/*
 * 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.
 */

#include <machine/asm.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 an 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
END(swab)

        .section .note.GNU-stack,"",%progbits