1/*- 2 * Copyright (c) 2006 Poul-Henning Kamp 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24 * SUCH DAMAGE. 25 * 26 * $FreeBSD: stable/11/sys/kern/subr_fattime.c 331503 2018-03-24 23:01:10Z ian $ 27 * 28 * Convert MS-DOS FAT format timestamps to and from unix timespecs 29 * 30 * FAT filestamps originally consisted of two 16 bit integers, encoded like 31 * this: 32 * 33 * yyyyyyymmmmddddd (year - 1980, month, day) 34 * 35 * hhhhhmmmmmmsssss (hour, minutes, seconds divided by two) 36 * 37 * Subsequently even Microsoft realized that files could be accessed in less 38 * than two seconds and a byte was added containing: 39 * 40 * sfffffff (second mod two, 100ths of second) 41 * 42 * FAT timestamps are in the local timezone, with no indication of which 43 * timezone much less if daylight savings time applies. 44 * 45 * Later on again, in Windows NT, timestamps were defined relative to GMT. 46 * 47 * Purists will point out that UTC replaced GMT for such uses around 48 * half a century ago, already then. Ironically "NT" was an abbreviation of 49 * "New Technology". Anyway... 50 * 51 * The 'utc' argument determines if the resulting FATTIME timestamp 52 * should be on the UTC or local timezone calendar. 53 * 54 * The conversion functions below cut time into four-year leap-year 55 * cycles rather than single years and uses table lookups inside those 56 * cycles to get the months and years sorted out. 57 * 58 * Obviously we cannot calculate the correct table index going from 59 * a posix seconds count to Y/M/D, but we can get pretty close by 60 * dividing the daycount by 32 (giving a too low index), and then 61 * adjusting upwards a couple of steps if necessary. 62 * 63 * FAT timestamps have 7 bits for the year and starts at 1980, so 64 * they can represent up to 2107 which means that the non-leap-year 65 * 2100 must be handled. 66 * 67 * XXX: As long as time_t is 32 bits this is not relevant or easily 68 * XXX: testable. Revisit when time_t grows bigger. 69 * XXX: grepfodder: 64 bit time_t, y2100, y2.1k, 2100, leap year 70 * 71 */ 72 73#include <sys/param.h> 74#include <sys/types.h> 75#include <sys/time.h> 76#include <sys/clock.h> 77 78#define DAY (24 * 60 * 60) /* Length of day in seconds */ 79#define YEAR 365 /* Length of normal year */ 80#define LYC (4 * YEAR + 1) /* Length of 4 year leap-year cycle */ 81#define T1980 (10 * 365 + 2) /* Days from 1970 to 1980 */ 82 83/* End of month is N days from start of (normal) year */ 84#define JAN 31 85#define FEB (JAN + 28) 86#define MAR (FEB + 31) 87#define APR (MAR + 30) 88#define MAY (APR + 31) 89#define JUN (MAY + 30) 90#define JUL (JUN + 31) 91#define AUG (JUL + 31) 92#define SEP (AUG + 30) 93#define OCT (SEP + 31) 94#define NOV (OCT + 30) 95#define DEC (NOV + 31) 96 97/* Table of months in a 4 year leap-year cycle */ 98 99#define ENC(y,m) (((y) << 9) | ((m) << 5)) 100 101static const struct { 102 uint16_t days; /* month start in days relative to cycle */ 103 uint16_t coded; /* encoded year + month information */ 104} mtab[48] = { 105 { 0 + 0 * YEAR, ENC(0, 1) }, 106 107 { JAN + 0 * YEAR, ENC(0, 2) }, { FEB + 0 * YEAR + 1, ENC(0, 3) }, 108 { MAR + 0 * YEAR + 1, ENC(0, 