projects/linux·blob v4.10 · refs

193 lines · 4.5 KiB

1/* bit search implementation
2 *
3 * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells ([email protected])
5 *
6 * Copyright (C) 2008 IBM Corporation
7 * 'find_last_bit' is written by Rusty Russell <[email protected]>
8 * (Inspired by David Howell's find_next_bit implementation)
9 *
10 * Rewritten by Yury Norov <[email protected]> to decrease
11 * size and improve performance, 2015.
12 *
13 * This program is free software; you can redistribute it and/or
14 * modify it under the terms of the GNU General Public License
15 * as published by the Free Software Foundation; either version
16 * 2 of the License, or (at your option) any later version.
17 */
18
19#include <linux/bitops.h>
20#include <linux/bitmap.h>
21#include <linux/export.h>
22#include <linux/kernel.h>
23
24#if !defined(find_next_bit) || !defined(find_next_zero_bit)
25
26/*
27 * This is a common helper function for find_next_bit and
28 * find_next_zero_bit. The difference is the "invert" argument, which
29 * is XORed with each fetched word before searching it for one bits.
30 */
31static unsigned long _find_next_bit(const unsigned long *addr,
32 unsigned long nbits, unsigned long start, unsigned long invert)
33{
34 unsigned long tmp;
35
36 if (!nbits || start >= nbits)
37 return nbits;
38
39 tmp = addr[start / BITS_PER_LONG] ^ invert;
40
41 /* Handle 1st word. */
42 tmp &= BITMAP_FIRST_WORD_MASK(start);
43 start = round_down(start, BITS_PER_LONG);
44
45 while (!tmp) {
46 start += BITS_PER_LONG;
47 if (start >= nbits)
48 return nbits;
49
50 tmp = addr[start / BITS_PER_LONG] ^ invert;
51 }
52
53 return min(start + __ffs(tmp), nbits);
54}
55#endif
56
57#ifndef find_next_bit
58/*
59 * Find the next set bit in a memory region.
60 */
61unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
62 unsigned long offset)
63{
64 return _find_next_bit(addr, size, offset, 0UL);
65}
66EXPORT_SYMBOL(find_next_bit);
67#endif
68
69#ifndef find_next_zero_bit
70unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
71 unsigned long offset)
72{
73 return _find_next_bit(addr, size, offset, ~0UL);
74}
75EXPORT_SYMBOL(find_next_zero_bit);
76#endif
77
78#ifndef find_first_bit
79/*
80 * Find the first set bit in a memory region.
81 */
82unsigned long find_first_bit(const unsigned long *addr, unsigned long size)
83{
84 unsigned long idx;
85
86 for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
87 if (addr[idx])
88 return min(idx * BITS_PER_LONG + __ffs(addr[idx]), size);
89 }
90
91 return size;
92}
93EXPORT_SYMBOL(find_first_bit);
94#endif
95
96#ifndef find_first_zero_bit
97/*
98 * Find the first cleared bit in a memory region.
99 */
100unsigned long find_first_zero_bit(const unsigned long *addr, unsigned long size)
101{
102 unsigned long idx;
103
104 for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
105 if (addr[idx] != ~0UL)
106 return min(idx * BITS_PER_LONG + ffz(addr[idx]), size);
107 }
108
109 return size;
110}
111EXPORT_SYMBOL(find_first_zero_bit);
112#endif
113
114#ifndef find_last_bit
115unsigned long find_last_bit(const unsigned long *addr, unsigned long size)
116{
117 if (size) {
118 unsigned long val = BITMAP_LAST_WORD_MASK(size);
119 unsigned long idx = (size-1) / BITS_PER_LONG;
120
121 do {
122 val &= addr[idx];
123 if (val)
124 return idx * BITS_PER_LONG + __fls(val);
125
126 val = ~0ul;
127 } while (idx--);
128 }
129 return size;
130}
131EXPORT_SYMBOL(find_last_bit);
132#endif
133
134#ifdef __BIG_ENDIAN
135
136/* include/linux/byteorder does not support "unsigned long" type */
137static inline unsigned long ext2_swab(const unsigned long y)
138{
139#if BITS_PER_LONG == 64
140 return (unsigned long) __swab64((u64) y);
141#elif BITS_PER_LONG == 32
142 return (unsigned long) __swab32((u32) y);
143#else
144#error BITS_PER_LONG not defined
145#endif
146}
147
148#if !defined(find_next_bit_le) || !defined(find_next_zero_bit_le)
149static unsigned long _find_next_bit_le(const unsigned long *addr,
150 unsigned long nbits, unsigned long start, unsigned long invert)
151{
152 unsigned long tmp;
153
154 if (!nbits || start >= nbits)
155 return nbits;
156
157 tmp = addr[start / BITS_PER_LONG] ^ invert;
158
159 /* Handle 1st word. */
160 tmp &= ext2_swab(BITMAP_FIRST_WORD_MASK(start));
161 start = round_down(start, BITS_PER_LONG);
162
163 while (!tmp) {
164 start += BITS_PER_LONG;
165 if (start >= nbits)
166 return nbits;
167
168 tmp = addr[start / BITS_PER_LONG] ^ invert;
169 }
170
171 return min(start + __ffs(ext2_swab(tmp)), nbits);
172}
173#endif
174
175#ifndef find_next_zero_bit_le
176unsigned long find_next_zero_bit_le(const void *addr, unsigned
177 long size, unsigned long offset)
178{
179 return _find_next_bit_le(addr, size, offset, ~0UL);
180}
181EXPORT_SYMBOL(find_next_zero_bit_le);
182#endif
183
184#ifndef find_next_bit_le
185unsigned long find_next_bit_le(const void *addr, unsigned
186 long size, unsigned long offset)
187{
188 return _find_next_bit_le(addr, size, offset, 0UL);
189}
190EXPORT_SYMBOL(find_next_bit_le);
191#endif
192
193#endif /* __BIG_ENDIAN */