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common/formats/disk_image.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 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/bitarray.h"
+#include "common/ptr.h"
+#include "common/file.h"
+#include "common/debug.h"
+
+#ifndef COMMON_FORMATS_DISK_IMAGE_H
+#define COMMON_FORMATS_DISK_IMAGE_H
+
+namespace Common {
+
+// Disk image parsers / decoders
+//
+// These classes handle floppy disk image files. Multiple formats are supported.
+// An image's file name extension determines its format. DiskImage::open selects
+// the format and expected disk size. Data can be read by track/sector/offset
+// or by the calculated stream position. Several file systems can also be read.
+//
+// Supported image formats:
+//  .do   Apple II disk sectors. 35 tracks, 16 sectors, no encoding.
+//  .dsk  Same as .do. Note that alternative sector orders are not handled.
+//        Currently, if clients want to support images with a different sector
+//        order, then they will have to detect and handle it themselves.
+//  .d13  Apple II disk sectors. 35 tracks, 13 sectors, no encoding.
+//  .nib  Apple II disk nibbles. 35 tracks, 13 or 16 sectors, nibble-encoded.
+//  .woz  Apple II comprehensive disk bitstream. 35 tracks, 13 or 16 sectors.
+//        This encoding format takes a noticeable amount of time to decode.
+//  .img  PC disk sectors. 40 tracks, 8 sectors, no encoding.
+//  .xfd  Atari disk sectors. 40 tracks, 18 sectors, no encoding.
+//
+// For encoded formats, the default behavior is to decode every track when
+// opening an image. Lazy decoding can also be enabled, causing tracks to be
+// decoded when they are first accessed. This can significantly speed up access
+// if the format is expensive to decode but only a little data is needed.
+//
+// This code was originally part of the ADL engine.
+
+class SeekableReadStream;
+class String;
+
+/**
+ * Disk image formats that require decoding to read their sectors
+ */
+enum DiskImageEncoding {
+	DiskImageEncodingNone,
+	DiskImageEncodingNib,
+	DiskImageEncodingWoz
+};
+
+// Used for disk image detection
+int32 computeMD5(const Common::FSNode &node, Common::String &md5, uint32 md5Bytes);
+
+class DataBlock {
+public:
+	virtual ~DataBlock() { }
+
+	virtual Common::SeekableReadStream *createReadStream() const = 0;
+};
+
+typedef Common::SharedPtr<DataBlock> DataBlockPtr;
+typedef Common::ScopedPtr<Common::SeekableReadStream> StreamPtr;
+
+class Files {
+public:
+	virtual ~Files() { }
+
+	virtual const DataBlockPtr getDataBlock(const Common::Path &filename, uint offset = 0) const = 0;
+	virtual Common::SeekableReadStream *createReadStream(const Common::Path &filename, uint offset = 0) const = 0;
+	virtual bool exists(const Common::Path &filename) const = 0;
+
+protected:
+	class DataBlock : public Common::DataBlock {
+	public:
+		DataBlock(const Files *files, const Common::Path &filename, uint offset) :
+				_files(files),
+				_filename(filename),
+				_offset(offset) { }
+
+		Common::SeekableReadStream *createReadStream() const override {
+			return _files->createReadStream(_filename, _offset);
+		}
+
+	private:
+		const Common::Path _filename;
+		uint _offset;
+		const Files *_files;
+	};
+};
+
+class DiskImage {
+public:
+	DiskImage() :
+			_inputStream(nullptr),
+			_decodeStream(nullptr),
+			_decodeBuffer(nullptr),
+			_encoding(DiskImageEncodingNone),
+			_lazyDecoding(false),
+			_tracks(0),
+			_sectorsPerTrack(0),
+			_bytesPerSector(0),
+			_sectorLimit(0),
+			_firstSector(0) { }
+
+	~DiskImage() {
+		delete _inputStream;
