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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.
+ *
+ */
+
+#ifndef SCI_ENGINE_FILE_H
+#define SCI_ENGINE_FILE_H
+
+#include "common/scummsys.h"
+
+namespace Sci {
+
+#ifdef ENABLE_SCI32
+
+/**
+ * An implementation of a virtual file that supports basic read and write
+ * operations simultaneously.
+ *
+ * This class has been initially implemented for Phantasmagoria, which has its
+ * own custom save/load code. The load code keeps checking for the existence
+ * of the save index file and keeps closing and reopening it for each save
+ * slot. This is notoriously slow and clumsy, and introduces noticeable delays,
+ * especially for non-desktop systems. Also, its game scripts request to open
+ * the index file for reading and writing with the same parameters
+ * (SaveManager::setCurrentSave and SaveManager::getCurrentSave). Moreover,
+ * the game scripts reopen the index file for writing in order to update it
+ * and seek within it. We do not support seeking in writeable streams, and the
+ * fact that our saved games are ZIP files makes this operation even more
+ * expensive. Finally, the savegame index file is supposed to be expanded when
+ * a new save slot is added.
+ * For the aforementioned reasons, this class has been implemented, which offers
+ * the basic functionality needed by the game scripts in Phantasmagoria.
+ */
+class VirtualIndexFile {
+public:
+	VirtualIndexFile(Common::String fileName);
+	~VirtualIndexFile();
+
+	uint32 read(char *buffer, uint32 size);
+	uint32 readLine(char *buffer, uint32 size);
+	uint32 write(const char *buffer, uint32 size);
+	bool seek(int32 offset, int whence);
+	void close();
+
+private:
+	char *_buffer;
+	uint32 _bufferSize;
+	char *_ptr;
+
+	Common::String _fileName;
+	bool _changed;
+};
+
+#endif
+
+} // End of namespace Sci
+
+#endif // SCI_ENGINE_FILE_H