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 !defined(find_next_and_bit)
26
27 /*
28 * This is a common helper function for find_next_bit, find_next_zero_bit, and
29 * find_next_and_bit. The differences are:
30 * - The "invert" argument, which is XORed with each fetched word before
31 * searching it for one bits.
32 * - The optional "addr2", which is anded with "addr1" if present.
33 */
_find_next_bit(const unsigned long * addr1,const unsigned long * addr2,unsigned long nbits,unsigned long start,unsigned long invert)34 static inline unsigned long _find_next_bit(const unsigned long *addr1,
35 const unsigned long *addr2, unsigned long nbits,
36 unsigned long start, unsigned long invert)
37 {
38 unsigned long tmp;
39
40 if (unlikely(start >= nbits))
41 return nbits;
42
43 tmp = addr1[start / BITS_PER_LONG];
44 if (addr2)
45 tmp &= addr2[start / BITS_PER_LONG];
46 tmp ^= invert;
47
48 /* Handle 1st word. */
49 tmp &= BITMAP_FIRST_WORD_MASK(start);
50 start = round_down(start, BITS_PER_LONG);
51
52 while (!tmp) {
53 start += BITS_PER_LONG;
54 if (start >= nbits)
55 return nbits;
56
57 tmp = addr1[start / BITS_PER_LONG];
58 if (addr2)
59 tmp &= addr2[start / BITS_PER_LONG];
60 tmp ^= invert;
61 }
62
63 return min(start + __ffs(tmp), nbits);
64 }
65 #endif
66
67 #ifndef find_next_bit
68 /*
69 * Find the next set bit in a memory region.
70 */
find_next_bit(const unsigned long * addr,unsigned long size,unsigned long offset)71 unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
72 unsigned long offset)
73 {
74 return _find_next_bit(addr, NULL, size, offset, 0UL);
75 }
76 EXPORT_SYMBOL(find_next_bit);
77 #endif
78
79 #ifndef find_next_zero_bit
find_next_zero_bit(const unsigned long * addr,unsigned long size,unsigned long offset)80 unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
81 unsigned long offset)
82 {
83 return _find_next_bit(addr, NULL, size, offset, ~0UL);
84 }
85 EXPORT_SYMBOL(find_next_zero_bit);
86 #endif
87
88 #if !defined(find_next_and_bit)
find_next_and_bit(const unsigned long * addr1,const unsigned long * addr2,unsigned long size,unsigned long offset)89 unsigned long find_next_and_bit(const unsigned long *addr1,
90 const unsigned long *addr2, unsigned long size,
91 unsigned long offset)
92 {
93 return _find_next_bit(addr1, addr2, size, offset, 0UL);
94 }
95 EXPORT_SYMBOL(find_next_and_bit);
96 #endif
97
98 #ifndef find_first_bit
99 /*
100 * Find the first set bit in a memory region.
101 */
find_first_bit(const unsigned long * addr,unsigned long size)102 unsigned long find_first_bit(const unsigned long *addr, unsigned long size)
103 {
104 unsigned long idx;
105
106 for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
107 if (addr[idx])
108 return min(idx * BITS_PER_LONG + __ffs(addr[idx]), size);
109 }
110
111 return size;
112 }
113 EXPORT_SYMBOL(find_first_bit);
114 #endif
115
116 #ifndef find_first_zero_bit
117 /*
118 * Find the first cleared bit in a memory region.
119 */
find_first_zero_bit(const unsigned long * addr,unsigned long size)120 unsigned long find_first_zero_bit(const unsigned long *addr, unsigned long size)
121 {
122 unsigned long idx;
123
124 for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
125 if (addr[idx] != ~0UL)
126 return min(idx * BITS_PER_LONG + ffz(addr[idx]), size);
127 }
128
129 return size;
130 }
131 EXPORT_SYMBOL(find_first_zero_bit);
132 #endif
133
134 #ifndef find_last_bit
find_last_bit(const unsigned long * addr,unsigned long size)135 unsigned long find_last_bit(const unsigned long *addr, unsigned long size)
136 {
137 if (size) {
138 unsigned long val = BITMAP_LAST_WORD_MASK(size);
139 unsigned long idx = (size-1) / BITS_PER_LONG;
140
141 do {
142 val &= addr[idx];
143 if (val)
144 return idx * BITS_PER_LONG + __fls(val);
145
146 val = ~0ul;
147 } while (idx--);
148 }
149 return size;
150 }
151 EXPORT_SYMBOL(find_last_bit);
152 #endif
153
154 #ifdef __BIG_ENDIAN
155
156 #if !defined(find_next_bit_le) || !defined(find_next_zero_bit_le)
_find_next_bit_le(const unsigned long * addr1,const unsigned long * addr2,unsigned long nbits,unsigned long start,unsigned long invert)157 static inline unsigned long _find_next_bit_le(const unsigned long *addr1,
158 const unsigned long *addr2, unsigned long nbits,
159 unsigned long start, unsigned long invert)
160 {
161 unsigned long tmp;
162
163 if (unlikely(start >= nbits))
164 return nbits;
165
166 tmp = addr1[start / BITS_PER_LONG];
167 if (addr2)
168 tmp &= addr2[start / BITS_PER_LONG];
169 tmp ^= invert;
170
171 /* Handle 1st word. */
172 tmp &= swab(BITMAP_FIRST_WORD_MASK(start));
173 start = round_down(start, BITS_PER_LONG);
174
175 while (!tmp) {
176 start += BITS_PER_LONG;
177 if (start >= nbits)
178 return nbits;
179
180 tmp = addr1[start / BITS_PER_LONG];
181 if (addr2)
182 tmp &= addr2[start / BITS_PER_LONG];
183 tmp ^= invert;
184 }
185
186 return min(start + __ffs(swab(tmp)), nbits);
187 }
188 #endif
189
190 #ifndef find_next_zero_bit_le
find_next_zero_bit_le(const void * addr,unsigned long size,unsigned long offset)191 unsigned long find_next_zero_bit_le(const void *addr, unsigned
192 long size, unsigned long offset)
193 {
194 return _find_next_bit_le(addr, NULL, size, offset, ~0UL);
195 }
196 EXPORT_SYMBOL(find_next_zero_bit_le);
197 #endif
198
199 #ifndef find_next_bit_le
find_next_bit_le(const void * addr,unsigned long size,unsigned long offset)200 unsigned long find_next_bit_le(const void *addr, unsigned
201 long size, unsigned long offset)
202 {
203 return _find_next_bit_le(addr, NULL, size, offset, 0UL);
204 }
205 EXPORT_SYMBOL(find_next_bit_le);
206 #endif
207
208 #endif /* __BIG_ENDIAN */
209