/*******************************************************************************
 * Copyright (c) 2002 - 2006 IBM Corporation.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package com.ibm.wala.util.intset;


/**
 * an int vector implementation designed for low occupancy. Note that get() from
 * this vector is a binary search.
 * 
 * This should only be used for small sets ... insertion and deletion are linear
 * in size of set.
 */
public class SparseIntVector implements IntVector {

  private final static int INITIAL_SIZE = 5;
  private final double EXPANSION = 1.5;
  int maxIndex = -1;

  /**
   * if indices[i] = x, then data[i] == get(x)
   */
  final private MutableSparseIntSet indices = MutableSparseIntSet.makeEmpty();
  private int[] data = new int[INITIAL_SIZE];

  private final int defaultValue;

  public SparseIntVector(int defaultValue) {
    this.defaultValue = defaultValue;
  }

  /*
   * @see com.ibm.wala.util.intset.IntVector#get(int)
   */
  public int get(int x) {
    int index = indices.getIndex(x);
    if (index == -1) {
      return defaultValue;
    } else {
      return data[index];
    }
  }

  /*
   * TODO: this can be optimized 
   * 
   * @see com.ibm.wala.util.intset.IntVector#set(int, int)
   */
  public void set(int x, int value) {
    maxIndex = Math.max(maxIndex,x);
    int index = indices.getIndex(x);
    if (index == -1) {
      indices.add(x);
      index = indices.getIndex(x);
      ensureCapacity(indices.size() + 1);
      if (index < (data.length - 1)) {
        System.arraycopy(data, index, data, index + 1, indices.size() - index);
      }
    }
    data[index] = value;
  }

  private void ensureCapacity(int capacity) {
    if (data.length  < capacity + 1) {
      int[] old = data;
      data = new int[1 + (int) (capacity * EXPANSION)];
      System.arraycopy(old, 0, data, 0, old.length);
    }
  }

  /*
   * @see com.ibm.wala.util.debug.VerboseAction#performVerboseAction()
   */
  public void performVerboseAction() {
    System.err.println((getClass() + " stats: "));
    System.err.println(("data.length " + data.length));
    System.err.println(("indices.size() " + indices.size()));
  }
  
  
  public int getMaxIndex() {
    return maxIndex;
  }
}