/// <summary>Prepares a new block for decompression if any remain in the stream</summary>
/// <remarks>If a previous block has completed, its CRC is checked and merged into the stream CRC.
/// If the previous block was the final block in the stream, the stream CRC is validated</remarks>
/// <return>true if a block was successfully initialised, or false if the end of file marker was encountered</return>
/// <exception>If either the block or stream CRC check failed, if the following data is
/// not a valid block-header or end-of-file marker, or if the following block could not be decoded</exception>
private bool InitialiseNextBlock() {
/* If we're already at the end of the stream, do nothing */
if (this.streamComplete)
return false;
/* If a block is complete, check the block CRC and integrate it into the stream CRC */
if (this.blockDecompressor != null) {
uint blockCRC = this.blockDecompressor.CheckCrc();
this.streamCRC = ((this.streamCRC << 1) | (this.streamCRC >> 31)) ^ blockCRC;
}
/* Read block-header or end-of-stream marker */
uint marker1 = this.bitInputStream.ReadBits(24);
uint marker2 = this.bitInputStream.ReadBits(24);
if (marker1 == BZip2BlockCompressor.BLOCK_HEADER_MARKER_1 && marker2 == BZip2BlockCompressor.BLOCK_HEADER_MARKER_2) {
// Initialise a new block
try {
this.blockDecompressor = new BZip2BlockDecompressor(this.bitInputStream, this.streamBlockSize);
} catch (IOException) {
// If the block could not be decoded, stop trying to read more data
this.streamComplete = true;
throw;
}
return true;
}
if (marker1 == BZip2OutputStream.STREAM_END_MARKER_1 && marker2 == BZip2OutputStream.STREAM_END_MARKER_2) {
// Read and verify the end-of-stream CRC
this.streamComplete = true;
uint storedCombinedCRC = this.bitInputStream.ReadInteger(); ///.ReadBits(32);
if (storedCombinedCRC != this.streamCRC)
throw new Exception ("BZip2 stream CRC error");
return false;
}
/* If what was read is not a valid block-header or end-of-stream marker, the stream is broken */
this.streamComplete = true;
throw new Exception ("BZip2 stream format error");
}
public override void Close()
{
if (this.bitInputStream == null)
return;
this.streamComplete = true;
this.blockDecompressor = null;
this.bitInputStream = null;
try {
this.inputStream.Close();
} finally {
this.inputStream = null;
}
}