1/*- 2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD 3 * 4 * Copyright (c) 2006 Poul-Henning Kamp 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 * 28 * $FreeBSD$ 29 * 30 * Convert MS-DOS FAT format timestamps to and from unix timespecs 31 * 32 * FAT filestamps originally consisted of two 16 bit integers, encoded like 33 * this: 34 * 35 * yyyyyyymmmmddddd (year - 1980, month, day) 36 * 37 * hhhhhmmmmmmsssss (hour, minutes, seconds divided by two) 38 * 39 * Subsequently even Microsoft realized that files could be accessed in less 40 * than two seconds and a byte was added containing: 41 * 42 * sfffffff (second mod two, 100ths of second) 43 * 44 * FAT timestamps are in the local timezone, with no indication of which 45 * timezone much less if daylight savings time applies. 46 * 47 * Later on again, in Windows NT, timestamps were defined relative to GMT. 48 * 49 * Purists will point out that UTC replaced GMT for such uses around 50 * half a century ago, already then. Ironically "NT" was an abbreviation of 51 * "New Technology". Anyway... 52 * 53 * The 'utc' argument determines if the resulting FATTIME timestamp 54 * should be on the UTC or local timezone calendar. 55 * 56 * The conversion functions below cut time into four-year leap-year 57 * cycles rather than single years and uses table lookups inside those 58 * cycles to get the months and years sorted out. 59 * 60 * Obviously we cannot calculate the correct table index going from 61 * a posix seconds count to Y/M/D, but we can get pretty close by 62 * dividing the daycount by 32 (giving a too low index), and then 63 * adjusting upwards a couple of steps if necessary. 64 * 65 * FAT timestamps have 7 bits for the year and starts at 1980, so 66 * they can represent up to 2107 which means that the non-leap-year 67 * 2100 must be handled. 68 * 69 * XXX: As long as time_t is 32 bits this is not relevant or easily 70 * XXX: testable. Revisit when time_t grows bigger. 71 * XXX: grepfodder: 64 bit time_t, y2100, y2.1k, 2100, leap year 72 * 73 */ 74 75#include <sys/param.h> 76#include <sys/types.h> 77#include <sys/time.h> 78#include <sys/clock.h> 79 80#define DAY (24 * 60 * 60) /* Length of day in seconds */ 81#define YEAR 365 /* Length of normal year */ 82#define LYC (4 * YEAR + 1) /* Length of 4 year leap-year cycle */ 83#define T1980 (10 * 365 + 2) /* Days from 1970 to 1980 */ 84 85/* End of month is N days from start of (normal) year */ 86#define JAN 31 87#define FEB (JAN + 28) 88#define MAR (FEB + 31) 89#define APR (MAR + 30) 90#define MAY (APR + 31) 91#define JUN (MAY + 30) 92#define JUL (JUN + 31) 93#define AUG (JUL + 31) 94#define SEP (AUG + 30) 95#define OCT (SEP + 31) 96#define NOV (OCT + 30) 97#define DEC (NOV + 31) 98 99/* Table of months in a 4 year leap-year cycle */ 100 101#define ENC(y,m) (((y) << 9) | ((m) << 5)) 102 103static const struct { 104 uint16_t days; /* month start in days relative to cycle */ 105 uint16_t coded; /* encoded year + month information */ 106} mtab[48] = { 107 { 0 + 0 * YEAR, ENC(0, 1) }, 108 109 { JAN + 0 * YEAR, ENC(0, 2) }, { FEB + 0 * YEAR + 1, ENC(0, 3) }, 110 { MAR + 0 * YEAR + 1, ENC(0, 4) }, { APR + 0 * YEAR + 1, ENC(0, 5) }, 111 { MAY + 0 * YEAR + 1, ENC(0, 6) }, { JUN + 0 * YEAR + 1, ENC(0, 7) }, 112 { JUL + 0 * YEAR + 1, ENC(0, 8) }, { AUG + 0 * YEAR + 1, ENC(0, 9) }, 113 { SEP + 0 * YEAR + 1, ENC(0, 10) }, { OCT + 0 * YEAR + 1, ENC(0, 11) }, 114 { NOV + 0 * YEAR + 1, ENC(0, 12) }, { DEC + 0 * YEAR + 1, ENC(1, 1) }, 115 116 { JAN + 1 * YEAR + 1, ENC(1, 2) }, { FEB + 1 * YEAR + 1, ENC(1, 3) }, 117 { MAR + 1 * YEAR + 1, ENC(1, 4) }, { APR + 1 * YEAR + 1, ENC(1, 5) }, 118 { MAY + 1 * YEAR + 1, ENC(1, 6) }, { JUN + 1 * YEAR + 1, ENC(1, 7) }, 119 { JUL + 1 * YEAR + 1, ENC(1, 8) }, { AUG + 1 * YEAR + 1, ENC(1, 9) }, 120 { SEP + 1 * YEAR + 1, ENC(1, 10) }, { OCT + 1 * YEAR + 1, ENC(1, 11) }, 121 { NOV + 1 * YEAR + 1, ENC(1, 12) }, { DEC + 1 * YEAR + 1, ENC(2, 1) }, 122 123 { JAN + 2 * YEAR + 1, ENC(2, 2) }, { FEB + 2 * YEAR + 1, ENC(2, 3) }, 124 { MAR + 2 * YEAR + 1, ENC(2, 4) }, { APR + 2 * YEAR + 1, ENC(2, 5) }, 125 { MAY + 2 * YEAR + 1, ENC(2, 6) }, { JUN + 2 * YEAR + 1, ENC(2, 7) }, 126 { JUL + 2 * YEAR + 1, ENC(2, 8) }, { AUG + 2 * YEAR + 1, ENC(2, 9) }, 127 { SEP + 2 * YEAR + 1, ENC(2, 10) }, { OCT + 2 * YEAR + 1, ENC(2, 11) }, 128 { NOV + 2 * YEAR + 1, ENC(2, 12) }, { DEC + 2 * YEAR + 1, ENC(3, 1) }, 129 130 { JAN + 3 * YEAR + 1, ENC(3, 2) }, { FEB + 3 * YEAR + 1, ENC(3, 3) }, 131 { MAR + 3 * YEAR + 1, ENC(3, 4) }, { APR + 3 * YEAR + 1, ENC(3, 5) }, 132 { MAY + 3 * YEAR + 1, ENC(3, 6) }, { JUN + 3 * YEAR + 1, ENC(3, 7) }, 133 { JUL + 3 * YEAR + 1, ENC(3, 8) }, { AUG + 3 * YEAR + 1, ENC(3, 9) }, 134 { SEP + 3 * YEAR + 1, ENC(3, 10) }, { OCT + 3 * YEAR + 1, ENC(3, 11) }, 135 { NOV + 3 * YEAR + 1, ENC(3, 12) } 136}; 137 138void 139timespec2fattime(const struct timespec *tsp, int utc, uint16_t *ddp, 140 uint16_t *dtp, uint8_t *dhp) 141{ 142 time_t t1; 143 unsigned t2, l, m; 144 145 t1 = tsp->tv_sec; 146 if (!utc) 147 t1 -= utc_offset(); 148 149 if (dhp != NULL) 150 *dhp = (tsp->tv_sec & 1) * 100 + tsp->tv_nsec / 10000000; 151 if (dtp != NULL) { 152 *dtp = (t1 / 2) % 30; 153 *dtp |= ((t1 / 60) % 60) << 5; 154 *dtp |= ((t1 / 3600) % 24) << 11; 155 } 156 if (ddp != NULL) { 157 t2 = t1 / DAY; 158 if (t2 < T1980) { 159 /* Impossible date, truncate to 1980-01-01 */ 160 *ddp = 0x0021; 161 } else { 162 t2 -= T1980; 163 164 /* 165 * 2100 is not a leap year. 166 * XXX: a 32 bit time_t can not get us here. 167 */ 168 if (t2 >= ((2100 - 1980) / 4 * LYC + FEB)) 169 t2++; 170 171 /* Account for full leapyear cycles */ 172 l = t2 / LYC; 173 *ddp = (l * 4) << 9; 174 t2 -= l * LYC; 175 176 /* Find approximate table entry */ 177 m = t2 / 32; 178 179 /* Find correct table entry */ 180 while (m < 47 && mtab[m + 1].days <= t2) 181 m++; 182 183 /* Get year + month from the table */ 184 *ddp += mtab[m].coded; 185 186 /* And apply the day in the month */ 187 t2 -= mtab[m].days - 1; 188 *ddp |= t2; 189 } 190 } 191} 192 193/* 194 * Table indexed by the bottom two bits of year + four bits of the month 195 * from the FAT timestamp, returning number of days into 4 year long 196 * leap-year cycle 197 */ 198 199#define DCOD(m, y, l) ((m) + YEAR * (y) + (l)) 200static const uint16_t daytab[64] = { 201 0, DCOD( 0, 0, 0), DCOD(JAN, 0, 