1/* 2 * Copyright (c) 1993 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 withough 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 * $Id: swab.S,v 1.1 1993/10/07 00:19:37 cgd Exp $ 31 */ 32 33#if defined(LIBC_RCS) && !defined(lint) 34 .text 35 .asciz "$Id: swab.S,v 1.1 1993/10/07 00:19:37 cgd Exp $" 36#endif 37 38#include "DEFS.h" 39 40/* 41 * void 42 * swab (const void *src, void *dst, size_t len) 43 * copy len bytes from src to dst, swapping adjacent bytes 44 * 45 * On the i486, this code is negligibly faster than the code generated 46 * by gcc at about half the size. If my i386 databook is correct, it 47 * should be considerably faster than the gcc code on a i386. 48 * 49 * Written by: 50 * J.T. Conklin (jtc@wimsey.com), Winning Strategies, Inc. 51 */ 52 53ENTRY(swab) 54 pushl %esi 55 pushl %edi 56 movl 12(%esp),%esi 57 movl 16(%esp),%edi 58 movl 20(%esp),%ecx 59 shrl $1,%ecx 60 jz L4 # len = 0, jmp to func exit 61 62 cld # set direction forward 63 64 testl $7,%ecx # copy first group of 1 to 7 words 65 je L2 # while swaping alternate bytes. 66 .align 2,0x90 67L1: lodsw 68 xchgb %al,%ah 69 stosw 70 decl %ecx 71 testl $7,%ecx 72 jne L1 73 74L2: shrl $3,%ecx # copy remainder 8 words at a time 75 jz L4 # while swapping alternate bytes. 76 .align 2,0x90 77L3: lodsw 78 xchgb %al,%ah 79 stosw 80 lodsw 81 xchgb %al,%ah 82 stosw 83 lodsw 84 xchgb %al,%ah 85 stosw 86 lodsw 87 xchgb %al,%ah 88 stosw 89 lodsw 90 xchgb %al,%ah 91 stosw 92 lodsw 93 xchgb %al,%ah 94 stosw 95 lodsw 96 xchgb %al,%ah 97 stosw 98 lodsw 99 xchgb %al,%ah 100 stosw 101 decl %ecx 102 jnz L3 103 104L4: 105 popl %edi 106 popl %esi 107 ret 108