Package org.tukaani.xz

Class XZOutputStream

java.lang.Object

java.io.OutputStream

org.tukaani.xz.FinishableOutputStream

org.tukaani.xz.XZOutputStream

All Implemented Interfaces:

Closeable, Flushable, AutoCloseable

public class XZOutputStream
extends FinishableOutputStream

Compresses into the .xz file format.

Examples

Getting an output stream to compress with LZMA2 using the default settings and the default integrity check type (CRC64):

 FileOutputStream outfile = new FileOutputStream("foo.xz");
 XZOutputStream outxz = new XZOutputStream(outfile, new LZMA2Options());
 

Using the preset level 8 for LZMA2 (the default is 6) and SHA-256 instead of CRC64 for integrity checking:

 XZOutputStream outxz = new XZOutputStream(outfile, new LZMA2Options(8),
                                           XZ.CHECK_SHA256);
 

Using the x86 BCJ filter together with LZMA2 to compress x86 executables and printing the memory usage information before creating the XZOutputStream:

 X86Options x86 = new X86Options();
 LZMA2Options lzma2 = new LZMA2Options();
 FilterOptions[] options = { x86, lzma2 };
 System.out.println("Encoder memory usage: "
                    + FilterOptions.getEncoderMemoryUsage(options)
                    + " KiB");
 System.out.println("Decoder memory usage: "
                    + FilterOptions.getDecoderMemoryUsage(options)
                    + " KiB");
 XZOutputStream outxz = new XZOutputStream(outfile, options);
 

Constructor Summary

Constructors

Constructor	Description
XZOutputStream(OutputStream out, FilterOptions filterOptions)	Creates a new XZ compressor using one filter and CRC64 as the integrity check.
XZOutputStream(OutputStream out, FilterOptions[] filterOptions)	Creates a new XZ compressor using 1-4 filters and CRC64 as the integrity check.
XZOutputStream(OutputStream out, FilterOptions[] filterOptions, int checkType)	Creates a new XZ compressor using 1-4 filters and the specified integrity check type.
XZOutputStream(OutputStream out, FilterOptions[] filterOptions, int checkType, ArrayCache arrayCache)	Creates a new XZ compressor using 1-4 filters and the specified integrity check type.
XZOutputStream(OutputStream out, FilterOptions[] filterOptions, ArrayCache arrayCache)	Creates a new XZ compressor using 1-4 filters and CRC64 as the integrity check.
XZOutputStream(OutputStream out, FilterOptions filterOptions, int checkType)	Creates a new XZ compressor using one filter and the specified integrity check type.
XZOutputStream(OutputStream out, FilterOptions filterOptions, int checkType, ArrayCache arrayCache)	Creates a new XZ compressor using one filter and the specified integrity check type.
XZOutputStream(OutputStream out, FilterOptions filterOptions, ArrayCache arrayCache)	Creates a new XZ compressor using one filter and CRC64 as the integrity check.

Method Summary

Modifier and Type	Method	Description
void	close()	Finishes compression and closes the underlying stream.
void	endBlock()	Finishes the current XZ Block (but not the whole XZ Stream).
void	finish()	Finishes compression without closing the underlying stream.
void	flush()	Flushes the encoder and calls out.flush().
void	updateFilters(FilterOptions filterOptions)	Updates the filter chain with a single filter.
void	updateFilters(FilterOptions[] filterOptions)	Updates the filter chain with 1-4 filters.
void	write(byte[] buf, int off, int len)	Writes an array of bytes to be compressed.
void	write(int b)	Writes one byte to be compressed.

Methods inherited from class java.io.OutputStream

nullOutputStream, write

Methods inherited from class java.lang.Object

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

Constructor Details

XZOutputStream

public XZOutputStream(OutputStream out,
FilterOptions filterOptions)
               throws IOException

Creates a new XZ compressor using one filter and CRC64 as the integrity check. This constructor is equivalent to passing a single-member FilterOptions array to XZOutputStream(OutputStream, FilterOptions[]).

