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 */
34static 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 */
71unsigned 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}
76EXPORT_SYMBOL(find_next_bit);
77#endif
78
79#ifndef find_next_zero_bit
80unsigned 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}
85EXPORT_SYMBOL(find_next_zero_bit);
86#endif
87
88#if !defined(find_next_and_bit)
89unsigned 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}
95EXPORT_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 */
102unsigned 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}
113EXPORT_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 */
120unsigned 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}
131EXPORT_SYMBOL(find_first_zero_bit);
132#endif
133
134#ifndef find_last_bit
135unsigned 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}
151EXPORT_SYMBOL(find_last_bit);
152#endif
153
154#ifdef __BIG_ENDIAN
155
156/* include/linux/byteorder does not support "unsigned long" type */
157static inline unsigned long ext2_swab(const unsigned long y)
158{
159#if BITS_PER_LONG == 64
160 return (unsigned long) __swab64((u64) y);
161#elif BITS_PER_LONG == 32
162 return (unsigned long) __swab32((u32) y);
163#else
164#error BITS_PER_LONG not defined
165#endif
166}
167
168#if !defined(find_next_bit_le) || !defined(find_next_zero_bit_le)
169static inline unsigned long _find_next_bit_le(const unsigned long *addr1,
170 const unsigned long *addr2, unsigned long nbits,
171 unsigned long start, unsigned long invert)
172{
173 unsigned long tmp;
174
175 if (unlikely(start >= nbits))
176 return nbits;
177
178 tmp = addr1[start / BITS_PER_LONG];
179 if (addr2)
180 tmp &= addr2[start / BITS_PER_LONG];
181 tmp ^= invert;
182
183 /* Handle 1st word. */
184 tmp &= ext2_swab(BITMAP_FIRST_WORD_MASK(start));
185 start = round_down(start, BITS_PER_LONG);
186
187 while (!tmp) {
188 start += BITS_PER_LONG;
189 if (start >= nbits)
190 return nbits;
191
192 tmp = addr1[start / BITS_PER_LONG];
193 if (addr2)
194 tmp &= addr2[start / BITS_PER_LONG];
195 tmp ^= invert;
196 }
197
198 return min(start + __ffs(ext2_swab(tmp)), nbits);
199}
200#endif
201
202#ifndef find_next_zero_bit_le
203unsigned long find_next_zero_bit_le(const void *addr, unsigned
204 long size, unsigned long offset)
205{
206 return _find_next_bit_le(addr, NULL, size, offset, ~0UL);
207}
208EXPORT_SYMBOL(find_next_zero_bit_le);
209#endif
210
211#ifndef find_next_bit_le
212unsigned long find_next_bit_le(const void *addr, unsigned
213 long size, unsigned long offset)
214{
215 return _find_next_bit_le(addr, NULL, size, offset, 0UL);
216}
217EXPORT_SYMBOL(find_next_bit_le);
218#endif
219
220#endif /* __BIG_ENDIAN */
221