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2.2.1
Standard C library for AVR-GCC
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include
util
parity.h
Go to the documentation of this file.
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/* Copyright (c) 2002, Marek Michalkiewicz
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Copyright (c) 2004,2005,2007 Joerg Wunsch
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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* Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in
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the documentation and/or other materials provided with the
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distribution.
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* Neither the name of the copyright holders nor the names of
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contributors may be used to endorse or promote products derived
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from this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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POSSIBILITY OF SUCH DAMAGE. */
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/* $Id$ */
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#ifndef _UTIL_PARITY_H_
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#define _UTIL_PARITY_H_
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#include <
stdint.h
>
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#ifndef __DOXYGEN__
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#ifndef __ATTR_ALWAYS_INLINE__
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#define __ATTR_ALWAYS_INLINE__ __inline__ __attribute__((__always_inline__))
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#endif
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#endif
/* !DOXYGEN */
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/** \file */
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/** \defgroup util_parity <util/parity.h>: Parity bit generation
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\code #include <util/parity.h> \endcode
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This header file contains optimized assembler code to calculate
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the parity bit for a byte.
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*/
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/** \fn uint8_t parity_even_bit (uint8_t val);
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\ingroup util_parity
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\returns 1 if \c val has an odd number of bits set, and 0 otherwise. */
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static
__ATTR_ALWAYS_INLINE__
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uint8_t
parity_even_bit (
uint8_t
__val)
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{
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if
(__builtin_constant_p (__builtin_parity (__val)))
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return
(
uint8_t
) __builtin_parity (__val);
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__asm (
/* parity is in [0..7] */
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"mov __tmp_reg__, %0"
"\n\t"
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"swap __tmp_reg__"
"\n\t"
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"eor %0, __tmp_reg__"
"\n\t"
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/* parity is in [0..3] */
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"subi %0, -4"
"\n\t"
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"andi %0, -5"
"\n\t"
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"subi %0, -6"
"\n\t"
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/* parity is in [0,3] */
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"sbrc %0, 3"
"\n\t"
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"inc %0"
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/* parity is in [0] */
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:
"+d"
(__val) ::
"r0"
);
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return
__val & 1;
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}
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#endif
/* _UTIL_PARITY_H_ */
uint8_t
unsigned char uint8_t
Definition
stdint.h:83
stdint.h
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