Class LZ4BlockOutputStream

java.lang.Object

java.io.OutputStream

java.io.FilterOutputStream

net.jpountz.lz4.LZ4BlockOutputStream

All Implemented Interfaces:

Closeable, Flushable, AutoCloseable

public class LZ4BlockOutputStream
extends FilterOutputStream

Streaming LZ4 (not compatible with the LZ4 Frame format). This class compresses data into fixed-size blocks of compressed data. This class uses its own format and is not compatible with the LZ4 Frame format. For interoperability with other LZ4 tools, use LZ4FrameOutputStream, which is compatible with the LZ4 Frame format. This class remains for backward compatibility.

Each block starts with a header made of the magic bytes "LZ4Block", a token byte, the compressed length, the decompressed length and a checksum of the decompressed data (all three as 32-bit little-endian integers), followed by the block data. The high nibble of the token is the compression method (0x10 for raw, 0x20 for LZ4) and the low nibble is the block size exponent, max(0, ceil(log2(blockSize)) - 10). When the default checksum is used, the checksum field is the XXHash32 (seed 0x9747b28c) of the uncompressed block, masked to its low 28 bits (see StreamingXXHash32.asChecksum()). The exception is the end-of-stream block written by finish(), which is a raw block whose lengths and checksum are all 0.

See Also:

• LZ4BlockInputStream
• LZ4FrameOutputStream

Field Summary

Fields inherited from class FilterOutputStream

out

Constructor Summary

Constructors

Constructor	Description
LZ4BlockOutputStream(OutputStream out)	Creates a new instance which compresses into blocks of 64 KB.
LZ4BlockOutputStream(OutputStream out, int blockSize)	Creates a new instance which compresses with the standard LZ4 compression algorithm.
LZ4BlockOutputStream(OutputStream out, int blockSize, LZ4Compressor compressor)	Creates a new instance which checks stream integrity using StreamingXXHash32 and doesn't sync flush.
LZ4BlockOutputStream(OutputStream out, int blockSize, LZ4Compressor compressor, Checksum checksum, boolean syncFlush)	Creates a new OutputStream with configurable block size.

Method Summary

Modifier and Type	Method	Description
void	close()
void	finish()	Same as close() except that it doesn't close the underlying stream.
void	flush()	Flushes this compressed OutputStream.
String	toString()
void	write(byte[] b)
void	write(byte[] b, int off, int len)
void	write(int b)

Methods inherited from class OutputStream

nullOutputStream

Methods inherited from class Object

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

Constructor Details

LZ4BlockOutputStream

public LZ4BlockOutputStream(OutputStream out,
 int blockSize,
 LZ4Compressor compressor,
 Checksum checksum,
 boolean syncFlush)

Creates a new OutputStream with configurable block size. Large blocks require more memory at compression and decompression time but should improve the compression ratio.

Parameters:

out - the OutputStream to feed

blockSize - the maximum number of bytes to try to compress at once, must be >= 64 and <= 32 M

compressor - the LZ4Compressor instance to use to compress data

checksum - the Checksum instance to use to check data for integrity.

syncFlush - true if pending data should also be flushed on flush()

LZ4BlockOutputStream

public LZ4BlockOutputStream(OutputStream out,
 int blockSize,
 LZ4Compressor compressor)

Creates a new instance which checks stream integrity using StreamingXXHash32 and doesn't sync flush.

Parameters:

out - the OutputStream to feed

blockSize - the maximum number of bytes to try to compress at once, must be >= 64 and <= 32 M

compressor - the LZ4Compressor instance to use to compress data

See Also:

• LZ4BlockOutputStream(OutputStream, int, LZ4Compressor, Checksum, boolean)
• StreamingXXHash32.asChecksum()

LZ4BlockOutputStream

public LZ4BlockOutputStream(OutputStream out,
 int blockSize)

Creates a new instance which compresses with the standard LZ4 compression algorithm.

Parameters:

out - the OutputStream to feed

blockSize - the maximum number of bytes to try to compress at once, must be >= 64 and <= 32 M

See Also:

• LZ4BlockOutputStream(OutputStream, int, LZ4Compressor)
• LZ4Factory.fastCompressor()

LZ4BlockOutputStream

public LZ4BlockOutputStream(OutputStream out)

Creates a new instance which compresses into blocks of 64 KB.

Parameters:

out - the OutputStream to feed

See Also:

• LZ4BlockOutputStream(OutputStream, int)

Method Details

write

public void write(int b)
           throws IOException

Overrides:

write in class FilterOutputStream

Throws:

IOException

write

public void write(byte[] b,
 int off,
 int len)
           throws IOException

Overrides:

write in class FilterOutputStream

Throws:

IOException

write

public void write(byte[] b)
           throws IOException

Overrides:

write in class FilterOutputStream

Throws:

IOException

close

public void close()
           throws IOException

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Overrides:

close in class FilterOutputStream

Throws:

IOException

flush

public void flush()
           throws IOException

Flushes this compressed OutputStream.

If the stream has been created with syncFlush=true, pending data will be compressed and appended to the underlying OutputStream before calling OutputStream.flush() on the underlying stream. Otherwise, this method just flushes the underlying stream, so pending data might not be available for reading until finish() or close() is called.

Specified by:

flush in interface Flushable

Overrides:

flush in class FilterOutputStream

Throws:

IOException

finish

public void finish()
            throws IOException

Same as close() except that it doesn't close the underlying stream. This can be useful if you want to keep on using the underlying stream.

Throws:

IOException - if an I/O error occurs.

toString

public String toString()

Overrides:

toString in class Object