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_log_format.h"
20 #include "xfs_bit.h"
21
22 /*
23 * XFS bit manipulation routines, used in non-realtime code.
24 */
25
26 /*
27 * Return whether bitmap is empty.
28 * Size is number of words in the bitmap, which is padded to word boundary
29 * Returns 1 for empty, 0 for non-empty.
30 */
31 int
xfs_bitmap_empty(uint * map,uint size)32 xfs_bitmap_empty(uint *map, uint size)
33 {
34 uint i;
35 uint ret = 0;
36
37 for (i = 0; i < size; i++) {
38 ret |= map[i];
39 }
40
41 return (ret == 0);
42 }
43
44 /*
45 * Count the number of contiguous bits set in the bitmap starting with bit
46 * start_bit. Size is the size of the bitmap in words.
47 */
48 int
xfs_contig_bits(uint * map,uint size,uint start_bit)49 xfs_contig_bits(uint *map, uint size, uint start_bit)
50 {
51 uint * p = ((unsigned int *) map) + (start_bit >> BIT_TO_WORD_SHIFT);
52 uint result = 0;
53 uint tmp;
54
55 size <<= BIT_TO_WORD_SHIFT;
56
57 ASSERT(start_bit < size);
58 size -= start_bit & ~(NBWORD - 1);
59 start_bit &= (NBWORD - 1);
60 if (start_bit) {
61 tmp = *p++;
62 /* set to one first offset bits prior to start */
63 tmp |= (~0U >> (NBWORD-start_bit));
64 if (tmp != ~0U)
65 goto found;
66 result += NBWORD;
67 size -= NBWORD;
68 }
69 while (size) {
70 if ((tmp = *p++) != ~0U)
71 goto found;
72 result += NBWORD;
73 size -= NBWORD;
74 }
75 return result - start_bit;
76 found:
77 return result + ffz(tmp) - start_bit;
78 }
79
80 /*
81 * This takes the bit number to start looking from and
82 * returns the next set bit from there. It returns -1
83 * if there are no more bits set or the start bit is
84 * beyond the end of the bitmap.
85 *
86 * Size is the number of words, not bytes, in the bitmap.
87 */
xfs_next_bit(uint * map,uint size,uint start_bit)88 int xfs_next_bit(uint *map, uint size, uint start_bit)
89 {
90 uint * p = ((unsigned int *) map) + (start_bit >> BIT_TO_WORD_SHIFT);
91 uint result = start_bit & ~(NBWORD - 1);
92 uint tmp;
93
94 size <<= BIT_TO_WORD_SHIFT;
95
96 if (start_bit >= size)
97 return -1;
98 size -= result;
99 start_bit &= (NBWORD - 1);
100 if (start_bit) {
101 tmp = *p++;
102 /* set to zero first offset bits prior to start */
103 tmp &= (~0U << start_bit);
104 if (tmp != 0U)
105 goto found;
106 result += NBWORD;
107 size -= NBWORD;
108 }
109 while (size) {
110 if ((tmp = *p++) != 0U)
111 goto found;
112 result += NBWORD;
113 size -= NBWORD;
114 }
115 return -1;
116 found:
117 return result + ffs(tmp) - 1;
118 }
119