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); \
66 out: \
67 sz; \
68 })
69
70 #ifndef find_first_bit
71 /*
72 * Find the first set bit in a memory region.
73 */
74 unsigned 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 */
84 unsigned 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 */
96 unsigned 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
103 unsigned 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
110 unsigned 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
118 unsigned 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
124
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