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 */
_find_next_bit(const unsigned long * addr1,const unsigned long * addr2,unsigned long nbits,unsigned long start,unsigned long invert,unsigned long le)31 unsigned long _find_next_bit(const unsigned long *addr1,
32 const unsigned long *addr2, unsigned long nbits,
33 unsigned long start, unsigned long invert, unsigned long le)
34 {
35 unsigned long tmp, mask;
36 (void) le;
37
38 if (unlikely(start >= nbits))
39 return nbits;
40
41 tmp = addr1[start / BITS_PER_LONG];
42 if (addr2)
43 tmp &= addr2[start / BITS_PER_LONG];
44 tmp ^= invert;
45
46 /* Handle 1st word. */
47 mask = BITMAP_FIRST_WORD_MASK(start);
48
49 /*
50 * Due to the lack of swab() in tools, and the fact that it doesn't
51 * need little-endian support, just comment it out
52 */
53 #if (0)
54 if (le)
55 mask = swab(mask);
56 #endif
57
58 tmp &= mask;
59
60 start = round_down(start, BITS_PER_LONG);
61
62 while (!tmp) {
63 start += BITS_PER_LONG;
64 if (start >= nbits)
65 return nbits;
66
67 tmp = addr1[start / BITS_PER_LONG];
68 if (addr2)
69 tmp &= addr2[start / BITS_PER_LONG];
70 tmp ^= invert;
71 }
72
73 #if (0)
74 if (le)
75 tmp = swab(tmp);
76 #endif
77
78 return min(start + __ffs(tmp), nbits);
79 }
80 #endif
81
82 #ifndef find_first_bit
83 /*
84 * Find the first set bit in a memory region.
85 */
_find_first_bit(const unsigned long * addr,unsigned long size)86 unsigned long _find_first_bit(const unsigned long *addr, unsigned long size)
87 {
88 unsigned long idx;
89
90 for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
91 if (addr[idx])
92 return min(idx * BITS_PER_LONG + __ffs(addr[idx]), size);
93 }
94
95 return size;
96 }
97 #endif
98
99 #ifndef find_first_zero_bit
100 /*
101 * Find the first cleared bit in a memory region.
102 */
_find_first_zero_bit(const unsigned long * addr,unsigned long size)103 unsigned long _find_first_zero_bit(const unsigned long *addr, unsigned long size)
104 {
105 unsigned long idx;
106
107 for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
108 if (addr[idx] != ~0UL)
109 return min(idx * BITS_PER_LONG + ffz(addr[idx]), size);
110 }
111
112 return size;
113 }
114 #endif
115