CnC_Remastered_Collection/REDALERT/CRC.H

119 lines
4.7 KiB
C++

//
// 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
// GNU General Public License along with permitted additional restrictions
// with this program. If not, see https://github.com/electronicarts/CnC_Remastered_Collection
/* $Header: /CounterStrike/CRC.H 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.H *
* *
* Programmer : Joe L. Bostic *
* *
* Start Date : 03/02/96 *
* *
* Last Update : March 2, 1996 [JLB] *
* *
*---------------------------------------------------------------------------------------------*
* Functions: *
* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
#ifndef CRC_H
#define CRC_H
#include <stdlib.h>
/*
** The "bool" integral type was defined by the C++ comittee in
** November of '94. Until the compiler supports this, use the following
** definition.
*/
#ifndef __BORLANDC__
#ifndef TRUE_FALSE_DEFINED
#define TRUE_FALSE_DEFINED
enum {false=0,true=1};
typedef int bool;
#endif
#endif
/*
** This is a CRC engine class. It will process submitted data and generate a CRC from it.
** Well, actually, the value returned is not a true CRC. However, it shares the same strength
** characteristic and is faster to generate than the traditional CRC. This object is treated like
** a method class. If it is called as a function (using the function operator), it will return
** the CRC value. There are other function operators to submit data for processing.
*/
class CRCEngine {
public:
// Constructor for CRC engine (it can have an override initial CRC value).
CRCEngine(long initial=0) : CRC(initial), Index(0) {
StagingBuffer.Composite = 0;
};
// Fetches CRC value.
long operator() (void) const {return(Value());};
// Submits one byte sized datum to the CRC accumulator.
void operator() (char datum);
// Submits an arbitrary buffer to the CRC accumulator.
long operator() (void const * buffer, int length);
// Implicit conversion operator so this object appears like a 'long integer'.
operator long(void) const {return(Value());};
protected:
bool Buffer_Needs_Data(void) const {
return(Index != 0);
};
long Value(void) const {
if (Buffer_Needs_Data()) {
return(_lrotl(CRC, 1) + StagingBuffer.Composite);
}
return(CRC);
};
/*
** Current accumulator of the CRC value. This value doesn't take into
** consideration any pending data in the staging buffer.
*/
long CRC;
/*
** This is the sub index into the staging buffer used to keep track of
** partial data blocks as they are submitted to the CRC engine.
*/
int Index;
/*
** This is the buffer that holds the incoming partial data. When the buffer
** is filled, the value is transformed into the CRC and the buffer is flushed
** in preparation for additional data.
*/
union {
long Composite;
char Buffer[sizeof(long)];
} StagingBuffer;
};
#endif