Package org.apache.lucene.util.packed
Class BlockPackedWriter
- java.lang.Object
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- org.apache.lucene.util.packed.AbstractBlockPackedWriter
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- org.apache.lucene.util.packed.BlockPackedWriter
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public final class BlockPackedWriter extends AbstractBlockPackedWriter
A writer for large sequences of longs.The sequence is divided into fixed-size blocks and for each block, the difference between each value and the minimum value of the block is encoded using as few bits as possible. Memory usage of this class is proportional to the block size. Each block has an overhead between 1 and 10 bytes to store the minimum value and the number of bits per value of the block.
Format:
- <BLock>BlockCount
- BlockCount: ⌈ ValueCount / BlockSize ⌉
- Block: <Header, (Ints)>
- Header: <Token, (MinValue)>
- Token: a
byte
, first 7 bits are the number of bits per value (bitsPerValue). If the 8th bit is 1, then MinValue (see next) is 0, otherwise MinValue and needs to be decoded - MinValue: a
zigzag-encoded
variable-length long
whose value should be added to every int from the block to restore the original values - Ints: If the number of bits per value is 0, then there is
nothing to decode and all ints are equal to MinValue. Otherwise: BlockSize
packed ints
encoded on exactly bitsPerValue bits per value. They are the subtraction of the original values and MinValue
- See Also:
BlockPackedReaderIterator
,BlockPackedReader
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Field Summary
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Fields inherited from class org.apache.lucene.util.packed.AbstractBlockPackedWriter
blocks, BPV_SHIFT, finished, MAX_BLOCK_SIZE, MIN_BLOCK_SIZE, MIN_VALUE_EQUALS_0, off, ord, out, values
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Constructor Summary
Constructors Constructor Description BlockPackedWriter(DataOutput out, int blockSize)
Sole constructor.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description protected void
flush()
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Methods inherited from class org.apache.lucene.util.packed.AbstractBlockPackedWriter
add, addBlockOfZeros, finish, ord, reset, writeValues, writeVLong
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Constructor Detail
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BlockPackedWriter
public BlockPackedWriter(DataOutput out, int blockSize)
Sole constructor.- Parameters:
blockSize
- the number of values of a single block, must be a power of 2
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Method Detail
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flush
protected void flush() throws java.io.IOException
- Specified by:
flush
in classAbstractBlockPackedWriter
- Throws:
java.io.IOException
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