org.apache.lucene.util
Class OpenBitSetIterator

java.lang.Object
  extended by org.apache.lucene.search.DocIdSetIterator
      extended by 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
OpenBitSetIterator(long[] bits, int numWords)
           
OpenBitSetIterator(OpenBitSet obs)
           
 
Method Summary
 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:

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


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