BZip2CompressorOutputStream (Apache Commons Compress 1.20 API)

java.lang.Object
- java.io.OutputStream
- - org.apache.commons.compress.compressors.CompressorOutputStream
  - - org.apache.commons.compress.compressors.bzip2.BZip2CompressorOutputStream

All Implemented Interfaces:: Closeable, Flushable, AutoCloseable

public class BZip2CompressorOutputStream
extends CompressorOutputStream

An output stream that compresses into the BZip2 format into another stream.

The compression requires large amounts of memory. Thus you should call the close() method as soon as possible, to force BZip2CompressorOutputStream to release the allocated memory.

You can shrink the amount of allocated memory and maybe raise the compression speed by choosing a lower blocksize, which in turn may cause a lower compression ratio. You can avoid unnecessary memory allocation by avoiding using a blocksize which is bigger than the size of the input.

You can compute the memory usage for compressing by the following formula:

 <code>400k + (9 * blocksize)</code>.

To get the memory required for decompression by BZip2CompressorInputStream use

 <code>65k + (5 * blocksize)</code>.

Memory usage by blocksize
Blocksize	Compression memory usage	Decompression memory usage
100k	1300k	565k
200k	2200k	1065k
300k	3100k	1565k
400k	4000k	2065k
500k	4900k	2565k
600k	5800k	3065k
700k	6700k	3565k
800k	7600k	4065k
900k	8500k	4565k

For decompression BZip2CompressorInputStream allocates less memory if the bzipped input is smaller than one block.

Instances of this class are not threadsafe.

TODO: Update to BZip2 1.0.1

This class is not thread-safe

Field Summary

Fields
Modifier and Type	Field and Description
`static int`	`BASEBLOCKSIZE`
`static int`	`G_SIZE`
`static int`	`MAX_ALPHA_SIZE`
`static int`	`MAX_BLOCKSIZE` The maximum supported blocksize `== 9`.
`static int`	`MAX_CODE_LEN`
`static int`	`MAX_SELECTORS`
`static int`	`MIN_BLOCKSIZE` The minimum supported blocksize `== 1`.
`static int`	`N_GROUPS`
`static int`	`N_ITERS`
`static int`	`NUM_OVERSHOOT_BYTES`
`static int`	`RUNA`
`static int`	`RUNB`

Constructor Summary

Constructors
Constructor and Description
`BZip2CompressorOutputStream(OutputStream out)` Constructs a new `BZip2CompressorOutputStream` with a blocksize of 900k.
`BZip2CompressorOutputStream(OutputStream out, int blockSize)` Constructs a new `BZip2CompressorOutputStream` with specified blocksize.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`static int`	`chooseBlockSize(long inputLength)` Chooses a blocksize based on the given length of the data to compress.
`void`	`close()`
`protected void`	`finalize()` Overriden to warn about an unclosed stream.
`void`	`finish()`
`void`	`flush()`
`int`	`getBlockSize()` Returns the blocksize parameter specified at construction time.
`void`	`write(byte[] buf, int offs, int len)`
`void`	`write(int b)`

Methods inherited from class java.io.OutputStream
write

Methods inherited from class java.lang.Object
clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - MIN_BLOCKSIZE
```
public static final int MIN_BLOCKSIZE
```
    The minimum supported blocksize == 1.
    
    See Also:
    
    Constant Field Values
  - MAX_BLOCKSIZE
```
public static final int MAX_BLOCKSIZE
```
    The maximum supported blocksize == 9.
    
