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
76 // Modified to support the Haiku FAT driver.
77
78 #include <sys/time.h>
79
80 #include "sys/param.h"
81 #include "sys/types.h"
82 #include "sys/clock.h"
83
84
85 #define DAY (24 * 60 * 60) /* Length of day in seconds */
86 #define YEAR 365 /* Length of normal year */
87 #define LYC (4 * YEAR + 1) /* Length of 4 year leap-year cycle */
88 #define T1980 (10 * 365 + 2) /* Days from 1970 to 1980 */
89
90 /* End of month is N days from start of (normal) year */
91 #define JAN 31
92 #define FEB (JAN + 28)
93 #define MAR (FEB + 31)
94 #define APR (MAR + 30)
95 #define MAY (APR + 31)
96 #define JUN (MAY + 30)
97 #define JUL (JUN + 31)
98 #define AUG (JUL + 31)
99 #define SEP (AUG + 30)
100 #define OCT (SEP + 31)
101 #define NOV (OCT + 30)
102 #define DEC (NOV + 31)
103
104 /* Table of months in a 4 year leap-year cycle */
105
106 #define ENC(y, m) (((y) << 9) | ((m) << 5))
107
108 static const struct {
109 uint16_t days; /* month start in days relative to cycle */
110 uint16_t coded; /* encoded year + month information */
111 } mtab[48] = {
112 { 0 + 0 * YEAR, ENC(0, 1) },
113
114 { JAN + 0 * YEAR, ENC(0, 2) }, { FEB + 0 * YEAR + 1, ENC(0, 3) },
115 { MAR + 0 * YEAR + 1, ENC(0, 4) }, { APR + 0 * YEAR + 1, ENC(0, 5) },
116 { MAY + 0 * YEAR + 1, ENC(0, 6) }, { JUN + 0 * YEAR + 1, ENC(0, 7) },
117 { JUL + 0 * YEAR + 1, ENC(0, 8) }, { AUG + 0 * YEAR + 1, ENC(0, 9) },
118 { SEP + 0 * YEAR + 1, ENC(0, 10) }, { OCT + 0 * YEAR + 1, ENC(0, 11) },
119 { NOV + 0 * YEAR + 1, ENC(0, 12) }, { DEC + 0 * YEAR + 1, ENC(1, 1) },
120
121 { JAN + 1 * YEAR + 1, ENC(1, 2) }, { FEB + 1 * YEAR + 1, ENC(1, 3) },
122 { MAR + 1 * YEAR + 1, ENC(1, 4) }, { APR + 1 * YEAR + 1, ENC(1, 5) },
123 { MAY + 1 * YEAR + 1, ENC(1, 6) }, { JUN + 1 * YEAR + 1, ENC(1, 7) },
124 { JUL + 1 * YEAR + 1, ENC(1, 8) }, { AUG + 1 * YEAR + 1, ENC(1, 9) },
125 { SEP + 1 * YEAR + 1, ENC(1, 10) }, { OCT + 1 * YEAR + 1, ENC(1, 11) },
126 { NOV + 1 * YEAR + 1, ENC(1, 12) }, { DEC + 1 * YEAR + 1, ENC(2, 1) },
127
128 { JAN + 2 * YEAR + 1, ENC(2, 2) }, { FEB + 2 * YEAR + 1, ENC(2, 3) },
129 { MAR + 2 * YEAR + 1, ENC(2, 4) }, { APR + 2 * YEAR + 1, ENC(2, 5) },
130 { MAY + 2 * YEAR + 1, ENC(2, 6) }, { JUN + 2 * YEAR + 1, ENC(2, 7) },
131 { JUL + 2 * YEAR + 1, ENC(2, 8) }, { AUG + 2 * YEAR + 1, ENC(2, 9) },
132 { SEP + 2 * YEAR + 1, ENC(2, 10) }, { OCT + 2 * YEAR + 1, ENC(2, 11) },
133 { NOV + 2 * YEAR + 1, ENC(2, 12) }, { DEC + 2 * YEAR + 1, ENC(3, 1) },
134
135 { JAN + 3 * YEAR + 1, ENC(3, 2) }, { FEB + 3 * YEAR + 1, ENC(3, 3) },
136 { MAR + 3 * YEAR + 1, ENC(3, 4) }, { APR + 3 * YEAR + 1, ENC(3, 5) },
137 { MAY + 3 * YEAR + 1, ENC(3, 6) }, { JUN + 3 * YEAR + 1, ENC(3, 7) },
138 { JUL + 3 * YEAR + 1, ENC(3, 8) }, { AUG + 3 * YEAR + 1, ENC(3, 9) },
139 { SEP + 3 * YEAR + 1, ENC(3, 10) }, { OCT + 3 * YEAR + 1, ENC(3, 11) },
140 { NOV + 3 * YEAR + 1, ENC(3, 12) }
141 };
142
143
144 void
timespec2fattime(const struct timespec * tsp,int utc,uint16_t * ddp,uint16_t * dtp,uint8_t * dhp)145 timespec2fattime(const struct timespec* tsp, int utc, uint16_t* ddp, uint16_t* dtp, uint8_t* dhp)
146 {
147 time_t t1;
148 unsigned t2, l, m;
149
150 t1 = tsp->tv_sec;
151 if (!utc)
152 t1 -= utc_offset();
153 if (dhp != NULL)
154 *dhp = (tsp->tv_sec & 1) * 100 + tsp->tv_nsec / 10000000;
155 if (dtp != NULL) {
156 *dtp = (t1 / 2) % 30;
157 *dtp |= ((t1 / 60) % 60) << 5;
158 *dtp |= ((t1 / 3600) % 24) << 11;
159 }
160 if (ddp != NULL) {
161 t2 = t1 / DAY;
162 if (t2 < T1980) {
163 /* Impossible date, truncate to 1980-01-01 */
164 *ddp = 0x0021;
165 } else {
166 t2 -= T1980;
167
168 /*
169 * 2100 is not a leap year.
