diff options
Diffstat (limited to 'sysdeps/arm/strlen.S')
| -rw-r--r-- | sysdeps/arm/strlen.S | 55 |
1 files changed, 55 insertions, 0 deletions
diff --git a/sysdeps/arm/strlen.S b/sysdeps/arm/strlen.S new file mode 100644 index 0000000..9acef4f --- /dev/null +++ b/sysdeps/arm/strlen.S @@ -0,0 +1,55 @@ +/* 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 Library General Public License as + published by the Free Software Foundation; either version 2 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 + Library General Public License for more details. + + You should have received a copy of the GNU Library General Public + License along with the GNU C Library; see the file COPYING.LIB. If not, + write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, + Boston, MA 02111-1307, USA. */ + +#include <sysdep.h> + +/* size_t strlen(const char *S) + * entry: r0 -> string + * exit: r0 = len + */ + +ENTRY(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 + 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. +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) + RETINSTR(mov,pc,lr) +END(strlen) |