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1 | /* bit search implementation | |
2 | * | |
3 | * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved. | |
4 | * Written by David Howells (dhowells@redhat.com) | |
5 | * | |
6 | * Copyright (C) 2008 IBM Corporation | |
7 | * 'find_last_bit' is written by Rusty Russell <rusty@rustcorp.com.au> | |
8 | * (Inspired by David Howell's find_next_bit implementation) | |
9 | * | |
10 | * Rewritten by Yury Norov <yury.norov@gmail.com> 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 | */ | |
31 | static 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 (unlikely(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 | */ | |
61 | unsigned 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 | } | |
66 | EXPORT_SYMBOL(find_next_bit); | |
67 | #endif | |
68 | ||
69 | #ifndef find_next_zero_bit | |
70 | unsigned 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 | } | |
75 | EXPORT_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 | */ | |
82 | unsigned 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 | } | |
93 | EXPORT_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 | */ | |
100 | unsigned 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 | } | |
111 | EXPORT_SYMBOL(find_first_zero_bit); | |
112 | #endif | |
113 | ||
114 | #ifndef find_last_bit | |
115 | unsigned 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 | } | |
131 | EXPORT_SYMBOL(find_last_bit); | |
132 | #endif | |
133 | ||
134 | #ifdef __BIG_ENDIAN | |
135 | ||
136 | /* include/linux/byteorder does not support "unsigned long" type */ | |
137 | static 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) | |
149 | static 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 (unlikely(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 | |
176 | unsigned 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 | } | |
181 | EXPORT_SYMBOL(find_next_zero_bit_le); | |
182 | #endif | |
183 | ||
184 | #ifndef find_next_bit_le | |
185 | unsigned 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 | } | |
190 | EXPORT_SYMBOL(find_next_bit_le); | |
191 | #endif | |
192 | ||
193 | #endif /* __BIG_ENDIAN */ |