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/* Copyright (c) 2002, Reiner Patommel
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. */
/*
strrev.S
Reverse a string
Contributors:
Created by Reiner Patommel
*/
#include "macros.inc"
#define str_hi r25
#define str_lo r24
#define ltemp r23
#define rtemp r22
/** \ingroup avr_string
\fn char *strrev(char *string)
\brief Reverse a string.
The strrev() function reverses the order of the string.
\returns The strrev() function returns a pointer to the beginning of the
reversed string. */
#if !defined(DOXYGEN)
.text
.global _U(strrev)
.type _U(strrev), @function
_U(strrev):
LOAD_X(str_lo, str_hi) ; X is start of string
LOAD_Z(str_lo, str_hi) ; Z becomes end of string
.strrev_eos:
LD __tmp_reg__, Z+
TST __tmp_reg__
BRNE .strrev_eos
SBIW ZL, 2 ; now Z points at end of string
.strrev_loop:
CP XL, ZL
CPC XH, ZH ; if X >= Z we are done
BRSH .strrev_done
LD ltemp, X ; get left character
LD rtemp, Z ; get right character
ST Z, ltemp
SBIW ZL, 1
ST X+, rtemp ; swap chars
RJMP .strrev_loop ; next pair
.strrev_done:
RET
.strrev_end:
.size _U(strrev), .strrev_end - _U(strrev)
#endif /* not DOXYGEN */
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