disk_image.h

/* 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;

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