1/* Copyright (c) 2002, 2007 Marek Michalkiewicz
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: strnlen.S 1944 2009-04-01 23:12:20Z arcanum $ */
30
31/** \file */
32/** \ingroup avr_string
33    \fn size_t strnlen(const char *src, size_t len)
34    \brief Determine the length of a fixed-size string.
35
36    The strnlen function returns the number of characters in the string
37    pointed to by src, not including the terminating '\\0' character, but at
38    most len. In doing this, strnlen looks only at the first len characters at
39    src and never beyond src+len.
40
41    \returns The strnlen function returns strlen(src), if that is less than
42    len, or len if there is no '\\0' character among the first len
43    characters pointed to by src. */
44
45#if !defined(__DOXYGEN__)
46
47#include "macros.inc"
48
49#define src_hi r25
50#define src_lo r24
51#define len_hi r23
52#define len_lo r22
53
54	ASSEMBLY_CLIB_SECTION
55	.global	_U(strnlen)
56	.type	_U(strnlen), @function
57_U(strnlen):
58	X_movw	ZL, src_lo
59.L_strnlen_loop:
60	subi	len_lo, lo8(1)
61	sbci	len_hi, hi8(1)
62	ld	__tmp_reg__, Z+
63	cpse	__tmp_reg__, __zero_reg__
64	brcc	.L_strnlen_loop
65; Z points one character past the terminating NUL
66; return Z - 1 - src = (-1 - src) + Z = ~src + Z
67	com	src_lo
68	com	src_hi
69	add	src_lo, ZL
70	adc	src_hi, ZH
71	ret
72.L_strnlen_end:
73	.size	_U(strnlen), .L_strnlen_end - _U(strnlen)
74
75#endif /* not __DOXYGEN__ */
76