4.143.1 memrchr.S

/* 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
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   * 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
  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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/* $Id$ */

#if !defined(__AVR_TINY__)

#if !defined(__DOXYGEN__)

#include "asmdef.h"

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

#define ret_lo  r24

ENTRY memrchr
    X_movw  ZL, len_lo
    adiw    ZL, 0
    breq    2f          ; len is 0, return NULL
    add ZL, src_lo
    adc ZH, src_hi

1:  ld  r0, -Z
    cp  r0, val
    breq    2f          ; val is found
    subi    len_lo, lo8(1)
    sbci    len_hi, hi8(1)
    brne    1b

    X_movw  ZL, len_lo      ; is zero
2:  X_movw  ret_lo, ZL
    ret
ENDFUNC

#endif /* not __DOXYGEN__ */

#endif /* !defined(__AVR_TINY__) */