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
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