Initial commit

engines/cine/unpack.cpp

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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 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/>.
+ *
+ */
+
+
+#include "common/endian.h"
+
+#include "cine/unpack.h"
+
+namespace Cine {
+
+uint32 CineUnpacker::readSource() {
+	if (_src < _srcBegin || _src + 4 > _srcEnd) {
+		_error = true;
+		return 0; // The source pointer is out of bounds, returning a default value
+	}
+	uint32 value = READ_BE_UINT32(_src);
+	_src -= 4;
+	return value;
+}
+
+uint CineUnpacker::rcr(bool inputCarry) {
+	uint outputCarry = (_chunk32b & 1);
+	_chunk32b >>= 1;
+	if (inputCarry) {
+		_chunk32b |= 0x80000000;
+	}
+	return outputCarry;
+}
+
+uint CineUnpacker::nextBit() {
+	uint carry = rcr(false);
+	// Normally if the chunk becomes zero then the carry is one as
+	// the end of chunk marker is always the last to be shifted out.
+	if (_chunk32b == 0) {
+		_chunk32b = readSource();
+		_crc ^= _chunk32b;
+		carry = rcr(true); // Put the end of chunk marker in the most significant bit
+	}
+	return carry;
+}
+
+uint CineUnpacker::getBits(uint numBits) {
+	uint c = 0;
+	while (numBits--) {
+		c <<= 1;
+		c |= nextBit();
+	}
+	return c;
+}
+
+void CineUnpacker::unpackRawBytes(uint numBytes) {
+	if (_dst >= _dstEnd || _dst - numBytes + 1 < _dstBegin) {
+		_error = true;
+		return; // Destination pointer is out of bounds for this operation
+	}
+	while (numBytes--) {
+		*_dst = (byte)getBits(8);
+		--_dst;
+	}
+}
+
+void CineUnpacker::copyRelocatedBytes(uint offset, uint numBytes) {
+	if (_dst + offset >= _dstEnd || _dst - numBytes + 1 < _dstBegin) {
+		_error = true;
+		return; // Destination pointer is out of bounds for this operation
+	}
+	while (numBytes--) {
+		*_dst = *(_dst + offset);
+		--_dst;
+	}
+}
+
+bool CineUnpacker::unpack(const byte *src, uint srcLen, byte *dst, uint dstLen) {
+	// Initialize variables used for detecting errors during unpacking
+	_error    = false;
+	_srcBegin = src;
+	_srcEnd   = src + srcLen;
+	_dstBegin = dst;
+	_dstEnd   = dst + dstLen;
+
+	// Handle already unpacked data here
+	if (srcLen == dstLen) {
+		// Source length is same as destination length so the source
+		// data is already unpacked. Let's just copy it then.
+		memcpy(dst, src, srcLen);
+		return true;
+	}
+
+	// Initialize other variables
+	_src = _srcBegin + srcLen - 4;
+	uint32 unpackedLength = readSource(); // Unpacked length in bytes
+	_dst = _dstBegin + unpackedLength - 1;
+	_crc = readSource();
+	_chunk32b = readSource();
+	_crc ^= _chunk32b;
+
+	while (_dst >= _dstBegin && !_error) {
+		/*
+		Bits  => Action:
+		0 0   => unpackRawBytes(3 bits + 1)              i.e. unpackRawBytes(1..8)
+		1 1 1 => unpackRawBytes(8 bits + 9)              i.e. unpackRawBytes(9..264)
+		0 1   => copyRelocatedBytes(8 bits, 2)           i.e. copyRelocatedBytes(0..255, 2)
+		1 0 0 => copyRelocatedBytes(9 bits, 3)           i.e. copyRelocatedBytes(0..511, 3)
+		1 0 1 => copyRelocatedBytes(10 bits, 4)          i.e. copyRelocatedBytes(0..1023, 4)
+		1 1 0 => copyRelocatedBytes(12 bits, 8 bits + 1) i.e. copyRelocatedBytes(0..4095, 1..256)
+		*/
+		if (!nextBit()) { // 0...
+			if (!nextBit()) { // 0 0
+				uint numBytes = getBits(3) + 1;
+				unpackRawBytes(numBytes);
+			} else { // 0 1
+				uint numBytes = 2;
+				uint offset   = getBits(8);
+				copyRelocatedBytes(offset, numBytes);
+			}
+		} else { // 1...
+			uint c = getBits(2);
+			if (c == 3) { // 1 1 1
+				uint numBytes = getBits(8) + 9;
+				unpackRawBytes(numBytes);
+			} else if (c < 2) { // 1 0 x
+				uint numBytes = c + 3;
+				uint offset   = getBits(c + 9);
+				copyRelocatedBytes(offset, numBytes);
+			} else { // 1 1 0
+				uint numBytes = getBits(8) + 1;
+				uint offset   = getBits(12);
+				copyRelocatedBytes(offset, numBytes);
+			}
+		}
+	}
+	return !_error && (_crc == 0);
+}
+
+} // End of namespace Cine