lib/libc/i386/string/strlen.s

/*
 * Copyright (c) 1993 Winning Strategies, Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by Winning Strategies, Inc.
 * 4. The name of the author may not be used to endorse or promote products
 *    derived from this software withough specific prior written permission
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 *      $Id: strlen.s,v 1.1 1993/08/16 18:40:46 jtc Exp $
 */

#if defined(LIBC_RCS) && !defined(lint)
        .asciz "$Id: strlen.s,v 1.1 1993/08/16 18:40:46 jtc Exp $"
#endif /* LIBC_RCS and not lint */

#include "DEFS.h"

/*
 * strlen (s)
 *      compute the length of the string s.
 *
 * Written by:
 *      J.T. Conklin (jtc@wimsey.com), Winning Strategies, Inc.
 */

ENTRY(strlen)
        pushl   %edi
        movl    8(%esp),%edi            /* string address */
        cld                             /* set search forward */
        xorl    %eax,%eax               /* set search for null terminator */
        movl    $-1,%ecx                /* set search for lots of characters */
        repne                           /* search! */
        scasb
        notl    %ecx                    /* get length by taking complement */
        leal    -1(%ecx),%eax           /* and subtracting one */
        popl    %edi
        ret