    See Also:
    
    Constant Field Values
  - BASEBLOCKSIZE
```
public static final int BASEBLOCKSIZE
```
    See Also:
    
    Constant Field Values
  - MAX_ALPHA_SIZE
```
public static final int MAX_ALPHA_SIZE
```
    See Also:
    
    Constant Field Values
  - MAX_CODE_LEN
```
public static final int MAX_CODE_LEN
```
    See Also:
    
    Constant Field Values
  - RUNA
```
public static final int RUNA
```
    See Also:
    
    Constant Field Values
  - RUNB
```
public static final int RUNB
```
    See Also:
    
    Constant Field Values
  - N_GROUPS
```
public static final int N_GROUPS
```
    See Also:
    
    Constant Field Values
  - G_SIZE
```
public static final int G_SIZE
```
    See Also:
    
    Constant Field Values
  - N_ITERS
```
public static final int N_ITERS
```
    See Also:
    
    Constant Field Values
  - MAX_SELECTORS
```
public static final int MAX_SELECTORS
```
    See Also:
    
    Constant Field Values
  - NUM_OVERSHOOT_BYTES
```
public static final int NUM_OVERSHOOT_BYTES
```
    See Also:
    
    Constant Field Values
- Constructor Detail
  - BZip2CompressorOutputStream
```
public BZip2CompressorOutputStream(OutputStream out)
                            throws IOException
```
    Constructs a new BZip2CompressorOutputStream with a blocksize of 900k.
    
    Parameters:
    
    out - the destination stream.
    
    Throws:
    
    IOException - if an I/O error occurs in the specified stream.
    
    NullPointerException - if out == null.
  - BZip2CompressorOutputStream
```
public BZip2CompressorOutputStream(OutputStream out,
                                   int blockSize)
                            throws IOException
```
    Constructs a new BZip2CompressorOutputStream with specified blocksize.
    
    Parameters:
    
    out - the destination stream.
    
    blockSize - the blockSize as 100k units.
    
    Throws:
    
    IOException - if an I/O error occurs in the specified stream.
    
    IllegalArgumentException - if (blockSize < 1) || (blockSize > 9).
    
    NullPointerException - if out == null.
    
    See Also:
    
    MIN_BLOCKSIZE, MAX_BLOCKSIZE
- Method Detail
  - chooseBlockSize
```
public static int chooseBlockSize(long inputLength)
```
    Chooses a blocksize based on the given length of the data to compress.
    
    Parameters:
    
    inputLength - The length of the data which will be compressed by BZip2CompressorOutputStream.
    
    Returns:
    
    The blocksize, between MIN_BLOCKSIZE and MAX_BLOCKSIZE both inclusive. For a negative inputLength this method returns MAX_BLOCKSIZE always.
  - write
```
public void write(int b)
           throws IOException
```
    Specified by:
    
    write in class OutputStream
    
    Throws:
    
    IOException
  - finalize
```
protected void finalize()
                 throws Throwable
```
    Overriden to warn about an unclosed stream.
    
    Overrides:
    
    finalize in class Object
    
    Throws:
    
    Throwable
  - finish
```
public void finish()
            throws IOException
```
    Throws:
    
    IOException
  - close
```
public void close()
           throws IOException
```
    Specified by:
    
    close in interface Closeable
    
    Specified by:
    
    close in interface AutoCloseable
    
    Overrides:
    
    close in class OutputStream
    
    Throws:
    
    IOException
  - flush
```
public void flush()
           throws IOException
```
    Specified by:
    
    flush in interface Flushable
    
    Overrides:
    
    flush in class OutputStream
    
    Throws:
    
    IOException
  - getBlockSize
```
public final int getBlockSize()
```
    Returns the blocksize parameter specified at construction time.
    
    Returns:
    
    the blocksize parameter specified at construction time
  - write
```
public void write(byte[] buf,
                  int offs,
                  int len)
           throws IOException
```
    Overrides:
    
    write in class OutputStream
    
    Throws:
    
    IOException

Class BZip2CompressorOutputStream

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.io.OutputStream

Methods inherited from class java.lang.Object

Field Detail

MIN_BLOCKSIZE

MAX_BLOCKSIZE

BASEBLOCKSIZE

MAX_ALPHA_SIZE

MAX_CODE_LEN

RUNA

RUNB

N_GROUPS

G_SIZE

N_ITERS

MAX_SELECTORS

NUM_OVERSHOOT_BYTES

Constructor Detail

BZip2CompressorOutputStream

BZip2CompressorOutputStream

Method Detail

chooseBlockSize

write

finalize

finish

close

flush

getBlockSize

write