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## org.apache.commons.compress.compressors.bzip2
Class BZip2CompressorOutputStream

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

All Implemented Interfaces:
  Closeable, Flushable

    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

Field Summary
`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
`BZip2CompressorOutputStream(OutputStream out)` Constructs a new `CBZip2OutputStream` with a blocksize of 900k.
`BZip2CompressorOutputStream(OutputStream out, int blockSize)` Constructs a new `CBZip2OutputStream` with specified blocksize.

Method Summary
`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 close the 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 `CBZip2OutputStream` 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 `CBZip2OutputStream` 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 `CBZip2OutputStream`.
  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 close the 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`
  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.

### write

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

  Overrides:
    `write` in class `OutputStream`
  Throws:
    `IOException`

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