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)) 102 103 static 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 }; 137 138 139 void 140 timespec2fattime(const struct timespec *tsp, int utc, uint16_t *ddp, 141 uint16_t *dtp, uint8_t *dhp) 142 { 143 time_t t1; 144 unsigned t2, l, m; 145 146 t1 = tsp->tv_sec; 147 if (!utc) 148 t1 -= utc_offset(); 149 150 if (dhp != NULL) 151 *dhp = (tsp->tv_sec & 1) * 100 + tsp->tv_nsec / 10000000; 152 if (dtp != NULL) { 153 *dtp = (t1 / 2) % 30; 154 *dtp |= ((t1 / 60) % 60) << 5; 155 *dtp |= ((t1 / 3600) % 24) << 11; 156 } 157 if (ddp != NULL) { 158 t2 = t1 / DAY; 159 if (t2 < T1980) { 160 /* Impossible date, truncate to 1980-01-01 */ 161 *ddp = 0x0021; 162 } else { 163 t2 -= T1980; 164 165 /* 166 * 2100 is not a leap year. 167 * XXX: a 32 bit time_t can not get us here. 168 */ 169 if (t2 >= ((2100 - 1980) / 4 * LYC + FEB)) 170 t2++; 171 172 /* Account for full leapyear cycles */ 173 l = t2 / LYC; 174 *ddp = (l * 4) << 9; 175 t2 -= l * LYC; 176 177 /* Find approximate table entry */ 178 m = t2 / 32; 179 180 /* Find correct table entry */ 181 while (m < 47 && mtab[m + 1].days <= t2) 182 m++; 183 184 /* Get year + month from the table */ 185 *ddp += mtab[m].coded; 186 187 /* And apply the day in the month */ 188 t2 -= mtab[m].days - 1; 189 *ddp |= t2; 190 } 191 } 192 } 193 194 /* 195 * Table indexed by the bottom two bits of year + four bits of the month 196 * from the FAT timestamp, returning number of days into 4 year long 197 * leap-year cycle 198 */ 199 200 #define DCOD(m, y, l) ((m) + YEAR * (y) + (l)) 201 static const uint16_t daytab[64] = { 202 0, DCOD( 0, 0, 0), DCOD(JAN, 0, 0), DCOD(FEB, 0, 1), 203 DCOD(MAR, 0, 1), DCOD(APR, 0, 1), DCOD(MAY, 0, 1), DCOD(JUN, 0, 1), 204 DCOD(JUL, 0, 1), DCOD(AUG, 0, 1), DCOD(SEP, 0, 1), DCOD(OCT, 0, 1), 205 DCOD(NOV, 0, 1), DCOD(DEC, 0, 1), 0, 0, 206 0, DCOD( 0, 1, 1), DCOD(JAN, 1, 1), DCOD(FEB, 1, 1), 207 DCOD(MAR, 1, 1), DCOD(APR, 1, 1), DCOD(MAY, 1, 1), DCOD(JUN, 1, 1), 208 DCOD(JUL, 1, 1), DCOD(AUG, 1, 1), DCOD(SEP, 1, 1), DCOD(OCT, 1, 1), 209 DCOD(NOV, 1, 1), DCOD(DEC, 1, 1), 0, 0, 210 0, DCOD( 0, 2, 1), DCOD(JAN, 2, 1), DCOD(FEB, 2, 1), 211 DCOD(MAR, 2, 1), DCOD(APR, 2, 1), DCOD(MAY, 2, 1), DCOD(JUN, 2, 1), 212 DCOD(JUL, 2, 1), DCOD(AUG, 2, 1), DCOD(SEP, 2, 1), DCOD(OCT, 2, 1), 213 DCOD(NOV, 2, 1), DCOD(DEC, 2, 1), 0, 0, 214 0, DCOD( 0, 3, 1), DCOD(JAN, 3, 1), DCOD(FEB, 3, 1), 215 