public final class BlockPackedWriter extends 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 zigzag-encoded
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
bitsPerValuebits per value. They are the subtraction of the original values and MinValue
- See Also:
- NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.
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
protected DataOutput out
protected final long values
protected byte blocks
protected int off
protected long ord
protected boolean finished
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 finish() throws 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.