1/* Copyright (c) 2007  Dmitry Xmelkov
2   All rights reserved.
3
4   Redistribution and use in source and binary forms, with or without
5   modification, are permitted provided that the following conditions are met:
6
7   * Redistributions of source code must retain the above copyright
8     notice, this list of conditions and the following disclaimer.
9   * Redistributions in binary form must reproduce the above copyright
10     notice, this list of conditions and the following disclaimer in
11     the documentation and/or other materials provided with the
12     distribution.
13   * Neither the name of the copyright holders nor the names of
14     contributors may be used to endorse or promote products derived
15     from this software without specific prior written permission.
16
17  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
18  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
21  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
22  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
23  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
24  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
25  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
26  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
27  POSSIBILITY OF SUCH DAMAGE. */
28
29/* $Id: memrchr.S 2191 2010-11-05 13:45:57Z arcanum $ */
30
31/** \file */
32/** \ingroup avr_string
33    \fn void *memrchr(const void *src, int val, size_t len)
34
35    The memrchr() function is like the memchr() function, except that it
36    searches backwards from the end of the \p len bytes pointed to by \p
37    src instead of forwards from the front. (Glibc, GNU extension.)
38
39    \return The memrchr() function returns a pointer to the matching
40    byte or \c NULL if the character does not occur in the given memory
41    area.	*/
42
43#if !defined(__AVR_TINY__)
44
45#if !defined(__DOXYGEN__)
46
47#include "asmdef.h"
48
49#define src_hi	r25
50#define src_lo	r24
51#define val	r22
52#define len_hi	r21
53#define len_lo	r20
54
55#define ret_lo	r24
56
57ENTRY memrchr
58	X_movw	ZL, len_lo
59	adiw	ZL, 0
60	breq	2f			; len is 0, return NULL
61	add	ZL, src_lo
62	adc	ZH, src_hi
63
641:	ld	r0, -Z
65	cp	r0, val
66	breq	2f			; val is found
67	subi	len_lo, lo8(1)
68	sbci	len_hi, hi8(1)
69	brne	1b
70
71	X_movw	ZL, len_lo		; is zero
722:	X_movw	ret_lo, ZL
73	ret
74ENDFUNC
75
76#endif /* not __DOXYGEN__ */
77
78#endif /* !defined(__AVR_TINY__) */
79