Parameters:

out - output stream to which the compressed data will be written

filterOptions - filter options to use

Throws:

UnsupportedOptionsException - invalid filter chain

IOException - may be thrown from out

XZOutputStream

public XZOutputStream(OutputStream out,
FilterOptions filterOptions,
ArrayCache arrayCache)
               throws IOException

Creates a new XZ compressor using one filter and CRC64 as the integrity check. This constructor is equivalent to passing a single-member FilterOptions array to XZOutputStream(OutputStream, FilterOptions[], ArrayCache).

Parameters:

out - output stream to which the compressed data will be written

filterOptions - filter options to use

arrayCache - cache to be used for allocating large arrays

Throws:

UnsupportedOptionsException - invalid filter chain

IOException - may be thrown from out

Since:

1.7

XZOutputStream

public XZOutputStream(OutputStream out,
FilterOptions filterOptions,
int checkType)
               throws IOException

Creates a new XZ compressor using one filter and the specified integrity check type. This constructor is equivalent to passing a single-member FilterOptions array to XZOutputStream(OutputStream, FilterOptions[], int).

Parameters:

out - output stream to which the compressed data will be written

filterOptions - filter options to use

checkType - type of the integrity check, for example XZ.CHECK_CRC32

Throws:

UnsupportedOptionsException - invalid filter chain

IOException - may be thrown from out

XZOutputStream

public XZOutputStream(OutputStream out,
FilterOptions filterOptions,
int checkType,
ArrayCache arrayCache)
               throws IOException

Creates a new XZ compressor using one filter and the specified integrity check type. This constructor is equivalent to passing a single-member FilterOptions array to XZOutputStream(OutputStream, FilterOptions[], int, ArrayCache).

Parameters:

out - output stream to which the compressed data will be written

filterOptions - filter options to use

checkType - type of the integrity check, for example XZ.CHECK_CRC32

arrayCache - cache to be used for allocating large arrays

Throws:

UnsupportedOptionsException - invalid filter chain

IOException - may be thrown from out

Since:

1.7

XZOutputStream

public XZOutputStream(OutputStream out,
FilterOptions[] filterOptions)
               throws IOException

Creates a new XZ compressor using 1-4 filters and CRC64 as the integrity check. This constructor is equivalent XZOutputStream(out, filterOptions, XZ.CHECK_CRC64).

Parameters:

out - output stream to which the compressed data will be written

filterOptions - array of filter options to use

Throws:

UnsupportedOptionsException - invalid filter chain

IOException - may be thrown from out

XZOutputStream

public XZOutputStream(OutputStream out,
FilterOptions[] filterOptions,
ArrayCache arrayCache)
               throws IOException

Creates a new XZ compressor using 1-4 filters and CRC64 as the integrity check. This constructor is equivalent XZOutputStream(out, filterOptions, XZ.CHECK_CRC64, arrayCache).

Parameters:

out - output stream to which the compressed data will be written

filterOptions - array of filter options to use

arrayCache - cache to be used for allocating large arrays

Throws:

UnsupportedOptionsException - invalid filter chain

IOException - may be thrown from out

Since:

1.7

XZOutputStream

public XZOutputStream(OutputStream out,
FilterOptions[] filterOptions,
int checkType)
               throws IOException

Creates a new XZ compressor using 1-4 filters and the specified integrity check type.

Parameters:

out - output stream to which the compressed data will be written

filterOptions - array of filter options to use

checkType - type of the integrity check, for example XZ.CHECK_CRC32

Throws:

UnsupportedOptionsException - invalid filter chain

IOException - may be thrown from out

XZOutputStream

public XZOutputStream(OutputStream out,
FilterOptions[] filterOptions,
int checkType,
ArrayCache arrayCache)
               throws IOException

Creates a new XZ compressor using 1-4 filters and the specified integrity check type.

Parameters:

out - output stream to which the compressed data will be written

filterOptions - array of filter options to use

checkType - type of the integrity check, for example XZ.CHECK_CRC32

arrayCache - cache to be used for allocating large arrays

Throws:

UnsupportedOptionsException - invalid filter chain

IOException - may be thrown from out

Since:

1.7

Method Details

updateFilters

public void updateFilters(FilterOptions filterOptions)
                   throws XZIOException

Updates the filter chain with a single filter. This is equivalent to passing a single-member FilterOptions array to updateFilters(FilterOptions[]).

