strstr_P.S

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

/* $Id$ */

/*
   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__) */