subr_fattime.c revision 163611
1163611Sphk/*- 2163611Sphk * Copyright (c) 2006 Poul-Henning Kamp 3163611Sphk * All rights reserved. 4163611Sphk * 5163611Sphk * Redistribution and use in source and binary forms, with or without 6163611Sphk * modification, are permitted provided that the following conditions 7163611Sphk * are met: 8163611Sphk * 1. Redistributions of source code must retain the above copyright 9163611Sphk * notice, this list of conditions and the following disclaimer. 10163611Sphk * 2. Redistributions in binary form must reproduce the above copyright 11163611Sphk * notice, this list of conditions and the following disclaimer in the 12163611Sphk * documentation and/or other materials provided with the distribution. 13163611Sphk * 14163611Sphk * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15163611Sphk * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16163611Sphk * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17163611Sphk * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18163611Sphk * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19163611Sphk * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20163611Sphk * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21163611Sphk * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22163611Sphk * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23163611Sphk * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24163611Sphk * SUCH DAMAGE. 25163611Sphk * 26163611Sphk * $FreeBSD: head/sys/kern/subr_fattime.c 163611 2006-10-22 18:19:08Z phk $ 27163611Sphk * 28163611Sphk * Convert MS-DOS FAT format timestamps to and from unix timespecs 29163611Sphk * 30163611Sphk * FAT filestamps originally consisted of two 16 bit integers, encoded like 31163611Sphk * this: 32163611Sphk * 33163611Sphk * yyyyyyymmmmddddd (year - 1980, month, day) 34163611Sphk * 35163611Sphk * hhhhhmmmmmmsssss (hour, minutes, seconds divided by two) 36163611Sphk * 37163611Sphk * Subsequently even Microsoft realized that files could be accessed in less 38163611Sphk * than two seconds and a byte was added containing: 39163611Sphk * 40163611Sphk * sfffffff (second mod two, 100ths of second) 41163611Sphk * 42163611Sphk * FAT timestamps are in the local timezone, with no indication of which 43163611Sphk * timezone much less if daylight savings time applies. 44163611Sphk * 45163611Sphk * Later on again, in Windows NT, timestamps were defined relative to GMT. 46163611Sphk * 47163611Sphk * Purists will point out that UTC replaced GMT for such uses around 48163611Sphk * a century ago, already then. Ironically "NT" was an abbreviation of 49163611Sphk * "New Technology". Anyway... 50163611Sphk * 51163611Sphk * The functions below always assume UTC time, and the calling code 52163611Sphk * must apply the local timezone offset as appropriate. Unless special 53163611Sphk * conditions apply, the utc_offset() function be used for this. 54163611Sphk * 55163611Sphk * The conversion functions below cut time into four-year leap-second 56163611Sphk * cycles rather than single years and uses table lookups inside those 57163611Sphk * cycles to get the months and years sorted out. 58163611Sphk * 59163611Sphk * Obviously we cannot calculate the correct table index going from 60163611Sphk * a posix seconds count to Y/M/D, but we can get pretty close by 61163611Sphk * dividing the daycount by 32 (giving a too low index), and then 62163611Sphk * adjusting upwards a couple of steps if necessary. 