/*
* Copyright (c) 2006 Apple Computer, Inc. All rights reserved.
*
* @APPLE_LICENSE_HEADER_START@
*
* This file contains Original Code and/or Modifications of Original Code
* as defined in and that are subject to the Apple Public Source License
* Version 2.0 (the 'License'). You may not use this file except in
* compliance with the License. Please obtain a copy of the License at
* http://www.opensource.apple.com/apsl/ and read it before using this
* file.
*
* The Original Code and all software distributed under the License are
* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
* Please see the License for the specific language governing rights and
* limitations under the License.
*
* @APPLE_LICENSE_HEADER_END@
*/
.text
.align 2
.globl _strlen
/* size_t strlen(const char *s) /* save the original pointer */
mov r12, r0
/* see if the string is aligned */
ands r3, r0, #3
/* load the first word, address rounded down */
bic r0, r0, #3
ldr r2, [r0], #4
/* skip the next part if the string is already aligned */
beq Laligned
Lunaligned:
/* unaligned pointer, mask out the bytes that we've read that we should be ignoring */
cmp r3, #2
orr r2, r2, #0x000000ff
orrge r2, r2, #0x0000ff00
orrgt r2, r2, #0x00ff0000
Laligned:
/* load 0x01010101 into r1 */
mov r1, #0x01
orr r1, r1, r1, lsl #8
orr r1, r1, r1, lsl #16
Laligned_loop:
/* ((x - 0x01010101) & ~x & 0x80808080) == hasnull(word) */
sub r3, r2, r1 /* x - 0x01010101 */
bic r3, r3, r2 /* above & ~x */
tst r3, r1, lsl #7 /* above & 0x80808080 */
ldreq r2, [r0], #4 /* load next word */
beq Laligned_loop
/* we found a nullbyte */
/* r0 (ptr) has overshot by up to 4 bytes, so subtract off until we find a nullbyte */
sub r0, r0, #1
tst r2, #0x000000ff
subeq r0, r0, #1
tstne r2, #0x0000ff00
subeq r0, r0, #1
tstne r2, #0x00ff0000
subeq r0, r0, #1
Lexit:
/* len = ptr - original pointer */
sub r0, r0, r12
bx lr