DCOD(MAR, 3, 1), DCOD(APR, 3, 1), DCOD(MAY, 3, 1), DCOD(JUN, 3, 1), 216 DCOD(JUL, 3, 1), DCOD(AUG, 3, 1), DCOD(SEP, 3, 1), DCOD(OCT, 3, 1), 217 DCOD(NOV, 3, 1), DCOD(DEC, 3, 1), 0, 0 218 }; 219 220 void 221 fattime2timespec(unsigned dd, unsigned dt, unsigned dh, int utc, 222 struct timespec *tsp) 223 { 224 unsigned day; 225 226 /* Unpack time fields */ 227 tsp->tv_sec = (dt & 0x1f) << 1; 228 tsp->tv_sec += ((dt & 0x7e0) >> 5) * 60; 229 tsp->tv_sec += ((dt & 0xf800) >> 11) * 3600; 230 tsp->tv_sec += dh / 100; 231 tsp->tv_nsec = (dh % 100) * 10000000; 232 233 /* Day of month */ 234 day = (dd & 0x1f) - 1; 235 236 /* Full leap-year cycles */ 237 day += LYC * ((dd >> 11) & 0x1f); 238 239 /* Month offset from leap-year cycle */ 240 day += daytab[(dd >> 5) & 0x3f]; 241 242 /* 243 * 2100 is not a leap year. 244 * XXX: a 32 bit time_t can not get us here. 245 */ 246 if (day >= ((2100 - 1980) / 4 * LYC + FEB)) 247 day--; 248 249 /* Align with time_t epoch */ 250 day += T1980; 251 252 tsp->tv_sec += DAY * day; 253 if (!utc) 254 tsp->tv_sec += utc_offset(); 255 } 256 257 #ifdef TEST_DRIVER 258 259 #include <stdio.h> 260 #include <unistd.h> 261 #include <stdlib.h> 262 263 int 264 main(int argc __unused, char **argv __unused) 265 { 266 int i; 267 struct timespec ts; 268 struct tm tm; 269 double a; 270 uint16_t d, t; 271 uint8_t p; 272 char buf[100]; 273 274 for (i = 0; i < 10000; i++) { 275 do { 276 ts.tv_sec = random(); 277 } while (ts.tv_sec < T1980 * 86400); 278 ts.tv_nsec = random() % 1000000000; 279 280 printf("%10d.%03ld -- ", ts.tv_sec, ts.tv_nsec / 1000000); 281 282 gmtime_r(&ts.tv_sec, &tm); 283 strftime(buf, sizeof buf, "%Y %m %d %H %M %S", &tm); 284 printf("%s -- ", buf); 285 286 a = ts.tv_sec + ts.tv_nsec * 1e-9; 287 d = t = p = 0; 288 timet2fattime(&ts, &d, &t, &p); 289 printf("%04x %04x %02x -- ", d, t, p); 290 printf("%3d %02d %02d %02d %02d %02d -- ", 291 ((d >> 9) & 0x7f) + 1980, 292 (d >> 5) & 0x0f, 293 (d >> 0) & 0x1f, 294 (t >> 11) & 0x1f, 295 (t >> 5) & 0x3f, 296 ((t >> 0) & 0x1f) * 2); 297 298 ts.tv_sec = ts.tv_nsec = 0; 299 fattime2timet(d, t, p, &ts); 300 printf("%10d.%03ld == ", ts.tv_sec, ts.tv_nsec / 1000000); 301 gmtime_r(&ts.tv_sec, &tm); 302 strftime(buf, sizeof buf, "%Y %m %d %H %M %S", &tm); 303 printf("%s -- ", buf); 304 a -= ts.tv_sec + ts.tv_nsec * 1e-9; 305 printf("%.3f", a); 306 printf("\n"); 307 } 308 return (0); 309 } 310 311 #endif /* TEST_DRIVER */ 312