/// <exception cref="System.IO.IOException"/>
public BZip2CompressionInputStream(InputStream @in, long start, long end, SplittableCompressionCodec.READ_MODE
readMode)
: base(@in, start, end)
{
// class data starts here//
// Following state machine handles different states of compressed stream
// position
// HOLD : Don't advertise compressed stream position
// ADVERTISE : Read 1 more character and advertise stream position
// See more comments about it before updatePos method.
// class data ends here//
needsReset = false;
bufferedIn = new BufferedInputStream(base.@in);
this.startingPos = base.GetPos();
this.readMode = readMode;
if (this.startingPos == 0)
{
// We only strip header if it is start of file
bufferedIn = ReadStreamHeader();
}
input = new CBZip2InputStream(bufferedIn, readMode);
if (this.isHeaderStripped)
{
input.UpdateReportedByteCount(HeaderLen);
}
if (this.isSubHeaderStripped)
{
input.UpdateReportedByteCount(SubHeaderLen);
}
this.UpdatePos(false);
}
/// <summary>Create a stream as dictated by the readMode.</summary>
/// <remarks>
/// Create a stream as dictated by the readMode. This method is used when
/// the codecs wants the ability to work with the underlying stream positions.
/// </remarks>
/// <param name="seekableIn">The seekable input stream (seeks in compressed data)</param>
/// <param name="start">
/// The start offset into the compressed stream. May be changed
/// by the underlying codec.
/// </param>
/// <param name="end">
/// The end offset into the compressed stream. May be changed by
/// the underlying codec.
/// </param>
/// <param name="readMode">
/// Controls whether stream position is reported continuously
/// from the compressed stream only only at block boundaries.
/// </param>
/// <returns>a stream to read uncompressed bytes from</returns>
/// <exception cref="System.IO.IOException"/>
public abstract SplitCompressionInputStream CreateInputStream(InputStream seekableIn
, Decompressor decompressor, long start, long end, SplittableCompressionCodec.READ_MODE
readMode);
/// <summary>
/// Creates CompressionInputStream to be used to read off uncompressed data
/// in one of the two reading modes.
/// </summary>
/// <remarks>
/// Creates CompressionInputStream to be used to read off uncompressed data
/// in one of the two reading modes. i.e. Continuous or Blocked reading modes
/// </remarks>
/// <param name="seekableIn">The InputStream</param>
/// <param name="start">The start offset into the compressed stream</param>
/// <param name="end">The end offset into the compressed stream</param>
/// <param name="readMode">
/// Controls whether progress is reported continuously or
/// only at block boundaries.
/// </param>
/// <returns>CompressionInputStream for BZip2 aligned at block boundaries</returns>
/// <exception cref="System.IO.IOException"/>
public virtual SplitCompressionInputStream CreateInputStream(InputStream seekableIn
, Decompressor decompressor, long start, long end, SplittableCompressionCodec.READ_MODE
readMode)
{
if (!(seekableIn is Seekable))
{
throw new IOException("seekableIn must be an instance of " + typeof(Seekable).FullName
);
}
//find the position of first BZip2 start up marker
((Seekable)seekableIn).Seek(0);
// BZip2 start of block markers are of 6 bytes. But the very first block
// also has "BZh9", making it 10 bytes. This is the common case. But at
// time stream might start without a leading BZ.
long FirstBzip2BlockMarkerPosition = CBZip2InputStream.NumberOfBytesTillNextMarker
(seekableIn);
long adjStart = Math.Max(0L, start - FirstBzip2BlockMarkerPosition);
((Seekable)seekableIn).Seek(adjStart);
SplitCompressionInputStream @in = new BZip2Codec.BZip2CompressionInputStream(seekableIn
, adjStart, end, readMode);
// The following if clause handles the following case:
// Assume the following scenario in BZip2 compressed stream where
// . represent compressed data.
// .....[48 bit Block].....[48 bit Block].....[48 bit Block]...
// ........................[47 bits][1 bit].....[48 bit Block]...
// ................................^[Assume a Byte alignment here]
// ........................................^^[current position of stream]
// .....................^^[We go back 10 Bytes in stream and find a Block marker]
// ........................................^^[We align at wrong position!]
// ...........................................................^^[While this pos is correct]
if (@in.GetPos() < start)
{
((Seekable)seekableIn).Seek(start);
@in = new BZip2Codec.BZip2CompressionInputStream(seekableIn, start, end, readMode
);
}
return(@in);
}
