projects/linux·blob master · refs

123 lines · 3.4 KiB

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 ([email protected])
8 *
9 * Copyright (C) 2008 IBM Corporation
10 * 'find_last_bit' is written by Rusty Russell <[email protected]>
11 * (Inspired by David Howell's find_next_bit implementation)
12 *
13 * Rewritten by Yury Norov <[email protected]> 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