1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* |
3 | * Copyright (c) 2000-2005 Silicon Graphics, Inc. |
4 | * All Rights Reserved. |
5 | */ |
6 | #include "xfs.h" |
7 | #include "xfs_log_format.h" |
8 | #include "xfs_bit.h" |
9 | |
10 | /* |
11 | * XFS bit manipulation routines, used in non-realtime code. |
12 | */ |
13 | |
14 | /* |
15 | * Return whether bitmap is empty. |
16 | * Size is number of words in the bitmap, which is padded to word boundary |
17 | * Returns 1 for empty, 0 for non-empty. |
18 | */ |
19 | int |
20 | xfs_bitmap_empty(uint *map, uint size) |
21 | { |
22 | uint i; |
23 | |
24 | for (i = 0; i < size; i++) { |
25 | if (map[i] != 0) |
26 | return 0; |
27 | } |
28 | |
29 | return 1; |
30 | } |
31 | |
32 | /* |
33 | * Count the number of contiguous bits set in the bitmap starting with bit |
34 | * start_bit. Size is the size of the bitmap in words. |
35 | */ |
36 | int |
37 | xfs_contig_bits(uint *map, uint size, uint start_bit) |
38 | { |
39 | uint * p = ((unsigned int *) map) + (start_bit >> BIT_TO_WORD_SHIFT); |
40 | uint result = 0; |
41 | uint tmp; |
42 | |
43 | size <<= BIT_TO_WORD_SHIFT; |
44 | |
45 | ASSERT(start_bit < size); |
46 | size -= start_bit & ~(NBWORD - 1); |
47 | start_bit &= (NBWORD - 1); |
48 | if (start_bit) { |
49 | tmp = *p++; |
50 | /* set to one first offset bits prior to start */ |
51 | tmp |= (~0U >> (NBWORD-start_bit)); |
52 | if (tmp != ~0U) |
53 | goto found; |
54 | result += NBWORD; |
55 | size -= NBWORD; |
56 | } |
57 | while (size) { |
58 | if ((tmp = *p++) != ~0U) |
59 | goto found; |
60 | result += NBWORD; |
61 | size -= NBWORD; |
62 | } |
63 | return result - start_bit; |
64 | found: |
65 | return result + ffz(tmp) - start_bit; |
66 | } |
67 | |
68 | /* |
69 | * This takes the bit number to start looking from and |
70 | * returns the next set bit from there. It returns -1 |
71 | * if there are no more bits set or the start bit is |
72 | * beyond the end of the bitmap. |
73 | * |
74 | * Size is the number of words, not bytes, in the bitmap. |
75 | */ |
76 | int xfs_next_bit(uint *map, uint size, uint start_bit) |
77 | { |
78 | uint * p = ((unsigned int *) map) + (start_bit >> BIT_TO_WORD_SHIFT); |
79 | uint result = start_bit & ~(NBWORD - 1); |
80 | uint tmp; |
81 | |
82 | size <<= BIT_TO_WORD_SHIFT; |
83 | |
84 | if (start_bit >= size) |
85 | return -1; |
86 | size -= result; |
87 | start_bit &= (NBWORD - 1); |
88 | if (start_bit) { |
89 | tmp = *p++; |
90 | /* set to zero first offset bits prior to start */ |
91 | tmp &= (~0U << start_bit); |
92 | if (tmp != 0U) |
93 | goto found; |
94 | result += NBWORD; |
95 | size -= NBWORD; |
96 | } |
97 | while (size) { |
98 | if ((tmp = *p++) != 0U) |
99 | goto found; |
100 | result += NBWORD; |
101 | size -= NBWORD; |
102 | } |
103 | return -1; |
104 | found: |
105 | return result + ffs(tmp) - 1; |
106 | } |
107 | |