1995-01-22 21:36:15 +00:00
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/*
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* Copyright (c) 1993,94 Winning Strategies, Inc.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by Winning Strategies, Inc.
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* 4. The name of the author may not be used to endorse or promote products
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* derived from this software without specific prior written permission
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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1995-01-23 01:30:24 +00:00
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* $Id: swab.S,v 1.1 1995/01/22 21:36:15 davidg Exp $
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1995-01-22 21:36:15 +00:00
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*/
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1995-01-23 01:30:24 +00:00
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#if defined(LIBC_RCS) && !defined(lint)
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.text
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.asciz "$Id: swab.S,v 1.1 1995/01/22 21:36:15 davidg Exp $"
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1995-01-22 21:36:15 +00:00
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#endif
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#include "DEFS.h"
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/*
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* void
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* swab (const void *src, void *dst, size_t len)
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* copy len bytes from src to dst, swapping adjacent bytes
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*
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* On the i486, this code is negligibly faster than the code generated
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* by gcc at about half the size. If my i386 databook is correct, it
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* should be considerably faster than the gcc code on a i386.
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*
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* Written by:
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* J.T. Conklin (jtc@wimsey.com), Winning Strategies, Inc.
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*/
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ENTRY(swab)
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pushl %esi
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pushl %edi
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movl 12(%esp),%esi
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movl 16(%esp),%edi
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movl 20(%esp),%ecx
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cld # set direction forward
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shrl $1,%ecx
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testl $7,%ecx # copy first group of 1 to 7 words
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jz L2 # while swaping alternate bytes.
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.align 2,0x90
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L1: lodsw
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rorw $8,%ax
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stosw
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decl %ecx
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testl $7,%ecx
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jnz L1
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L2: shrl $3,%ecx # copy remainder 8 words at a time
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jz L4 # while swapping alternate bytes.
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.align 2,0x90
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L3: lodsw
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rorw $8,%ax
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stosw
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lodsw
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rorw $8,%ax
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stosw
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lodsw
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rorw $8,%ax
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stosw
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lodsw
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rorw $8,%ax
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stosw
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lodsw
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rorw $8,%ax
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stosw
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lodsw
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rorw $8,%ax
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stosw
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lodsw
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rorw $8,%ax
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stosw
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lodsw
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rorw $8,%ax
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stosw
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decl %ecx
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jnz L3
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L4: popl %edi
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popl %esi
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ret
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