+		delete _decodeStream; // frees _decodeBuffer
+	}
+
+	bool open(const Common::Path &filename);
+	bool open(const Common::FSNode &node);
+	const DataBlockPtr getDataBlock(uint track, uint sector, uint offset = 0, uint size = 0) const;
+	Common::SeekableReadStream *createReadStream(uint track, uint sector, uint offset = 0, uint size = 0, uint sectorsUsed = 0) const;
+	Common::SeekableReadStream *releaseStream();
+	Common::SeekableReadStream *getDiskStream() const { return _decodeBuffer ? _decodeStream : _inputStream; }
+	uint32 read(void *dataPtr, uint32 diskPosition, uint32 dataSize);
+	void setLazyDecoding(bool lazyDecoding) { _lazyDecoding = lazyDecoding; }
+	void setSectorLimit(uint sectorLimit) { _sectorLimit = sectorLimit; } // Maximum number of sectors to read per track before stepping
+	uint getBytesPerSector() const { return _bytesPerSector; }
+	uint getSectorsPerTrack() const { return _sectorsPerTrack; }
+	uint getTracks() const { return _tracks; }
+
+protected:
+	class DataBlock : public Common::DataBlock {
+	public:
+		DataBlock(const DiskImage *disk, uint track, uint sector, uint offset, uint size, uint sectorLimit) :
+				_track(track),
+				_sector(sector),
+				_offset(offset),
+				_size(size),
+				_sectorLimit(sectorLimit),
+				_disk(disk) { }
+
+		Common::SeekableReadStream *createReadStream() const override {
+			return _disk->createReadStream(_track, _sector, _offset, _size, _sectorLimit);
+		}
+
+	private:
+		uint _track, _sector, _offset, _size;
+		uint _sectorLimit;
+		const DiskImage *_disk;
+	};
+
+	Common::String _name;
+	Common::SeekableReadStream *_inputStream;
+	Common::SeekableReadStream *_decodeStream;
+	byte *_decodeBuffer;
+	Common::BitArray _decodedTracks;
+	DiskImageEncoding _encoding;
+	bool _lazyDecoding;
+
+	uint _tracks, _sectorsPerTrack, _bytesPerSector, _firstSector;
+	uint _sectorLimit;
+
+private:
+	bool open(const Common::String &name, Common::File *f);
+	void decodeTrack(uint track);
+};
+
+// Data in plain files
+class Files_Plain : public Files {
+public:
+	const DataBlockPtr getDataBlock(const Common::Path &filename, uint offset = 0) const override;
+	Common::SeekableReadStream *createReadStream(const Common::Path &filename, uint offset = 0) const override;
+	bool exists(const Common::Path &filename) const override { return Common::File::exists(filename); }
+};
+
+// Data in files contained in Apple DOS 3.3 disk image
+class Files_AppleDOS : public Files {
+public:
+	Files_AppleDOS();
+	~Files_AppleDOS() override;
+
+	bool open(const Common::Path &filename);
+	const DataBlockPtr getDataBlock(const Common::Path &filename, uint offset = 0) const override;
+	Common::SeekableReadStream *createReadStream(const Common::Path &filename, uint offset = 0) const override;
+	bool exists(const Common::Path &filename) const override { return _toc.contains(filename); }
+
+private:
+	enum FileType {
+		kFileTypeText = 0,
+		kFileTypeAppleSoft = 2,
+		kFileTypeBinary = 4
+	};
+
+	enum {
+		kSectorSize = 256,
+		kFilenameLen = 30
+	};
+
+	struct TrackSector {
+		byte track;
+		byte sector;
+	};
+
+	struct TOCEntry {
+		byte type;
+		uint16 totalSectors;
+		Common::Array<TrackSector> sectors;
+	};
+
+	void readVTOC();
+	void readSectorList(TrackSector start, Common::Array<TrackSector> &list);
+	Common::SeekableReadStream *createReadStreamText(const TOCEntry &entry) const;
+	Common::SeekableReadStream *createReadStreamBinary(const TOCEntry &entry) const;
+
+	DiskImage *_disk;
+	Common::HashMap<Common::Path, TOCEntry, Common::Path::IgnoreCase_Hash, Common::Path::IgnoreCase_EqualTo> _toc;
+};
+
+} // End of namespace Common
+
+#endif