/*

 * 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 2005 Sun Microsystems, Inc.  All rights reserved.

 * Use is subject to license terms.

 */

/

/ strcpy(s1, s2)

/

/ Copies string s2 to s1.  s1 must be large enough.

/ Returns s1

/

/

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

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

/

/	char *

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

/	{

/		char	*os1 = 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(strcpy)

	push	%edi				/ save reg as per calling cvntn

	mov	12(%esp), %ecx			/ src ptr

	mov	8(%esp), %edi			/ dst ptr

	mov	%ecx, %eax			/ src

	sub	%edi, %ecx			/ src - dst

	and	$3, %eax			/ check src alignment

	jz	load

	sub	$4, %eax

byte_loop:

	movb	(%edi, %ecx, 1), %dl		/ load src byte

	movb	%dl, (%edi)			/ load dest byte

	inc	%edi				/ increment src and dest

	testb	%dl, %dl			/ is src zero?

	jz 	done

	inc	%eax				/ check src alignment

	jnz	byte_loop

	jmp 	load

store:

	mov	%eax, (%edi)			/ store word

	add	$4, %edi			/ incrment src and dest by 4

load:

	mov	(%edi, %ecx, 1), %eax		/ load word

	lea	-0x01010101(%eax), %edx		/ (word - 0x01010101)

	not	%eax				/ ~word

	and	%eax, %edx			/ (word - 0x01010101) & ~word

	not	%eax				/ word

	and	$0x80808080, %edx	/ (wd - 0x01010101) & ~wd & 0x80808080

	jz	store				/ store word w/o zero byte

has_zero_byte:

	movb	%al, (%edi)			/ store first byte

	testb	%al, %al			/ check first byte for zero

	jz	done

	movb	%ah, 1(%edi)			/ continue storing and checking

	testb	%ah, %ah

	jz	done

	shr	$16, %eax			/ grab last two bytes

	movb	%al, 2(%edi)

	testb	%al, %al

	jz	done

	movb	%ah, 3(%edi)

done:

	mov	8(%esp), %eax			/ return ptr to dest

	pop	%edi				/ restore as per calling cvntn

	ret

	SET_SIZE(strcpy)