bzero.S revision 1849 
1118824Sharti/*
2118824Sharti * Copyright (c) 1993 Winning Strategies, Inc.
3118824Sharti * All rights reserved.
4119075Sobrien *
5118824Sharti * Redistribution and use in source and binary forms, with or without
6118824Sharti * modification, are permitted provided that the following conditions
7119075Sobrien * are met:
8265420Simp * 1. Redistributions of source code must retain the above copyright
9226440Scognet *    notice, this list of conditions and the following disclaimer.
10118824Sharti * 2. Redistributions in binary form must reproduce the above copyright
11270027Sngie *    notice, this list of conditions and the following disclaimer in the
12118824Sharti *    documentation and/or other materials provided with the distribution.
13290083Sbdrewery * 3. All advertising materials mentioning features or use of this software
14129215Scognet *    must display the following acknowledgement:
15133565Sharti *      This product includes software developed by Winning Strategies, Inc.
16133565Sharti * 4. The name of the author may not be used to endorse or promote products
17270027Sngie *    derived from this software withough specific prior written permission
18270027Sngie *
19270027Sngie * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
20275030Sbapt * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
21226440Scognet * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
22275030Sbapt * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
23226440Scognet * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
24133565Sharti * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25133565Sharti * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26133565Sharti * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27133565Sharti * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
28211725Simp * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29211725Simp *
30129215Scognet *	$Id: bzero.S,v 1.1 1993/12/05 13:01:42 ats Exp $
31129215Scognet */
32118824Sharti
33133565Sharti#if defined(LIBC_RCS) && !defined(lint)
34290083Sbdrewery        .asciz "$Id: bzero.S,v 1.1 1993/12/05 13:01:42 ats Exp $"
35118824Sharti#endif /* LIBC_RCS and not lint */
36133565Sharti
37143617Sharti#include "DEFS.h"
38133565Sharti
39270027Sngie/*
40133565Sharti * bzero (void *b, size_t len)
41270027Sngie *	write len zero bytes to the string b.
42133565Sharti *
43118824Sharti * Written by:
44 *	J.T. Conklin (jtc@wimsey.com), Winning Strategies, Inc.
45 */
46
47ENTRY(bzero)
48	pushl	%edi
49	pushl	%ebx
50	movl	12(%esp),%edi
51	movl	16(%esp),%ecx
52
53	cld				/* set fill direction forward */
54	xorl	%eax,%eax		/* set fill data to 0 */
55
56	/*
57	 * if the string is too short, it's really not worth the overhead
58	 * of aligning to word boundries, etc.  So we jump to a plain
59	 * unaligned set.
60	 */
61	cmpl	$0x0f,%ecx
62	jle	L1
63
64	movl	%edi,%edx		/* compute misalignment */
65	negl	%edx
66	andl	$3,%edx
67	movl	%ecx,%ebx
68	subl	%edx,%ebx
69
70	movl	%edx,%ecx		/* zero until word aligned */
71	rep
72	stosb
73
74	movl	%ebx,%ecx		/* zero by words */
75	shrl	$2,%ecx
76	rep
77	stosl
78
79	movl	%ebx,%ecx
80	andl	$3,%ecx			/* zero remainder by bytes */
81L1:	rep
82	stosb
83
84	popl	%ebx
85	popl	%edi
86	ret
87