1/*******************************************************************************
2 *
3 * Copyright (c) 1993 Intel Corporation
4 *
5 * Intel hereby grants you permission to copy, modify, and distribute this
6 * software and its documentation.  Intel grants this permission provided
7 * that the above copyright notice appears in all copies and that both the
8 * copyright notice and this permission notice appear in supporting
9 * documentation.  In addition, Intel grants this permission provided that
10 * you prominently mark as "not part of the original" any modifications
11 * made to this software or documentation, and that the name of Intel
12 * Corporation not be used in advertising or publicity pertaining to
13 * distribution of the software or the documentation without specific,
14 * written prior permission.
15 *
16 * Intel Corporation provides this AS IS, WITHOUT ANY WARRANTY, EXPRESS OR
17 * IMPLIED, INCLUDING, WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY
18 * OR FITNESS FOR A PARTICULAR PURPOSE.  Intel makes no guarantee or
19 * representations regarding the use of, or the results of the use of,
20 * the software and documentation in terms of correctness, accuracy,
21 * reliability, currentness, or otherwise; and you rely on the software,
22 * documentation and results solely at your own risk.
23 *
24 * IN NO EVENT SHALL INTEL BE LIABLE FOR ANY LOSS OF USE, LOSS OF BUSINESS,
25 * LOSS OF PROFITS, INDIRECT, INCIDENTAL, SPECIAL OR CONSEQUENTIAL DAMAGES
26 * OF ANY KIND.  IN NO EVENT SHALL INTEL'S TOTAL LIABILITY EXCEED THE SUM
27 * PAID TO INTEL FOR THE PRODUCT LICENSED HEREUNDER.
28 *
29 ******************************************************************************/
30
31	.file "strlen.s"
32#ifdef	__PIC
33	.pic
34#endif
35#ifdef	__PID
36	.pid
37#endif
38
39/*
40 * (c) copyright 1988,1993 Intel Corp., all rights reserved
41 */
42
43/*
44	procedure strlen  (optimized assembler version for the 80960K series)
45
46	src_addr = strlen (src_addr)
47
48	return the number of bytes that precede the null byte in the
49	string pointed to by src_addr.
50
51	Undefined behavior will occur if the end of the source string (i.e.
52	the terminating null byte) is in the last four words of the program's
53	allocated memory space.  This is so because strlen fetches ahead
54	several words.  Disallowing the fetch ahead would impose a severe
55	performance penalty.
56
57	Strategy:
58
59	Fetch the source array by long-words and scanbyte the words for the
60	null byte until found.  Examine the word in which the null byte is
61	found, to determine its actual position, and return the length.
62
63	Tactics:
64
65	1) Do NOT try to fetch the words in a word aligned manner because,
66	in my judgement, the performance degradation experienced due to
67	non-aligned accesses does NOT outweigh the time and complexity added
68	by the preamble that would be necessary to assure alignment.  This
69	is supported by the intuition that many source strings will be word
70	aligned to begin with.
71*/
72
73	.globl	_strlen
74	.globl	__strlen
75	.leafproc	_strlen, __strlen
76	.align	2
77_strlen:
78#ifndef __PIC
79	lda 	Lrett,g14
80#else
81	lda 	Lrett-(.+8)(ip),g14
82#endif
83__strlen:
84
85	mov	g14,g13		# preserve return address
86	ldl	(g0),g4		# fetch first two words
87	addo	8,g0,g2		# post-increment src word pointer
88	lda	0xff,g3		# byte extraction mask
89
90
91Lsearch_for_word_with_null_byte:
92	scanbyte 0,g4		# check for null byte
93	mov	g5,g7		# copy second word
94	bo.f	Lsearch_for_null	# branch if null found
95	scanbyte 0,g7		# check for null byte
96	ldl	(g2),g4		# fetch next pair of word of src
97	addo	8,g2,g2		# post-increment src word pointer
98	bno	Lsearch_for_word_with_null_byte	# branch if null not found yet
99
100	subo	4,g2,g2		# back up the byte pointer
101	mov	g7,g4		# move word with null to search word
102Lsearch_for_null:
103	subo	9,g2,g2		# back up the byte pointer
104Lsearch_for_null.a:
105	and	g4,g3,g14	# extract byte
106	cmpo	0,g14		# is it null?
107	addo	1,g2,g2		# bump src byte ptr
108	shro	8,g4,g4		# shift word to position next byte
109	bne	Lsearch_for_null.a
110
111Lexit_code:
112	subo	g0,g2,g0	# calculate string length
113	bx	(g13)		# g0 = addr of src;  g14 = 0
114Lrett:
115	ret
116
117/* end of strlen */
118