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__FBSDID("$FreeBSD$"); 33 34/* 35 * void 36 * swab (const void *src, void *dst, size_t len) 37 * copy len bytes from src to dst, swapping adjacent bytes 38 * 39 * On the i486, this code is negligibly faster than the code generated 40 * by gcc at about half the size. If my i386 databook is correct, it 41 * should be considerably faster than the gcc code on an i386. 42 * 43 * Written by: 44 * J.T. Conklin (jtc@wimsey.com), Winning Strategies, Inc. 45 */ 46 47ENTRY(swab) 48 pushl %esi 49 pushl %edi 50 movl 12(%esp),%esi 51 movl 16(%esp),%edi 52 movl 20(%esp),%ecx 53 54 cld # set direction forward 55 56 shrl $1,%ecx 57 testl $7,%ecx # copy first group of 1 to 7 words 58 jz L2 # while swaping alternate bytes. 59 .align 2,0x90 60L1: lodsw 61 rorw $8,%ax 62 stosw 63 decl %ecx 64 testl $7,%ecx 65 jnz L1 66 67L2: shrl $3,%ecx # copy remainder 8 words at a time 68 jz L4 # while swapping alternate bytes. 69 .align 2,0x90 70L3: lodsw 71 rorw $8,%ax 72 stosw 73 lodsw 74 rorw $8,%ax 75 stosw 76 lodsw 77 rorw $8,%ax 78 stosw 79 lodsw 80 rorw $8,%ax 81 stosw 82 lodsw 83 rorw $8,%ax 84 stosw 85 lodsw 86 rorw $8,%ax 87 stosw 88 lodsw 89 rorw $8,%ax 90 stosw 91 lodsw 92 rorw $8,%ax 93 stosw 94 decl %ecx 95 jnz L3 96 97L4: popl %edi 98 popl %esi 99 ret 100END(swab) 101 102 .section .note.GNU-stack,"",%progbits 103