0), DCOD(FEB, 0, 1), 202 DCOD(MAR, 0, 1), DCOD(APR, 0, 1), DCOD(MAY, 0, 1), DCOD(JUN, 0, 1), 203 DCOD(JUL, 0, 1), DCOD(AUG, 0, 1), DCOD(SEP, 0, 1), DCOD(OCT, 0, 1), 204 DCOD(NOV, 0, 1), DCOD(DEC, 0, 1), 0, 0, 205 0, DCOD( 0, 1, 1), DCOD(JAN, 1, 1), DCOD(FEB, 1, 1), 206 DCOD(MAR, 1, 1), DCOD(APR, 1, 1), DCOD(MAY, 1, 1), DCOD(JUN, 1, 1), 207 DCOD(JUL, 1, 1), DCOD(AUG, 1, 1), DCOD(SEP, 1, 1), DCOD(OCT, 1, 1), 208 DCOD(NOV, 1, 1), DCOD(DEC, 1, 1), 0, 0, 209 0, DCOD( 0, 2, 1), DCOD(JAN, 2, 1), DCOD(FEB, 2, 1), 210 DCOD(MAR, 2, 1), DCOD(APR, 2, 1), DCOD(MAY, 2, 1), DCOD(JUN, 2, 1), 211 DCOD(JUL, 2, 1), DCOD(AUG, 2, 1), DCOD(SEP, 2, 1), DCOD(OCT, 2, 1), 212 DCOD(NOV, 2, 1), DCOD(DEC, 2, 1), 0, 0, 213 0, DCOD( 0, 3, 1), DCOD(JAN, 3, 1), DCOD(FEB, 3, 1), 214 DCOD(MAR, 3, 1), DCOD(APR, 3, 1), DCOD(MAY, 3, 1), DCOD(JUN, 3, 1), 215 DCOD(JUL, 3, 1), DCOD(AUG, 3, 1), DCOD(SEP, 3, 1), DCOD(OCT, 3, 1), 216 DCOD(NOV, 3, 1), DCOD(DEC, 3, 1), 0, 0 217}; 218 219void 220fattime2timespec(unsigned dd, unsigned dt, unsigned dh, int utc, 221 struct timespec *tsp) 222{ 223 unsigned day; 224 225 /* Unpack time fields */ 226 tsp->tv_sec = (dt & 0x1f) << 1; 227 tsp->tv_sec += ((dt & 0x7e0) >> 5) * 60; 228 tsp->tv_sec += ((dt & 0xf800) >> 11) * 3600; 229 tsp->tv_sec += dh / 100; 230 tsp->tv_nsec = (dh % 100) * 10000000; 231 232 /* Day of month */ 233 day = (dd & 0x1f) - 1; 234 235 /* Full leap-year cycles */ 236 day += LYC * ((dd >> 11) & 0x1f); 237 238 /* Month offset from leap-year cycle */ 239 day += daytab[(dd >> 5) & 0x3f]; 240 241 /* 242 * 2100 is not a leap year. 243 * XXX: a 32 bit time_t can not get us here. 244 */ 245 if (day >= ((2100 - 1980) / 4 * LYC + FEB)) 246 day--; 247 248 /* Align with time_t epoch */ 249 day += T1980; 250 251 tsp->tv_sec += DAY * day; 252 if (!utc) 253 tsp->tv_sec += utc_offset(); 254} 255 256#ifdef TEST_DRIVER 257 258#include <stdio.h> 259#include <unistd.h> 260#include <stdlib.h> 261 262int 263main(int argc __unused, char **argv __unused) 264{ 265 int i; 266 struct timespec ts; 267 struct tm tm; 268 double a; 269 uint16_t d, t; 270 uint8_t p; 271 char buf[100]; 272 273 for (i = 0; i < 10000; i++) { 274 do { 275 ts.tv_sec = random(); 276 } while (ts.tv_sec < T1980 * 86400); 277 ts.tv_nsec = random() % 1000000000; 278 279 printf("%10d.%03ld -- ", ts.tv_sec, ts.tv_nsec / 1000000); 280 281 gmtime_r(&ts.tv_sec, &tm); 282 strftime(buf, sizeof buf, "%Y %m %d %H %M %S", &tm); 283 printf("%s -- ", buf); 284 285 a = ts.tv_sec + ts.tv_nsec * 1e-9; 286 d = t = p = 0; 287 timet2fattime(&ts, &d, &t, &p); 288 printf("%04x %04x %02x -- ", d, t, p); 289 printf("%3d %02d %02d %02d %02d %02d -- ", 290 ((d >> 9) & 0x7f) + 1980, 291 (d >> 5) & 0x0f, 292 (d >> 0) & 0x1f, 293 (t >> 11) & 0x1f, 294 (t >> 5) & 0x3f, 295 ((t >> 0) & 0x1f) * 2); 296 297 ts.tv_sec = ts.tv_nsec = 0; 298 fattime2timet(d, t, p, &ts); 299 printf("%10d.%03ld == ", ts.tv_sec, ts.tv_nsec / 1000000); 300 gmtime_r(&ts.tv_sec, &tm); 301 strftime(buf, sizeof buf, "%Y %m %d %H %M %S", &tm); 302 printf("%s -- ", buf); 303 a -= ts.tv_sec + ts.tv_nsec * 1e-9; 304 printf("%.3f", a); 305 printf("\n"); 306 } 307 return (0); 308} 309 310#endif /* TEST_DRIVER */ 311