usr/src/cmd/picl/plugins/sun4u/lib/fruaccess/crcmodel.c

   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 #pragma ident   "%Z%%M% %I%     %E% SMI"
  27
  28 /*
  29  *
  30  *                             Start of crcmodel.c
  31  *
  32  *
  33  * Author : Ross Williams (ross@guest.adelaide.edu.au.).
  34  * Date   : 3 June 1993.
  35  * Status : Public domain.
  36  *
  37  * Description : This is the implementation (.c) file for the reference
  38  * implementation of the Rocksoft^tm Model CRC Algorithm. For more
  39  * information on the Rocksoft^tm Model CRC Algorithm, see the document
  40  * titled "A Painless Guide to CRC Error Detection Algorithms" by Ross
  41  * Williams (ross@guest.adelaide.edu.au.). This document is likely to be in
  42  * "ftp.adelaide.edu.au/pub/rocksoft".
  43  *
  44  * Note: Rocksoft is a trademark of Rocksoft Pty Ltd, Adelaide, Australia.
  45  *
  46  *
  47  *
  48  * Implementation Notes
  49  * --------------------
  50  * To avoid inconsistencies, the specification of each function is not echoed
  51  * here. See the header file for a description of these functions.
  52  * This package is light on checking because I want to keep it short and
  53  * simple and portable (i.e. it would be too messy to distribute my entire
  54  * C culture (e.g. assertions package) with this package.
  55  *
  56  *
  57  */
  58
  59 #include "crcmodel.h"
  60
  61 /* The following definitions make the code more readable. */
  62
  63 #define BITMASK(X) (1L << (X))
  64 #define MASK32 0xFFFFFFFFL
  65 #define LOCAL static
  66
  67 LOCAL uint32_t reflect P_((uint32_t v, int b));
  68 LOCAL uint32_t
  69 reflect(v, b)
  70 /* Returns the value v with the bottom b [0,32] bits reflected. */
  71 /* Example: reflect(0x3e23L,3) == 0x3e26 */
  72 uint32_t v;
  73 int   b;
  74 {
  75         int i;
  76         uint32_t t = v;
  77         for (i = 0; i < b; i++) {
  78                 if (t & 1L)
  79                         v |=  BITMASK((b-1)-i);
  80                 else
  81                         v &= ~BITMASK((b-1)-i);
  82                 t >>= 1;
  83         }
  84         return (v);
  85 }
  86
  87 LOCAL uint32_t widmask P_((p_cm_t));
  88 LOCAL uint32_t
  89 widmask(p_cm)
  90 /* Returns a longword whose value is (2^p_cm->cm_width)-1. */
  91 /* The trick is to do this portably (e.g. without doing <<32). */
  92 p_cm_t p_cm;
  93 {
  94         return ((((1L<<(p_cm->cm_width-1))-1L)<<1)|1L);
  95 }
  96
  97 void
  98 cm_ini(p_cm)
  99 p_cm_t p_cm;
 100 {
 101         p_cm->cm_reg = p_cm->cm_init;
 102 }
 103
 104 void
 105 cm_nxt(p_cm, ch)
 106 p_cm_t p_cm;
 107 int    ch;
 108 {
 109         int i;
 110         uint32_t uch = (uint32_t)ch;
 111         uint32_t topbit = BITMASK(p_cm->cm_width-1);
 112
 113         if (p_cm->cm_refin)
 114                 uch = reflect(uch, 8);
 115
 116         p_cm->cm_reg ^= (uch << (p_cm->cm_width-8));
 117         for (i = 0; i < 8; i++) {
 118                 if (p_cm->cm_reg & topbit)
 119                         p_cm->cm_reg = (p_cm->cm_reg << 1) ^ p_cm->cm_poly;
 120                 else
 121                         p_cm->cm_reg <<= 1;
 122
 123                 p_cm->cm_reg &= widmask(p_cm);
 124         }
 125 }
 126
 127 void
 128 cm_blk(p_cm, blk_adr, blk_len)
 129 p_cm_t   p_cm;
 130 p_ubyte_ blk_adr;
 131 uint32_t    blk_len;
 132 {
 133         while (blk_len--)
 134                 cm_nxt(p_cm, *blk_adr++);
 135 }
 136
 137 uint32_t
 138 cm_crc(p_cm)
 139 p_cm_t p_cm;
 140 {
 141         if (p_cm->cm_refot)
 142                 return (p_cm->cm_xorot ^ reflect(p_cm->cm_reg, p_cm->cm_width));
 143         else
 144                 return (p_cm->cm_xorot ^ p_cm->cm_reg);
 145 }
 146
 147 uint32_t
 148 cm_tab(p_cm, index)
 149 p_cm_t p_cm;
 150 int    index;
 151 {
 152         int   i;
 153         uint32_t r;
 154         uint32_t topbit = BITMASK(p_cm->cm_width-1);
 155         uint32_t inbyte = (uint32_t)index;
 156
 157         if (p_cm->cm_refin)
 158                 inbyte = reflect(inbyte, 8);
 159
 160         r = inbyte << (p_cm->cm_width-8);
 161         for (i = 0; i < 8; i++)
 162                 if (r & topbit)
 163                         r = (r << 1) ^ p_cm->cm_poly;
 164                 else
 165                         r <<= 1;
 166
 167         if (p_cm->cm_refin)
 168                 r = reflect(r, p_cm->cm_width);
 169
 170         return (r & widmask(p_cm));
 171 }