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1// SPDX-License-Identifier: GPL-2.0-or-later
2/* bit search implementation
3 *
4 * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 *
7 * Copyright (C) 2008 IBM Corporation
8 * 'find_last_bit' is written by Rusty Russell <rusty@rustcorp.com.au>
9 * (Inspired by David Howell's find_next_bit implementation)
10 *
11 * Rewritten by Yury Norov <yury.norov@gmail.com> to decrease
12 * size and improve performance, 2015.
13 */
14
15#include <linux/bitops.h>
16#include <linux/bitmap.h>
17#include <linux/export.h>
18#include <linux/math.h>
19#include <linux/minmax.h>
20#include <linux/swab.h>
21
22#if !defined(find_next_bit) || !defined(find_next_zero_bit) || \
23 !defined(find_next_bit_le) || !defined(find_next_zero_bit_le) || \
24 !defined(find_next_and_bit)
25/*
26 * This is a common helper function for find_next_bit, find_next_zero_bit, and
27 * find_next_and_bit. The differences are:
28 * - The "invert" argument, which is XORed with each fetched word before
29 * searching it for one bits.
30 * - The optional "addr2", which is anded with "addr1" if present.
31 */
32unsigned long _find_next_bit(const unsigned long *addr1,
33 const unsigned long *addr2, unsigned long nbits,
34 unsigned long start, unsigned long invert, unsigned long le)
35{
36 unsigned long tmp, mask;
37
38 if (unlikely(start >= nbits))
39 return nbits;
40
41 tmp = addr1[start / BITS_PER_LONG];
42 if (addr2)
43 tmp &= addr2[start / BITS_PER_LONG];
44 tmp ^= invert;
45
46 /* Handle 1st word. */
47 mask = BITMAP_FIRST_WORD_MASK(start);
48 if (le)
49 mask = swab(mask);
50
51 tmp &= mask;
52
53 start = round_down(start, BITS_PER_LONG);
54
55 while (!tmp) {
56 start += BITS_PER_LONG;
57 if (start >= nbits)
58 return nbits;
59
60 tmp = addr1[start / BITS_PER_LONG];
61 if (addr2)
62 tmp &= addr2[start / BITS_PER_LONG];
63 tmp ^= invert;
64 }
65
66 if (le)
67 tmp = swab(tmp);
68
69 return min(start + __ffs(tmp), nbits);
70}
71EXPORT_SYMBOL(_find_next_bit);
72#endif
73
74#ifndef find_first_bit
75/*
76 * Find the first set bit in a memory region.
77 */
78unsigned long _find_first_bit(const unsigned long *addr, unsigned long size)
79{
80 unsigned long idx;
81
82 for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
83 if (addr[idx])
84 return min(idx * BITS_PER_LONG + __ffs(addr[idx]), size);
85 }
86
87 return size;
88}
89EXPORT_SYMBOL(_find_first_bit);
90#endif
91
92#ifndef find_first_and_bit
93/*
94 * Find the first set bit in two memory regions.
95 */
96unsigned long _find_first_and_bit(const unsigned long *addr1,
97 const unsigned long *addr2,
98 unsigned long size)
99{
100 unsigned long idx, val;
101
102 for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
103 val = addr1[idx] & addr2[idx];
104 if (val)
105 return min(idx * BITS_PER_LONG + __ffs(val), size);
106 }
107
108 return size;
109}
110EXPORT_SYMBOL(_find_first_and_bit);
111#endif
112
113#ifndef find_first_zero_bit
114/*
115 * Find the first cleared bit in a memory region.
116 */
117unsigned long _find_first_zero_bit(const unsigned long *addr, unsigned long size)
118{
119 unsigned long idx;
120
121 for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
122 if (addr[idx] != ~0UL)
123 return min(idx * BITS_PER_LONG + ffz(addr[idx]), size);
124 }
125
126 return size;
127}
128EXPORT_SYMBOL(_find_first_zero_bit);
129#endif
130
131#ifndef find_last_bit
132unsigned long _find_last_bit(const unsigned long *addr, unsigned long size)
133{
134 if (size) {
135 unsigned long val = BITMAP_LAST_WORD_MASK(size);
136 unsigned long idx = (size-1) / BITS_PER_LONG;
137
138 do {
139 val &= addr[idx];
140 if (val)
141 return idx * BITS_PER_LONG + __fls(val);
142
143 val = ~0ul;
144 } while (idx--);
145 }
146 return size;
147}
148EXPORT_SYMBOL(_find_last_bit);
149#endif
150
151unsigned long find_next_clump8(unsigned long *clump, const unsigned long *addr,
152 unsigned long size, unsigned long offset)
153{
154 offset = find_next_bit(addr, size, offset);
155 if (offset == size)
156 return size;
157
158 offset = round_down(offset, 8);
159 *clump = bitmap_get_value8(addr, offset);
160
161 return offset;
162}
163EXPORT_SYMBOL(find_next_clump8);