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/* Copyright (C) 1998 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Code contributed by Matthew Wilcox <willy@odie.barnet.ac.uk>
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <features.h>
#include <endian.h>
#include <bits/arm_asm.h>
#include <bits/arm_bx.h>
/* size_t strlen(const char *S)
* entry: r0 -> string
* exit: r0 = len
*/
.text
.global strlen
.type strlen,%function
.align 4
#if defined(THUMB1_ONLY)
/* A simple implementation for when the ARM implementation can't be used. */
.thumb_func
strlen:
mov r2, #0
1:
ldrb r1, [r0, r2]
add r2, r2, #1
cmp r1, #0
bne 1b
sub r0, r2, #1
bx lr
#else
strlen:
bic r1, r0, $3 @ addr of word containing first byte
ldr r2, [r1], $4 @ get the first word
ands r3, r0, $3 @ how many bytes are duff?
rsb r0, r3, $0 @ get - that number into counter.
beq Laligned @ skip into main check routine if no
@ more
#if __BYTE_ORDER == __BIG_ENDIAN
orr r2, r2, $0xff000000 @ set this byte to non-zero
subs r3, r3, $1 @ any more to do?
IT(t, gt)
orrgt r2, r2, $0x00ff0000 @ if so, set this byte
subs r3, r3, $1 @ more?
IT(t, gt)
orrgt r2, r2, $0x0000ff00 @ then set.
#else
orr r2, r2, $0x000000ff @ set this byte to non-zero
subs r3, r3, $1 @ any more to do?
IT(t, gt)
orrgt r2, r2, $0x0000ff00 @ if so, set this byte
subs r3, r3, $1 @ more?
IT(t, gt)
orrgt r2, r2, $0x00ff0000 @ then set.
#endif
Laligned: @ here, we have a word in r2. Does it
tst r2, $0x000000ff @ contain any zeroes?
IT(tttt, ne)
tstne r2, $0x0000ff00 @
tstne r2, $0x00ff0000 @
tstne r2, $0xff000000 @
addne r0, r0, $4 @ if not, the string is 4 bytes longer
IT(t, ne)
ldrne r2, [r1], $4 @ and we continue to the next word
bne Laligned @
Llastword: @ drop through to here once we find a
#if __BYTE_ORDER == __BIG_ENDIAN
tst r2, $0xff000000 @ word that has a zero byte in it
IT(tttt, ne)
addne r0, r0, $1 @
tstne r2, $0x00ff0000 @ and add up to 3 bytes on to it
addne r0, r0, $1 @
tstne r2, $0x0000ff00 @ (if first three all non-zero, 4th
IT(t, ne)
addne r0, r0, $1 @ must be zero)
#else
tst r2, $0x000000ff @
IT(tttt, ne)
addne r0, r0, $1 @
tstne r2, $0x0000ff00 @ and add up to 3 bytes on to it
addne r0, r0, $1 @
tstne r2, $0x00ff0000 @ (if first three all non-zero, 4th
IT(t, ne)
addne r0, r0, $1 @ must be zero)
#endif
BX(lr)
#endif
.size strlen,.-strlen
libc_hidden_def(strlen)
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