# strstr_P.S

/* Copyright (c) 2002, Philip Soeberg
Copyright (c) 2005, 2006, 2007 Werner Boellmann

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. */

/* $Id$ */

/*
strstr_P.S
Search string contained in a string

Originally contributed by:
Philip Soeberg <philip@soeberg.net>

Modified for string s2 in program space by:
Werner Boellmann <wb@muekno.de>
*/

/** \file */

/** \ingroup avr_pgmspace
\fn char *strstr_P(const char *s1, PGM_P s2)
\brief Locate a substring.

The strstr_P() function finds the first occurrence of the substring
\p s2 in the string \p s1.  The terminating '\\0' characters are not
compared. The strstr_P() function is similar to strstr() except that
\p s2 is pointer to a string in program space.

\returns The strstr_P() function returns a pointer to the beginning
of the substring, or NULL if the substring is not found. If \p s2
points to a string of zero length, the function returns \p s1. */

#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 chr1   r20
#define beg2   r21      /* begin of s2: s2[0]   */
#define chr2   r0

ASSEMBLY_CLIB_SECTION
.global _U(strstr_P)
.type _U(strstr_P), @function
_U(strstr_P):

X_movw  ZL, s2_lo
X_lpm   beg2, Z+
tst     beg2            ; is str2 empty?
breq    .L_ret          ; return original string (req'd by standard)
X_movw  s2_lo, ZL       ; save: address of second s2 byte

0:      X_movw  XL, s1_lo

1:      ld      chr1, X+        ; Find first char
cp      chr1, beg2
cpse    chr1, __zero_reg__
brne    1b

brne    .L_no_match     ; end of s1
X_movw  s1_lo, XL       ; store return value

2:      X_lpm   chr2, Z+        ; compare strings
tst     chr2
breq    .L_match        ; end of s2
ld      chr1, X+
cp      chr1, chr2
cpse    chr1, __zero_reg__      ; break, if end of s1
breq    2b

X_movw  ZL, s2_lo       ; restore s2+1
cpse    chr1, __zero_reg__
rjmp    0b

.L_no_match:
ldi     s1_lo, lo8(1)
ldi     s1_hi, hi8(1)
.L_match:
sbiw    s1_lo, 1        ; restore after post-increment
.L_ret:
ret

.size _U(strstr_P), . - _U(strstr_P)

#endif /* not __DOXYGEN__ */

#endif /* !defined(__AVR_TINY__) */