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#include <machine/asm.h> 32/* 33 * void 34 * swab (const void *src, void *dst, size_t len) 35 * copy len bytes from src to dst, swapping adjacent bytes 36 * 37 * On the i486, this code is negligibly faster than the code generated 38 * by gcc at about half the size. If my i386 databook is correct, it 39 * should be considerably faster than the gcc code on an i386. 40 * 41 * Written by: 42 * J.T. Conklin (jtc@wimsey.com), Winning Strategies, Inc. 43 */ 44 45ENTRY(swab) 46 pushl %esi 47 pushl %edi 48 movl 12(%esp),%esi 49 movl 16(%esp),%edi 50 movl 20(%esp),%ecx 51 52 cld # set direction forward 53 54 shrl $1,%ecx 55 testl $7,%ecx # copy first group of 1 to 7 words 56 jz L2 # while swaping alternate bytes. 57 .align 2,0x90 58L1: lodsw 59 rorw $8,%ax 60 stosw 61 decl %ecx 62 testl $7,%ecx 63 jnz L1 64 65L2: shrl $3,%ecx # copy remainder 8 words at a time 66 jz L4 # while swapping alternate bytes. 67 .align 2,0x90 68L3: lodsw 69 rorw $8,%ax 70 stosw 71 lodsw 72 rorw $8,%ax 73 stosw 74 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 decl %ecx 93 jnz L3 94 95L4: popl %edi 96 popl %esi 97 ret 98END(swab) 99 100 .section .note.GNU-stack,"",%progbits 101