Class BZip2CompressorOutputStream
- All Implemented Interfaces:
Closeable,Flushable,AutoCloseable
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
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Field Summary
FieldsModifier and TypeFieldDescriptionstatic final intConstant 100000.static final intConstant 50.static final intConstant 258.static final intThe maximum supported blocksize== 9.static final intConstant 23.static final intConstant 18002.static final intThe minimum supported blocksize== 1.static final intConstant 6.static final intConstant 4.static final intConstant 20.static final intConstant 0.static final intConstant 1.Fields inherited from class java.io.FilterOutputStream
out -
Constructor Summary
ConstructorsConstructorDescriptionConstructs a newBZip2CompressorOutputStreamwith a blocksize of 900k.BZip2CompressorOutputStream(OutputStream out, int blockSize) Constructs a newBZip2CompressorOutputStreamwith specified blocksize. -
Method Summary
Modifier and TypeMethodDescriptionstatic intchooseBlockSize(long inputLength) Chooses a blocksize based on the given length of the data to compress.voidclose()voidfinish()Finishes the addition of entries to this stream, without closing it.voidflush()final intReturns the blocksize parameter specified at construction time.voidwrite(byte[] buf, int offs, int len) voidwrite(int b) Methods inherited from class org.apache.commons.compress.CompressFilterOutputStream
checkOpen, isClosed, isFinished, out, write, write, writeUsAscii, writeUsAsciiRaw, writeUtf8Methods inherited from class java.io.FilterOutputStream
write
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Field Details
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MIN_BLOCKSIZE
The minimum supported blocksize== 1.- See Also:
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MAX_BLOCKSIZE
The maximum supported blocksize== 9.- See Also:
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BASEBLOCKSIZE
static final int BASEBLOCKSIZEConstant 100000.- See Also:
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MAX_ALPHA_SIZE
static final int MAX_ALPHA_SIZEConstant 258.- See Also:
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MAX_CODE_LEN
static final int MAX_CODE_LENConstant 23.- See Also:
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RUNA
static final int RUNAConstant 0.- See Also:
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RUNB
static final int RUNBConstant 1.- See Also:
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N_GROUPS
static final int N_GROUPSConstant 6.- See Also:
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G_SIZE
static final int G_SIZEConstant 50.- See Also:
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N_ITERS
static final int N_ITERSConstant 4.- See Also:
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MAX_SELECTORS
static final int MAX_SELECTORSConstant 18002.- See Also:
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NUM_OVERSHOOT_BYTES
static final int NUM_OVERSHOOT_BYTESConstant 20.- See Also:
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Constructor Details
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BZip2CompressorOutputStream
Constructs a newBZip2CompressorOutputStreamwith a blocksize of 900k.- Parameters:
out- the destination stream.- Throws:
IOException- if an I/O error occurs in the specified stream.NullPointerException- ifout == null.
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BZip2CompressorOutputStream
Constructs a newBZip2CompressorOutputStreamwith 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- ifout == null.- See Also:
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Method Details
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chooseBlockSize
Chooses a blocksize based on the given length of the data to compress.- Parameters:
inputLength- The length of the data which will be compressed byBZip2CompressorOutputStream.- Returns:
- The blocksize, between
MIN_BLOCKSIZEandMAX_BLOCKSIZEboth inclusive. For a negativeinputLengththis method returnsMAX_BLOCKSIZEalways.
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close
- Specified by:
closein interfaceAutoCloseable- Specified by:
closein interfaceCloseable- Overrides:
closein classCompressFilterOutputStream<OutputStream>- Throws:
IOException
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finish
Description copied from class:CompressFilterOutputStreamFinishes the addition of entries to this stream, without closing it. Additional data can be written, if the format supports it.- Overrides:
finishin classCompressFilterOutputStream<OutputStream>- Throws:
IOException- Maybe thrown by subclasses if the user forgets to close the entry.
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flush
- Specified by:
flushin interfaceFlushable- Overrides:
flushin classFilterOutputStream- Throws:
IOException
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getBlockSize
Returns the blocksize parameter specified at construction time.- Returns:
- the blocksize parameter specified at construction time
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write
- Overrides:
writein classFilterOutputStream- Throws:
IOException
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write
- Overrides:
writein classFilterOutputStream- Throws:
IOException
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