1/* 2 * Copyright (c) 1993,94 Winning Strategies, Inc. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by Winning Strategies, Inc. 16 * 4. The name of the author may not be used to endorse or promote products 17 * derived from this software without specific prior written permission 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 20 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 21 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 22 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 23 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 24 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 28 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 29 */ 30 31#if defined(LIBC_RCS) && !defined(lint) 32 .text 33 .asciz "$FreeBSD$" 34#endif 35 36#include <machine/asm.h> 37 38/* 39 * void 40 * swab (const void *src, void *dst, size_t len) 41 * copy len bytes from src to dst, swapping adjacent bytes 42 * 43 * On the i486, this code is negligibly faster than the code generated 44 * by gcc at about half the size. If my i386 databook is correct, it 45 * should be considerably faster than the gcc code on a i386. 46 * 47 * Written by: 48 * J.T. Conklin (jtc@wimsey.com), Winning Strategies, Inc. 49 */ 50 51ENTRY(swab) 52 pushl %esi 53 pushl %edi 54 movl 12(%esp),%esi 55 movl 16(%esp),%edi 56 movl 20(%esp),%ecx 57 58 cld # set direction forward 59 60 shrl $1,%ecx 61 testl $7,%ecx # copy first group of 1 to 7 words 62 jz L2 # while swaping alternate bytes. 63 .align 2,0x90 64L1: lodsw 65 rorw $8,%ax 66 stosw 67 decl %ecx 68 testl $7,%ecx 69 jnz L1 70 71L2: shrl $3,%ecx # copy remainder 8 words at a time 72 jz L4 # while swapping alternate bytes. 73 .align 2,0x90 74L3: lodsw 75 rorw $8,%ax 76 stosw 77 lodsw 78 rorw $8,%ax 79 stosw 80 lodsw 81 rorw $8,%ax 82 stosw 83 lodsw 84 rorw $8,%ax 85 stosw 86 lodsw 87 rorw $8,%ax 88 stosw 89 lodsw 90 rorw $8,%ax 91 stosw 92 lodsw 93 rorw $8,%ax 94 stosw 95 lodsw 96 rorw $8,%ax 97 stosw 98 decl %ecx 99 jnz L3 100 101L4: popl %edi 102 popl %esi 103 ret 104