1/* Copyright (C) 1998 Free Software Foundation, Inc.
2   This file is part of the GNU C Library.
3   Code contributed by Matthew Wilcox <willy@odie.barnet.ac.uk>
4
5   The GNU C Library is free software; you can redistribute it and/or
6   modify it under the terms of the GNU Lesser General Public
7   License as published by the Free Software Foundation; either
8   version 2.1 of the License, or (at your option) any later version.
9
10   The GNU C Library is distributed in the hope that it will be useful,
11   but WITHOUT ANY WARRANTY; without even the implied warranty of
12   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13   Lesser General Public License for more details.
14
15   You should have received a copy of the GNU Lesser General Public
16   License along with the GNU C Library; if not, see
17   <http://www.gnu.org/licenses/>.  */
18
19#include <features.h>
20#include <endian.h>
21#include <bits/arm_asm.h>
22#include <bits/arm_bx.h>
23
24/* size_t strlen(const char *S)
25 * entry: r0 -> string
26 * exit: r0 = len
27 */
28
29.text
30.global strlen
31.type strlen,%function
32.align 4
33
34#if defined(THUMB1_ONLY)
35/* A simple implementation for when the ARM implementation can't be used.  */
36.thumb_func
37strlen:
38	mov r2, #0
391:
40	ldrb	r1, [r0, r2]
41	add	r2, r2, #1
42	cmp	r1, #0
43	bne	1b
44	sub	r0, r2, #1
45	bx lr
46#else
47strlen:
48	bic     r1, r0, $3              @ addr of word containing first byte
49	ldr     r2, [r1], $4            @ get the first word
50	ands    r3, r0, $3              @ how many bytes are duff?
51	rsb     r0, r3, $0              @ get - that number into counter.
52	beq     Laligned                @ skip into main check routine if no
53					@ more
54#if __BYTE_ORDER == __BIG_ENDIAN
55	orr     r2, r2, $0xff000000     @ set this byte to non-zero
56	subs    r3, r3, $1              @ any more to do?
57	IT(t, gt)
58	orrgt   r2, r2, $0x00ff0000     @ if so, set this byte
59	subs    r3, r3, $1              @ more?
60	IT(t, gt)
61	orrgt   r2, r2, $0x0000ff00     @ then set.
62#else
63	orr     r2, r2, $0x000000ff     @ set this byte to non-zero
64	subs    r3, r3, $1              @ any more to do?
65	IT(t, gt)
66	orrgt   r2, r2, $0x0000ff00     @ if so, set this byte
67	subs    r3, r3, $1              @ more?
68	IT(t, gt)
69	orrgt   r2, r2, $0x00ff0000     @ then set.
70#endif
71Laligned:				@ here, we have a word in r2.  Does it
72	tst     r2, $0x000000ff         @ contain any zeroes?
73	IT(tttt, ne)
74	tstne   r2, $0x0000ff00         @
75	tstne   r2, $0x00ff0000         @
76	tstne   r2, $0xff000000         @
77	addne   r0, r0, $4              @ if not, the string is 4 bytes longer
78	IT(t, ne)
79	ldrne   r2, [r1], $4            @ and we continue to the next word
80	bne     Laligned                @
81Llastword:				@ drop through to here once we find a
82#if __BYTE_ORDER == __BIG_ENDIAN
83	tst     r2, $0xff000000         @ word that has a zero byte in it
84	IT(tttt, ne)
85	addne   r0, r0, $1              @
86	tstne   r2, $0x00ff0000         @ and add up to 3 bytes on to it
87	addne   r0, r0, $1              @
88	tstne   r2, $0x0000ff00         @ (if first three all non-zero, 4th
89	IT(t, ne)
90	addne   r0, r0, $1              @  must be zero)
91#else
92	tst     r2, $0x000000ff         @
93	IT(tttt, ne)
94	addne   r0, r0, $1              @
95	tstne   r2, $0x0000ff00         @ and add up to 3 bytes on to it
96	addne   r0, r0, $1              @
97	tstne   r2, $0x00ff0000         @ (if first three all non-zero, 4th
98	IT(t, ne)
99	addne   r0, r0, $1              @  must be zero)
100#endif
101	BX(lr)
102#endif
103
104.size strlen,.-strlen
105
106libc_hidden_def(strlen)
107