/// <summary>
/// Create a Dragon tape block object.
/// Note that it is possible to create illegal blocks using this method by providing an unsupported block type or an invalid
/// checksum. Use the <see cref="Validate">Validate</see> method to verify that the block is actually valid.
/// For supported block types, the returned object will be of the appropriate type.
/// </summary>
/// <param name="blocktype">Block type idenfifier.</param>
/// <param name="data">Array containing the block payload data, or <value>null</value> for no payload.</param>
/// <param name="offset">Offset into the data array of first byte of block payload data.</param>
/// <param name="length">Size of the block payload data.</param>
/// <param name="checksum">Block checksum.</param>
/// <returns>Dragon tape block object.</returns>
public static DragonTapeBlock CreateBlock(DragonTapeBlockType blocktype, byte[] data, int offset, int length, int checksum)
{
DragonTapeBlock block = null;
switch (blocktype)
{
case DragonTapeBlockType.Header:
block = new DragonTapeHeaderBlock(data, offset, length, checksum);
break;
case DragonTapeBlockType.Data:
block = new DragonTapeDataBlock(data, offset, length, checksum);
break;
case DragonTapeBlockType.EndOfFile:
block = new DragonTapeEofBlock(data, offset, length, checksum);
break;
default:
block = new DragonTapeBlock(blocktype);
block.SetData(data, offset, length);
block.Checksum = checksum;
break;
}
return(block);
}
/// <summary>
/// Reads the next file header block from tape.
/// This function will continue reading tape data until it finds a header block.
/// </summary>
/// <returns>The header block.</returns>
private DragonTapeHeaderBlock ReadHeaderBlock()
{
while (true)
{
DragonTapeBlock.Sync(Tape, 1);
var block = DragonTapeBlock.ReadBlockSynced(Tape);
if (block is DragonTapeHeaderBlock)
{
return((DragonTapeHeaderBlock)block);
}
}
}
/// <summary>
/// Reads a sequence of data blocks.
/// Reads data blocks until an EOF block is encoutered. Return the combined payload from the data blocks. Assumes that the tape is located
/// just following the header block.
/// </summary>
/// <param name="isgapped">Set if the blocks are recorded with gaps.</param>
/// <returns>Data payload</returns>
private byte[] ReadDataBlocks(string filename, bool isgapped)
{
/* Read blocks and put the block payloads into the blocks list. End when the EOF block is encountered. */
var blocks = new List <byte[]>();
var datalength = 0;
var eof = false;
while (!eof)
{
DragonTapeBlock.Sync(Tape, 0);
var block = DragonTapeBlock.ReadBlockSynced(Tape);
switch (block.BlockType)
{
case DragonTapeBlockType.Data:
blocks.Add(block.Data);
datalength += block.Length;
break;
case DragonTapeBlockType.EndOfFile:
eof = true;
break;
default:
throw new InvalidFileException(filename, String.Format("Unexpected block of type {0}", (int)block.BlockType));
}
}
/* Convert the individual blocks into a single byte array. */
var data = new byte[datalength];
var offset = 0;
for (int i = 0; i < blocks.Count; i++)
{
Array.Copy(blocks[i], 0, data, offset, blocks[i].Length);
offset += blocks[i].Length;
}
return(data);
}
