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