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/* Copyright (c) 2005, 2006, 2007 Helmut Wallner
based on libc/string/strnlen.S which is
Copyright (c) 2002, Marek Michalkiewicz
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: strnlen_P.S,v 1.7 2007/12/01 06:03:30 dmix Exp $ */
/** \file */
/** \ingroup avr_pgmspace
\fn size_t strnlen_P(PGM_P src, size_t len)
\brief Determine the length of a fixed-size string.
The strnlen_P() function is similar to strnlen(), except that \c src is a
pointer to a string in program space.
\returns The strnlen_P function returns strlen_P(src), if that is less than
\c len, or \c len if there is no '\\0' character among the first \c len
characters pointed to by \c src. */
#if !defined(__DOXYGEN__)
#include "macros.inc"
#define src_hi r25
#define src_lo r24
#define len_hi r23
#define len_lo r22
.text
.global _U(strnlen_P)
.type _U(strnlen_P), @function
_U(strnlen_P):
X_movw ZL, src_lo
.L_strnlen_P_loop:
X_lpm r0, Z+
subi len_lo, lo8(1)
sbci len_hi, hi8(1)
cpse r0, __zero_reg__
brcc .L_strnlen_P_loop
; Z points one character past the terminating NUL
; return Z - 1 - src = (-1 - src) + Z = ~src + Z
com src_lo
com src_hi
add src_lo, ZL
adc src_hi, ZH
ret
.L_strnlen_P_end:
.size _U(strnlen_P), .L_strnlen_P_end - _U(strnlen_P)
#endif /* not __DOXYGEN__ */
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