63163611Sphk * 64163611Sphk * FAT timestamps have 7 bits for the year and starts at 1980, so 65163611Sphk * they can represent up to 2107 which means that the non-leap-year 66163611Sphk * 2100 must be handled. 67163611Sphk * 68163611Sphk * XXX: As long as time_t is 32 bits this is not relevant or easily 69163611Sphk * XXX: testable. Revisit when time_t grows bigger. 70163611Sphk * XXX: grepfodder: 64 bit time_t, y2100, y2.1k, 2100, leap year 71163611Sphk * 72163611Sphk */ 73163611Sphk 74163611Sphk#include <sys/param.h> 75163611Sphk#include <sys/types.h> 76163611Sphk#include <sys/time.h> 77163611Sphk#include <sys/clock.h> 78163611Sphk 79163611Sphk#define DAY (24 * 60 * 60) /* Length of day in seconds */ 80163611Sphk#define YEAR 365 /* Length of normal year */ 81163611Sphk#define LYC (4 * YEAR + 1) /* Length of 4 year leap-year cycle */ 82163611Sphk#define T1980 (10 * 365 + 2) /* Days from 1970 to 1980 */ 83163611Sphk 84163611Sphk/* End of month is N days from start of (normal) year */ 85163611Sphk#define JAN 31 86163611Sphk#define FEB (JAN + 28) 87163611Sphk#define MAR (FEB + 31) 88163611Sphk#define APR (MAR + 30) 89163611Sphk#define MAY (APR + 31) 90163611Sphk#define JUN (MAY + 30) 91163611Sphk#define JUL (JUN + 31) 92163611Sphk#define AUG (JUL + 31) 93163611Sphk#define SEP (AUG + 30) 94163611Sphk#define OCT (SEP + 31) 95163611Sphk#define NOV (OCT + 30) 96163611Sphk#define DEC (NOV + 31) 97163611Sphk 98163611Sphk/* Table of months in a 4 year leap-year cycle */ 99163611Sphk 100163611Sphk#define ENC(y,m) (((y) << 9) | ((m) << 5)) 101163611Sphk 102163611Sphkstatic const struct { 103163611Sphk uint16_t days; /* month start in days relative to cycle */ 104163611Sphk uint16_t coded; /* encoded year + month information */ 105163611Sphk} mtab[48] = { 106163611Sphk { 0 + 0 * YEAR, ENC(0, 1) }, 107163611Sphk 108163611Sphk { JAN + 0 * YEAR, ENC(0, 2) }, { FEB + 0 * YEAR + 1, ENC(0, 3) }, 109163611Sphk { MAR + 0 * YEAR + 1, ENC(0, 4) }, { APR + 0 * YEAR + 1, ENC(0, 5) }, 110163611Sphk { MAY + 0 * YEAR + 1, ENC(0, 6) }, { JUN + 0 * YEAR + 1, ENC(0, 7) }, 111163611Sphk { JUL + 0 * YEAR + 1, ENC(0, 8) }, { AUG + 0 * YEAR + 1, ENC(0, 9) }, 112163611Sphk { SEP + 0 * YEAR + 1, ENC(0, 10) }, { OCT + 0 * YEAR + 1, ENC(0, 11) }, 113163611Sphk { NOV + 0 * YEAR + 1, ENC(0, 12) }, { DEC + 0 * YEAR + 1, ENC(1, 1) }, 114163611Sphk 115163611Sphk { JAN + 1 * YEAR + 1, ENC(1, 2) }, { FEB + 1 * YEAR + 1, ENC(1, 3) }, 116163611Sphk { MAR + 1 * YEAR + 1, ENC(1, 4) }, { APR + 1 * YEAR + 1, ENC(1, 5) }, 117163611Sphk { MAY + 1 * YEAR + 1, ENC(1, 6) }, { JUN + 1 * YEAR + 1, ENC(1, 7) }, 118163611Sphk { JUL + 1 * YEAR + 1, ENC(1, 8) }, { AUG + 1 * YEAR + 1, ENC(1, 9) }, 119163611Sphk { SEP + 1 * YEAR + 1, ENC(1, 10) }, { OCT + 1 * YEAR + 1, ENC(1, 11) }, 120163611Sphk { NOV + 1 * YEAR + 1, ENC(1, 12) }, { DEC + 1 * YEAR + 1, ENC(2, 1) }, 121163611Sphk 122163611Sphk { JAN + 2 * YEAR + 1, ENC(2, 2) }, { FEB + 2 * YEAR + 1, ENC(2, 3) }, 123163611Sphk { MAR + 2 * YEAR + 1, ENC(2, 4) }, { APR + 2 * YEAR + 1, ENC(2, 5) }, 124163611Sphk { MAY + 2 * YEAR + 1, ENC(2, 6) }, { JUN + 2 * YEAR + 1, ENC(2, 7) }, 125163611Sphk { JUL + 2 * YEAR + 1, ENC(2, 8) }, { AUG + 2 * YEAR + 1, ENC(2, 9) }, 126163611Sphk { SEP + 2 * YEAR + 1, ENC(2, 10) }, { OCT + 2 * YEAR + 1, ENC(2, 11) }, 127163611Sphk { NOV + 2 * YEAR + 