! 203: yourtm.tm_mday +=
! 204: year_lengths[isleap(yourtm.tm_year + TM_YEAR_BASE)];
! 205: }
! 206: for ( ; ; ) {
! 207: i = mon_lengths[isleap(yourtm.tm_year +
! 208: TM_YEAR_BASE)][yourtm.tm_mon];
! 209: if (yourtm.tm_mday <= i)
! 210: break;
! 211: yourtm.tm_mday -= i;
! 212: if (++yourtm.tm_mon >= MONSPERYEAR) {
! 213: yourtm.tm_mon = 0;
! 214: ++yourtm.tm_year;
! 215: }
! 216: }
! 217: saved_seconds = yourtm.tm_sec;
! 218: yourtm.tm_sec = 0;
! 219: /*
! 220: ** Calculate the number of magnitude bits in a time_t
! 221: ** (this works regardless of whether time_t is
! 222: ** signed or unsigned, though lint complains if unsigned).
! 223: */
! 224: for (bits = 0, t = 1; t > 0; ++bits, t <<= 1)
! 225: ;
! 226: /*
! 227: ** If time_t is signed, then 0 is the median value,
! 228: ** if time_t is unsigned, then 1 << bits is median.
! 229: */
! 230: t = (t < 0) ? 0 : ((time_t) 1 << bits);
! 231: for ( ; ; ) {
! 232: if (usezn)
! 233: mytm = *localtime(&t);
! 234: else
! 235: mytm = *gmtime(&t);
! 236: dir = tmcomp(&mytm, &yourtm);
! 237: if (dir != 0) {
! 238: if (bits-- < 0)
! 239: return WRONG;
! 240: if (bits < 0)
! 241: --t;
! 242: else if (dir > 0)
! 243: t -= (time_t) 1 << bits;
! 244: else t += (time_t) 1 << bits;
! 245: continue;
! 246: }
! 247: if (yourtm.tm_isdst < 0 || mytm.tm_isdst == yourtm.tm_isdst)
! 248: break;
! 249:
! 250: return WRONG;
! 251: }
! 252: t += saved_seconds;
! 253: if (usezn)
! 254: *tmp = *localtime(&t);
! 255: else
! 256: *tmp = *gmtime(&t);
! 257: *okayp = TRUE;
! 258: return t;
! 259: }
! 260: #else
! 261: int mktime_bs;
! 262: #endif /* !HAVE_MKTIME || !HAVE_TIMEGM */
! 263:
! 264: #ifndef HAVE_MKTIME
! 265: static time_t
! 266: time1(
! 267: struct tm * tmp
! 268: )
! 269: {
! 270: register time_t t;
! 271: int okay;
! 272:
! 273: if (tmp->tm_isdst > 1)
! 274: tmp->tm_isdst = 1;
! 275: t = time2(tmp, &okay, 1);
! 276: if (okay || tmp->tm_isdst < 0)
! 277: return t;
! 278:
! 279: return WRONG;
! 280: }
! 281:
! 282: time_t
! 283: mktime(
! 284: struct tm * tmp
! 285: )
! 286: {
! 287: return time1(tmp);
! 288: }
! 289: #endif /* !HAVE_MKTIME */
! 290:
! 291: #ifndef HAVE_TIMEGM
! 292: time_t
! 293: timegm(
! 294: struct tm * tmp
! 295: )
! 296: {
! 297: register time_t t;
! 298: int okay;
! 299:
! 300: tmp->tm_isdst = 0;
! 301: t = time2(tmp, &okay, 0);
! 302: if (okay || tmp->tm_isdst < 0)
! 303: return t;
! 304:
! 305: return WRONG;
! 306: }
! 307: #endif /* !HAVE_TIMEGM */
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