Commit | Line | Data |
---|---|---|
aacf29bf DH |
1 | /* Count leading and trailing zeros functions |
2 | * | |
3 | * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved. | |
4 | * Written by David Howells (dhowells@redhat.com) | |
5 | * | |
6 | * This program is free software; you can redistribute it and/or | |
7 | * modify it under the terms of the GNU General Public Licence | |
8 | * as published by the Free Software Foundation; either version | |
9 | * 2 of the Licence, or (at your option) any later version. | |
10 | */ | |
11 | ||
a1164a3a CH |
12 | #ifndef _LINUX_BITOPS_COUNT_ZEROS_H_ |
13 | #define _LINUX_BITOPS_COUNT_ZEROS_H_ | |
aacf29bf DH |
14 | |
15 | #include <asm/bitops.h> | |
16 | ||
17 | /** | |
18 | * count_leading_zeros - Count the number of zeros from the MSB back | |
19 | * @x: The value | |
20 | * | |
21 | * Count the number of leading zeros from the MSB going towards the LSB in @x. | |
22 | * | |
23 | * If the MSB of @x is set, the result is 0. | |
24 | * If only the LSB of @x is set, then the result is BITS_PER_LONG-1. | |
25 | * If @x is 0 then the result is COUNT_LEADING_ZEROS_0. | |
26 | */ | |
27 | static inline int count_leading_zeros(unsigned long x) | |
28 | { | |
29 | if (sizeof(x) == 4) | |
30 | return BITS_PER_LONG - fls(x); | |
31 | else | |
32 | return BITS_PER_LONG - fls64(x); | |
33 | } | |
34 | ||
35 | #define COUNT_LEADING_ZEROS_0 BITS_PER_LONG | |
36 | ||
37 | /** | |
38 | * count_trailing_zeros - Count the number of zeros from the LSB forwards | |
39 | * @x: The value | |
40 | * | |
41 | * Count the number of trailing zeros from the LSB going towards the MSB in @x. | |
42 | * | |
43 | * If the LSB of @x is set, the result is 0. | |
44 | * If only the MSB of @x is set, then the result is BITS_PER_LONG-1. | |
45 | * If @x is 0 then the result is COUNT_TRAILING_ZEROS_0. | |
46 | */ | |
47 | static inline int count_trailing_zeros(unsigned long x) | |
48 | { | |
49 | #define COUNT_TRAILING_ZEROS_0 (-1) | |
50 | ||
51 | if (sizeof(x) == 4) | |
52 | return ffs(x); | |
53 | else | |
54 | return (x != 0) ? __ffs(x) : COUNT_TRAILING_ZEROS_0; | |
55 | } | |
56 | ||
a1164a3a | 57 | #endif /* _LINUX_BITOPS_COUNT_ZEROS_H_ */ |