1, ENC(2, 12) }, { DEC + 2 * YEAR + 1, ENC(3, 1) }, 128163611Sphk 129163611Sphk { JAN + 3 * YEAR + 1, ENC(3, 2) }, { FEB + 3 * YEAR + 1, ENC(3, 3) }, 130163611Sphk { MAR + 3 * YEAR + 1, ENC(3, 4) }, { APR + 3 * YEAR + 1, ENC(3, 5) }, 131163611Sphk { MAY + 3 * YEAR + 1, ENC(3, 6) }, { JUN + 3 * YEAR + 1, ENC(3, 7) }, 132163611Sphk { JUL + 3 * YEAR + 1, ENC(3, 8) }, { AUG + 3 * YEAR + 1, ENC(3, 9) }, 133163611Sphk { SEP + 3 * YEAR + 1, ENC(3, 10) }, { OCT + 3 * YEAR + 1, ENC(3, 11) }, 134163611Sphk { NOV + 3 * YEAR + 1, ENC(3, 12) } 135163611Sphk}; 136163611Sphk 137163611Sphk 138163611Sphkvoid 139163611Sphktimet2fattime(struct timespec *tsp, u_int16_t *ddp, u_int16_t *dtp, u_int8_t *dhp) 140163611Sphk{ 141163611Sphk time_t t1; 142163611Sphk unsigned t2, l, m; 143163611Sphk 144163611Sphk t1 = tsp->tv_sec; 145163611Sphk 146163611Sphk if (dhp != NULL) 147163611Sphk *dhp = (tsp->tv_sec & 1) * 100 + tsp->tv_nsec / 10000000; 148163611Sphk if (dtp != NULL) { 149163611Sphk *dtp = (t1 / 2) % 30; 150163611Sphk *dtp |= ((t1 / 60) % 60) << 5; 151163611Sphk *dtp |= ((t1 / 3600) % 24) << 11; 152163611Sphk } 153163611Sphk if (ddp != NULL) { 154163611Sphk t2 = t1 / DAY; 155163611Sphk if (t2 < T1980) { 156163611Sphk /* Impossible date, truncate to 1980-01-01 */ 157163611Sphk *ddp = 0x0021; 158163611Sphk } else { 159163611Sphk t2 -= T1980; 160163611Sphk 161163611Sphk /* 162163611Sphk * 2100 is not a leap year. 163163611Sphk * XXX: a 32 bit time_t can not get us here. 164163611Sphk */ 165163611Sphk if (t2 >= ((2100 - 1980) / 4 * LYC + FEB)) 166163611Sphk t2++; 167163611Sphk 168163611Sphk /* Account for full leapyear cycles */ 169163611Sphk l = t2 / LYC; 170163611Sphk *ddp = (l * 4) << 9; 171163611Sphk t2 -= l * LYC; 172163611Sphk 173163611Sphk /* Find approximate table entry */ 174163611Sphk m = t2 / 32; 175163611Sphk 176163611Sphk /* Find correct table entry */ 177163611Sphk while (m < 47 && mtab[m + 1].days <= t2) 178163611Sphk m++; 179163611Sphk 180163611Sphk /* Get year + month from the table */ 181163611Sphk *ddp += mtab[m].coded; 182163611Sphk 183163611Sphk /* And apply the day in the month */ 184163611Sphk t2 -= mtab[m].days - 1; 185163611Sphk *ddp |= t2; 186163611Sphk } 187163611Sphk } 188163611Sphk} 189163611Sphk 190163611Sphk/* 191163611Sphk * Table indexed by the bottom two bits of year + four bits of the month 192163611Sphk * from the FAT timestamp, returning number of days into 4 year long 193163611Sphk * leap-year cycle 194163611Sphk */ 195163611Sphk 196163611Sphk#define DCOD(m, y, l) ((m) + YEAR * (y) + (l)) 197163611Sphkstatic const uint16_t daytab[64] = { 198163611Sphk 0, DCOD( 0, 0, 0), DCOD(JAN, 0, 0), DCOD(FEB, 0, 1), 199163611Sphk DCOD(MAR, 0, 1), DCOD(APR, 0, 1), DCOD(MAY, 0, 1), DCOD(JUN, 0, 1), 200163611Sphk DCOD(JUL, 0, 1), DCOD(AUG, 0, 1), DCOD(SEP, 0, 1), DCOD(OCT, 0, 1), 201163611Sphk DCOD(NOV, 0, 1), DCOD(DEC, 0, 1), 0, 0, 202163611Sphk 0, DCOD( 0, 1, 1), DCOD(JAN, 1, 1), DCOD(FEB, 1, 1), 203163611Sphk DCOD(MAR, 1, 1), DCOD(APR, 1, 1), DCOD(MAY, 1, 1), DCOD(JUN, 1, 1), 204163611Sphk DCOD(JUL, 1, 1), DCOD(AUG, 1, 1), DCOD(SEP, 1, 1), DCOD(OCT, 1, 1), 205163611Sphk DCOD(NOV, 1, 1), DCOD(DEC, 1, 1), 0, 0, 206163611Sphk 0, DCOD( 0, 2, 1), DCOD(JAN, 2, 1), DCOD(FEB, 2, 1), 207163611Sphk DCOD(MAR, 2, 1), DCOD(APR, 2, 1), DCOD(MAY, 2, 1), DCOD(JUN, 2, 1), 208163611Sphk DCOD(JUL, 2, 1), DCOD(AUG, 2, 1), DCOD(SEP, 2, 1), DCOD(OCT, 2, 1), 209163611Sphk