/* 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: memchr_P.S 1944 2009-04-01 23:12:20Z arcanum $ */

/** \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(__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__ */
