CBZip2OutputStream (Hadoop 1.2.2-SNAPSHOT API)

java.lang.Object
- java.io.OutputStream
- - org.apache.hadoop.io.compress.bzip2.CBZip2OutputStream

所有已实现的接口:: Closeable, Flushable, AutoCloseable, BZip2Constants

public class CBZip2OutputStream
extends OutputStream
implements BZip2Constants

An output stream that compresses into the BZip2 format (without the file header chars) into another stream.

The compression requires large amounts of memory. Thus you should call the close() method as soon as possible, to force CBZip2OutputStream 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 CBZip2InputStream 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 CBZip2InputStream 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

字段概要

字段
限定符和类型	字段和说明
`protected static int`	`CLEARMASK` This constant is accessible by subclasses for historical purposes.
`protected static int`	`DEPTH_THRESH` This constant is accessible by subclasses for historical purposes.
`protected static int`	`GREATER_ICOST` This constant is accessible by subclasses for historical purposes.
`protected static int`	`LESSER_ICOST` This constant is accessible by subclasses for historical purposes.
`static int`	`MAX_BLOCKSIZE` The maximum supported blocksize `== 9`.
`static int`	`MIN_BLOCKSIZE` The minimum supported blocksize `== 1`.
`protected static int`	`QSORT_STACK_SIZE` This constant is accessible by subclasses for historical purposes.
`protected static int`	`SETMASK` This constant is accessible by subclasses for historical purposes.
`protected static int`	`SMALL_THRESH` This constant is accessible by subclasses for historical purposes.
`protected static int`	`WORK_FACTOR` This constant is accessible by subclasses for historical purposes.

从接口继承的字段 org.apache.hadoop.io.compress.bzip2.BZip2Constants
baseBlockSize, END_OF_BLOCK, END_OF_STREAM, G_SIZE, MAX_ALPHA_SIZE, MAX_CODE_LEN, MAX_SELECTORS, N_GROUPS, N_ITERS, NUM_OVERSHOOT_BYTES, rNums, RUNA, RUNB

构造器概要

构造器
构造器和说明
`CBZip2OutputStream(OutputStream out)` Constructs a new `CBZip2OutputStream` with a blocksize of 900k.
`CBZip2OutputStream(OutputStream out, int blockSize)` Constructs a new `CBZip2OutputStream` with specified blocksize.

方法概要

方法
限定符和类型	方法和说明
`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.
`protected static void`	`hbMakeCodeLengths(char[] len, int[] freq, int alphaSize, int maxLen)` This method is accessible by subclasses for historical purposes.
`void`	`write(byte[] buf, int offs, int len)`
`void`	`write(int b)`

从类继承的方法 java.io.OutputStream
write

从类继承的方法 java.lang.Object
clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- 字段详细资料
  - MIN_BLOCKSIZE
```
public static final int MIN_BLOCKSIZE
```
    The minimum supported blocksize == 1.
    
    另请参阅:
    常量字段值
  - MAX_BLOCKSIZE
```
public static final int MAX_BLOCKSIZE
```
    The maximum supported blocksize == 9.
    
    另请参阅:
    常量字段值
  - SETMASK
```
protected static final int SETMASK
```
    This constant is accessible by subclasses for historical purposes. If you don't know what it means then you don't need it.
    
    另请参阅:
    常量字段值
  - CLEARMASK
```
protected static final int CLEARMASK
```
    This constant is accessible by subclasses for historical purposes. If you don't know what it means then you don't need it.
    
    另请参阅:
    常量字段值
  - GREATER_ICOST
```
protected static final int GREATER_ICOST
```
    This constant is accessible by subclasses for historical purposes. If you don't know what it means then you don't need it.
    
    另请参阅:
    常量字段值
  - LESSER_ICOST
```
protected static final int LESSER_ICOST
```
    This constant is accessible by subclasses for historical purposes. If you don't know what it means then you don't need it.
    
    另请参阅:
    常量字段值
  - SMALL_THRESH
```
protected static final int SMALL_THRESH
```
    This constant is accessible by subclasses for historical purposes. If you don't know what it means then you don't need it.
    
