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1da177e4 | 1 | /* |
7b718769 NS |
2 | * Copyright (c) 2000-2005 Silicon Graphics, Inc. |
3 | * All Rights Reserved. | |
1da177e4 | 4 | * |
7b718769 NS |
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 | |
1da177e4 LT |
7 | * published by the Free Software Foundation. |
8 | * | |
7b718769 NS |
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. | |
1da177e4 | 13 | * |
7b718769 NS |
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 | |
1da177e4 | 17 | */ |
1da177e4 | 18 | #include "xfs.h" |
239880ef | 19 | #include "xfs_log_format.h" |
632b89e8 | 20 | #include "xfs_bit.h" |
1da177e4 | 21 | |
7b718769 NS |
22 | /* |
23 | * XFS bit manipulation routines, used in non-realtime code. | |
24 | */ | |
1da177e4 | 25 | |
1da177e4 | 26 | /* |
24ad33ff ES |
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. | |
1da177e4 LT |
30 | */ |
31 | int | |
24ad33ff | 32 | xfs_bitmap_empty(uint *map, uint size) |
1da177e4 | 33 | { |
24ad33ff ES |
34 | uint i; |
35 | uint ret = 0; | |
1da177e4 | 36 | |
24ad33ff ES |
37 | for (i = 0; i < size; i++) { |
38 | ret |= map[i]; | |
1da177e4 LT |
39 | } |
40 | ||
24ad33ff | 41 | return (ret == 0); |
1da177e4 LT |
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 | |
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 | */ | |
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 | } |