org.apache.tools.bzip2
Class CBZip2OutputStream
OutputStream
org.apache.tools.bzip2.CBZip2OutputStream
- BZip2Constants
public class CBZip2OutputStream
extends OutputStream
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:
400k + (9 * blocksize)
.
To get the memory required for decompression by
CBZip2InputStream
use
65k + (5 * blocksize)
.
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
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.
|
G_SIZE , MAX_ALPHA_SIZE , MAX_CODE_LEN , MAX_SELECTORS , NUM_OVERSHOOT_BYTES , N_GROUPS , N_ITERS , RUNA , RUNB , baseBlockSize , rNums |
CBZip2OutputStream(OutputStream out) - Constructs a new CBZip2OutputStream with a blocksize of 900k.
|
CBZip2OutputStream(OutputStream out, int blockSize) - Constructs a new CBZip2OutputStream with specified blocksize.
|
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 | 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)
|
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.
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.
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.
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.
MAX_BLOCKSIZE
public static final int MAX_BLOCKSIZE
The maximum supported blocksize == 9.
MIN_BLOCKSIZE
public static final int MIN_BLOCKSIZE
The minimum supported blocksize == 1.
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.
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.
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.
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.
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.
out
- the destination stream.
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.
out
- the destination stream.blockSize
- the blockSize as 100k units.
chooseBlockSize
public static int chooseBlockSize(long inputLength)
Chooses a blocksize based on the given length of the data to compress.
inputLength
- The length of the data which will be compressed by
CBZip2OutputStream.
- The blocksize, between
MIN_BLOCKSIZE
and MAX_BLOCKSIZE
both inclusive. For a negative inputLength this method returns
MAX_BLOCKSIZE always.
close
public void close()
throws IOException
finalize
protected void finalize()
throws Throwable
Overriden to close the stream.
flush
public void flush()
throws IOException
getBlockSize
public final int getBlockSize()
Returns the blocksize parameter specified at construction time.
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.
write
public void write(byte[] buf,
int offs,
int len)
throws IOException
write
public void write(int b)
throws IOException