org.apache.lucene.util

Class SparseFixedBitSet

java.lang.Object

org.apache.lucene.util.BitSet

org.apache.lucene.util.SparseFixedBitSet

All Implemented Interfaces:

Accountable, Bits

public class SparseFixedBitSet
extends BitSet
implements Bits, Accountable

A bit set that only stores longs that have at least one bit which is set. The way it works is that the space of bits is divided into blocks of 4096 bits, which is 64 longs. Then for each block, we have:

• a long[] which stores the non-zero longs for that block
• a long so that bit i being set means that the i-th long of the block is non-null, and its offset in the array of longs is the number of one bits on the right of the i-th bit.

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

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.lucene.util.Bits

Bits.MatchAllBits, Bits.MatchNoBits

Field Summary

Fields inherited from interface org.apache.lucene.util.Bits

EMPTY_ARRAY

Fields inherited from interface org.apache.lucene.util.Accountable

NULL_ACCOUNTABLE

Constructor Summary

Constructors

Constructor and Description
SparseFixedBitSet(int length) Create a SparseFixedBitSet that can contain bits between 0 included and length excluded.

Method Summary

Modifier and Type	Method and Description
int	approximateCardinality() Return an approximation of the cardinality of this set.
int	cardinality() Return the number of bits that are set.
void	clear(int i) Clear the bit at index i.
void	clear(int from, int to) Clears a range of bits.
boolean	get(int i) Returns the value of the bit with the specified index.
int	length() Returns the number of bits in this set
int	nextSetBit(int i) Returns the index of the first set bit starting at the index specified.
void	or(DocIdSetIterator it) Does in-place OR of the bits provided by the iterator.
int	prevSetBit(int i) Returns the index of the last set bit before or on the index specified.
long	ramBytesUsed() Return the memory usage of this object in bytes.
void	set(int i) Set the bit at index i.
String	toString()

Methods inherited from class org.apache.lucene.util.BitSet

checkUnpositioned, of

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.lucene.util.Accountable

getChildResources

Constructor Detail

SparseFixedBitSet

public SparseFixedBitSet(int length)

Create a SparseFixedBitSet that can contain bits between 0 included and length excluded.

Method Detail

length

public int length()

Description copied from interface: Bits

Returns the number of bits in this set

Specified by:

length in interface Bits

cardinality

public int cardinality()

Description copied from class: BitSet

Return the number of bits that are set. NOTE: this method is likely to run in linear time

Specified by:

cardinality in class BitSet

approximateCardinality

public int approximateCardinality()

Description copied from class: BitSet

Return an approximation of the cardinality of this set. Some implementations may trade accuracy for speed if they have the ability to estimate the cardinality of the set without iterating over all the data. The default implementation returns BitSet.cardinality().

Overrides:

approximateCardinality in class BitSet

get

public boolean get(int i)

Description copied from interface: Bits

Returns the value of the bit with the specified index.

Specified by:

get in interface Bits

Parameters:

i - index, should be non-negative and < Bits.length(). The result of passing negative or out of bounds values is undefined by this interface, just don't do it!

Returns:

true if the bit is set, false otherwise.

set

public void set(int i)

Set the bit at index i.

Specified by:

set in class BitSet

clear

public void clear(int i)

Clear the bit at index i.

Specified by:

clear in class BitSet

clear

public void clear(int from,
                  int to)

Description copied from class: BitSet

Clears a range of bits.

Specified by:

clear in class BitSet

Parameters:

from - lower index

to - one-past the last bit to clear

nextSetBit

public int nextSetBit(int i)

Description copied from class: BitSet

Returns the index of the first set bit starting at the index specified. DocIdSetIterator.NO_MORE_DOCS is returned if there are no more set bits.

Specified by:

nextSetBit in class BitSet

prevSetBit

public int prevSetBit(int i)

Description copied from class: BitSet

Returns the index of the last set bit before or on the index specified. -1 is returned if there are no more set bits.

Specified by:

prevSetBit in class BitSet

or

public void or(DocIdSetIterator it)
        throws IOException

Description copied from class: BitSet

Does in-place OR of the bits provided by the iterator. The state of the iterator after this operation terminates is undefined.

Overrides:

or in class BitSet

Throws:

IOException

ramBytesUsed

public long ramBytesUsed()

Description copied from interface: Accountable

Return the memory usage of this object in bytes. Negative values are illegal.

Specified by:

ramBytesUsed in interface Accountable

toString

public String toString()

Overrides:

toString in class Object