Branch data Line data Source code
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 : 150 : static inline int count_leading_zeros(unsigned long x) 24 : : { 25 : 150 : if (sizeof(x) == 4) 26 : : return BITS_PER_LONG - fls(x); 27 : : else 28 [ - + ]: 150 : 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_ */