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  */
count_leading_zeros(unsigned long x)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  */
count_trailing_zeros(unsigned long x)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