sysdeps/i386/strlen.c

   1 /* Determine the length of a string.  For Intel 80x86, x>=3.
   2    Copyright (C) 1991, 1992, 1993, 1996, 1997 Free Software Foundation, Inc.
   3    Contributed by Torbjorn Granlund (tege@sics.se).
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #include <string.h>
  21
  22 size_t
  23 strlen (const char *str)
  24 {
  25   int cnt;
  26
  27   asm("cld\n"                   /* Search forward.  */
  28       /* Some old versions of gas need `repne' instead of `repnz'.  */
  29       "repnz\n"                 /* Look for a zero byte.  */
  30       "scasb" /* %0, %1, %3 */ :
  31       "=c" (cnt) : "D" (str), "0" (-1), "a" (0));
  32
  33   return -2 - cnt;
  34 }