    另请参阅:
    常量字段值
  - DEPTH_THRESH
```
protected static final int DEPTH_THRESH
```
    This constant is accessible by subclasses for historical purposes. If you don't know what it means then you don't need it.
    
    另请参阅:
    常量字段值
  - WORK_FACTOR
```
protected static final int WORK_FACTOR
```
    This constant is accessible by subclasses for historical purposes. If you don't know what it means then you don't need it.
    
    另请参阅:
    常量字段值
  - QSORT_STACK_SIZE
```
protected static final int QSORT_STACK_SIZE
```
    This constant is accessible by subclasses for historical purposes. If you don't know what it means then you don't need it.
    If you are ever unlucky/improbable enough to get a stack overflow whilst sorting, increase the following constant and try again. In practice I have never seen the stack go above 27 elems, so the following limit seems very generous.
    
    另请参阅:
    常量字段值
- 构造器详细资料
  - CBZip2OutputStream
```
public CBZip2OutputStream(OutputStream out)
                   throws IOException
```
    Constructs a new CBZip2OutputStream with a blocksize of 900k.
    Attention: The caller is resonsible to write the two BZip2 magic bytes "BZ" to the specified stream prior to calling this constructor.
    
    参数:
    out - * the destination stream.
    
    抛出:
    
    IOException - if an I/O error occurs in the specified stream.
    
    NullPointerException - if out == null.
  - CBZip2OutputStream
```
public CBZip2OutputStream(OutputStream out,
                  int blockSize)
                   throws IOException
```
    Constructs a new CBZip2OutputStream with specified blocksize.
    Attention: The caller is resonsible to write the two BZip2 magic bytes "BZ" to the specified stream prior to calling this constructor.
    
    参数:
    out - the destination stream.
    blockSize - the blockSize as 100k units.
    
    抛出:
    
    IOException - if an I/O error occurs in the specified stream.
    
    IllegalArgumentException - if (blockSize < 1) || (blockSize > 9).
    
    NullPointerException - if out == null.
    另请参阅:
    MIN_BLOCKSIZE, MAX_BLOCKSIZE
- 方法详细资料
  - hbMakeCodeLengths
```
protected static void hbMakeCodeLengths(char[] len,
                     int[] freq,
                     int alphaSize,
                     int maxLen)
```
    This method is accessible by subclasses for historical purposes. If you don't know what it does then you don't need it.
  - chooseBlockSize
```
public static int chooseBlockSize(long inputLength)
```
    Chooses a blocksize based on the given length of the data to compress.
    
    参数:
    inputLength - The length of the data which will be compressed by CBZip2OutputStream.
    
    返回:
    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
```
    指定者:
    
    write 在类中 OutputStream
    
    抛出:
    
    IOException
  - finalize
```
protected void finalize()
                 throws Throwable
```
    Overriden to close the stream.
    
    覆盖:
    
    finalize 在类中 Object
    
    抛出:
    
    Throwable
  - finish
```
public void finish()
            throws IOException
```
    抛出:
    
    IOException
  - close
```
public void close()
           throws IOException
```
    指定者:
    
    close 在接口中 Closeable
    
    指定者:
    
    close 在接口中 AutoCloseable
    
    覆盖:
    
    close 在类中 OutputStream
    
    抛出:
    
    IOException
  - flush
```
public void flush()
           throws IOException
```
    指定者:
    
    flush 在接口中 Flushable
    
    覆盖:
    
    flush 在类中 OutputStream
    
    抛出:
    
    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
```
    覆盖:
    
    write 在类中 OutputStream
    
    抛出:
    
    IOException

类 CBZip2OutputStream

字段概要

从接口继承的字段 org.apache.hadoop.io.compress.bzip2.BZip2Constants

构造器概要

方法概要

从类继承的方法 java.io.OutputStream

从类继承的方法 java.lang.Object

字段详细资料

MIN_BLOCKSIZE

MAX_BLOCKSIZE

SETMASK

CLEARMASK

GREATER_ICOST

LESSER_ICOST

SMALL_THRESH

DEPTH_THRESH

WORK_FACTOR

QSORT_STACK_SIZE

构造器详细资料

CBZip2OutputStream

CBZip2OutputStream

方法详细资料

hbMakeCodeLengths

chooseBlockSize

write

finalize

finish

close

flush

getBlockSize

write