sysdeps/i386/strlen.c

   1 /* strlen -- determine the length of a string.
   2    For Intel 80x86, x>=3.
   3    Copyright (C) 1991, 1992, 1993 Free Software Foundation, Inc.
   4    Contributed by Torbjorn Granlund (tege@sics.se).
   5
   6 The GNU C Library is free software; you can redistribute it and/or
   7 modify it under the terms of the GNU Library General Public License as
   8 published by the Free Software Foundation; either version 2 of the
   9 License, or (at your option) any later version.
  10
  11 The GNU C Library is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 Library General Public License for more details.
  15
  16 You should have received a copy of the GNU Library General Public
  17 License along with the GNU C Library; see the file COPYING.LIB.  If
  18 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  19 Cambridge, MA 02139, USA.  */
  20
  21 #include <ansidecl.h>
  22 #include <string.h>
  23
  24 size_t
  25 DEFUN(strlen, (str), CONST char *str)
  26 {
  27   int cnt;
  28
  29   asm("cld\n"                   /* Search forward.  */
  30       /* Some old versions of gas need `repne' instead of `repnz'.  */
  31       "repnz\n"                 /* Look for a zero byte.  */
  32       "scasb" /* %0, %1, %3 */ :
  33       "=c" (cnt) : "D" (str), "0" (-1), "a" (0));
  34
  35   return -2 - cnt;
  36 }