4) }, { APR + 0 * YEAR + 1, ENC(0, 5) }, 109 { MAY + 0 * YEAR + 1, ENC(0, 6) }, { JUN + 0 * YEAR + 1, ENC(0, 7) }, 110 { JUL + 0 * YEAR + 1, ENC(0, 8) }, { AUG + 0 * YEAR + 1, ENC(0, 9) }, 111 { SEP + 0 * YEAR + 1, ENC(0, 10) }, { OCT + 0 * YEAR + 1, ENC(0, 11) }, 112 { NOV + 0 * YEAR + 1, ENC(0, 12) }, { DEC + 0 * YEAR + 1, ENC(1, 1) }, 113 114 { JAN + 1 * YEAR + 1, ENC(1, 2) }, { FEB + 1 * YEAR + 1, ENC(1, 3) }, 115 { MAR + 1 * YEAR + 1, ENC(1, 4) }, { APR + 1 * YEAR + 1, ENC(1, 5) }, 116 { MAY + 1 * YEAR + 1, ENC(1, 6) }, { JUN + 1 * YEAR + 1, ENC(1, 7) }, 117 { JUL + 1 * YEAR + 1, ENC(1, 8) }, { AUG + 1 * YEAR + 1, ENC(1, 9) }, 118 { SEP + 1 * YEAR + 1, ENC(1, 10) }, { OCT + 1 * YEAR + 1, ENC(1, 11) }, 119 { NOV + 1 * YEAR + 1, ENC(1, 12) }, { DEC + 1 * YEAR + 1, ENC(2, 1) }, 120 121 { JAN + 2 * YEAR + 1, ENC(2, 2) }, { FEB + 2 * YEAR + 1, ENC(2, 3) }, 122 { MAR + 2 * YEAR + 1, ENC(2, 4) }, { APR + 2 * YEAR + 1, ENC(2, 5) }, 123 { MAY + 2 * YEAR + 1, ENC(2, 6) }, { JUN + 2 * YEAR + 1, ENC(2, 7) }, 124 { JUL + 2 * YEAR + 1, ENC(2, 8) }, { AUG + 2 * YEAR + 1, ENC(2, 9) }, 125 { SEP + 2 * YEAR + 1, ENC(2, 10) }, { OCT + 2 * YEAR + 1, ENC(2, 11) }, 126 { NOV + 2 * YEAR + 1, ENC(2, 12) }, { DEC + 2 * YEAR + 1, ENC(3, 1) }, 127 128 { JAN + 3 * YEAR + 1, ENC(3, 2) }, { FEB + 3 * YEAR + 1, ENC(3, 3) }, 129 { MAR + 3 * YEAR + 1, ENC(3, 4) }, { APR + 3 * YEAR + 1, ENC(3, 5) }, 130 { MAY + 3 * YEAR + 1, ENC(3, 6) }, { JUN + 3 * YEAR + 1, ENC(3, 7) }, 131 { JUL + 3 * YEAR + 1, ENC(3, 8) }, { AUG + 3 * YEAR + 1, ENC(3, 9) }, 132 { SEP + 3 * YEAR + 1, ENC(3, 10) }, { OCT + 3 * YEAR + 1, ENC(3, 11) }, 133 { NOV + 3 * YEAR + 1, ENC(3, 12) } 134}; 135 136 137void 138timespec2fattime(const struct timespec *tsp, int utc, uint16_t *ddp, 139 uint16_t *dtp, uint8_t *dhp) 140{ 141 time_t t1; 142 unsigned t2, l, m; 143 144 t1 = tsp->tv_sec; 145 if (!utc) 146 t1 -= utc_offset(); 147 148 if (dhp != NULL) 149 *dhp = (tsp->tv_sec & 1) * 100 + tsp->tv_nsec / 10000000; 150 if (dtp != NULL) { 151 *dtp = (t1 / 2) % 30; 152 *dtp |= ((t1 / 60) % 60) << 5; 153 *dtp |= ((t1 / 3600) % 24) << 11; 154 } 155 if (ddp != NULL) { 156 t2 = t1 / DAY; 157 if (t2 < T1980) { 158 /* Impossible date, truncate to 1980-01-01 */ 159 *ddp = 0x0021; 160 } else { 161 t2 -= T1980; 162 163 /* 164 * 2100 is not a leap year. 165 * XXX: a 32 bit time_t can not get us here. 166 */ 167 if (t2 >= ((2100 - 1980) / 4 * LYC + FEB)) 168 t2++; 169 170 /* Account for full leapyear cycles */ 171 l = t2 / LYC; 172 *ddp = (l * 4) << 9; 173 t2 -= l * LYC; 174 175 /* Find approximate table entry */ 176 m = t2 / 32; 177 178 /* Find correct table entry */ 179 while (m < 47 && mtab[m + 1].days <= t2) 180 m++; 181 182 /* Get year + month from the table */ 183 *ddp += mtab[m].coded; 184 185 /* And apply the day in the month */ 186 t2 -= mtab[m].days - 1; 187 *ddp |= t2; 188 } 189 } 190} 191 192/* 193 * Table indexed by the bottom two bits of year + four bits of the month 194 * from the FAT timestamp, returning number of days into 4 year long 195 * leap-year cycle 196 */ 197 198#define DCOD(m, y, l) ((m) + YEAR * (y) + (l)) 199static const uint16_t daytab[64] = { 200 0, DCOD( 0, 0, 0), DCOD(JAN, 