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/* Copyright (c) 2007 Dmitry Xmelkov
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the
distribution.
* Neither the name of the copyright holders nor the names of
contributors may be used to endorse or promote products derived
from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE. */
/* $Id: memrchr.S,v 1.1 2007/03/03 12:41:25 dmix Exp $ */
/** \file */
/** \ingroup avr_string
\fn void *memrchr(const void *src, int val, size_t len)
The memrchr() function is like the memchr() function, except that it
searches backwards from the end of the \p len bytes pointed to by \p
src instead of forwards from the front. (Glibc, GNU extension.)
\return The memrchr() function returns a pointer to the matching
byte or \c NULL if the character does not occur in the given memory
area. */
#if !defined(__DOXYGEN__)
#include "asmdef.h"
#define src_hi r25
#define src_lo r24
#define val r22
#define len_hi r21
#define len_lo r20
#define ret_lo r24
ENTRY memrchr
X_movw ZL, len_lo
adiw ZL, 0
breq 2f ; len is 0, return NULL
add ZL, src_lo
adc ZH, src_hi
1: ld r0, -Z
cp r0, val
breq 2f ; val is found
subi len_lo, lo8(1)
sbci len_hi, hi8(1)
brne 1b
X_movw ZL, len_lo ; is zero
2: X_movw ret_lo, ZL
ret
ENDFUNC
#endif /* not __DOXYGEN__ */
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