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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#if !defined(find_next_bit) || !defined(find_next_zero_bit) || \
22 !defined(find_next_and_bit)
23
24/*
25 * This is a common helper function for find_next_bit, find_next_zero_bit, and
26 * find_next_and_bit. The differences are:
27 * - The "invert" argument, which is XORed with each fetched word before
28 * searching it for one bits.
29 * - The optional "addr2", which is anded with "addr1" if present.
30 */
31static inline unsigned long _find_next_bit(const unsigned long *addr1,
32 const unsigned long *addr2, unsigned long nbits,
33 unsigned long start, unsigned long invert)
34{
35 unsigned long tmp;
36
37 if (unlikely(start >= nbits))
38 return nbits;
39
40 tmp = addr1[start / BITS_PER_LONG];
41 if (addr2)
42 tmp &= addr2[start / BITS_PER_LONG];
43 tmp ^= invert;
44
45 /* Handle 1st word. */
46 tmp &= BITMAP_FIRST_WORD_MASK(start);
47 start = round_down(start, BITS_PER_LONG);
48
49 while (!tmp) {
50 start += BITS_PER_LONG;
51 if (start >= nbits)
52 return nbits;
53
54 tmp = addr1[start / BITS_PER_LONG];
55 if (addr2)
56 tmp &= addr2[start / BITS_PER_LONG];
57 tmp ^= invert;
58 }
59
60 return min(start + __ffs(tmp), nbits);
61}
62#endif
63
64#ifndef find_next_bit
65/*
66 * Find the next set bit in a memory region.
67 */
68unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
69 unsigned long offset)
70{
71 return _find_next_bit(addr, NULL, size, offset, 0UL);
72}
73#endif
74
75#ifndef find_first_bit
76/*
77 * Find the first set bit in a memory region.
78 */
79unsigned long find_first_bit(const unsigned long *addr, unsigned long size)
80{
81 unsigned long idx;
82
83 for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
84 if (addr[idx])
85 return min(idx * BITS_PER_LONG + __ffs(addr[idx]), size);
86 }
87
88 return 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 unsigned long idx;
99
100 for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
101 if (addr[idx] != ~0UL)
102 return min(idx * BITS_PER_LONG + ffz(addr[idx]), size);
103 }
104
105 return size;
106}
107#endif
108
109#ifndef find_next_zero_bit
110unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
111 unsigned long offset)
112{
113 return _find_next_bit(addr, NULL, size, offset, ~0UL);
114}
115#endif
116
117#ifndef find_next_and_bit
118unsigned long find_next_and_bit(const unsigned long *addr1,
119 const unsigned long *addr2, unsigned long size,
120 unsigned long offset)
121{
122 return _find_next_bit(addr1, addr2, size, offset, 0UL);
123}
124#endif