0, 0), DCOD(FEB, 0, 1), 201 DCOD(MAR, 0, 1), DCOD(APR, 0, 1), DCOD(MAY, 0, 1), DCOD(JUN, 0, 1), 202 DCOD(JUL, 0, 1), DCOD(AUG, 0, 1), DCOD(SEP, 0, 1), DCOD(OCT, 0, 1), 203 DCOD(NOV, 0, 1), DCOD(DEC, 0, 1), 0, 0, 204 0, DCOD( 0, 1, 1), DCOD(JAN, 1, 1), DCOD(FEB, 1, 1), 205 DCOD(MAR, 1, 1), DCOD(APR, 1, 1), DCOD(MAY, 1, 1), DCOD(JUN, 1, 1), 206 DCOD(JUL, 1, 1), DCOD(AUG, 1, 1), DCOD(SEP, 1, 1), DCOD(OCT, 1, 1), 207 DCOD(NOV, 1, 1), DCOD(DEC, 1, 1), 0, 0, 208 0, DCOD( 0, 2, 1), DCOD(JAN, 2, 1), DCOD(FEB, 2, 1), 209 DCOD(MAR, 2, 1), DCOD(APR, 2, 1), DCOD(MAY, 2, 1), DCOD(JUN, 2, 1), 210 DCOD(JUL, 2, 1), DCOD(AUG, 2, 1), DCOD(SEP, 2, 1), DCOD(OCT, 2, 1), 211 DCOD(NOV, 2, 1), DCOD(DEC, 2, 1), 0, 0, 212 0, DCOD( 0, 3, 1), DCOD(JAN, 3, 1), DCOD(FEB, 3, 1), 213 DCOD(MAR, 3, 1), DCOD(APR, 3, 1), DCOD(MAY, 3, 1), DCOD(JUN, 3, 1), 214 DCOD(JUL, 3, 1), DCOD(AUG, 3, 1), DCOD(SEP, 3, 1), DCOD(OCT, 3, 1), 215 DCOD(NOV, 3, 1), DCOD(DEC, 3, 1), 0, 0 216}; 217 218void 219fattime2timespec(unsigned dd, unsigned dt, unsigned dh, int utc, 220 struct timespec *tsp) 221{ 222 unsigned day; 223 224 /* Unpack time fields */ 225 tsp->tv_sec = (dt & 0x1f) << 1; 226 tsp->tv_sec += ((dt & 0x7e0) >> 5) * 60; 227 tsp->tv_sec += ((dt & 0xf800) >> 11) * 3600; 228 tsp->tv_sec += dh / 100; 229 tsp->tv_nsec = (dh % 100) * 10000000; 230 231 /* Day of month */ 232 day = (dd & 0x1f) - 1; 233 234 /* Full leap-year cycles */ 235 day += LYC * ((dd >> 11) & 0x1f); 236 237 /* Month offset from leap-year cycle */ 238 day += daytab[(dd >> 5) & 0x3f]; 239 240 /* 241 * 2100 is not a leap year. 242 * XXX: a 32 bit time_t can not get us here. 243 */ 244 if (day >= ((2100 - 1980) / 4 * LYC + FEB)) 245 day--; 246 247 /* Align with time_t epoch */ 248 day += T1980; 249 250 tsp->tv_sec += DAY * day; 251 if (!utc) 252 tsp->tv_sec += utc_offset(); 253} 254 255#ifdef TEST_DRIVER 256 257#include <stdio.h> 258#include <unistd.h> 259#include <stdlib.h> 260 261int 262main(int argc __unused, char **argv __unused) 263{ 264 int i; 265 struct timespec ts; 266 struct tm tm; 267 double a; 268 uint16_t d, t; 269 uint8_t p; 270 char buf[100]; 271 272 for (i = 0; i < 10000; i++) { 273 do { 274 ts.tv_sec = random(); 275 } while (ts.tv_sec < T1980 * 86400); 276 ts.tv_nsec = random() % 1000000000; 277 278 printf("%10d.%03ld -- ", ts.tv_sec, ts.tv_nsec / 1000000); 279 280 gmtime_r(&ts.tv_sec, &tm); 281 strftime(buf, sizeof buf, "%Y %m %d %H %M %S", &tm); 282 printf("%s -- ", buf); 283 284 a = ts.tv_sec + ts.tv_nsec * 1e-9; 285 d = t = p = 0; 286 timet2fattime(&ts, &d, &t, &p); 287 printf("%04x %04x %02x -- ", d, t, p); 288 printf("%3d %02d %02d %02d %02d %02d -- ", 289 ((d >> 9) & 0x7f) + 1980, 290 (d >> 5) & 0x0f, 291 (d >> 0) & 0x1f, 292 (t >> 11) & 0x1f, 293 (t >> 5) & 0x3f, 294 ((t >> 0) & 0x1f) * 2); 295 296 ts.tv_sec = ts.tv_nsec = 0; 297 fattime2timet(d, t, p, &ts); 298 printf("%10d.%03ld == ", ts.tv_sec, ts.tv_nsec / 1000000); 299 gmtime_r(&ts.tv_sec, &tm); 300 strftime(buf, sizeof buf, "%Y %m %d %H %M %S", &tm); 301 printf("%s -- ", buf); 302 a -= ts.tv_sec + ts.tv_nsec * 1e-9; 303 printf("%.3f", a); 304 printf("\n"); 305 } 306 return (0); 307} 308 309#endif /* TEST_DRIVER */ 310