1 /*
2 * Copyright (c) 2000-2005 Silicon Graphics, Inc.
3 * All Rights Reserved.
4 *
5 * This program is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU General Public License as
7 * published by the Free Software Foundation.
8 *
9 * This program is distributed in the hope that it would be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write the Free Software Foundation,
16 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
17 */
18 #include "xfs.h"
19 #include "xfs_bit.h"
20 #include "xfs_log.h"
21 #include "xfs_trans.h"
22 #include "xfs_buf_item.h"
23
24 /*
25 * XFS bit manipulation routines, used in non-realtime code.
26 */
27
28 #ifndef HAVE_ARCH_HIGHBIT
29 /*
30 * Index of high bit number in byte, -1 for none set, 0..7 otherwise.
31 */
32 STATIC const char xfs_highbit[256] = {
33 -1, 0, 1, 1, 2, 2, 2, 2, /* 00 .. 07 */
34 3, 3, 3, 3, 3, 3, 3, 3, /* 08 .. 0f */
35 4, 4, 4, 4, 4, 4, 4, 4, /* 10 .. 17 */
36 4, 4, 4, 4, 4, 4, 4, 4, /* 18 .. 1f */
37 5, 5, 5, 5, 5, 5, 5, 5, /* 20 .. 27 */
38 5, 5, 5, 5, 5, 5, 5, 5, /* 28 .. 2f */
39 5, 5, 5, 5, 5, 5, 5, 5, /* 30 .. 37 */
40 5, 5, 5, 5, 5, 5, 5, 5, /* 38 .. 3f */
41 6, 6, 6, 6, 6, 6, 6, 6, /* 40 .. 47 */
42 6, 6, 6, 6, 6, 6, 6, 6, /* 48 .. 4f */
43 6, 6, 6, 6, 6, 6, 6, 6, /* 50 .. 57 */
44 6, 6, 6, 6, 6, 6, 6, 6, /* 58 .. 5f */
45 6, 6, 6, 6, 6, 6, 6, 6, /* 60 .. 67 */
46 6, 6, 6, 6, 6, 6, 6, 6, /* 68 .. 6f */
47 6, 6, 6, 6, 6, 6, 6, 6, /* 70 .. 77 */
48 6, 6, 6, 6, 6, 6, 6, 6, /* 78 .. 7f */
49 7, 7, 7, 7, 7, 7, 7, 7, /* 80 .. 87 */
50 7, 7, 7, 7, 7, 7, 7, 7, /* 88 .. 8f */
51 7, 7, 7, 7, 7, 7, 7, 7, /* 90 .. 97 */
52 7, 7, 7, 7, 7, 7, 7, 7, /* 98 .. 9f */
53 7, 7, 7, 7, 7, 7, 7, 7, /* a0 .. a7 */
54 7, 7, 7, 7, 7, 7, 7, 7, /* a8 .. af */
55 7, 7, 7, 7, 7, 7, 7, 7, /* b0 .. b7 */
56 7, 7, 7, 7, 7, 7, 7, 7, /* b8 .. bf */
57 7, 7, 7, 7, 7, 7, 7, 7, /* c0 .. c7 */
58 7, 7, 7, 7, 7, 7, 7, 7, /* c8 .. cf */
59 7, 7, 7, 7, 7, 7, 7, 7, /* d0 .. d7 */
60 7, 7, 7, 7, 7, 7, 7, 7, /* d8 .. df */
61 7, 7, 7, 7, 7, 7, 7, 7, /* e0 .. e7 */
62 7, 7, 7, 7, 7, 7, 7, 7, /* e8 .. ef */
63 7, 7, 7, 7, 7, 7, 7, 7, /* f0 .. f7 */
64 7, 7, 7, 7, 7, 7, 7, 7, /* f8 .. ff */
65 };
66 #endif
67
68 /*
69 * Count of bits set in byte, 0..8.
