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 (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21
22 /*
23 * Copyright 2009 Sun Microsystems, Inc. All rights reserved.
24 * Use is subject to license terms.
25 */
26
27 /*
28 *
29 * Start of crcmodel.c
30 *
31 *
32 * Author : Ross Williams (ross@guest.adelaide.edu.au.).
33 * Date : 3 June 1993.
34 * Status : Public domain.
35 *
36 * Description : This is the implementation (.c) file for the reference
37 * implementation of the Rocksoft^tm Model CRC Algorithm. For more
38 * information on the Rocksoft^tm Model CRC Algorithm, see the document
39 * titled "A Painless Guide to CRC Error Detection Algorithms" by Ross
40 * Williams (ross@guest.adelaide.edu.au.). This document is likely to be in
41 * "ftp.adelaide.edu.au/pub/rocksoft".
42 *
43 * Note: Rocksoft is a trademark of Rocksoft Pty Ltd, Adelaide, Australia.
44 *
45 *
46 *
47 * Implementation Notes
48 * --------------------
49 * To avoid inconsistencies, the specification of each function is not echoed
50 * here. See the header file for a description of these functions.
51 * This package is light on checking because I want to keep it short and
52 * simple and portable (i.e. it would be too messy to distribute my entire
53 * C culture (e.g. assertions package) with this package.
54 *
55 *
56 */
57
58 #include "crcmodel.h"
59
60 /* The following definitions make the code more readable. */
61
62 #define BITMASK(X) (1L << (X))
63 #define MASK32 0xFFFFFFFFL
64 #define LOCAL static
65
66 LOCAL uint32_t reflect P_((uint32_t v, int b));
67 LOCAL uint32_t
reflect(v,b)68 reflect(v, b)
69 /* Returns the value v with the bottom b [0,32] bits reflected. */
70 /* Example: reflect(0x3e23L,3) == 0x3e26 */
71 uint32_t v;
72 int b;
73 {
74 int i;
75 uint32_t t = v;
76 for (i = 0; i < b; i++) {
77 if (t & 1L)
78 v |= BITMASK((b-1)-i);
79 else
80 v &= ~BITMASK((b-1)-i);
81 t >>= 1;
82 }
83 return (v);
84 }
85
86 LOCAL uint32_t widmask P_((p_cm_t));
87 LOCAL uint32_t
widmask(p_cm)88 widmask(p_cm)
89 /* Returns a longword whose value is (2^p_cm->cm_width)-1. */
90 /* The trick is to do this portably (e.g. without doing <<32). */
91 p_cm_t p_cm;
92 {
93 return ((((1L<<(p_cm->cm_width-1))-1L)<<1)|1L);
94 }
95
96 void
cm_ini(p_cm)97 cm_ini(p_cm)
98 p_cm_t p_cm;
99 {
100 p_cm->cm_reg = p_cm->cm_init;
101 }
102
103 void
cm_nxt(p_cm,ch)104 cm_nxt(p_cm, ch)
105 p_cm_t p_cm;
106 int ch;
107 {
108 int i;
109 uint32_t uch = (uint32_t)ch;
110 uint32_t topbit = BITMASK(p_cm->cm_width-1);
111
112 if (p_cm->cm_refin)
113 uch = reflect(uch, 8);
114
115 p_cm->cm_reg ^= (uch << (p_cm->cm_width-8));
116 for (i = 0; i < 8; i++) {
117 if (p_cm->cm_reg & topbit)
118 p_cm->cm_reg = (p_cm->cm_reg << 1) ^ p_cm->cm_poly;
119 else
120 p_cm->cm_reg <<= 1;
121
122 p_cm->cm_reg &= widmask(p_cm);
123 }
124 }
125
126 void
cm_blk(p_cm,blk_adr,blk_len)127 cm_blk(p_cm, blk_adr, blk_len)
128 p_cm_t p_cm;
129 p_ubyte_ blk_adr;
130 uint32_t blk_len;
131 {
132 while (blk_len--)
133 cm_nxt(p_cm, *blk_adr++);
134 }
135
136 uint32_t
cm_crc(p_cm)137 cm_crc(p_cm)
138 p_cm_t p_cm;
139 {
140 if (p_cm->cm_refot)
141 return (p_cm->cm_xorot ^ reflect(p_cm->cm_reg, p_cm->cm_width));
142 else
143 return (p_cm->cm_xorot ^ p_cm->cm_reg);
144 }
145
146 uint32_t
cm_tab(p_cm,index)147 cm_tab(p_cm, index)
148 p_cm_t p_cm;
149 int index;
150 {
151 int i;
152 uint32_t r;
153 uint32_t topbit = BITMASK(p_cm->cm_width-1);
154 uint32_t inbyte = (uint32_t)index;
155
156 if (p_cm->cm_refin)
157 inbyte = reflect(inbyte, 8);
158
159 r = inbyte << (p_cm->cm_width-8);
160 for (i = 0; i < 8; i++)
161 if (r & topbit)
162 r = (r << 1) ^ p_cm->cm_poly;
163 else
164 r <<= 1;
165
166 if (p_cm->cm_refin)
167 r = reflect(r, p_cm->cm_width);
168
169 return (r & widmask(p_cm));
170 }
171