BigFloatArray.java

package com.browseengine.bobo.util;

public class BigFloatArray {

  private float[][] _array;
  private int _numrows;
  /* Remember that 2^SHIFT_SIZE = BLOCK_SIZE */
  final private static int BLOCK_SIZE = 1024;
  final private static int SHIFT_SIZE = 10;
  final private static int MASK = BLOCK_SIZE - 1;

  public BigFloatArray(int size) {
    _numrows = size >> SHIFT_SIZE;
    _array = new float[_numrows + 1][];
    for (int i = 0; i <= _numrows; i++) {
      _array[i] = new float[BLOCK_SIZE];
    }
  }

  public void add(int docId, float val) {
    _array[docId >> SHIFT_SIZE][docId & MASK] = val;
  }

  public float get(int docId) {
    return _array[docId >> SHIFT_SIZE][docId & MASK];
  }

  public int capacity() {
    return _numrows * BLOCK_SIZE;
  }

  public void ensureCapacity(int size) {
    int newNumrows = (size >> SHIFT_SIZE) + 1;
    if (newNumrows > _array.length) {
      float[][] newArray = new float[newNumrows][]; // grow
      System.arraycopy(_array, 0, newArray, 0, _array.length);
      for (int i = _array.length; i < newNumrows; ++i) {
        newArray[i] = new float[BLOCK_SIZE];
      }
      _array = newArray;
    }
    _numrows = newNumrows;
  }
}