//
// Copyright 2020 Electronic Arts Inc.
//
// TiberianDawn.DLL and RedAlert.dll and corresponding source code 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 3 of the License, or (at your option) any later version.
// TiberianDawn.DLL and RedAlert.dll and corresponding source code is distributed
// in the hope that it will be useful, but with permitted additional restrictions
// under Section 7 of the GPL. See the GNU General Public License in LICENSE.TXT
// distributed with this program. You should have received a copy of the
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/* $Header: /CounterStrike/CRC.CPP 1 3/03/97 10:24a Joe_bostic $ */
/***********************************************************************************************
*** C O N F I D E N T I A L --- W E S T W O O D S T U D I O S ***
***********************************************************************************************
* *
* Project Name : Command & Conquer *
* *
* File Name : CRC.CPP *
* *
* Programmer : Joe L. Bostic *
* *
* Start Date : 03/02/96 *
* *
* Last Update : March 2, 1996 [JLB] *
* *
*---------------------------------------------------------------------------------------------*
* Functions: *
* CRCEngine::operator() -- Submits one byte of data to the CRC engine. *
* CRCEngine::operator() -- Submits an arbitrary data block to the CRC engine. *
* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
#include "crc.h"
/***********************************************************************************************
* CRCEngine::operator() -- Submits one byte of data to the CRC engine. *
* *
* This routine will take the specified byte of data and submit it to the CRC engine *
* for processing. This routine is designed to be as fast as possible since the typical *
* use of this routine is to feed one of presumably many byte sized chunks of data to the *
* CRC engine. *
* *
* INPUT: datum -- One byte of data to submit to the CRC engine. *
* *
* OUTPUT: none *
* *
* WARNINGS: If possible, use the buffer/size operator to submit data rather than repeated *
* calls to this routine. *
* *
* HISTORY: *
* 03/02/1996 JLB : Created. *
*=============================================================================================*/
void CRCEngine::operator() (char datum)
{
StagingBuffer.Buffer[Index++] = datum;
if (Index == sizeof(long)) {
CRC = Value();
StagingBuffer.Composite = 0;
Index = 0;
}
}
/***********************************************************************************************
* CRCEngine::operator() -- Submits an arbitrary data block to the CRC engine. *
* *
* This routine will submit the specified block to the CRC engine. The block can be of *
* arbitrary length. *
* *
* INPUT: buffer -- Pointer to the buffer that contains the data. The buffer will not *
* be modified. *
* *
* length -- The length of the buffer (in bytes). *
* *
* OUTPUT: Returns with the current CRC value accumulated so far. *
* *
* WARNINGS: none *
* *
* HISTORY: *
* 03/02/1996 JLB : Created. *
*=============================================================================================*/
long CRCEngine::operator() (void const * buffer, int length)
{
if (buffer != NULL && length > 0) {
char const * dataptr = (char const *)buffer;
int bytes_left = length;
/*
** If there are any leader bytes (needed to fill the staging buffer)
** then process those by first using them to fill up the staging
** buffer. The bulk of the data block will be processed by the high
** speed longword processing loop.
*/
while (bytes_left && Buffer_Needs_Data()) {
operator()(*dataptr);
dataptr++;
bytes_left--;
}
/*
** Perform the fast 'bulk' processing by reading long word sized
** data blocks.
*/
long const * longptr = (long const *)dataptr;
int longcount = bytes_left / sizeof(long); // Whole 'long' elements remaining.
while (longcount--) {
CRC = _lrotl(CRC, 1) + *longptr++;
bytes_left -= sizeof(long);
}
/*
** If there are remainder bytes, then process these by adding them
** to the staging buffer.
*/
dataptr = (char const *)longptr;
while (bytes_left) {
operator()(*dataptr);
dataptr++;
bytes_left--;
}
}
/*
** Return the current CRC value.
*/
return(Value());
}