170 * XXX: a 32 bit time_t can not get us here.
171 */
172 if (t2 >= ((2100 - 1980) / 4 * LYC + FEB))
173 t2++;
174
175 /* Account for full leapyear cycles */
176 l = t2 / LYC;
177 *ddp = (l * 4) << 9;
178 t2 -= l * LYC;
179
180 /* Find approximate table entry */
181 m = t2 / 32;
182
183 /* Find correct table entry */
184 while (m < 47 && mtab[m + 1].days <= t2)
185 m++;
186
187 /* Get year + month from the table */
188 *ddp += mtab[m].coded;
189
190 /* And apply the day in the month */
191 t2 -= mtab[m].days - 1;
192 *ddp |= t2;
193 }
194 }
195 }
196
197
198 /*
199 * Table indexed by the bottom two bits of year + four bits of the month
200 * from the FAT timestamp, returning number of days into 4 year long
201 * leap-year cycle
202 */
203
204 #define DCOD(m, y, l) ((m) + YEAR * (y) + (l))
205 static const uint16_t daytab[64] = {
206 0, DCOD( 0, 0, 0), DCOD(JAN, 0, 0), DCOD(FEB, 0, 1),
207 DCOD(MAR, 0, 1), DCOD(APR, 0, 1), DCOD(MAY, 0, 1), DCOD(JUN, 0, 1),
208 DCOD(JUL, 0, 1), DCOD(AUG, 0, 1), DCOD(SEP, 0, 1), DCOD(OCT, 0, 1),
209 DCOD(NOV, 0, 1), DCOD(DEC, 0, 1), 0, 0,
210 0, DCOD( 0, 1, 1), DCOD(JAN, 1, 1), DCOD(FEB, 1, 1),
211 DCOD(MAR, 1, 1), DCOD(APR, 1, 1), DCOD(MAY, 1, 1), DCOD(JUN, 1, 1),
212 DCOD(JUL, 1, 1), DCOD(AUG, 1, 1), DCOD(SEP, 1, 1), DCOD(OCT, 1, 1),
213 DCOD(NOV, 1, 1), DCOD(DEC, 1, 1), 0, 0,
214 0, DCOD( 0, 2, 1), DCOD(JAN, 2, 1), DCOD(FEB, 2, 1),
215 DCOD(MAR, 2, 1), DCOD(APR, 2, 1), DCOD(MAY, 2, 1), DCOD(JUN, 2, 1),
216 DCOD(JUL, 2, 1), DCOD(AUG, 2, 1), DCOD(SEP, 2, 1), DCOD(OCT, 2, 1),
217 DCOD(NOV, 2, 1), DCOD(DEC, 2, 1), 0, 0,
218 0, DCOD( 0, 3, 1), DCOD(JAN, 3, 1), DCOD(FEB, 3, 1),
219 DCOD(MAR, 3, 1), DCOD(APR, 3, 1), DCOD(MAY, 3, 1), DCOD(JUN, 3, 1),
220 DCOD(JUL, 3, 1), DCOD(AUG, 3, 1), DCOD(SEP, 3, 1), DCOD(OCT, 3, 1),
221 DCOD(NOV, 3, 1), DCOD(DEC, 3, 1), 0, 0
222 };
223
224
225 void
fattime2timespec(unsigned dd,unsigned dt,unsigned dh,int utc,struct timespec * tsp)226 fattime2timespec(unsigned dd, unsigned dt, unsigned dh, int utc, struct timespec* tsp)
227 {
228 unsigned day;
229
230 /* Unpack time fields */
231 tsp->tv_sec = (dt & 0x1f) << 1;
232 tsp->tv_sec += ((dt & 0x7e0) >> 5) * 60;
233 tsp->tv_sec += ((dt & 0xf800) >> 11) * 3600;
234 tsp->tv_sec += dh / 100;
235 tsp->tv_nsec = (dh % 100) * 10000000;
236
237 /* Day of month */
238 day = (dd & 0x1f) - 1;
239
240 /* Full leap-year cycles */
241 day += LYC * ((dd >> 11) & 0x1f);
242
243 /* Month offset from leap-year cycle */
244 day += daytab[(dd >> 5) & 0x3f];
245
246 /*
247 * 2100 is not a leap year.
248 * XXX: a 32 bit time_t can not get us here.
249 */
250 if (day >= ((2100 - 1980) / 4 * LYC + FEB))
251 day--;
252
253 /* Align with time_t epoch */
254 day += T1980;
255
256 tsp->tv_sec += DAY * day;
257 if (!utc)
258 tsp->tv_sec += utc_offset();
259 }
260