Initial commit

engines/cine/unpack.h

@@ -0,0 +1,113 @@
+/* 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 3 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, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifndef CINE_UNPACK_H
+#define CINE_UNPACK_H
+
+
+#include "common/scummsys.h"
+
+namespace Cine {
+
+/**
+ * A LZ77 style decompressor for Delphine's data files
+ * used in at least Future Wars and Operation Stealth.
+ * @note Works backwards in the source and destination buffers.
+ * @warning Having the source and destination in the same buffer when unpacking can cause errors!
+ */
+class CineUnpacker {
+public:
+	/**
+	 * Unpacks packed data from the source buffer to the destination buffer.
+	 * @note You may call this on already unpacked data but then source length must be equal to destination length.
+	 * @warning The source and destination should not point to the same buffer. If they do, errors may occur!
+	 * @param src Pointer to the source buffer.
+	 * @param srcLen Length of the source buffer.
+	 * @param dst Pointer to the destination buffer.
+	 * @param dstLen Length of the destination buffer.
+	 * @return True if no errors were detected in the source data and unpacking was successful, otherwise false.
+	 */
+	bool unpack(const byte *src, uint srcLen, byte *dst, uint dstLen);
+private:
+	/**
+	 * Reads an unsigned big endian 32-bit integer from the source stream and goes backwards 4 bytes.
+	 * @return If the operation is valid, an unsigned big endian 32-bit integer read from the source stream.
+	 * @return If the operation is invalid, zero.
+	 * @note Sets internal error state if the read operation would be out of source bounds.
+	 */
+	uint32 readSource();
+
+	/**
+	 * Shifts the current internal 32-bit chunk to the right by one.
+	 * Puts input carry into internal chunk's topmost (i.e. leftmost) bit.
+	 * @return The least significant bit that was shifted out from the chunk.
+	 */
+	uint rcr(bool inputCarry);
+
+	/**
+	 * Get the next bit from the source stream.
+	 * @note Changes the bit position in the source stream.
+	 * @return The next bit from the source stream.
+	 */
+	uint nextBit();
+
+	/**
+	 * Get bits from the source stream.
+	 * @note Changes the bit position in the source stream.
+	 * @param numBits Number of bits to read from the source stream.
+	 * @return Integer value consisting of the bits read from the source stream (In range [0, (2 ** numBits) - 1]).
+	 * @return Later the bit was read from the source, the less significant it is in the return value.
+	 */
+	uint getBits(uint numBits);
+
+	/**
+	 * Copy raw bytes from the input stream and write them to the destination stream.
+	 * This is used when no adequately long match is found in the sliding window.
+	 * @note Sets internal error state if the operation would be out of bounds.
+	 * @param numBytes Amount of bytes to copy from the input stream
+	 */
+	void unpackRawBytes(uint numBytes);
+
+	/**
+	 * Copy bytes from the sliding window in the destination buffer.
+	 * This is used when a match of two bytes or longer is found.
+	 * @note Sets internal error state if the operation would be out of bounds.
+	 * @param offset Offset in the sliding window
+	 * @param numBytes Amount of bytes to copy
+	 */
+	void copyRelocatedBytes(uint offset, uint numBytes);
+private:
+	uint32 _crc;      ///< Error-detecting code (This should be zero after successful unpacking)
+	uint32 _chunk32b; ///< The current internal 32-bit chunk of source data
+	byte *_dst;       ///< Pointer to the current position in the destination buffer
+	const byte *_src; ///< Pointer to the current position in the source buffer
+
+	// These are used for detecting errors (e.g. out of bounds issues) during unpacking
+	bool _error;           ///< Did an error occur during unpacking?
+	const byte *_srcBegin; ///< Source buffer's beginning
+	const byte *_srcEnd;   ///< Source buffer's end
+	byte *_dstBegin;       ///< Destination buffer's beginning
+	byte *_dstEnd;         ///< Destination buffer's end
+};
+
+} // End of namespace Cine
+
+#endif