mirror of https://gitee.com/openkylin/linux.git
54 lines
1.4 KiB
C
54 lines
1.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later */
|
|
/* Count leading and trailing zeros functions
|
|
*
|
|
* Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
|
|
* Written by David Howells (dhowells@redhat.com)
|
|
*/
|
|
|
|
#ifndef _LINUX_BITOPS_COUNT_ZEROS_H_
|
|
#define _LINUX_BITOPS_COUNT_ZEROS_H_
|
|
|
|
#include <asm/bitops.h>
|
|
|
|
/**
|
|
* count_leading_zeros - Count the number of zeros from the MSB back
|
|
* @x: The value
|
|
*
|
|
* Count the number of leading zeros from the MSB going towards the LSB in @x.
|
|
*
|
|
* If the MSB of @x is set, the result is 0.
|
|
* If only the LSB of @x is set, then the result is BITS_PER_LONG-1.
|
|
* If @x is 0 then the result is COUNT_LEADING_ZEROS_0.
|
|
*/
|
|
static inline int count_leading_zeros(unsigned long x)
|
|
{
|
|
if (sizeof(x) == 4)
|
|
return BITS_PER_LONG - fls(x);
|
|
else
|
|
return BITS_PER_LONG - fls64(x);
|
|
}
|
|
|
|
#define COUNT_LEADING_ZEROS_0 BITS_PER_LONG
|
|
|
|
/**
|
|
* count_trailing_zeros - Count the number of zeros from the LSB forwards
|
|
* @x: The value
|
|
*
|
|
* Count the number of trailing zeros from the LSB going towards the MSB in @x.
|
|
*
|
|
* If the LSB of @x is set, the result is 0.
|
|
* If only the MSB of @x is set, then the result is BITS_PER_LONG-1.
|
|
* If @x is 0 then the result is COUNT_TRAILING_ZEROS_0.
|
|
*/
|
|
static inline int count_trailing_zeros(unsigned long x)
|
|
{
|
|
#define COUNT_TRAILING_ZEROS_0 (-1)
|
|
|
|
if (sizeof(x) == 4)
|
|
return ffs(x);
|
|
else
|
|
return (x != 0) ? __ffs(x) : COUNT_TRAILING_ZEROS_0;
|
|
}
|
|
|
|
#endif /* _LINUX_BITOPS_COUNT_ZEROS_H_ */
|