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1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* bit search implementation
4 * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
7 * Copyright (C) 2008 IBM Corporation
8 * 'find_last_bit' is written by Rusty Russell <rusty@rustcorp.com.au>
9 * (Inspired by David Howell's find_next_bit implementation)
11 * Rewritten by Yury Norov <yury.norov@gmail.com> to decrease
12 * size and improve performance, 2015.
15 #include <linux/bitops.h>
16 #include <linux/bitmap.h>
17 #include <linux/export.h>
18 #include <linux/math.h>
19 #include <linux/minmax.h>
20 #include <linux/swab.h>
22 #if !defined(find_next_bit) || !defined(find_next_zero_bit) || \
23 !defined(find_next_bit_le) || !defined(find_next_zero_bit_le) || \
24 !defined(find_next_and_bit)
26 * This is a common helper function for find_next_bit, find_next_zero_bit, and
27 * find_next_and_bit. The differences are:
28 * - The "invert" argument, which is XORed with each fetched word before
29 * searching it for one bits.
30 * - The optional "addr2", which is anded with "addr1" if present.
32 unsigned long _find_next_bit(const unsigned long *addr1
,
33 const unsigned long *addr2
, unsigned long nbits
,
34 unsigned long start
, unsigned long invert
, unsigned long le
)
36 unsigned long tmp
, mask
;
38 if (unlikely(start
>= nbits
))
41 tmp
= addr1
[start
/ BITS_PER_LONG
];
43 tmp
&= addr2
[start
/ BITS_PER_LONG
];
46 /* Handle 1st word. */
47 mask
= BITMAP_FIRST_WORD_MASK(start
);
53 start
= round_down(start
, BITS_PER_LONG
);
56 start
+= BITS_PER_LONG
;
60 tmp
= addr1
[start
/ BITS_PER_LONG
];
62 tmp
&= addr2
[start
/ BITS_PER_LONG
];
69 return min(start
+ __ffs(tmp
), nbits
);
71 EXPORT_SYMBOL(_find_next_bit
);
74 #ifndef find_first_bit
76 * Find the first set bit in a memory region.
78 unsigned long _find_first_bit(const unsigned long *addr
, unsigned long size
)
82 for (idx
= 0; idx
* BITS_PER_LONG
< size
; idx
++) {
84 return min(idx
* BITS_PER_LONG
+ __ffs(addr
[idx
]), size
);
89 EXPORT_SYMBOL(_find_first_bit
);
92 #ifndef find_first_zero_bit
94 * Find the first cleared bit in a memory region.
96 unsigned long _find_first_zero_bit(const unsigned long *addr
, unsigned long size
)
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
);
107 EXPORT_SYMBOL(_find_first_zero_bit
);
110 #ifndef find_last_bit
111 unsigned long _find_last_bit(const unsigned long *addr
, unsigned long size
)
114 unsigned long val
= BITMAP_LAST_WORD_MASK(size
);
115 unsigned long idx
= (size
-1) / BITS_PER_LONG
;
120 return idx
* BITS_PER_LONG
+ __fls(val
);
127 EXPORT_SYMBOL(_find_last_bit
);
130 unsigned long find_next_clump8(unsigned long *clump
, const unsigned long *addr
,
131 unsigned long size
, unsigned long offset
)
133 offset
= find_next_bit(addr
, size
, offset
);
137 offset
= round_down(offset
, 8);
138 *clump
= bitmap_get_value8(addr
, offset
);
142 EXPORT_SYMBOL(find_next_clump8
);