xfs_bit.c
2.78 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
/*
* Copyright (c) 2000-2005 Silicon Graphics, Inc.
* All Rights Reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it would be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "xfs.h"
#include "xfs_log_format.h"
#include "xfs_bit.h"
/*
* XFS bit manipulation routines, used in non-realtime code.
*/
/*
* Return whether bitmap is empty.
* Size is number of words in the bitmap, which is padded to word boundary
* Returns 1 for empty, 0 for non-empty.
*/
int
xfs_bitmap_empty(uint *map, uint size)
{
uint i;
uint ret = 0;
for (i = 0; i < size; i++) {
ret |= map[i];
}
return (ret == 0);
}
/*
* Count the number of contiguous bits set in the bitmap starting with bit
* start_bit. Size is the size of the bitmap in words.
*/
int
xfs_contig_bits(uint *map, uint size, uint start_bit)
{
uint * p = ((unsigned int *) map) + (start_bit >> BIT_TO_WORD_SHIFT);
uint result = 0;
uint tmp;
size <<= BIT_TO_WORD_SHIFT;
ASSERT(start_bit < size);
size -= start_bit & ~(NBWORD - 1);
start_bit &= (NBWORD - 1);
if (start_bit) {
tmp = *p++;
/* set to one first offset bits prior to start */
tmp |= (~0U >> (NBWORD-start_bit));
if (tmp != ~0U)
goto found;
result += NBWORD;
size -= NBWORD;
}
while (size) {
if ((tmp = *p++) != ~0U)
goto found;
result += NBWORD;
size -= NBWORD;
}
return result - start_bit;
found:
return result + ffz(tmp) - start_bit;
}
/*
* This takes the bit number to start looking from and
* returns the next set bit from there. It returns -1
* if there are no more bits set or the start bit is
* beyond the end of the bitmap.
*
* Size is the number of words, not bytes, in the bitmap.
*/
int xfs_next_bit(uint *map, uint size, uint start_bit)
{
uint * p = ((unsigned int *) map) + (start_bit >> BIT_TO_WORD_SHIFT);
uint result = start_bit & ~(NBWORD - 1);
uint tmp;
size <<= BIT_TO_WORD_SHIFT;
if (start_bit >= size)
return -1;
size -= result;
start_bit &= (NBWORD - 1);
if (start_bit) {
tmp = *p++;
/* set to zero first offset bits prior to start */
tmp &= (~0U << start_bit);
if (tmp != 0U)
goto found;
result += NBWORD;
size -= NBWORD;
}
while (size) {
if ((tmp = *p++) != 0U)
goto found;
result += NBWORD;
size -= NBWORD;
}
return -1;
found:
return result + ffs(tmp) - 1;
}