Initial commit

engines/grim/update/packfile.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 "common/stream.h"
+
+#include "engines/grim/update/packfile.h"
+
+namespace Grim {
+
+const uint32 PackFile::_knownOffsets[] = { 0x1c000, 0x21000, 0x23000, 0x24000, 0 };
+
+PackFile::PackFile(Common::SeekableReadStream *data):
+	_codeTable(nullptr), _orgStream(data), _offset(0), _kCodeTableSize(0x100) {
+
+	uint32 magicContainer, magicCabinet, key;
+
+	for (int i = 0; _knownOffsets[i] != 0; ++i) {
+		if (_knownOffsets[i] > uint32(_orgStream->size()))
+			continue;
+
+		_orgStream->seek(_knownOffsets[i]);
+
+		// Check for content signature
+		magicContainer = _orgStream->readUint32BE();
+		if (!err() && magicContainer == MKTAG('1','C','N','T')) {
+			key = _orgStream->readUint32LE();
+			createCodeTable(key);
+			_offset = _orgStream->pos();
+
+			// Check for cabinet signature
+			magicCabinet = readUint32BE();
+			if (!err() && magicCabinet == MKTAG('M','S','C','F'))
+				break;
+			else {
+				delete[] _codeTable;
+				_codeTable = nullptr;
+				_offset = 0;
+				continue;
+			}
+		}
+	}
+
+	_size = _orgStream->size() - _offset;
+	_orgStream->seek(_offset);
+}
+
+PackFile::~PackFile() {
+	delete[] _codeTable;
+	delete _orgStream;
+}
+
+bool PackFile::err() const {
+	return _orgStream->err();
+}
+
+void PackFile::clearErr() {
+	_orgStream->clearErr();
+}
+
+void PackFile::createCodeTable(uint32 key) {
+	const uint32 kRandA = 0x343FD;
+	const uint32 kRandB = 0x269EC3;
+	uint32 value = key;
+
+	delete[] _codeTable;
+	_codeTable = new uint16[_kCodeTableSize * 2];
+
+	for (uint i = 0; i < _kCodeTableSize; i++) {
+		value = kRandA * value + kRandB;
+		_codeTable[i] = uint16((value >> 16) & 0x7FFF);
+	}
+}
+
+void PackFile::decode(uint8 *data, uint32 dataSize, uint32 start_point) {
+	for (uint32 i = 0; i < dataSize; i++) {
+		data[i] ^= uint8(_codeTable[(i + start_point) % _kCodeTableSize]);
+		data[i] -= uint8(_codeTable[(i + start_point) % _kCodeTableSize] >> 8);
+	}
+}
+
+uint32 PackFile::read(void *dataPtr, uint32 dataSize) {
+	uint32 start_point, count;
+
+	start_point = uint32(pos());
+	count = _orgStream->read(dataPtr, dataSize);
+
+	if (err() || count != dataSize)
+		return 0;
+
+	if (_codeTable)
+		decode((uint8*)dataPtr, count, start_point);
+
+	return count;
+}
+
+bool PackFile::eos() const {
+	return _orgStream->eos();
+}
+
+int64 PackFile::pos() const {
+	return _orgStream->pos() - _offset;
+}
+
+int64 PackFile::size() const {
+	return _size;
+}
+
+bool PackFile::seek(int64 offset, int whence) {
+	if (_codeTable && whence == SEEK_SET)
+		offset += _offset;
+	return _orgStream->seek(offset, whence);
+}
+
+} // end of namespace Grim