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_bit.h"
20#include "xfs_log.h"
21#include "xfs_trans.h"
22#include "xfs_buf_item.h"
23
24/*
25 * XFS bit manipulation routines, used in non-realtime code.
26 */
27
28/*
29 * Return whether bitmap is empty.
30 * Size is number of words in the bitmap, which is padded to word boundary
31 * Returns 1 for empty, 0 for non-empty.
32 */
33int
34xfs_bitmap_empty(uint *map, uint size)
35{
36	uint i;
37	uint ret = 0;
38
39	for (i = 0; i < size; i++) {
40		ret |= map[i];
41	}
42
43	return (ret == 0);
44}
45
46/*
47 * Count the number of contiguous bits set in the bitmap starting with bit
48 * start_bit.  Size is the size of the bitmap in words.
49 */
50int
51xfs_contig_bits(uint *map, uint	size, uint start_bit)
52{
53	uint * p = ((unsigned int *) map) + (start_bit >> BIT_TO_WORD_SHIFT);
54	uint result = 0;
55	uint tmp;
56
57	size <<= BIT_TO_WORD_SHIFT;
58
59	ASSERT(start_bit < size);
60	size -= start_bit & ~(NBWORD - 1);
61	start_bit &= (NBWORD - 1);
62	if (start_bit) {
63		tmp = *p++;
64		/* set to one first offset bits prior to start */
65		tmp |= (~0U >> (NBWORD-start_bit));
66		if (tmp != ~0U)
67			goto found;
68		result += NBWORD;
69		size -= NBWORD;
70	}
71	while (size) {
72		if ((tmp = *p++) != ~0U)
73			goto found;
74		result += NBWORD;
75		size -= NBWORD;
76	}
77	return result - start_bit;
78found:
79	return result + ffz(tmp) - start_bit;
80}
81
82/*
83 * This takes the bit number to start looking from and
84 * returns the next set bit from there.  It returns -1
85 * if there are no more bits set or the start bit is
86 * beyond the end of the bitmap.
87 *
88 * Size is the number of words, not bytes, in the bitmap.
89 */
90int xfs_next_bit(uint *map, uint size, uint start_bit)
91{
92	uint * p = ((unsigned int *) map) + (start_bit >> BIT_TO_WORD_SHIFT);
93	uint result = start_bit & ~(NBWORD - 1);
94	uint tmp;
95
96	size <<= BIT_TO_WORD_SHIFT;
97
98	if (start_bit >= size)
99		return -1;
100	size -= result;
101	start_bit &= (NBWORD - 1);
102	if (start_bit) {
103		tmp = *p++;
104		/* set to zero first offset bits prior to start */
105		tmp &= (~0U << start_bit);
106		if (tmp != 0U)
107			goto found;
108		result += NBWORD;
109		size -= NBWORD;
110	}
111	while (size) {
112		if ((tmp = *p++) != 0U)
113			goto found;
114		result += NBWORD;
115		size -= NBWORD;
116	}
117	return -1;
118found:
119	return result + ffs(tmp) - 1;
120}
121