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 /* Count leading and trailing zeros functions * * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved. * Written by David Howells (dhowells@redhat.com) * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public Licence * as published by the Free Software Foundation; either version * 2 of the Licence, or (at your option) any later version. */ #ifndef _LINUX_BITOPS_COUNT_ZEROS_H_ #define _LINUX_BITOPS_COUNT_ZEROS_H_ #include /** * 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_ */