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_log_format.h"
20#include "xfs_bit.h"
21
22/*
23 * XFS bit manipulation routines, used in non-realtime code.
24 */
25
26/*
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.
30 */
31int
32xfs_bitmap_empty(uint *map, uint size)
33{
34	uint i;
35	uint ret = 0;
36
37	for (i = 0; i < size; i++) {
38		ret |= map[i];
39	}
40
41	return (ret == 0);
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 */
48int
49xfs_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;
76found:
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 */
88int 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;
116found:
117	return result + ffs(tmp) - 1;
118}
119