/* Based on "File Verification Using CRC" by Mark R. Nelson in Dr. Dobbs'
* Journal, May 1992, pp. 64-67. This algorithm generates the same CRC
* values as ZMODEM and PKZIP
*
* Copyright (C) 2002-2005 SBE, Inc.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*/
#include <linux/types.h>
#include "pmcc4_sysdep.h"
#include "sbecom_inline_linux.h"
#include "sbe_promformat.h"
/* defines */
#define CRC32_POLYNOMIAL 0xEDB88320L
#define CRC_TABLE_ENTRIES 256
static u_int32_t crcTableInit;
#ifdef STATIC_CRC_TABLE
static u_int32_t CRCTable[CRC_TABLE_ENTRIES];
#endif
/***************************************************************************
*
* genCrcTable - fills in CRCTable, as used by sbeCrc()
*
* RETURNS: N/A
*
* ERRNO: N/A
***************************************************************************/
static void
genCrcTable(u_int32_t *CRCTable)
{
int ii, jj;
u_int32_t crc;
for (ii = 0; ii < CRC_TABLE_ENTRIES; ii++) {
crc = ii;
for (jj = 8; jj > 0; jj--) {
if (crc & 1)
crc = (crc >> 1) ^ CRC32_POLYNOMIAL;
else
crc >>= 1;
}
CRCTable[ii] = crc;
}
crcTableInit++;
}
/***************************************************************************
*
* sbeCrc - generates a CRC on a given buffer, and initial CRC
*
* This routine calculates the CRC for a buffer of data using the
* table lookup method. It accepts an original value for the crc,
* and returns the updated value. This permits "catenation" of
* discontiguous buffers. An original value of 0 for the "first"
* buffer is the norm.
*
* Based on "File Verification Using CRC" by Mark R. Nelson in Dr. Dobb's
* Journal, May 1992, pp. 64-67. This algorithm generates the same CRC
* values as ZMODEM and PKZIP.
*
* RETURNS: calculated crc of block
*
*/
void
sbeCrc(u_int8_t *buffer, /* data buffer to crc */
u_int32_t count, /* length of block in bytes */
u_int32_t initialCrc, /* starting CRC */
u_int32_t *result)
{
u_int32_t *tbl = NULL;
u_int32_t temp1, temp2, crc;
/*
* if table not yet created, do so. Don't care about "extra" time
* checking this every time sbeCrc() is called, since CRC calculations
* are already time consuming
*/
if (!crcTableInit) {
#ifdef STATIC_CRC_TABLE
tbl = &CRCTable;
genCrcTable(tbl);
#else
tbl = kzalloc(CRC_TABLE_ENTRIES * sizeof(u_int32_t),
GFP_KERNEL);
if (!tbl) {
*result = 0; /* dummy up return value due to malloc
* failure */
return;
}
genCrcTable(tbl);
#endif
}
/* inverting bits makes ZMODEM & PKZIP compatible */
crc = initialCrc ^ 0xFFFFFFFFL;
while (count-- != 0) {
temp1 = (crc >> 8) & 0x00FFFFFFL;
temp2 = tbl[((int) crc ^ *buffer++) & 0xff];
crc = temp1 ^ temp2;
}
crc ^= 0xFFFFFFFFL;
*result = crc;
#ifndef STATIC_CRC_TABLE
crcTableInit = 0;
kfree(tbl);
#endif
}
/*** End-of-File ***/