Parameters:

filterOptions - new filter to use

Throws:

UnsupportedOptionsException - unsupported filter chain, or trying to change the filter chain in the middle of a Block

XZIOException

updateFilters

public void updateFilters(FilterOptions[] filterOptions)
                   throws XZIOException

Updates the filter chain with 1-4 filters.

Currently this cannot be used to update e.g. LZMA2 options in the middle of a XZ Block. Use endBlock() to finish the current XZ Block before calling this function. The new filter chain will then be used for the next XZ Block.

Parameters:

filterOptions - new filter chain to use

Throws:

UnsupportedOptionsException - unsupported filter chain, or trying to change the filter chain in the middle of a Block

XZIOException

write

public void write(int b)
           throws IOException

Writes one byte to be compressed.

Specified by:

write in class OutputStream

Throws:

XZIOException - XZ Stream has grown too big

XZIOException - finish() or close() was already called

IOException - may be thrown by the underlying output stream

write

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

Writes an array of bytes to be compressed. The compressors tend to do internal buffering and thus the written data won't be readable from the compressed output immediately. Use flush() to force everything written so far to be written to the underlaying output stream, but be aware that flushing reduces compression ratio.

Overrides:

write in class OutputStream

Parameters:

buf - buffer of bytes to be written

off - start offset in buf

len - number of bytes to write

Throws:

XZIOException - XZ Stream has grown too big: total file size about 8 EiB or the Index field exceeds 16 GiB; you shouldn't reach these sizes in practice

XZIOException - finish() or close() was already called and len > 0

IOException - may be thrown by the underlying output stream

endBlock

public void endBlock()
              throws IOException

Finishes the current XZ Block (but not the whole XZ Stream). This doesn't flush the stream so it's possible that not all data will be decompressible from the output stream when this function returns. Call also flush() if flushing is wanted in addition to finishing the current XZ Block.

If there is no unfinished Block open, this function will do nothing. (No empty XZ Block will be created.)

This function can be useful, for example, to create random-accessible .xz files.

Starting a new XZ Block means that the encoder state is reset. Doing this very often will increase the size of the compressed file a lot (more than plain flush() would do).

Throws:

XZIOException - XZ Stream has grown too big

XZIOException - stream finished or closed

IOException - may be thrown by the underlying output stream

flush

public void flush()
           throws IOException

Flushes the encoder and calls out.flush(). All buffered pending data will then be decompressible from the output stream.

Calling this function very often may increase the compressed file size a lot. The filter chain options may affect the size increase too. For example, with LZMA2 the HC4 match finder has smaller penalty with flushing than BT4.

Some filters don't support flushing. If the filter chain has such a filter, flush() will call endBlock() before flushing.

Specified by:

flush in interface Flushable

Overrides:

flush in class OutputStream

Throws:

XZIOException - XZ Stream has grown too big

XZIOException - stream finished or closed

IOException - may be thrown by the underlying output stream

finish

public void finish()
            throws IOException

Finishes compression without closing the underlying stream. No more data can be written to this stream after finishing (calling write with an empty buffer is OK).

Repeated calls to finish() do nothing unless an exception was thrown by this stream earlier. In that case the same exception is thrown again.

After finishing, the stream may be closed normally with close(). If the stream will be closed anyway, there usually is no need to call finish() separately.

Overrides:

finish in class FinishableOutputStream

Throws:

XZIOException - XZ Stream has grown too big

IOException - may be thrown by the underlying output stream

close

public void close()
           throws IOException

Finishes compression and closes the underlying stream. The underlying stream out is closed even if finishing fails. If both finishing and closing fail, the exception thrown by finish() is thrown and the exception from the failed out.close() is lost.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Overrides:

close in class OutputStream

Throws:

XZIOException - XZ Stream has grown too big

IOException - may be thrown by the underlying output stream