# memcmp_P.S

/* Copyright (c) 2002, 2007 Marek Michalkiewicz
Copyright (c) 2007  Dmitry Xmelkov

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
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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
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE. */

/* $Id$ */

/** \file */

/** \ingroup avr_pgmspace
\fn int memcmp_P(const void *s1, PGM_VOID_P s2, size_t len)
\brief Compare memory areas

The memcmp_P() function compares the first \p len bytes of the memory
areas \p s1 and flash \p s2. The comparision is performed using unsigned
char operations.

\returns The memcmp_P() function returns an integer less than, equal
to, or greater than zero if the first \p len bytes of \p s1 is found,
respectively, to be less than, to match, or be greater than the first
\p len bytes of \p s2.      */

#if !defined(__AVR_TINY__)

#if !defined(__DOXYGEN__)

#include "macros.inc"

#define s1_hi r25
#define s1_lo r24
#define s2_hi r23
#define s2_lo r22
#define len_hi r21
#define len_lo r20

#define ret_hi r25
#define ret_lo r24

ASSEMBLY_CLIB_SECTION
.global _U(memcmp_P)
.type   _U(memcmp_P), @function
_U(memcmp_P):
X_movw  ZL, s2_lo
X_movw  XL, s1_lo
rjmp    2f

1:      ld      ret_lo, X+
X_lpm   r0, Z+
sub     ret_lo, r0
brne    3f
2:      subi    len_lo, lo8(1)
sbci    len_hi, hi8(1)
brsh    1b

sub     ret_lo, ret_lo
3:      sbc     ret_hi, ret_hi
ret

.size   _U(memcmp_P), . - _U(memcmp_P)

#endif /* not __DOXYGEN__ */

#endif /* !defined(__AVR_TINY__) */