/// <summary>
/// Write sector data, including the CRC, to the stream. The stream must be positioned at the first byte of the sector
/// payload data.
/// </summary>
/// <param name="data">Sector data buffer.</param>
/// <param name="offset">Offset of the first byte of sector data into the data buffer.</param>
/// <param name="length">Size of the sector data.</param>
private void WriteSectorData(byte[] data, int offset, int length)
{
Sync();
var blockId = trackStream.ReadByte();
if (blockId == -1)
{
throw new DiskImageFormatException("Sector data not found after sector address mark");
}
if (blockId != DataAddressMark)
{
throw new DiskImageFormatException(String.Format("Unexpected block type {0}", blockId));
}
var crc = new Crc16Ccitt();
crc.Add(0xa1);
crc.Add(0xa1);
crc.Add(0xa1);
crc.Add(DataAddressMark);
for (int i = 0; i < length; i++)
{
crc.Add(data[offset + i]);
}
trackStream.Write(data, offset, length);
trackStream.WriteByte((byte)((crc.Crc >> 8) & 0xff));
trackStream.WriteByte((byte)(crc.Crc & 0xff));
}
/// <summary>
/// Initialize (format) a track by writing headers and sectors to it.
/// </summary>
/// <param name="diskStream">Stream for writing the disk track.</param>
/// <param name="trackOffset">Byte offset of the track data in the disk image.</param>
/// <param name="headId">Side of disk for initializing the track.</param>
/// <param name="sectors">Collection of sectors to be written to the track.</param>
/// <returns>The track length in the disk image stream.</returns>
static internal int InitializeTrack(Stream diskStream, int trackOffset, int headId, IEnumerable <HfeSector> sectors)
{
var rawStream = new HfeRawTrack(diskStream, trackOffset, headId);
var trackStream = new MfmStream(rawStream);
trackStream.WriteBytes(0x4e, PreableLength);
foreach (var sector in sectors)
{
// Write gap preceeding sector ID record
trackStream.WriteBytes(0x4e, 24);
trackStream.WriteBytes(0x00, 12);
trackStream.WriteSync();
trackStream.WriteSync();
trackStream.WriteSync();
// Write sector ID record
var sectorInfo = sector.GetSectorInfo();
var encodedIdRecord = sectorInfo.Encode();
trackStream.Write(encodedIdRecord, 0, encodedIdRecord.Length);
// Write gap preceeding sector data record
trackStream.WriteBytes(0x4e, 22);
trackStream.WriteBytes(0x00, 12);
trackStream.WriteSync();
trackStream.WriteSync();
trackStream.WriteSync();
// Write sector data record
var encodedDataRecord = sector.Encode();
trackStream.Write(encodedDataRecord, 0, encodedDataRecord.Length);
}
trackStream.WriteBytes(0x4e, PostambleLength);
trackStream.Flush();
return(rawStream.TrackLength - trackOffset);
}