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/*
* Copyright (c) 1993,94 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 without 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.
*
* $FreeBSD$
*/
#if defined(LIBC_RCS) && !defined(lint)
.text
.asciz "$FreeBSD$"
#endif
#include "DEFS.h"
/*
* void
* swab (const void *src, void *dst, size_t len)
* copy len bytes from src to dst, swapping adjacent bytes
*
* On the i486, this code is negligibly faster than the code generated
* by gcc at about half the size. If my i386 databook is correct, it
* should be considerably faster than the gcc code on a i386.
*
* Written by:
* J.T. Conklin (jtc@wimsey.com), Winning Strategies, Inc.
*/
ENTRY(swab)
pushl %esi
pushl %edi
movl 12(%esp),%esi
movl 16(%esp),%edi
movl 20(%esp),%ecx
cld # set direction forward
shrl $1,%ecx
testl $7,%ecx # copy first group of 1 to 7 words
jz L2 # while swaping alternate bytes.
.align 2,0x90
L1: lodsw
rorw $8,%ax
stosw
decl %ecx
testl $7,%ecx
jnz L1
L2: shrl $3,%ecx # copy remainder 8 words at a time
jz L4 # while swapping alternate bytes.
.align 2,0x90
L3: lodsw
rorw $8,%ax
stosw
lodsw
rorw $8,%ax
stosw
lodsw
rorw $8,%ax
stosw
lodsw
rorw $8,%ax
stosw
lodsw
rorw $8,%ax
stosw
lodsw
rorw $8,%ax
stosw
lodsw
rorw $8,%ax
stosw
lodsw
rorw $8,%ax
stosw
decl %ecx
jnz L3
L4: popl %edi
popl %esi
ret
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