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                 crc = ii;
  54                 for (jj = 8; jj > 0; jj--) {
  55                         if (crc & 1)
  56                                 crc = (crc >> 1) ^ CRC32_POLYNOMIAL;
  57                         else
  58                                 crc >>= 1;
  59                 }
  60                 CRCTable[ii] = crc;
  61         }
  62
  63         crcTableInit++;
  64 }
  65
  66
  67 /***************************************************************************
  68 *
  69 * sbeCrc - generates a CRC on a given buffer, and initial CRC
  70 *
  71 * This routine calculates the CRC for a buffer of data using the
  72 * table lookup method. It accepts an original value for the crc,
  73 * and returns the updated value. This permits "catenation" of
  74 * discontiguous buffers. An original value of 0 for the "first"
  75 * buffer is the norm.
  76 *
  77 * Based on "File Verification Using CRC" by Mark R. Nelson in Dr. Dobb's
  78 * Journal, May 1992, pp. 64-67.  This algorithm generates the same CRC
  79 * values as ZMODEM and PKZIP.
  80 *
  81 * RETURNS: calculated crc of block
  82 *
  83 */
  84
  85 void
  86 sbeCrc(u_int8_t *buffer,          /* data buffer to crc */
  87         u_int32_t count,           /* length of block in bytes */
  88         u_int32_t initialCrc,      /* starting CRC */
  89         u_int32_t *result)
  90 {
  91         u_int32_t     *tbl = NULL;
  92         u_int32_t      temp1, temp2, crc;
  93
  94         /*
  95         * if table not yet created, do so. Don't care about "extra" time
  96         * checking this every time sbeCrc() is called, since CRC calculations
  97         * are already time consuming
  98         */
  99         if (!crcTableInit) {
 100 #ifdef STATIC_CRC_TABLE
 101                 tbl = &CRCTable;
 102                 genCrcTable(tbl);
 103 #else
 104                 tbl = (u_int32_t *) OS_kmalloc(CRC_TABLE_ENTRIES * sizeof(u_int32_t));
 105                 if (!tbl) {
 106                         *result = 0;   /* dummy up return value due to malloc
 107                                         * failure */
 108                         return;
 109                 }
 110                 genCrcTable(tbl);
 111 #endif
 112         }
 113         /* inverting bits makes ZMODEM & PKZIP compatible */
 114         crc = initialCrc ^ 0xFFFFFFFFL;
 115
 116         while (count-- != 0) {
 117                 temp1 = (crc >> 8) & 0x00FFFFFFL;
 118                 temp2 = tbl[((int) crc ^ *buffer++) & 0xff];
 119                 crc = temp1 ^ temp2;
 120         }
 121
 122         crc ^= 0xFFFFFFFFL;
 123
 124         *result = crc;
 125
 126 #ifndef STATIC_CRC_TABLE
 127         crcTableInit = 0;
 128         OS_kfree(tbl);
 129 #endif
 130 }
 131
 132 /*** End-of-File ***/