IntArrayDocIdSet.java

IntArrayDocIdSet.java

import java.io.IOException;
import java.util.Arrays;

import org.apache.lucene.search.DocIdSet;
import org.apache.lucene.search.DocIdSetIterator;
import org.apache.lucene.util.ArrayUtil;
import org.apache.lucene.util.RamUsageEstimator;


public class IntArrayDocIdSet extends DocIdSet {

  private static final long BASE_RAM_BYTES_USED = RamUsageEstimator.shallowSizeOfInstance(IntArrayDocIdSet.class);

  public static class Builder {
    private int[] docIDs = new int[0];
    int off;

    public void add(int docID) {
      if (off > 0 && docID <= docIDs[off - 1]) {
        throw new IllegalArgumentException();
      }
      if (off == docIDs.length) {
        docIDs = ArrayUtil.grow(docIDs);
      }
      docIDs[off++] = docID;
    }

    public IntArrayDocIdSet build() {
      add(DocIdSetIterator.NO_MORE_DOCS);
      final IntArrayDocIdSet set = new IntArrayDocIdSet(Arrays.copyOf(docIDs, off));
      docIDs = null;
      return set;
    }
  }

  private final int[] docIDs;

  public IntArrayDocIdSet(int[] docIDs) {
    this.docIDs = docIDs;
  }

  @Override
  public long ramBytesUsed() {
    return BASE_RAM_BYTES_USED + RamUsageEstimator.sizeOf(docIDs);
  }

  @Override
  public DocIdSetIterator iterator() throws IOException {
    return new Iterator(docIDs);
  }

  private static class Iterator extends DocIdSetIterator {

    private final int[] docIDs;
    int i;

    public Iterator(int[] docIDs) {
      this.docIDs = docIDs;
      i = -1;
    }

    @Override
    public int docID() {
      if (i == -1) {
        return -1;
      }
      return docIDs[i];
    }

    @Override
    public int nextDoc() throws IOException {
      return docIDs[++i];
    }

    @Override
    public int advance(int target) throws IOException {
      int lo = i + 1;
      int hi = lo + 1;
      while (hi < docIDs.length && docIDs[hi] < target) {
        final int diff = hi - lo;
        lo = hi;
        hi += 2 * diff;
      }
      hi = Math.min(hi, docIDs.length);
      
      i = Arrays.binarySearch(docIDs, lo, hi, target);
      if (i < 0) {
        i = -1 - i;
      }
      return docIDs[i];
    }

    @Override
    public long cost() {
      return docIDs.length - 1;
    }

  }

}