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
reflect(v,b)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
widmask(p_cm)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
cm_ini(p_cm)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
cm_nxt(p_cm,ch)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
cm_blk(p_cm,blk_adr,blk_len)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
cm_crc(p_cm)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
cm_tab(p_cm,index)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