/*

 * CDDL HEADER START

 *

 * The contents of this file are subject to the terms of the

 *

 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE

 * or http://www.opensolaris.org/os/licensing.

 * See the License for the specific language governing permissions

 * and limitations under the License.

 *

 * When distributing Covered Code, include this CDDL HEADER in each

 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.

 * If applicable, add the following below this CDDL HEADER, with the

 * fields enclosed by brackets "[]" replaced with your own identifying

 * information: Portions Copyright [yyyy] [name of copyright owner]

 *

 * CDDL HEADER END

 */

/*

 * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.

 * Use is subject to license terms.

 */

/

/ strcat(s1, s2)

/

/ Concatenates s2 on the end of s1.  s1's space must be large enough.

/ Returns s1.

/

/ Fast assembly language version of the following C-program strcat

/ which represents the `standard' for the C-library.

/

/	char *

/	strcat(char *s1, const char *s2)

/	{

/		char	*os1 = s1;

/

/		while (*s1++)

/			;

/		--s1;

/		while (*s1++ = *s2++)

/			;

/		return (os1);

/	}

/

/ In this assembly language version, the following expression is used

/ to check if a 32-bit word data contains a null byte or not:

/	(((A & 0x7f7f7f7f) + 0x7f7f7f7f) | A) & 0x80808080

/ If the above expression geneates a value other than 0x80808080,

/ that means the 32-bit word data contains a null byte.

/

#include "SYS.h"

	ENTRY(strcat)

	pushl	%edi			/ save register variable

	/ find a null byte in destination string 

	movl	8(%esp), %edi		/ %edi = destination string address

	testl	$3, %edi		/ if %edi not word aligned

	jnz	.L1			/ goto .L1

	.align	4

.L2:

	movl	(%edi), %edx		/ move 1 word from (%edi) to %edx

	movl	$0x7f7f7f7f, %ecx

	andl	%edx, %ecx		/ %ecx = %edx & 0x7f7f7f7f

	addl	$4, %edi		/ next word

	addl	$0x7f7f7f7f, %ecx	/ %ecx += 0x7f7f7f7f

	orl	%edx, %ecx		/ %ecx |= %edx

	andl	$0x80808080, %ecx	/ %ecx &= 0x80808080

	cmpl	$0x80808080, %ecx	/ if no null byte in this word

	je	.L2			/ goto .L2

	subl	$4, %edi		/ post-incremented

.L1:

	cmpb	$0, (%edi)		/ if a byte in (%edi) is null

	je	.L3			/ goto .L3

	incl	%edi			/ next byte

	testl	$3, %edi		/ if %edi not word aligned

	jnz	.L1			/ goto .L1

	jmp	.L2			/ goto .L2 (%edi word aligned)

	.align	4

.L3:

	/ %edi points to a null byte in destination string

	movl	12(%esp), %eax		/ %eax = source string address

	testl	$3, %eax		/ if %eax not word aligned

	jnz	.L4			/ goto .L4

	.align	4

.L5:

	movl	(%eax), %edx		/ move 1 word from (%eax) to %edx

	movl	$0x7f7f7f7f, %ecx

	andl	%edx, %ecx		/ %ecx = %edx & 0x7f7f7f7f

	addl	$4, %eax		/ next word

	addl	$0x7f7f7f7f, %ecx	/ %ecx += 0x7f7f7f7f	

	orl	%edx, %ecx		/ %ecx |= %edx

	andl	$0x80808080, %ecx	/ %ecx &= 0x80808080

	cmpl	$0x80808080, %ecx	/ if null byte in this word

	jne	.L7			/ goto .L7

	movl	%edx, (%edi)		/ copy this word to (%edi)

	addl	$4, %edi		/ next word

	jmp	.L5			/ goto .L5

.L7:

	subl	$4, %eax		/ post-incremented

	.align	4

.L4:

	movb	(%eax), %dl		/ %dl = a byte in (%eax)

	cmpb	$0, %dl			/ compare %dl with a null byte

	movb	%dl, (%edi)		/ copy %dl to (%edi)

	je	.L6			/ if %dl is a null, goto .L6

	incl	%eax			/ next byte

	incl	%edi			/ next byte

	testl	$3, %eax		/ if %eax not word aligned

	jnz	.L4			/ goto .L4

	jmp	.L5			/ goto .L5 (%eax word aligned)

	.align	4

.L6:

	movl	8(%esp), %eax		/ return the destination address

	popl	%edi			/ restore register variable

	ret

	SET_SIZE(strcat)