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1// SPDX-License-Identifier: GPL-2.0-or-later
2/* bit search implementation
3 *
4 * Copied from lib/find_bit.c to tools/lib/find_bit.c
5 *
6 * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
7 * Written by David Howells (dhowells@redhat.com)
8 *
9 * Copyright (C) 2008 IBM Corporation
10 * 'find_last_bit' is written by Rusty Russell <rusty@rustcorp.com.au>
11 * (Inspired by David Howell's find_next_bit implementation)
12 *
13 * Rewritten by Yury Norov <yury.norov@gmail.com> to decrease
14 * size and improve performance, 2015.
15 */
16
17#include <linux/bitops.h>
18#include <linux/bitmap.h>
19#include <linux/kernel.h>
20
21/*
22 * Common helper for find_bit() function family
23 * @FETCH: The expression that fetches and pre-processes each word of bitmap(s)
24 * @MUNGE: The expression that post-processes a word containing found bit (may be empty)
25 * @size: The bitmap size in bits
26 */
27#define FIND_FIRST_BIT(FETCH, MUNGE, size) \
28({ \
29 unsigned long idx, val, sz = (size); \
30 \
31 for (idx = 0; idx * BITS_PER_LONG < sz; idx++) { \
32 val = (FETCH); \
33 if (val) { \
34 sz = min(idx * BITS_PER_LONG + __ffs(MUNGE(val)), sz); \
35 break; \
36 } \
37 } \
38 \
39 sz; \
40})
41
42/*
43 * Common helper for find_next_bit() function family
44 * @FETCH: The expression that fetches and pre-processes each word of bitmap(s)
45 * @MUNGE: The expression that post-processes a word containing found bit (may be empty)
46 * @size: The bitmap size in bits
47 * @start: The bitnumber to start searching at
48 */
49#define FIND_NEXT_BIT(FETCH, MUNGE, size, start) \
50({ \
51 unsigned long mask, idx, tmp, sz = (size), __start = (start); \
52 \
53 if (unlikely(__start >= sz)) \
54 goto out; \
55 \
56 mask = MUNGE(BITMAP_FIRST_WORD_MASK(__start)); \
57 idx = __start / BITS_PER_LONG; \
58 \
59 for (tmp = (FETCH) & mask; !tmp; tmp = (FETCH)) { \
60 if ((idx + 1) * BITS_PER_LONG >= sz) \
61 goto out; \
62 idx++; \
63 } \
64 \
65 sz = min(idx * BITS_PER_LONG + __ffs(MUNGE(tmp)), sz); \
66out: \
67 sz; \
68})
69
70#ifndef find_first_bit
71/*
72 * Find the first set bit in a memory region.
73 */
74unsigned long _find_first_bit(const unsigned long *addr, unsigned long size)
75{
76 return FIND_FIRST_BIT(addr[idx], /* nop */, size);
77}
78#endif
79
80#ifndef find_first_and_bit
81/*
82 * Find the first set bit in two memory regions.
83 */
84unsigned long _find_first_and_bit(const unsigned long *addr1,
85 const unsigned long *addr2,
86 unsigned long size)
87{
88 return FIND_FIRST_BIT(addr1[idx] & addr2[idx], /* nop */, size);
89}
90#endif
91
92#ifndef find_first_zero_bit
93/*
94 * Find the first cleared bit in a memory region.
95 */
96unsigned long _find_first_zero_bit(const unsigned long *addr, unsigned long size)
97{
98 return FIND_FIRST_BIT(~addr[idx], /* nop */, size);
99}
100#endif
101
102#ifndef find_next_bit
103unsigned long _find_next_bit(const unsigned long *addr, unsigned long nbits, unsigned long start)
104{
105 return FIND_NEXT_BIT(addr[idx], /* nop */, nbits, start);
106}
107#endif
108
109#ifndef find_next_and_bit
110unsigned long _find_next_and_bit(const unsigned long *addr1, const unsigned long *addr2,
111 unsigned long nbits, unsigned long start)
112{
113 return FIND_NEXT_BIT(addr1[idx] & addr2[idx], /* nop */, nbits, start);
114}
115#endif
116
117#ifndef find_next_zero_bit
118unsigned long _find_next_zero_bit(const unsigned long *addr, unsigned long nbits,
119 unsigned long start)
120{
121 return FIND_NEXT_BIT(~addr[idx], /* nop */, nbits, start);
122}
123#endif
1/* bit search implementation
2 *
3 * Copied from lib/find_bit.c to tools/lib/find_bit.c
4 *
5 * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
6 * Written by David Howells (dhowells@redhat.com)
7 *
8 * Copyright (C) 2008 IBM Corporation
9 * 'find_last_bit' is written by Rusty Russell <rusty@rustcorp.com.au>
10 * (Inspired by David Howell's find_next_bit implementation)
11 *
12 * Rewritten by Yury Norov <yury.norov@gmail.com> to decrease
13 * size and improve performance, 2015.
14 *
15 * This program is free software; you can redistribute it and/or
16 * modify it under the terms of the GNU General Public License
17 * as published by the Free Software Foundation; either version
18 * 2 of the License, or (at your option) any later version.
19 */
20
21#include <linux/bitops.h>
22#include <linux/bitmap.h>
23#include <linux/kernel.h>
24
25#if !defined(find_next_bit)
26
27/*
28 * This is a common helper function for find_next_bit and
29 * find_next_zero_bit. The difference is the "invert" argument, which
30 * is XORed with each fetched word before searching it for one bits.
31 */
32static unsigned long _find_next_bit(const unsigned long *addr,
33 unsigned long nbits, unsigned long start, unsigned long invert)
34{
35 unsigned long tmp;
36
37 if (!nbits || start >= nbits)
38 return nbits;
39
40 tmp = addr[start / BITS_PER_LONG] ^ invert;
41
42 /* Handle 1st word. */
43 tmp &= BITMAP_FIRST_WORD_MASK(start);
44 start = round_down(start, BITS_PER_LONG);
45
46 while (!tmp) {
47 start += BITS_PER_LONG;
48 if (start >= nbits)
49 return nbits;
50
51 tmp = addr[start / BITS_PER_LONG] ^ invert;
52 }
53
54 return min(start + __ffs(tmp), nbits);
55}
56#endif
57
58#ifndef find_next_bit
59/*
60 * Find the next set bit in a memory region.
61 */
62unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
63 unsigned long offset)
64{
65 return _find_next_bit(addr, size, offset, 0UL);
66}
67#endif
68
69#ifndef find_first_bit
70/*
71 * Find the first set bit in a memory region.
72 */
73unsigned long find_first_bit(const unsigned long *addr, unsigned long size)
74{
75 unsigned long idx;
76
77 for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
78 if (addr[idx])
79 return min(idx * BITS_PER_LONG + __ffs(addr[idx]), size);
80 }
81
82 return size;
83}
84#endif