org.bouncycastle.openpgp
Class PGPCompressedData

java.lang.Object
  org.bouncycastle.openpgp.PGPCompressedData

All Implemented Interfaces:

CompressionAlgorithmTags

public class PGPCompressedData

extends java.lang.Object

implements CompressionAlgorithmTags

A PGP compressed data object.

Field Summary

Fields inherited from interface org.bouncycastle.bcpg.CompressionAlgorithmTags

BZIP2, UNCOMPRESSED, ZIP, ZLIB

Constructor Summary

PGPCompressedData(BCPGInputStream pIn)
Construct a compressed data object, reading a single PacketTags.COMPRESSED_DATA packet from the stream.

PGPCompressedData(byte[] encData)
Construct a PGP compressed data object from the passed in byte array.

PGPCompressedData(java.io.InputStream inStream)
Construct a PGP compressed data object from the passed in input stream.

Method Summary

int	getAlgorithm() Return the compression algorithm used for this packet.
java.io.InputStream	getDataStream() Return an input stream that decompresses and returns data in the compressed packet.
java.io.InputStream	getDataStream(long limit) Return an input stream that decompresses and returns data in the compressed packet, failing with a StreamOverflowException (an IOException) once more than decompressed bytes have been read.
java.io.InputStream	getInputStream() Return the raw input stream contained in the object.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

PGPCompressedData

public PGPCompressedData(byte[] encData)
                  throws java.io.IOException

Construct a PGP compressed data object from the passed in byte array.

Parameters:

encData - an encoding of PGP compressed data.

Throws:

java.io.IOException - if an error occurs reading from the PGP input.

PGPCompressedData

public PGPCompressedData(java.io.InputStream inStream)
                  throws java.io.IOException

Construct a PGP compressed data object from the passed in input stream.

Parameters:

inStream - an input stream containing an encoding of PGP compressed data.

Throws:

java.io.IOException - if an error occurs reading from the PGP input.

PGPCompressedData

public PGPCompressedData(BCPGInputStream pIn)
                  throws java.io.IOException

Construct a compressed data object, reading a single PacketTags.COMPRESSED_DATA packet from the stream.

Parameters:

pIn - a PGP input stream, with a compressed data packet as the current packet.

Throws:

java.io.IOException - if an error occurs reading the packet from the stream.

Method Detail

getAlgorithm

public int getAlgorithm()

Return the compression algorithm used for this packet.

Returns:

the compression algorithm code

getInputStream

public java.io.InputStream getInputStream()

Return the raw input stream contained in the object.

Note that this stream is shared with the decompression stream, so consuming the returned stream will affect decompression.

Returns:

the raw data in the compressed data packet.

getDataStream

public java.io.InputStream getDataStream()
                                  throws PGPException

Return an input stream that decompresses and returns data in the compressed packet.

The OpenPGP compressed data packet carries no decompressed-length field, so the returned stream is unbounded: a small compressed packet can expand into an arbitrarily large amount of data (a "decompression bomb"). When processing untrusted input, a caller that buffers the full decompressed output should bound it — by reading incrementally, or by using getDataStream(long) to cap the number of decompressed bytes.

Returns:

a stream over the uncompressed data.

Throws:

PGPException - if an error occurs constructing the decompression stream.

getDataStream

public java.io.InputStream getDataStream(long limit)
                                  throws PGPException

Return an input stream that decompresses and returns data in the compressed packet, failing with a StreamOverflowException (an IOException) once more than decompressed bytes have been read. This caps the "decompression bomb" amplification of an untrusted compressed packet for callers that buffer the decompressed output.

The limit applies to the decompressed byte count. For BZIP2 the underlying decompressor still allocates its fixed working buffers — sized by the packet's block-size header, up to ~4.5MB — when the stream is constructed, independently of this limit.

Parameters:

limit - the maximum number of decompressed bytes that may be read, or a negative value for no limit (equivalent to getDataStream()).

Returns:

a stream over the uncompressed data, bounded to bytes.

Throws:

PGPException - if an error occurs constructing the decompression stream.