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Current File : //sys/kern/subr_fattime.c |
/*- * Copyright (c) 2006 Poul-Henning Kamp * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * $FreeBSD: release/9.1.0/sys/kern/subr_fattime.c 209390 2010-06-21 09:55:56Z ed $ * * Convert MS-DOS FAT format timestamps to and from unix timespecs * * FAT filestamps originally consisted of two 16 bit integers, encoded like * this: * * yyyyyyymmmmddddd (year - 1980, month, day) * * hhhhhmmmmmmsssss (hour, minutes, seconds divided by two) * * Subsequently even Microsoft realized that files could be accessed in less * than two seconds and a byte was added containing: * * sfffffff (second mod two, 100ths of second) * * FAT timestamps are in the local timezone, with no indication of which * timezone much less if daylight savings time applies. * * Later on again, in Windows NT, timestamps were defined relative to GMT. * * Purists will point out that UTC replaced GMT for such uses around * a century ago, already then. Ironically "NT" was an abbreviation of * "New Technology". Anyway... * * The 'utc' argument determines if the resulting FATTIME timestamp * should b on the UTC or local timezone calendar. * * The conversion functions below cut time into four-year leap-second * cycles rather than single years and uses table lookups inside those * cycles to get the months and years sorted out. * * Obviously we cannot calculate the correct table index going from * a posix seconds count to Y/M/D, but we can get pretty close by * dividing the daycount by 32 (giving a too low index), and then * adjusting upwards a couple of steps if necessary. * * FAT timestamps have 7 bits for the year and starts at 1980, so * they can represent up to 2107 which means that the non-leap-year * 2100 must be handled. * * XXX: As long as time_t is 32 bits this is not relevant or easily * XXX: testable. Revisit when time_t grows bigger. * XXX: grepfodder: 64 bit time_t, y2100, y2.1k, 2100, leap year * */ #include <sys/param.h> #include <sys/types.h> #include <sys/time.h> #include <sys/clock.h> #define DAY (24 * 60 * 60) /* Length of day in seconds */ #define YEAR 365 /* Length of normal year */ #define LYC (4 * YEAR + 1) /* Length of 4 year leap-year cycle */ #define T1980 (10 * 365 + 2) /* Days from 1970 to 1980 */ /* End of month is N days from start of (normal) year */ #define JAN 31 #define FEB (JAN + 28) #define MAR (FEB + 31) #define APR (MAR + 30) #define MAY (APR + 31) #define JUN (MAY + 30) #define JUL (JUN + 31) #define AUG (JUL + 31) #define SEP (AUG + 30) #define OCT (SEP + 31) #define NOV (OCT + 30) #define DEC (NOV + 31) /* Table of months in a 4 year leap-year cycle */ #define ENC(y,m) (((y) << 9) | ((m) << 5)) static const struct { uint16_t days; /* month start in days relative to cycle */ uint16_t coded; /* encoded year + month