drivers/staging/cxt1e1/sbecrc.c

   1 /*   Based on "File Verification Using CRC" by Mark R. Nelson in Dr. Dobbs'
   2  *   Journal, May 1992, pp. 64-67.  This algorithm generates the same CRC
   3  *   values as ZMODEM and PKZIP
   4  *
   5  * Copyright (C) 2002-2005  SBE, Inc.
   6  *
   7  *   This program is free software; you can redistribute it and/or modify
   8  *   it under the terms of the GNU General Public License as published by
   9  *   the Free Software Foundation; either version 2 of the License, or
  10  *   (at your option) any later version.
  11  *
  12  *   This program is distributed in the hope that it will be useful,
  13  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  *   GNU General Public License for more details.
  16  */
  17
  18 #include <linux/types.h>
  19 #include "pmcc4_sysdep.h"
  20 #include "sbecom_inline_linux.h"
  21 #include "sbe_promformat.h"
  22
  23 /* defines */
  24 #define CRC32_POLYNOMIAL                0xEDB88320L
  25 #define CRC_TABLE_ENTRIES                       256
  26
  27
  28
  29 static      u_int32_t crcTableInit;
  30
  31 #ifdef STATIC_CRC_TABLE
  32 static u_int32_t CRCTable[CRC_TABLE_ENTRIES];
  33
  34 #endif
  35
  36
  37 /***************************************************************************
  38 *
  39 * genCrcTable - fills in CRCTable, as used by sbeCrc()
  40 *
  41 * RETURNS: N/A
  42 *
  43 * ERRNO: N/A
  44 ***************************************************************************/
  45
  46 static void
  47 genCrcTable (u_int32_t *CRCTable)
  48 {
  49     int         ii, jj;
  50     u_int32_t      crc;
  51
  52     for (ii = 0; ii < CRC_TABLE_ENTRIES; ii++)
  53     {
  54         crc = ii;
  55         for (jj = 8; jj > 0; jj--)
  56         {
  57             if (crc & 1)
  58                 crc = (crc >> 1) ^ CRC32_POLYNOMIAL;
  59             else
  60                 crc >>= 1;
  61         }
  62         CRCTable[ii] = crc;
  63     }
  64
  65     crcTableInit++;
  66 }
  67
  68
  69 /***************************************************************************
  70 *
  71 * sbeCrc - generates a CRC on a given buffer, and initial CRC
  72 *
  73 * This routine calculates the CRC for a buffer of data using the
  74 * table lookup method. It accepts an original value for the crc,
  75 * and returns the updated value. This permits "catenation" of
  76 * discontiguous buffers. An original value of 0 for the "first"
  77 * buffer is the norm.
  78 *
  79 * Based on "File Verification Using CRC" by Mark R. Nelson in Dr. Dobb's
  80 * Journal, May 1992, pp. 64-67.  This algorithm generates the same CRC
  81 * values as ZMODEM and PKZIP.
  82 *
  83 * RETURNS: calculated crc of block
  84 *
  85 */
  86
  87 void
  88 sbeCrc (u_int8_t *buffer,          /* data buffer to crc */
  89         u_int32_t count,           /* length of block in bytes */
  90         u_int32_t initialCrc,      /* starting CRC */
  91         u_int32_t *result)
  92 {
  93     u_int32_t     *tbl = 0;
  94     u_int32_t      temp1, temp2, crc;
  95
  96     /*
  97      * if table not yet created, do so. Don't care about "extra" time
  98      * checking this every time sbeCrc() is called, since CRC calculations are
  99      * already time consuming
 100      */
 101     if (!crcTableInit)
 102     {
 103 #ifdef STATIC_CRC_TABLE
 104         tbl = &CRCTable;
 105         genCrcTable (tbl);
 106 #else
 107         tbl = (u_int32_t *) OS_kmalloc (CRC_TABLE_ENTRIES * sizeof (u_int32_t));
 108         if (tbl == 0)
 109         {
 110             *result = 0;            /* dummy up return value due to malloc
 111                                      * failure */
 112             return;
 113         }
 114         genCrcTable (tbl);
 115 #endif
 116     }
 117     /* inverting bits makes ZMODEM & PKZIP compatible */
 118     crc = initialCrc ^ 0xFFFFFFFFL;
 119
 120     while (count-- != 0)
 121     {
 122         temp1 = (crc >> 8) & 0x00FFFFFFL;
 123         temp2 = tbl[((int) crc ^ *buffer++) & 0xff];
 124         crc = temp1 ^ temp2;
 125     }
 126
 127     crc ^= 0xFFFFFFFFL;
 128
 129     *result = crc;
 130
 131 #ifndef STATIC_CRC_TABLE
 132     crcTableInit = 0;
 133     OS_kfree (tbl);
 134 #endif
 135 }
 136
 137 /*** End-of-File ***/