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.

Version:

$Id$

Field Summary

Fields

Modifier and Type	Field and Description
protected static int[]	bitlist

Constructor Summary

Constructors

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

Method Summary

Methods

Modifier and Type	Method and Description
int	doc() Returns the current document number.
boolean	next() 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(); }
boolean	skipTo(int target) Skips entries to the first beyond the current whose document number is greater than or equal to target.

Methods inherited from class java.lang.Object

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

Field Detail

bitlist

protected static final int[] bitlist

Constructor Detail

OpenBitSetIterator

public OpenBitSetIterator(OpenBitSet obs)

OpenBitSetIterator

public OpenBitSetIterator(long[] bits,
                  int numWords)

Method Detail

next

public boolean next()

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:

next in class DocIdSetIterator

skipTo

public boolean skipTo(int target)

Description copied from class: DocIdSetIterator

Skips entries to the first beyond the current whose document number is greater than or equal to target.

Returns true iff there is such an entry.

Behaves as if written:

   boolean skipTo(int target) {
     do {
       if (!next())
         return false;
     } while (target > doc());
     return true;
   }
 

Some implementations are considerably more efficient than that.

Specified by:

skipTo in class DocIdSetIterator

doc

public int doc()

Description copied from class: DocIdSetIterator

Returns the current document number.

This is invalid until DocIdSetIterator.next() is called for the first time.

Specified by:

doc in class DocIdSetIterator