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b4d0d230 | 1 | /* SPDX-License-Identifier: GPL-2.0-or-later */ |
aacf29bf DH |
2 | /* Count leading and trailing zeros functions |
3 | * | |
4 | * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved. | |
5 | * Written by David Howells (dhowells@redhat.com) | |
aacf29bf DH |
6 | */ |
7 | ||
a1164a3a CH |
8 | #ifndef _LINUX_BITOPS_COUNT_ZEROS_H_ |
9 | #define _LINUX_BITOPS_COUNT_ZEROS_H_ | |
aacf29bf DH |
10 | |
11 | #include <asm/bitops.h> | |
12 | ||
13 | /** | |
14 | * count_leading_zeros - Count the number of zeros from the MSB back | |
15 | * @x: The value | |
16 | * | |
17 | * Count the number of leading zeros from the MSB going towards the LSB in @x. | |
18 | * | |
19 | * If the MSB of @x is set, the result is 0. | |
20 | * If only the LSB of @x is set, then the result is BITS_PER_LONG-1. | |
21 | * If @x is 0 then the result is COUNT_LEADING_ZEROS_0. | |
22 | */ | |
23 | static inline int count_leading_zeros(unsigned long x) | |
24 | { | |
25 | if (sizeof(x) == 4) | |
26 | return BITS_PER_LONG - fls(x); | |
27 | else | |
28 | return BITS_PER_LONG - fls64(x); | |
29 | } | |
30 | ||
31 | #define COUNT_LEADING_ZEROS_0 BITS_PER_LONG | |
32 | ||
33 | /** | |
34 | * count_trailing_zeros - Count the number of zeros from the LSB forwards | |
35 | * @x: The value | |
36 | * | |
37 | * Count the number of trailing zeros from the LSB going towards the MSB in @x. | |
38 | * | |
39 | * If the LSB of @x is set, the result is 0. | |
40 | * If only the MSB of @x is set, then the result is BITS_PER_LONG-1. | |
41 | * If @x is 0 then the result is COUNT_TRAILING_ZEROS_0. | |
42 | */ | |
43 | static inline int count_trailing_zeros(unsigned long x) | |
44 | { | |
45 | #define COUNT_TRAILING_ZEROS_0 (-1) | |
46 | ||
47 | if (sizeof(x) == 4) | |
48 | return ffs(x); | |
49 | else | |
50 | return (x != 0) ? __ffs(x) : COUNT_TRAILING_ZEROS_0; | |
51 | } | |
52 | ||
a1164a3a | 53 | #endif /* _LINUX_BITOPS_COUNT_ZEROS_H_ */ |