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glibc  2.9
strlen.c
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00001 /* Determine the length of a string.  For Intel 80x86, x>=3.
00002    Copyright (C) 1991,1992,1993,1996,1997,2003 Free Software Foundation, Inc.
00003    This file is part of the GNU C Library.
00004    Contributed by Torbjorn Granlund (tege@sics.se).
00005 
00006    The GNU C Library is free software; you can redistribute it and/or
00007    modify it under the terms of the GNU Lesser General Public
00008    License as published by the Free Software Foundation; either
00009    version 2.1 of the License, or (at your option) any later version.
00010 
00011    The GNU C Library is distributed in the hope that it will be useful,
00012    but WITHOUT ANY WARRANTY; without even the implied warranty of
00013    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00014    Lesser General Public License for more details.
00015 
00016    You should have received a copy of the GNU Lesser General Public
00017    License along with the GNU C Library; if not, write to the Free
00018    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00019    02111-1307 USA.  */
00020 
00021 #include <string.h>
00022 
00023 size_t
00024 strlen (const char *str)
00025 {
00026   int cnt;
00027 
00028   asm("cld\n"               /* Search forward.  */
00029       /* Some old versions of gas need `repne' instead of `repnz'.  */
00030       "repnz\n"                    /* Look for a zero byte.  */
00031       "scasb" /* %0, %1, %3 */ :
00032       "=c" (cnt) : "D" (str), "0" (-1), "a" (0));
00033 
00034   return -2 - cnt;
00035 }
00036 libc_hidden_builtin_def (strlen)