70 */
71 static const char xfs_countbit[256] = {
72 0, 1, 1, 2, 1, 2, 2, 3, /* 00 .. 07 */
73 1, 2, 2, 3, 2, 3, 3, 4, /* 08 .. 0f */
74 1, 2, 2, 3, 2, 3, 3, 4, /* 10 .. 17 */
75 2, 3, 3, 4, 3, 4, 4, 5, /* 18 .. 1f */
76 1, 2, 2, 3, 2, 3, 3, 4, /* 20 .. 27 */
77 2, 3, 3, 4, 3, 4, 4, 5, /* 28 .. 2f */
78 2, 3, 3, 4, 3, 4, 4, 5, /* 30 .. 37 */
79 3, 4, 4, 5, 4, 5, 5, 6, /* 38 .. 3f */
80 1, 2, 2, 3, 2, 3, 3, 4, /* 40 .. 47 */
81 2, 3, 3, 4, 3, 4, 4, 5, /* 48 .. 4f */
82 2, 3, 3, 4, 3, 4, 4, 5, /* 50 .. 57 */
83 3, 4, 4, 5, 4, 5, 5, 6, /* 58 .. 5f */
84 2, 3, 3, 4, 3, 4, 4, 5, /* 60 .. 67 */
85 3, 4, 4, 5, 4, 5, 5, 6, /* 68 .. 6f */
86 3, 4, 4, 5, 4, 5, 5, 6, /* 70 .. 77 */
87 4, 5, 5, 6, 5, 6, 6, 7, /* 78 .. 7f */
88 1, 2, 2, 3, 2, 3, 3, 4, /* 80 .. 87 */
89 2, 3, 3, 4, 3, 4, 4, 5, /* 88 .. 8f */
90 2, 3, 3, 4, 3, 4, 4, 5, /* 90 .. 97 */
91 3, 4, 4, 5, 4, 5, 5, 6, /* 98 .. 9f */
92 2, 3, 3, 4, 3, 4, 4, 5, /* a0 .. a7 */
93 3, 4, 4, 5, 4, 5, 5, 6, /* a8 .. af */
94 3, 4, 4, 5, 4, 5, 5, 6, /* b0 .. b7 */
95 4, 5, 5, 6, 5, 6, 6, 7, /* b8 .. bf */
96 2, 3, 3, 4, 3, 4, 4, 5, /* c0 .. c7 */
97 3, 4, 4, 5, 4, 5, 5, 6, /* c8 .. cf */
98 3, 4, 4, 5, 4, 5, 5, 6, /* d0 .. d7 */
99 4, 5, 5, 6, 5, 6, 6, 7, /* d8 .. df */
100 3, 4, 4, 5, 4, 5, 5, 6, /* e0 .. e7 */
101 4, 5, 5, 6, 5, 6, 6, 7, /* e8 .. ef */
102 4, 5, 5, 6, 5, 6, 6, 7, /* f0 .. f7 */
103 5, 6, 6, 7, 6, 7, 7, 8, /* f8 .. ff */
104 };
105
106 /*
107 * xfs_highbit32: get high bit set out of 32-bit argument, -1 if none set.
108 */
109 int
xfs_highbit32(__uint32_t v)110 xfs_highbit32(
111 __uint32_t v)
112 {
113 #ifdef HAVE_ARCH_HIGHBIT
114 return highbit32(v);
115 #else
116 int i;
117
118 if (v & 0xffff0000)
119 if (v & 0xff000000)
120 i = 24;
121 else
122 i = 16;
123 else if (v & 0x0000ffff)
124 if (v & 0x0000ff00)
125 i = 8;
126 else
127 i = 0;
128 else
129 return -1;
130 return i + xfs_highbit[(v >> i) & 0xff];
131 #endif
132 }
133
134 /*
135 * xfs_lowbit64: get low bit set out of 64-bit argument, -1 if none set.
136 */
137 int
xfs_lowbit64(__uint64_t v)138 xfs_lowbit64(
139 __uint64_t v)
140 {
141 __uint32_t w = (__uint32_t)v;
142 int n = 0;
143
144 if (w) { /* lower bits */
145 n = ffs(w);
146 } else { /* upper bits */
147 w = (__uint32_t)(v >> 32);
148 if (w && (n = ffs(w)))
149 n += 32;
150 }
151 return n - 1;
152 }
153
154 /*
155 * xfs_highbit64: get high bit set out of 64-bit argument, -1 if none set.
