org.apache.lucene.util
Class BitVector

java.lang.Object
  org.apache.lucene.util.BitVector

All Implemented Interfaces:

Cloneable

public final class BitVector
extends Object
implements Cloneable

Optimized implementation of a vector of bits. This is more-or-less like java.util.BitSet, but also includes the following:

• a count() method, which efficiently computes the number of one bits;
• optimized read from and write to disk;
• inlinable get() method;
• store and load, as bit set or d-gaps, depending on sparseness;

Constructor Summary

BitVector(Directory d, String name)
Constructs a bit vector from the file name in Directory d, as written by the write(org.apache.lucene.store.Directory, java.lang.String) method.

BitVector(int n)
Constructs a vector capable of holding n bits.

Method Summary

void	clear(int bit) Sets the value of bit to zero.
Object	clone()
int	count() Returns the total number of one bits in this vector.
boolean	get(int bit) Returns true if bit is one and false if it is zero.
boolean	getAndSet(int bit) Sets the value of bit to true, and returns true if bit was already set
int	getRecomputedCount() For testing
void	set(int bit) Sets the value of bit to one.
int	size() Returns the number of bits in this vector.
BitVector	subset(int start, int end) Retrieve a subset of this BitVector.
void	write(Directory d, String name) Writes this vector to the file name in Directory d, in a format that can be read by the constructor BitVector(Directory, String).

Methods inherited from class java.lang.Object

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

Constructor Detail

BitVector

public BitVector(int n)

Constructs a vector capable of holding n bits.

BitVector

public BitVector(Directory d,
                 String name)
          throws IOException

Constructs a bit vector from the file name in Directory d, as written by the write(org.apache.lucene.store.Directory, java.lang.String) method.

Throws:

IOException

Method Detail

clone

public Object clone()

Overrides:

clone in class Object

set

public final void set(int bit)

Sets the value of bit to one.

getAndSet

public final boolean getAndSet(int bit)

Sets the value of bit to true, and returns true if bit was already set

clear

public final void clear(int bit)

Sets the value of bit to zero.

get

public final boolean get(int bit)

Returns true if bit is one and false if it is zero.

size

public final int size()

Returns the number of bits in this vector. This is also one greater than the number of the largest valid bit number.

count

public final int count()

Returns the total number of one bits in this vector. This is efficiently computed and cached, so that, if the vector is not changed, no recomputation is done for repeated calls.

getRecomputedCount

public final int getRecomputedCount()

For testing

write

public final void write(Directory d,
                        String name)
                 throws IOException

Writes this vector to the file name in Directory d, in a format that can be read by the constructor BitVector(Directory, String).

Throws:

IOException

subset

public BitVector subset(int start,
                        int end)

Retrieve a subset of this BitVector.

Parameters:

start - starting index, inclusive

end - ending index, exclusive

Returns:

subset