DCOD(NOV, 2, 1), DCOD(DEC, 2, 1), 0, 0, 210163611Sphk 0, DCOD( 0, 3, 1), DCOD(JAN, 3, 1), DCOD(FEB, 3, 1), 211163611Sphk DCOD(MAR, 3, 1), DCOD(APR, 3, 1), DCOD(MAY, 3, 1), DCOD(JUN, 3, 1), 212163611Sphk DCOD(JUL, 3, 1), DCOD(AUG, 3, 1), DCOD(SEP, 3, 1), DCOD(OCT, 3, 1), 213163611Sphk DCOD(NOV, 3, 1), DCOD(DEC, 3, 1), 0, 0 214163611Sphk}; 215163611Sphk 216163611Sphkvoid 217163611Sphkfattime2timet(unsigned dd, unsigned dt, unsigned dh, struct timespec *tsp) 218163611Sphk{ 219163611Sphk unsigned day; 220163611Sphk 221163611Sphk /* Unpack time fields */ 222163611Sphk tsp->tv_sec = (dt & 0x1f) << 1; 223163611Sphk tsp->tv_sec += ((dt & 0x7e0) >> 5) * 60; 224163611Sphk tsp->tv_sec += ((dt & 0xf800) >> 11) * 3600; 225163611Sphk tsp->tv_sec += dh / 100; 226163611Sphk tsp->tv_nsec = (dh % 100) * 10000000; 227163611Sphk 228163611Sphk /* Day of month */ 229163611Sphk day = (dd & 0x1f) - 1; 230163611Sphk 231163611Sphk /* Full leap-year cycles */ 232163611Sphk day += LYC * ((dd >> 11) & 0x1f); 233163611Sphk 234163611Sphk /* Month offset from leap-year cycle */ 235163611Sphk day += daytab[(dd >> 5) & 0x3f]; 236163611Sphk 237163611Sphk /* 238163611Sphk * 2100 is not a leap year. 239163611Sphk * XXX: a 32 bit time_t can not get us here. 240163611Sphk */ 241163611Sphk if (day >= ((2100 - 1980) / 4 * LYC + FEB)) 242163611Sphk day--; 243163611Sphk 244163611Sphk /* Align with time_t epoch */ 245163611Sphk day += T1980; 246163611Sphk 247163611Sphk tsp->tv_sec += DAY * day; 248163611Sphk} 249163611Sphk 250163611Sphk#ifdef TEST_DRIVER 251163611Sphk 252163611Sphk#include <stdio.h> 253163611Sphk#include <unistd.h> 254163611Sphk#include <stdlib.h> 255163611Sphk 256163611Sphkint 257163611Sphkmain(int argc __unused, char **argv __unused) 258163611Sphk{ 259163611Sphk int i; 260163611Sphk struct timespec ts; 261163611Sphk struct tm tm; 262163611Sphk double a; 263163611Sphk u_int16_t d, t; 264163611Sphk u_int8_t p; 265163611Sphk char buf[100]; 266163611Sphk 267163611Sphk for (i = 0; i < 10000; i++) { 268163611Sphk do { 269163611Sphk ts.tv_sec = random(); 270163611Sphk } while (ts.tv_sec < T1980 * 86400); 271163611Sphk ts.tv_nsec = random() % 1000000000; 272163611Sphk 273163611Sphk printf("%10d.%03ld -- ", ts.tv_sec, ts.tv_nsec / 1000000); 274163611Sphk 275163611Sphk gmtime_r(&ts.tv_sec, &tm); 276163611Sphk strftime(buf, sizeof buf, "%Y %m %d %H %M %S", &tm); 277163611Sphk printf("%s -- ", buf); 278163611Sphk 279163611Sphk a = ts.tv_sec + ts.tv_nsec * 1e-9; 280163611Sphk d = t = p = 0; 281163611Sphk timet2fattime(&ts, &d, &t, &p); 282163611Sphk printf("%04x %04x %02x -- ", d, t, p); 283163611Sphk printf("%3d %02d %02d %02d %02d %02d -- ", 284163611Sphk ((d >> 9) & 0x7f) + 1980, 285163611Sphk (d >> 5) & 0x0f, 286163611Sphk (d >> 0) & 0x1f, 287163611Sphk (t >> 11) & 0x1f, 288163611Sphk (t >> 5) & 0x3f, 289163611Sphk ((t >> 0) & 0x1f) * 2); 290163611Sphk 291163611Sphk ts.tv_sec = ts.tv_nsec = 0; 292163611Sphk fattime2timet(d, t, p, &ts); 293163611Sphk printf("%10d.%03ld == ", ts.tv_sec, ts.tv_nsec / 1000000); 294163611Sphk gmtime_r(&ts.tv_sec, &tm); 295163611Sphk strftime(buf, sizeof buf, "%Y %m %d %H %M %S", &tm); 296163611Sphk printf("%s -- ", buf); 297163611Sphk a -= ts.tv_sec + ts.tv_nsec * 1e-9; 298163611Sphk printf("%.3f", a); 299163611Sphk printf("\n"); 300163611Sphk } 301163611Sphk return (0); 302163611Sphk} 303163611Sphk 304163611Sphk#endif /* TEST_DRIVER */ 305