org.apache.lucene.util

Class OpenBitSetIterator

java.lang.Object

org.apache.lucene.search.DocIdSetIterator

org.apache.lucene.util.OpenBitSetIterator

public class OpenBitSetIterator
extends DocIdSetIterator

An iterator to iterate over set bits in an OpenBitSet. This is faster than nextSetBit() for iterating over the complete set of bits, especially when the density of the bits set is high.

Field Summary

Fields inherited from class org.apache.lucene.search.DocIdSetIterator

NO_MORE_DOCS

Constructor Summary

Constructors

Constructor and Description
OpenBitSetIterator(long[] bits, int numWords)
OpenBitSetIterator(OpenBitSet obs)

Method Summary

Methods

Modifier and Type	Method and Description
int	advance(int target) Advances to the first beyond the current whose document number is greater than or equal to target, and returns the document number itself.
long	cost() Returns the estimated cost of this DocIdSetIterator.
int	docID() Returns the following: -1 or DocIdSetIterator.NO_MORE_DOCS if DocIdSetIterator.nextDoc() or DocIdSetIterator.advance(int) were not called yet.
int	nextDoc() alternate shift implementations // 32 bit shifts, but a long shift needed at the end private void shift2() { int y = (int)word; if (y==0) {wordShift +=32; y = (int)(word >>>32); } if ((y & 0x0000FFFF) == 0) { wordShift +=16; y>>>=16; } if ((y & 0x000000FF) == 0) { wordShift +=8; y>>>=8; } indexArray = bitlist[y & 0xff]; word >>>= (wordShift +1); } private void shift3() { int lower = (int)word; int lowByte = lower & 0xff; if (lowByte != 0) { indexArray=bitlist[lowByte]; return; } shift(); }

Methods inherited from class org.apache.lucene.search.DocIdSetIterator

empty, slowAdvance

Methods inherited from class java.lang.Object

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

Constructor Detail

OpenBitSetIterator

public OpenBitSetIterator(OpenBitSet obs)

OpenBitSetIterator

public OpenBitSetIterator(long[] bits,
                  int numWords)

Method Detail

nextDoc

public int nextDoc()

alternate shift implementations // 32 bit shifts, but a long shift needed at the end private void shift2() { int y = (int)word; if (y==0) {wordShift +=32; y = (int)(word >>>32); } if ((y & 0x0000FFFF) == 0) { wordShift +=16; y>>>=16; } if ((y & 0x000000FF) == 0) { wordShift +=8; y>>>=8; } indexArray = bitlist[y & 0xff]; word >>>= (wordShift +1); } private void shift3() { int lower = (int)word; int lowByte = lower & 0xff; if (lowByte != 0) { indexArray=bitlist[lowByte]; return; } shift(); }

Specified by:

nextDoc in class DocIdSetIterator

advance

public int advance(int target)

Description copied from class: DocIdSetIterator

Advances to the first beyond the current whose document number is greater than or equal to target, and returns the document number itself. Exhausts the iterator and returns DocIdSetIterator.NO_MORE_DOCS if target is greater than the highest document number in the set.

The behavior of this method is undefined when called with target ≤ current, or after the iterator has exhausted. Both cases may result in unpredicted behavior.

When target > current it behaves as if written:

 int advance(int target) {
   int doc;
   while ((doc = nextDoc()) < target) {
   }
   return doc;
 }
 

Some implementations are considerably more efficient than that.

NOTE: this method may be called with DocIdSetIterator.NO_MORE_DOCS for efficiency by some Scorers. If your implementation cannot efficiently determine that it should exhaust, it is recommended that you check for that value in each call to this method.

Specified by:

advance in class DocIdSetIterator

docID

public int docID()

Description copied from class: DocIdSetIterator

Returns the following:

• -1 or DocIdSetIterator.NO_MORE_DOCS if DocIdSetIterator.nextDoc() or DocIdSetIterator.advance(int) were not called yet.
• DocIdSetIterator.NO_MORE_DOCS if the iterator has exhausted.
• Otherwise it should return the doc ID it is currently on.

Specified by:

docID in class DocIdSetIterator

cost

public long cost()

Description copied from class: DocIdSetIterator

Returns the estimated cost of this DocIdSetIterator.

This is generally an upper bound of the number of documents this iterator might match, but may be a rough heuristic, hardcoded value, or otherwise completely inaccurate.

Specified by:

cost in class DocIdSetIterator