org.apache.lucene.util.packed
Class EliasFanoDecoder

java.lang.Object
  org.apache.lucene.util.packed.EliasFanoDecoder

public class EliasFanoDecoder
extends Object

A decoder for an EliasFanoEncoder.

NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

Field Summary

static long

NO_MORE_VALUES

Constructor Summary

EliasFanoDecoder(EliasFanoEncoder efEncoder)
Construct a decoder for a given EliasFanoEncoder.

Method Summary

boolean	advanceToIndex(long index) Advance the decoding index to a given index.
long	advanceToValue(long target) Given a target value, advance the decoding index to the first bigger or equal value and return it if it is available.
long	backToValue(long target) Given a target value, go back to the first smaller or equal value and return it if it is available.
long	currentIndex() The current decoding index.
long	currentValue() The value at the current decoding index.
EliasFanoEncoder	getEliasFanoEncoder()
long	nextValue() If another value is available after the current decoding index, return this value and and increase the decoding index by 1.
long	numEncoded() The number of values encoded by the encoder.
long	previousValue() If another value is available before the current decoding index, return this value and decrease the decoding index by 1.
void	toAfterSequence() Set the decoding index to just after the last encoded value.
void	toBeforeSequence() Set the decoding index to just before the first encoded value.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

NO_MORE_VALUES

public static final long NO_MORE_VALUES

See Also:

Constant Field Values

Constructor Detail

EliasFanoDecoder

public EliasFanoDecoder(EliasFanoEncoder efEncoder)

Construct a decoder for a given EliasFanoEncoder. The decoding index is set to just before the first encoded value.

Method Detail

getEliasFanoEncoder

public EliasFanoEncoder getEliasFanoEncoder()

Returns:

The Elias-Fano encoder that is decoded.

numEncoded

public long numEncoded()

The number of values encoded by the encoder.

Returns:

The number of values encoded by the encoder.

currentIndex

public long currentIndex()

The current decoding index. The first value encoded by EliasFanoEncoder.encodeNext(long) has index 0. Only valid directly after nextValue(), advanceToValue(long), previousValue(), or backToValue(long) returned another value than NO_MORE_VALUES, or advanceToIndex(long) returned true.

Returns:

The decoding index of the last decoded value, or as last set by advanceToIndex(long).

currentValue

public long currentValue()

The value at the current decoding index. Only valid when currentIndex() would return a valid result.
This is only intended for use after advanceToIndex(long) returned true.

Returns:

The value encoded at currentIndex().

toBeforeSequence

public void toBeforeSequence()

Set the decoding index to just before the first encoded value.

nextValue

public long nextValue()

If another value is available after the current decoding index, return this value and and increase the decoding index by 1. Otherwise return NO_MORE_VALUES.

advanceToIndex

public boolean advanceToIndex(long index)

Advance the decoding index to a given index. and return true iff it is available.
See also currentValue().
The current implementation does not use the index on the upper bit zero bit positions.
Note: there is currently no implementation of backToIndex.

advanceToValue

public long advanceToValue(long target)

Given a target value, advance the decoding index to the first bigger or equal value and return it if it is available. Otherwise return NO_MORE_VALUES.
The current implementation uses the index on the upper zero bit positions.

toAfterSequence

public void toAfterSequence()

Set the decoding index to just after the last encoded value.

previousValue

public long previousValue()

If another value is available before the current decoding index, return this value and decrease the decoding index by 1. Otherwise return NO_MORE_VALUES.

backToValue

public long backToValue(long target)

Given a target value, go back to the first smaller or equal value and return it if it is available. Otherwise return NO_MORE_VALUES.
The current implementation does not use the index on the upper zero bit positions.