org.at4j.comp.lzma
Class LzmaInputStream

java.lang.Object
  java.io.InputStream
      org.at4j.comp.lzma.LzmaInputStream

All Implemented Interfaces:

Closeable

public final class LzmaInputStream
extends InputStream

This class provides an InputStream for decoding data using the Lempel-Ziv-Markov chain algorithm. It uses the LZMA decoder from the LZMA SDK.

The API from the LZMA SDK is built around a standalone decoder. To adapt that into the Java streams API, the decoder is launched in a separate execution thread. The decoder writes data to a blocking queue that this stream reads its data from.

Errors are propagated up from the decoder to the calling thread. If an error occurs in the decoder, it will be reported to the calling thread the next time that it tries to read from or close the stream.

Decoding a file consumes a lot of memory – up to the dictionary size set when encoding it multiplied with the decoder data queue depth plus one. (The default dictionary size is 2^23 = 8.4 MB and the default data queue depth is 1.)

By default, data in an LZMA stream has the following format:

1. Settings used when encoding (5 bytes)
2. Total size of data in the stream when uncompressed (8 bytes, little endian). This may be set to -1 if the size of the data was unknown at the time of compression (stream mode). If so, the data part must be followed by an end of stream marker
3. Data
4. End of stream marker (if the total data size was set to -1)

When LZMA compressed data is used in a setting where some of the header data may be known before opening the stream, such as in a Zip file, the settings header may be omitted. When creating this stream, the client may pass in a LzmaInputStreamSettings object that says which headers the stream can expect to find.

Since:

1.0

Author:

Karl Gustafsson

See Also:

LzmaInputStreamSettings, LzmaOutputStream

Constructor Summary

LzmaInputStream(InputStream is)
Create a LZMA decoding stream using the default settings.

LzmaInputStream(InputStream is, LzmaInputStreamSettings settings)
Create a LZMA decoding stream using custom settings.

Method Summary

void	close()
protected void	finalize()
int	read()
int	read(byte[] barr)
int	read(byte[] barr, int off, int len)

Methods inherited from class java.io.InputStream

available, mark, markSupported, reset, skip

Methods inherited from class java.lang.Object

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

Constructor Detail

LzmaInputStream

public LzmaInputStream(InputStream is)

Create a LZMA decoding stream using the default settings.

Parameters:

is - The stream containing LZMA encoded data. Since this stream is read in a separate thread, a lock-aware stream such as one returned from Files.openForRead(org.entityfs.ReadableFile) cannot be used.

See Also:

LzmaInputStream(InputStream, LzmaInputStreamSettings), LzmaInputStreamSettings

LzmaInputStream

public LzmaInputStream(InputStream is,
                       LzmaInputStreamSettings settings)
                throws IllegalArgumentException

Create a LZMA decoding stream using custom settings.

Parameters:

is - The stream containing LZMA encoded data. Since this stream is read in a separate thread, a lock-aware stream such as one returned from Files.openForRead(org.entityfs.ReadableFile) cannot be used.

settings - The compression settings that were used when writing the compressed data.

Throws:

IllegalArgumentException - If the uncompressed size is less than -1.

Method Detail

read

public int read()
         throws IOException

Specified by:

read in class InputStream

Throws:

IOException

read

public int read(byte[] barr)
         throws IOException

Overrides:

read in class InputStream

Throws:

IOException

read

public int read(byte[] barr,
                int off,
                int len)
         throws IOException

Overrides:

read in class InputStream

Throws:

IOException

close

public void close()
           throws IOException

Specified by:

close in interface Closeable

Overrides:

close in class InputStream

Throws:

IOException

finalize

protected void finalize()
                 throws Throwable

Overrides:

finalize in class Object

Throws:

Throwable