Package org.apache.lucene.util

Class 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.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method 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 java.lang.Object

        equals, 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

      • 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