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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, write to the Free
- Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
- 02111-1307 USA. */
- #include <endian.h>
- #include <sys/syscall.h>
- /* size_t strlen(const char *S)
- * entry: r0 -> string
- * exit: r0 = len
- */
- .text
- .global strlen;
- .type strlen,%function
- .align 4; \
- 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?
- orrgt r2, r2, $0x00ff0000 @ if so, set this byte
- subs r3, r3, $1 @ more?
- 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?
- orrgt r2, r2, $0x0000ff00 @ if so, set this byte
- subs r3, r3, $1 @ more?
- orrgt r2, r2, $0x00ff0000 @ then set.
- #endif
- Laligned: @ here, we have a word in r2. Does it
- tst r2, $0x000000ff @ contain any zeroes?
- tstne r2, $0x0000ff00 @
- tstne r2, $0x00ff0000 @
- tstne r2, $0xff000000 @
- addne r0, r0, $4 @ if not, the string is 4 bytes longer
- ldrne r2, [r1], $4 @ and we continue to the next word
- bne Laligned @
- Llastword: @ drop through to here once we find a
- tst r2, $0x000000ff @ word that has a zero byte in it
- 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
- addne r0, r0, $1 @ must be zero)
- mov pc,lr
- .size strlen,.-strlen;
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