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 /*
29 * Return whether bitmap is empty.
30 * Size is number of words in the bitmap, which is padded to word boundary
31 * Returns 1 for empty, 0 for non-empty.
32 */
33 int
xfs_bitmap_empty(uint * map,uint size)34 xfs_bitmap_empty(uint *map, uint size)
35 {
36 uint i;
37 uint ret = 0;
38
39 for (i = 0; i < size; i++) {
40 ret |= map[i];
41 }
42
43 return (ret == 0);
44 }
45
46 /*
47 * Count the number of contiguous bits set in the bitmap starting with bit
48 * start_bit. Size is the size of the bitmap in words.
49 */
50 int
xfs_contig_bits(uint * map,uint size,uint start_bit)51 xfs_contig_bits(uint *map, uint size, uint start_bit)
52 {
53 uint * p = ((unsigned int *) map) + (start_bit >> BIT_TO_WORD_SHIFT);
54 uint result = 0;
55 uint tmp;
56
57 size <<= BIT_TO_WORD_SHIFT;
58
59 ASSERT(start_bit < size);
60 size -= start_bit & ~(NBWORD - 1);
61 start_bit &= (NBWORD - 1);
62 if (start_bit) {
63 tmp = *p++;
64 /* set to one first offset bits prior to start */
65 tmp |= (~0U >> (NBWORD-start_bit));
66 if (tmp != ~0U)
67 goto found;
68 result += NBWORD;
69 size -= NBWORD;
70 }
71 while (size) {
72 if ((tmp = *p++) != ~0U)
73 goto found;
74 result += NBWORD;
75 size -= NBWORD;
76 }
77 return result - start_bit;
78 found:
79 return result + ffz(tmp) - start_bit;
80 }
81
82 /*
83 * This takes the bit number to start looking from and
84 * returns the next set bit from there. It returns -1
85 * if there are no more bits set or the start bit is
86 * beyond the end of the bitmap.
87 *
88 * Size is the number of words, not bytes, in the bitmap.
89 */
xfs_next_bit(uint * map,uint size,uint start_bit)90 int xfs_next_bit(uint *map, uint size, uint start_bit)
91 {
92 uint * p = ((unsigned int *) map) + (start_bit >> BIT_TO_WORD_SHIFT);
93 uint result = start_bit & ~(NBWORD - 1);
94 uint tmp;
95
96 size <<= BIT_TO_WORD_SHIFT;
97
98 if (start_bit >= size)
99 return -1;
100 size -= result;
101 start_bit &= (NBWORD - 1);
102 if (start_bit) {
103 tmp = *p++;
104 /* set to zero first offset bits prior to start */
105 tmp &= (~0U << start_bit);
106 if (tmp != 0U)
107 goto found;
108 result += NBWORD;
109 size -= NBWORD;
110 }
111 while (size) {
112 if ((tmp = *p++) != 0U)
113 goto found;
114 result += NBWORD;
115 size -= NBWORD;
116 }
117 return -1;
118 found:
119 return result + ffs(tmp) - 1;
120 }
121