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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  */
33 int
xfs_bitmap_empty(uint * map,uint size)34 xfs_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  */
50 int
xfs_contig_bits(uint * map,uint size,uint start_bit)51 xfs_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;
78 found:
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  */
xfs_next_bit(uint * map,uint size,uint start_bit)90 int 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;
118 found:
119 	return result + ffs(tmp) - 1;
120 }
121