COMMON: Added common CRC implementation. Borrowed from Wintermute engine

common/crc.h

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+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ */
+
+/**********************************************************************
+ *
+ * Filename:    crc.c
+ *
+ * Description: Slow and fast implementations of the CRC standards.
+ *
+ * Notes:
+ *
+ *
+ * Copyright (c) 2000 by Michael Barr.  This software is placed into
+ * the public domain and may be used for any purpose.  However, this
+ * notice must not be changed or removed and no warranty is either
+ * expressed or implied by its publication or distribution.
+ **********************************************************************/
+
+#ifndef COMMON_CRC_H
+#define COMMON_CRC_H
+
+#include "common/system.h" // For types.
+
+namespace Common {
+
+template <typename T>
+class CRC {
+public:
+	CRC(T poly, T init_remainder, T final_xor, bool reflect);
+	T init(void);
+	T processByte(byte byteVal, T remainder);
+	T finalize(T remainder);
+
+	T crcSlow(byte const message[], int nBytes);
+	T crcFast(byte const message[], int nBytes);
+
+private:
+	T _poly;
+	T _init_remainder;
+	T _final_xor;
+	bool _reflect;
+
+	int _width;
+	int _topbit;
+
+	T _crcTable[256];
+
+	bool _inited;
+
+	uint32 reflect(uint32 data, byte nBits);
+
+	byte reflectData(byte x) { return _reflect ? (byte)reflect(x, 8) : x; }
+	T reflectRemainder(T x) { return _reflect ? (T)reflect(x, _width) : x; }
+};
+
+/*********************************************************************
+ *
+ * Function:    reflect()
+ *
+ * Description: Reorder the bits of a binary sequence, by reflecting
+ *              them about the middle position.
+ *
+ * Notes:       No checking is done that nBits <= 32.
+ *
+ * Returns:     The reflection of the original data.
+ *
+ *********************************************************************/
+template<typename T>
+uint32 CRC<T>::reflect(uint32 data, byte nBits) {
+	uint32 reflection = 0x00000000;
+
+	/*
+	 * Reflect the data about the center bit.
+	 */
+	for (byte bit = 0; bit < nBits; ++bit) {
+		/*
+		 * If the LSB bit is set, set the reflection of it.
+		 */
+		if (data & 0x01) {
+			reflection |= (1 << ((nBits - 1) - bit));
+		}
+
+		data = (data >> 1);
+	}
+
+	return reflection;
+}
+
+
+/*********************************************************************
+ *
+ * Function:    crcSlow()
+ *
+ * Description: Compute the CRC of a given message.
+ *
+ * Notes:
+ *
+ * Returns:     The CRC of the message.
+ *
+ *********************************************************************/
+template<typename T>
+T CRC<T>::crcSlow(byte const message[], int nBytes) {
+	T remainder = _init_remainder;
+
+	/*
+	 * Perform modulo-2 division, a byte at a time.
+	 */
+	for (int b = 0; b < nBytes; ++b) {
+		/*
+		 * Bring the next byte into the remainder.
+		 */
+		remainder ^= reflectData(message[b]) << (_width - 8);
+
+		/*
+		 * Perform modulo-2 division, a bit at a time.
+		 */
+		for (byte bit = 8; bit > 0; --bit) {
+			/*
+			 * Try to divide the current data bit.
+			 */
+			if (remainder & _topbit) {
+				remainder = (remainder << 1) ^ _poly;
+			} else {
+				remainder = (remainder << 1);
+			}
+		}
+	}
+
+	/*
+	 * The final remainder is the CRC result.
+	 */
+	return reflectRemainder(remainder) ^ _final_xor;
+}
+
+
+template<typename T>
+CRC<T>::CRC(T poly, T init_remainder, T final_xor, bool reflect) :
+		_poly(poly), _init_remainder(init_remainder), _final_xor(final_xor), _reflect(reflect) {
+	_width = 8 * sizeof(T);
+	_topbit = 1 << (_width - 1);
+
+	for (int i = 0; i < 256; ++i)
+		_crcTable[i] = 0;
+
+	_inited = false;
+}
+
+/*********************************************************************
+ *
+ * Function:    crcInit()
+ *
+ * Description: Populate the partial CRC lookup table.
+ *
+ * Notes:       This function must be rerun any time the CRC standard
+ *              is changed.  If desired, it can be run "offline" and
+ *              the table results stored in an embedded system's ROM.
+ *
+ * Returns:     Initial remainder.
+ *
+ *********************************************************************/
+template<typename T>
+T CRC<T>::init() {
+	/*
+	 * Compute the remainder of each possible dividend.
+	 */
+	for (int dividend = 0; dividend < 256; ++dividend) {
+		/*
+		 * Start with the dividend followed by zeros.
+		 */
+		T remainder = dividend << (_width - 8);
+
+		/*
+		 * Perform modulo-2 division, a bit at a time.
+		 */
+		for (byte bit = 8; bit > 0; --bit) {
+			/*
+			 * Try to divide the current data bit.
+			 */
+			if (remainder & _topbit) {
+				remainder = (remainder << 1) ^ _poly;
+			} else {
+				remainder = (remainder << 1);
+			}
+		}
+
+		/*
+		 * Store the result into the table.
+		 */
+		_crcTable[dividend] = remainder;
+	}
+
+	_inited = true;
+
+	return _init_remainder;
+}
+
+
+/*********************************************************************
+ *
+ * Function:    crcFast()
+ *
+ * Description: Compute the CRC of a given message.
+ *
+ * Notes:       crcInit() must be called first.
+ *
+ * Returns:     The CRC of the message.
+ *
+ *********************************************************************/
+template<typename T>
+T CRC<T>::crcFast(byte const message[], int nBytes) {
+	T remainder = _init_remainder;
+
+	if (!_inited)
+		error("CRC::crcFast(): init method must be called first");
+
+	/*
+	 * Divide the message by the polynomial, a byte at a time.
+	 */
+	for (int b = 0; b < nBytes; ++b) {
+		byte data = reflectData(message[b] ^ (remainder >> (_width - 8)));
+		remainder = _crcTable[data] ^ (remainder << 8);
+	}
+
+	/*
+	 * The final remainder is the CRC.
+	 */
+	return reflectRemainder(remainder) ^ _final_xor;
+
+}
+
+template<typename T>
+T CRC<T>::processByte(byte byteVal, T remainder) {
+	byte data = reflectData(byteVal) ^ (remainder >> (_width - 8));
+
+	remainder = _crcTable[data] ^ (remainder << 8);
+	return remainder;
+}
+
+template<typename T>
+T CRC<T>::finalize(T remainder) {
+	return reflectRemainder(remainder) ^ _final_xor;
+}
+
+class CRC_CCITT : public CRC<uint16> {
+public:
+	CRC_CCITT() : CRC(0x1021, 0xFFFF, 0x0000, false) {}
+};
+
+class CRC_BINHEX : public CRC<uint16> {
+public:
+	CRC_BINHEX() : CRC(0x1021, 0x0000, 0x0000, false) {}
+};
+
+class CRC16 : public CRC<uint16> {
+public:
+	CRC16() : CRC(0x8005, 0x0000, 0x0000, true) {}
+};
+
+class CRC32 : public CRC<uint32> {
+public:
+	CRC32() : CRC(0x04C11DB7, 0xFFFFFFFF, 0xFFFFFFFF, true) {}
+};
+
+} // End of namespace Common
+
+#endif