1 /* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License, Version 1.0 only 6 * (the "License"). You may not use this file except in compliance 7 * with the License. 8 * 9 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 10 * or http://www.opensolaris.org/os/licensing. 11 * See the License for the specific language governing permissions 12 * and limitations under the License. 13 * 14 * When distributing Covered Code, include this CDDL HEADER in each 15 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 16 * If applicable, add the following below this CDDL HEADER, with the 17 * fields enclosed by brackets "[]" replaced with your own identifying 18 * information: Portions Copyright [yyyy] [name of copyright owner] 19 * 20 * CDDL HEADER END 21 * 22 * Copyright 2000 Sun Microsystems, Inc. All rights reserved. 23 * Use is subject to license terms. 24 */ 25 26 /* 27 * 28 * Start of crcmodel.c 29 * 30 * 31 * Author : Ross Williams (ross@guest.adelaide.edu.au.). 32 * Date : 3 June 1993. 33 * Status : Public domain. 34 * 35 * Description : This is the implementation (.c) file for the reference 36 * implementation of the Rocksoft^tm Model CRC Algorithm. For more 37 * information on the Rocksoft^tm Model CRC Algorithm, see the document 38 * titled "A Painless Guide to CRC Error Detection Algorithms" by Ross 39 * Williams (ross@guest.adelaide.edu.au.). This document is likely to be in 40 * "ftp.adelaide.edu.au/pub/rocksoft". 41 * 42 * Note: Rocksoft is a trademark of Rocksoft Pty Ltd, Adelaide, Australia. 43 * 44 * 45 * 46 * Implementation Notes 47 * -------------------- 48 * To avoid inconsistencies, the specification of each function is not echoed 49 * here. See the header file for a description of these functions. 50 * This package is light on checking because I want to keep it short and 51 * simple and portable (i.e. it would be too messy to distribute my entire 52 * C culture (e.g. assertions package) with this package. 53 * 54 * 55 */ 56 57 #include "crcmodel.h" 58 59 /* The following definitions make the code more readable. */ 60 61 #define BITMASK(X) (1L << (X)) 62 #define MASK32 0xFFFFFFFFL 63 #define LOCAL static 64 65 LOCAL uint32_t reflect P_((uint32_t v, int b)); 66 LOCAL uint32_t 67 reflect(v, b) 68 /* Returns the value v with the bottom b [0,32] bits reflected. */ 69 /* Example: reflect(0x3e23L,3) == 0x3e26 */ 70 uint32_t v; 71 int b; 72 { 73 int i; 74 uint32_t t = v; 75 for (i = 0; i < b; i++) { 76 if (t & 1L) 77 v |= BITMASK((b-1)-i); 78 else 79 v &= ~BITMASK((b-1)-i); 80 t >>= 1; 81 } 82 return (v); 83 } 84 85 LOCAL uint32_t widmask P_((p_cm_t)); 86 LOCAL uint32_t 87 widmask(p_cm) 88 /* Returns a longword whose value is (2^p_cm->cm_width)-1. */ 89 /* The trick is to do this portably (e.g. without doing <<32). */ 90 p_cm_t p_cm; 91 { 92 return ((((1L<<(p_cm->cm_width-1))-1L)<<1)|1L); 93 } 94 95 void 96 cm_ini(p_cm) 97 p_cm_t p_cm; 98 { 99 p_cm->cm_reg = p_cm->cm_init; 100 } 101 102 void 103 cm_nxt(p_cm, ch) 104 p_cm_t p_cm; 105 int ch; 106 { 107 int i; 108 uint32_t uch = (uint32_t)ch; 109 uint32_t topbit = BITMASK(p_cm->cm_width-1); 110 111 if (p_cm->cm_refin) 112 uch = reflect(uch, 8); 113 114 p_cm->cm_reg ^= (uch << (p_cm->cm_width-8)); 115 for (i = 0; i < 8; i++) { 116 if (p_cm->cm_reg & topbit) 117 p_cm->cm_reg = (p_cm->cm_reg << 1) ^ p_cm->cm_poly; 118 else 119 p_cm->cm_reg <<= 1; 120 121 p_cm->cm_reg &= widmask(p_cm); 122 } 123 } 124 125 void 126 cm_blk(p_cm, blk_adr, blk_len) 127 p_cm_t p_cm; 128 p_ubyte_ blk_adr; 129 uint32_t blk_len; 130 { 131 while (blk_len--) 132 cm_nxt(p_cm, *blk_adr++); 133 } 134 135 uint32_t 136 cm_crc(p_cm) 137 p_cm_t p_cm; 138 { 139 if (p_cm->cm_refot) 140 return (p_cm->cm_xorot ^ reflect(p_cm->cm_reg, p_cm->cm_width)); 141 else 142 return (p_cm->cm_xorot ^ p_cm->cm_reg); 143 } 144 145 uint32_t 146 cm_tab(p_cm, index) 147 p_cm_t p_cm; 148 int index; 149 { 150 int i; 151 uint32_t r; 152 uint32_t topbit = BITMASK(p_cm->cm_width-1); 153 uint32_t inbyte = (uint32_t)index; 154 155 if (p_cm->cm_refin) 156 inbyte = reflect(inbyte, 8); 157 158 r = inbyte << (p_cm->cm_width-8); 159 for (i = 0; i < 8; i++) 160 if (r & topbit) 161 r = (r << 1) ^ p_cm->cm_poly; 162 else 163 r <<= 1; 164 165 if (p_cm->cm_refin) 166 r = reflect(r, p_cm->cm_width); 167 168 return (r & widmask(p_cm)); 169 } 170