156 */
157 int
xfs_highbit64(__uint64_t v)158 xfs_highbit64(
159 __uint64_t v)
160 {
161 __uint32_t h = (__uint32_t)(v >> 32);
162
163 if (h)
164 return xfs_highbit32(h) + 32;
165 return xfs_highbit32((__uint32_t)v);
166 }
167
168
169 /*
170 * Count the number of bits set in the bitmap starting with bit
171 * start_bit. Size is the size of the bitmap in words.
172 *
173 * Do the counting by mapping a byte value to the number of set
174 * bits for that value using the xfs_countbit array, i.e.
175 * xfs_countbit[0] == 0, xfs_countbit[1] == 1, xfs_countbit[2] == 1,
176 * xfs_countbit[3] == 2, etc.
177 */
178 int
xfs_count_bits(uint * map,uint size,uint start_bit)179 xfs_count_bits(uint *map, uint size, uint start_bit)
180 {
181 register int bits;
182 register unsigned char *bytep;
183 register unsigned char *end_map;
184 int byte_bit;
185
186 bits = 0;
187 end_map = (char*)(map + size);
188 bytep = (char*)(map + (start_bit & ~0x7));
189 byte_bit = start_bit & 0x7;
190
191 /*
192 * If the caller fell off the end of the map, return 0.
193 */
194 if (bytep >= end_map) {
195 return (0);
196 }
197
198 /*
199 * If start_bit is not byte aligned, then process the
200 * first byte separately.
201 */
202 if (byte_bit != 0) {
203 /*
204 * Shift off the bits we don't want to look at,
205 * before indexing into xfs_countbit.
206 */
207 bits += xfs_countbit[(*bytep >> byte_bit)];
208 bytep++;
209 }
210
211 /*
212 * Count the bits in each byte until the end of the bitmap.
213 */
214 while (bytep < end_map) {
215 bits += xfs_countbit[*bytep];
216 bytep++;
217 }
218
219 return (bits);
220 }
221
222 /*
223 * Count the number of contiguous bits set in the bitmap starting with bit
224 * start_bit. Size is the size of the bitmap in words.
225 */
226 int
xfs_contig_bits(uint * map,uint size,uint start_bit)227 xfs_contig_bits(uint *map, uint size, uint start_bit)
228 {
229 uint * p = ((unsigned int *) map) + (start_bit >> BIT_TO_WORD_SHIFT);
230 uint result = 0;
231 uint tmp;
232
233 size <<= BIT_TO_WORD_SHIFT;
234
235 ASSERT(start_bit < size);
236 size -= start_bit & ~(NBWORD - 1);
237 start_bit &= (NBWORD - 1);
238 if (start_bit) {
239 tmp = *p++;
240 /* set to one first offset bits prior to start */
241 tmp |= (~0U >> (NBWORD-start_bit));
242 if (tmp != ~0U)
243 goto found;
244 result += NBWORD;
245 size -= NBWORD;
246 }
247 while (size) {
248 if ((tmp = *p++) != ~0U)
249 goto found;
250 result += NBWORD;
251 size -= NBWORD;
252 }
253 return result - start_bit;
254 found:
255 return result + ffz(tmp) - start_bit;
256 }
257
258 /*
259 * This takes the bit number to start looking from and
260 * returns the next set bit from there. It returns -1
261 * if there are no more bits set or the start bit is
262 * beyond the end of the bitmap.
263 *
264 * Size is the number of words, not bytes, in the bitmap.
265 */
xfs_next_bit(uint * map,uint size,uint start_bit)266 int xfs_next_bit(uint *map, uint size, uint start_bit)
267 {
268 uint * p = ((unsigned int *) map) + (start_bit >> BIT_TO_WORD_SHIFT);
269 uint result = start_bit & ~(NBWORD - 1);
270 uint tmp;
271
272 size <<= BIT_TO_WORD_SHIFT;
273
274 if (start_bit >= size)
275 return -1;
276 size -= result;
277 start_bit &= (NBWORD - 1);
278 if (start_bit) {
279 tmp = *p++;
280 /* set to zero first offset bits prior to start */
281 tmp &= (~0U << start_bit);
282 if (tmp != 0U)
283 goto found;
284 result += NBWORD;
285 size -= NBWORD;
286 }
287 while (size) {
288 if ((tmp = *p++) != 0U)
289 goto found;
290 result += NBWORD;
291 size -= NBWORD;
292 }
293 return -1;
294 found:
295 return result + ffs(tmp) - 1;
296 }
297