Exemplo n.º 1
0
        /// <summary>
        /// Reads a single <see cref="Chunk"/> from the file.
        /// </summary>
        /// <returns>The parsed <see cref="Chunk"/> -or- <see langword="null"/> if the end of the file has been reached.</returns>
        /// <exception cref="IOException">An I/O error occurred.</exception>
        /// <exception cref="SmfDecoderException">The file is corrupt and/or cannot be decoded due to a fatal error.</exception>
        public Chunk ReadChunk()
        {
            var isEof = _source.BaseStream.Position >= _source.BaseStream.Length - 1;

            if (_ntrks == 0)
            {
                if (isEof)
                {
                    _logger?.Info(Strings.FinishedAtEnd, _source.BaseStream.Position);
                }
                else
                {
                    _logger?.Warn(Strings.FinishedBeforeEnd, _source.BaseStream.Position);
                }
                return(null);
            }
            if (isEof)
            {
                var msg = string.Format(Strings.UnexpectedEofTracks, _ntrks);
                _logger?.Fatal(msg, _source.BaseStream.Position);
                throw new SmfDecoderException(msg, _source.BaseStream.Position);
            }

            // Read id and length
            var id  = Encoding.ASCII.GetString(_source.ReadBytes(4));
            var len = MidiBytesConverter.ReadBigEndianUInt(_source.ReadBytes(4));

            // Begin decoding the data by chunk type
            switch (id)
            {
            case MidiHeader.HeaderIdentifier:
                if (_ntrks > -1)
                {
                    _logger?.Error(Strings.DuplicateHeader, _source.BaseStream.Position - 8);
                }
                var next = _source.BaseStream.Position + len;
                // Read the values
                var format = MidiBytesConverter.ReadBigEndianUShort(_source.ReadBytes(2));
                _ntrks = MidiBytesConverter.ReadBigEndianUShort(_source.ReadBytes(2));
                var div = MidiBytesConverter.ReadBigEndianShort(_source.ReadBytes(2));
                // Jump to next chunk if case the header is longer than 6 for some reason
                if (_source.BaseStream.Position < next)
                {
                    _logger?.Warn(Strings.WrongLength, _source.BaseStream.Position - 10);
                    _source.BaseStream.Position = next;
                }
                // Create the header chunk object, taking in to account the time division method used
                return(div < 0 ? new MidiHeader(format, (ushort)_ntrks, (sbyte)(div >> 8), (byte)(div & 0xFF)) : new MidiHeader(format, (ushort)_ntrks, div));

            case MidiTrack.TrackIdentifier:
                if (_ntrks == -1)
                {
                    _logger?.Warn(Strings.NoHeader, _source.BaseStream.Position - 8);
                }
                // Read all the events in the track and return the track
                return(new MidiTrack(ReadTrackEvents(len)));

            default:
                _logger?.Error(Strings.UnknownChunk, _source.BaseStream.Position - 8);
                return(new UnknownChunk(id, _source.ReadBytes((int)len)));
            }
        }
Exemplo n.º 2
0
        private TrackEvent ReadTrackEvent()
        {
            var deltaTime = ReadVariableLengthEncoding();
            // "Running Status": The last status byte is implied
            var statusByte = _lastStatusByte;
            var firstByte  = _source.ReadByte();

            // Check for new status byte
            if ((firstByte & 0x80) == 1)
            {
                statusByte = firstByte;
                firstByte  = _source.ReadByte();
            }

            var statusUpper = statusByte >> 4;

            // Save running status
            if (statusUpper > 0x7 && statusUpper < 0xF)
            {
                _lastStatusByte = statusByte;
            }
            // Parse the event
            var       statusLower = (byte)(statusByte & 0xF);
            MidiEvent ev          = null;

            switch (statusUpper)
            {
            case 0x8:
                ev = new NoteOff(statusLower, firstByte, _source.ReadByte());
                break;

            case 0x9:
                ev = new NoteOn(statusLower, firstByte, _source.ReadByte());
                break;

            case 0xA:
                ev = new PolyphonicKeyPressure(statusLower, firstByte, _source.ReadByte());
                break;

            case 0xB:
                if (firstByte < 120)
                {
                    ev = new ControlChange(statusLower, firstByte, _source.ReadByte());
                }
                else
                {
                    ev = new ChannelMode(statusLower, firstByte, _source.ReadByte());
                }
                break;

            case 0xC:
                ev = new ProgramChange(statusLower, firstByte);
                break;

            case 0xD:
                ev = new ChannelPressure(statusLower, firstByte);
                break;

            case 0xE:
                ev = new PitchBend(statusLower, firstByte, _source.ReadByte());
                break;

            case 0xF:
                switch (statusLower)
                {
                case 0x0:
                case 0x7:
                    ev = new SysEx(statusLower == 0, _source.ReadBytes(ReadVariableLengthEncoding(firstByte)));
                    break;

                case 0xF:
                    var len  = ReadVariableLengthEncoding();
                    var data = _source.ReadBytes(len);
                    switch (firstByte)
                    {
                    case 0x01:
                    case 0x02:
                    case 0x03:
                    case 0x04:
                    case 0x05:
                    case 0x06:
                    case 0x07:
                    case 0x08:
                    case 0x09:
                    case 0x0A:
                    case 0x0B:
                    case 0x0C:
                    case 0x0D:
                    case 0x0E:
                    case 0x0F:
                        ev = new TextEvent(Encoding.UTF8.GetString(data));             // TODO: Let user choose encoding
                        break;

                    case 0x20:
                        ev = new ChannelPrefix(data[0]);
                        break;

                    case 0x2F:
                        ev = new EndOfTrack();
                        break;

                    case 0x51:
                        ev = new SetTempo(MidiBytesConverter.ReadBigEndian24Bit(data));
                        break;

                    case 0x54:
                        ev = new SmpteOffset((byte)((data[0] >> 5) & 0x3), (byte)(data[0] & 0x1F), data[1], data[2], data[3], data[4]);
                        break;

                    case 0x58:
                        ev = new TimeSignature(data[0], data[1], data[2], data[3]);
                        break;

                    case 0x59:
                        ev = new KeySignature((sbyte)data[0], data[1] == 1);
                        break;

                    case 0x7F:
                        ev = new SequencerSpecificMetaEvent(data);
                        break;

                    default:
                        // TODO: Unrecognized metadata kind, non-fatal error
                        break;
                    }
                    break;

                default:
                    // At this point, if the event was not recognized: FATAL ERROR!
                    throw new NotImplementedException();
                }
                break;

            default:
                // At this point, if the event was not recognized: FATAL ERROR!
                throw new NotImplementedException();
            }

            return(new TrackEvent(deltaTime, ev));
        }