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 */
19int
20xfs_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 */
36int
37xfs_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;
64found:
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 */
76int 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;
104found:
105	return result + ffs(tmp) - 1;
106}
107