| David Howells | aacf29b | 2012-09-13 13:09:33 +0100 | [diff] [blame] | 1 | /* Count leading and trailing zeros functions |
| 2 | * |
| 3 | * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved. |
| 4 | * Written by David Howells (dhowells@redhat.com) |
| 5 | * |
| 6 | * This program is free software; you can redistribute it and/or |
| 7 | * modify it under the terms of the GNU General Public Licence |
| 8 | * as published by the Free Software Foundation; either version |
| 9 | * 2 of the Licence, or (at your option) any later version. |
| 10 | */ |
| 11 | |
| 12 | #ifndef _ASM_GENERIC_BITOPS_COUNT_ZEROS_H_ |
| 13 | #define _ASM_GENERIC_BITOPS_COUNT_ZEROS_H_ |
| 14 | |
| 15 | #include <asm/bitops.h> |
| 16 | |
| 17 | /** |
| 18 | * count_leading_zeros - Count the number of zeros from the MSB back |
| 19 | * @x: The value |
| 20 | * |
| 21 | * Count the number of leading zeros from the MSB going towards the LSB in @x. |
| 22 | * |
| 23 | * If the MSB of @x is set, the result is 0. |
| 24 | * If only the LSB of @x is set, then the result is BITS_PER_LONG-1. |
| 25 | * If @x is 0 then the result is COUNT_LEADING_ZEROS_0. |
| 26 | */ |
| 27 | static inline int count_leading_zeros(unsigned long x) |
| 28 | { |
| 29 | if (sizeof(x) == 4) |
| 30 | return BITS_PER_LONG - fls(x); |
| 31 | else |
| 32 | return BITS_PER_LONG - fls64(x); |
| 33 | } |
| 34 | |
| 35 | #define COUNT_LEADING_ZEROS_0 BITS_PER_LONG |
| 36 | |
| 37 | /** |
| 38 | * count_trailing_zeros - Count the number of zeros from the LSB forwards |
| 39 | * @x: The value |
| 40 | * |
| 41 | * Count the number of trailing zeros from the LSB going towards the MSB in @x. |
| 42 | * |
| 43 | * If the LSB of @x is set, the result is 0. |
| 44 | * If only the MSB of @x is set, then the result is BITS_PER_LONG-1. |
| 45 | * If @x is 0 then the result is COUNT_TRAILING_ZEROS_0. |
| 46 | */ |
| 47 | static inline int count_trailing_zeros(unsigned long x) |
| 48 | { |
| 49 | #define COUNT_TRAILING_ZEROS_0 (-1) |
| 50 | |
| 51 | if (sizeof(x) == 4) |
| 52 | return ffs(x); |
| 53 | else |
| 54 | return (x != 0) ? __ffs(x) : COUNT_TRAILING_ZEROS_0; |
| 55 | } |
| 56 | |
| 57 | #endif /* _ASM_GENERIC_BITOPS_COUNT_ZEROS_H_ */ |