public final class BlockPackedWriter extends java.lang.ObjectA 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.
- 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
variable-length longwhose 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 intsencoded on exactly bitsPerValue bits per value. They are the subtraction of the original values and MinValue
- See Also:
Constructors Constructor Description
BlockPackedWriter(DataOutput out, int blockSize)Sole constructor.
All Methods Instance Methods Concrete Methods Modifier and Type Method Description
add(long l)Append a new long.
finish()Flush all buffered data to disk.
ord()Return the number of values which have been added.
reset(DataOutput out)Reset this writer to wrap
public BlockPackedWriter(DataOutput out, int blockSize)Sole constructor.
blockSize- the number of values of a single block, must be a power of 2
public void reset(DataOutput out)Reset this writer to wrap
out. The block size remains unchanged.
public void add(long l) throws java.io.IOExceptionAppend a new long.
public void finish() throws java.io.IOExceptionFlush all buffered data to disk. This instance is not usable anymore after this method has been called until
reset(DataOutput)has been called.
public long ord()Return the number of values which have been added.