1 | /* SPDX-License-Identifier: GPL-2.0-or-later */ |
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) |
6 | */ |
7 | |
8 | #ifndef _LINUX_BITOPS_COUNT_ZEROS_H_ |
9 | #define _LINUX_BITOPS_COUNT_ZEROS_H_ |
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 | |
53 | #endif /* _LINUX_BITOPS_COUNT_ZEROS_H_ */ |
54 | |