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1 /* find_next_bit.c: fallback find next bit implementation
3 * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
12 #include <linux/bitops.h>
13 #include <linux/module.h>
14 #include <asm/types.h>
16 #define BITOP_WORD(nr) ((nr) / BITS_PER_LONG)
19 * find_next_bit - find the next set bit in a memory region
20 * @addr: The address to base the search on
21 * @offset: The bitnumber to start searching at
22 * @size: The maximum size to search
24 unsigned long find_next_bit(const unsigned long *addr
, unsigned long size
,
27 const unsigned long *p
= addr
+ BITOP_WORD(offset
);
28 unsigned long result
= offset
& ~(BITS_PER_LONG
-1);
34 offset
%= BITS_PER_LONG
;
37 tmp
&= (~0UL << offset
);
38 if (size
< BITS_PER_LONG
)
42 size
-= BITS_PER_LONG
;
43 result
+= BITS_PER_LONG
;
45 while (size
& ~(BITS_PER_LONG
-1)) {
48 result
+= BITS_PER_LONG
;
49 size
-= BITS_PER_LONG
;
56 tmp
&= (~0UL >> (BITS_PER_LONG
- size
));
57 if (tmp
== 0UL) /* Are any bits set? */
58 return result
+ size
; /* Nope. */
60 return result
+ __ffs(tmp
);
63 EXPORT_SYMBOL(find_next_bit
);
66 * This implementation of find_{first,next}_zero_bit was stolen from
67 * Linus' asm-alpha/bitops.h.
69 unsigned long find_next_zero_bit(const unsigned long *addr
, unsigned long size
,
72 const unsigned long *p
= addr
+ BITOP_WORD(offset
);
73 unsigned long result
= offset
& ~(BITS_PER_LONG
-1);
79 offset
%= BITS_PER_LONG
;
82 tmp
|= ~0UL >> (BITS_PER_LONG
- offset
);
83 if (size
< BITS_PER_LONG
)
87 size
-= BITS_PER_LONG
;
88 result
+= BITS_PER_LONG
;
90 while (size
& ~(BITS_PER_LONG
-1)) {
93 result
+= BITS_PER_LONG
;
94 size
-= BITS_PER_LONG
;
102 if (tmp
== ~0UL) /* Are any bits zero? */
103 return result
+ size
; /* Nope. */
105 return result
+ ffz(tmp
);
108 EXPORT_SYMBOL(find_next_zero_bit
);