information */ } mtab[48] = { { 0 + 0 * YEAR, ENC(0, 1) }, { JAN + 0 * YEAR, ENC(0, 2) }, { FEB + 0 * YEAR + 1, ENC(0, 3) }, { MAR + 0 * YEAR + 1, ENC(0, 4) }, { APR + 0 * YEAR + 1, ENC(0, 5) }, { MAY + 0 * YEAR + 1, ENC(0, 6) }, { JUN + 0 * YEAR + 1, ENC(0, 7) }, { JUL + 0 * YEAR + 1, ENC(0, 8) }, { AUG + 0 * YEAR + 1, ENC(0, 9) }, { SEP + 0 * YEAR + 1, ENC(0, 10) }, { OCT + 0 * YEAR + 1, ENC(0, 11) }, { NOV + 0 * YEAR + 1, ENC(0, 12) }, { DEC + 0 * YEAR + 1, ENC(1, 1) }, { JAN + 1 * YEAR + 1, ENC(1, 2) }, { FEB + 1 * YEAR + 1, ENC(1, 3) }, { MAR + 1 * YEAR + 1, ENC(1, 4) }, { APR + 1 * YEAR + 1, ENC(1, 5) }, { MAY + 1 * YEAR + 1, ENC(1, 6) }, { JUN + 1 * YEAR + 1, ENC(1, 7) }, { JUL + 1 * YEAR + 1, ENC(1, 8) }, { AUG + 1 * YEAR + 1, ENC(1, 9) }, { SEP + 1 * YEAR + 1, ENC(1, 10) }, { OCT + 1 * YEAR + 1, ENC(1, 11) }, { NOV + 1 * YEAR + 1, ENC(1, 12) }, { DEC + 1 * YEAR + 1, ENC(2, 1) }, { JAN + 2 * YEAR + 1, ENC(2, 2) }, { FEB + 2 * YEAR + 1, ENC(2, 3) }, { MAR + 2 * YEAR + 1, ENC(2, 4) }, { APR + 2 * YEAR + 1, ENC(2, 5) }, { MAY + 2 * YEAR + 1, ENC(2, 6) }, { JUN + 2 * YEAR + 1, ENC(2, 7) }, { JUL + 2 * YEAR + 1, ENC(2, 8) }, { AUG + 2 * YEAR + 1, ENC(2, 9) }, { SEP + 2 * YEAR + 1, ENC(2, 10) }, { OCT + 2 * YEAR + 1, ENC(2, 11) }, { NOV + 2 * YEAR + 1, ENC(2, 12) }, { DEC + 2 * YEAR + 1, ENC(3, 1) }, { JAN + 3 * YEAR + 1, ENC(3, 2) }, { FEB + 3 * YEAR + 1, ENC(3, 3) }, { MAR + 3 * YEAR + 1, ENC(3, 4) }, { APR + 3 * YEAR + 1, ENC(3, 5) }, { MAY + 3 * YEAR + 1, ENC(3, 6) }, { JUN + 3 * YEAR + 1, ENC(3, 7) }, { JUL + 3 * YEAR + 1, ENC(3, 8) }, { AUG + 3 * YEAR + 1, ENC(3, 9) }, { SEP + 3 * YEAR + 1, ENC(3, 10) }, { OCT + 3 * YEAR + 1, ENC(3, 11) }, { NOV + 3 * YEAR + 1, ENC(3, 12) } }; void timespec2fattime(struct timespec *tsp, int utc, uint16_t *ddp, uint16_t *dtp, uint8_t *dhp) { time_t t1; unsigned t2, l, m; t1 = tsp->tv_sec; if (!utc) t1 -= utc_offset(); if (dhp != NULL) *dhp = (tsp->tv_sec & 1) * 100 + tsp->tv_nsec / 10000000; if (dtp != NULL) { *dtp = (t1 / 2) % 30; *dtp |= ((t1 / 60) % 60) << 5; *dtp |= ((t1 / 3600) % 24) << 11; } if (ddp != NULL) { t2 = t1 / DAY; if (t2 < T1980) { /* Impossible date, truncate to 1980-01-01 */ *ddp = 0x0021; } else { t2 -= T1980; /* * 2100 is not a leap year. * XXX: a 32 bit time_t can not get us here. */ if (t2 >= ((2100 - 1980) / 4 * LYC + FEB)) t2++; /* Account for full leapyear cycles */ l = t2 / LYC; *ddp = (l * 4) << 9; t2 -= l * LYC; /* Find approximate table entry */ m = t2 / 32; /* Find correct table entry */ while (m < 47 && mtab[m + 1].days <= t2) m++; /* Get year + month from the table */ *ddp += mtab[m].coded; /* And apply the day in the month */ t2 -= mtab[m].days - 1; *ddp |= t2; } } } /* * Table indexed by the bottom two bits of year + four bits of the month * from the FAT timestamp, returning number of days into 4 year long * leap-year cycle */ #define DCOD(m, y, l) ((m) + YEAR * (y) + (l)) static const uint16_t daytab[64] = { 0, DCOD( 0, 0, 0), DCOD(JAN, 0, 0), DCOD(FEB, 0, 1), DCOD(MAR, 0, 1), DCOD(APR, 0, 1), DCOD(MAY, 0, 1), DCOD(JUN, 0, 1), DCOD(JUL, 0, 1), DCOD(AUG, 0, 1), DCOD(SEP, 0, 1), DCOD(OCT, 0, 1), DCOD(NOV, 0, 1), DCOD(DEC, 0, 1), 0, 0, 0, DCOD( 0, 1, 1), DCOD(JAN, 1, 1), DCOD(FEB, 1, 1), DCOD(MAR, 1, 1), DCOD(APR, 1, 1), DCOD(MAY, 1, 1), DCOD(JUN, 1, 1), DCOD(JUL, 1, 1), DCOD(AUG, 1, 1), DCOD(SEP, 1, 1), DCOD(OCT, 1, 1), DCOD(NOV, 1, 1), DCOD(DEC, 1, 1), 0, 0, 0, DCOD( 0, 2, 1), DCOD(JAN, 2, 1), DCOD(FEB, 2, 1), DCOD(MAR, 2, 1), DCOD(APR, 2, 1), DCOD(MAY, 2, 1), DCOD(JUN, 2, 1), DCOD(JUL, 2, 1), DCOD(AUG, 2, 1), DCOD(SEP, 2, 1), DCOD(OCT, 2, 1), DCOD(NOV, 2, 1), DCOD(DEC, 2, 1), 0, 0, 0, DCOD( 0, 3, 1), DCOD(JAN, 3, 1), DCOD(FEB, 3, 1), DCOD(MAR, 3, 1), DCOD(APR, 3, 1), DCOD(MAY, 3, 1), DCOD(JUN, 3, 1), DCOD(JUL, 3, 1), DCOD(AUG, 3, 1), DCOD(SEP, 3, 1), DCOD(OCT, 3, 1), DCOD(NOV, 3, 1), DCOD(DEC, 3, 1), 0, 0 }; void fattime2timespec(unsigned dd, unsigned dt, unsigned dh, int utc, struct timespec *tsp) { unsigned day; /* Unpack time fields */ tsp->tv_sec = (dt & 0x1f) << 1; tsp->tv_sec += ((dt & 0x7e0) >> 5) * 60; tsp->tv_sec += ((dt & 0xf800) >> 11) * 3600; tsp->tv_sec += dh / 100; tsp->tv_nsec = (dh % 100) * 10000000; /* Day of month */ day = (dd & 0x1f) - 1; /* Full leap-year cycles */ day += LYC * ((dd >> 11) & 0x1f); /* Month offset from leap-year cycle */ day += daytab[(dd >> 5) & 0x3f]; /* * 2100 is not a leap year. * XXX: a 32 bit time_t can not get us here. */ if (day >= ((2100 - 1980) / 4 * LYC + FEB)) day--; /* Align with time_t epoch */ day += T1980; tsp->tv_sec += DAY * day; if (!utc) tsp->tv_sec += utc_offset(); } #ifdef TEST_DRIVER #include <stdio.h> #include <unistd.h> #include <stdlib.h> int main(int argc __unused, char **argv __unused) { int i; struct timespec ts; struct tm tm; double a; uint16_t d, t; uint8_t p; char buf[100]; for (i = 0; i < 10000; i++) { do { ts.tv_sec = random(); } while (ts.tv_sec < T1980 * 86400); ts.tv_nsec = random() % 1000000000; printf("%10d.%03ld -- ", ts.tv_sec, ts.tv_nsec / 1000000); gmtime_r(&ts.tv_sec, &tm); strftime(buf, sizeof buf, "%Y %m %d %H %M %S", &tm); printf("%s -- ", buf); a = ts.tv_sec + ts.tv_nsec * 1e-9; d = t = p = 0; timet2fattime(&ts, &d, &t, &p); printf("%04x %04x %02x -- ", d, t, p); printf("%3d %02d %02d %02d %02d %02d -- ", ((d >> 9) & 0x7f) + 1980, (d >> 5) & 0x0f, (d >> 0) & 0x1f, (t >> 11) & 0x1f, (t >> 5) & 0x3f, ((t >> 0) & 0x1f) * 2); ts.tv_sec = ts.tv_nsec = 0; fattime2timet(d, t, p, &ts); printf("%10d.%03ld == ", ts.tv_sec, ts.tv_nsec / 1000000); gmtime_r(&ts.tv_sec, &tm); strftime(buf, sizeof buf, "%Y %m %d %H %M %S", &tm); printf("%s -- ", buf); a -= ts.tv_sec + ts.tv_nsec * 1e-9; printf("%.3f", a); printf("\n"); } return (0); } #endif /* TEST_DRIVER */