memchr_P.S

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

/* $Id$ */

/** \file */
/** \ingroup avr_pgmspace
    \fn PGM_VOID_P memchr_P(PGM_VOID_P s, int val, size_t len)
    \brief Scan flash memory for a character.

    The memchr_P() function scans the first \p len bytes of the flash
    memory area pointed to by \p s for the character \p val.  The first
    byte to match \p val (interpreted as an unsigned character) stops
    the operation.

    \return The memchr_P() function returns a pointer to the matching
    byte or \c NULL if the character does not occur in the given memory
    area.       */

#if !defined(__AVR_TINY__)

#if !defined(__DOXYGEN__)

#include "macros.inc"

#define src_hi  r25
#define src_lo  r24
#define val     r22
#define len_hi  r21
#define len_lo  r20

#define ret_hi  r25
#define ret_lo  r24

        ASSEMBLY_CLIB_SECTION
        .global _U(memchr_P)
        .type   _U(memchr_P), @function
_U(memchr_P):
        X_movw  ZL, src_lo

#if  __AVR_HAVE_LPMX__
1:      subi    len_lo, lo8(1)
        sbci    len_hi, hi8(1)
        brlo    2f
        lpm     r0, Z+
        cp      r0, val
        brne    1b
  ; OK, val is founded
        sbiw    ZL, 1
        X_movw  ret_lo, ZL
        ret
  ; fault, val is't founded
2:      clr     ret_lo
        clr     ret_hi
        ret
#else
        rjmp    2f

1:      lpm
        cp      r0, val
        breq    3f
        adiw    ZL, 1
2:      subi    len_lo, lo8(1)
        sbci    len_hi, hi8(1)
        brsh    1b

        clr     ZL
        clr     ZH
3:      X_movw  ret_lo, ZL      ; practicaly, this will be 2 movs
        ret
#endif

        .size   _U(memchr_P), . - _U(memchr_P)
#endif /* not __DOXYGEN__ */

#endif /* !defined(__AVR_TINY__) */