HashKey.java

/*
 * Copyright (c) 1998-2010 Caucho Technology -- all rights reserved
 *
 * This file is part of Resin(R) Open Source
 *
 * Each copy or derived work must preserve the copyright notice and this
 * notice unmodified.
 *
 * Resin Open Source is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * Resin Open Source is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE, or any warranty
 * of NON-INFRINGEMENT.  See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Resin Open Source; if not, write to the
 *
 *   Free Software Foundation, Inc.
 *   59 Temple Place, Suite 330
 *   Boston, MA 02111-1307  USA
 *
 * @author Scott Ferguson
 */

package com.caucho.util;

/**
 * Creates hashes for the identifiers.
 */
public class HashKey {
  private final byte []_hash;
  
  /**
   * Creates the manager
   */
  public HashKey(byte []hash)
  {
    if (hash == null)
      throw new NullPointerException();
    
    _hash = hash;
  }
  
  public byte []getHash()
  {
    return _hash;
  }

  public static String toString(byte []hash)
  {
    return toString(hash, hash.length);
  }
  
  public static String toString(byte []hash, int len)
  {
    StringBuilder sb = new StringBuilder();

    for (int i = 0; i < len; i++) {
      int d1 = (hash[i] >> 4) & 0xf;
      int d2 = (hash[i]) & 0xf;

      if (d1 < 10)
        sb.append((char) ('0' + d1));
      else
        sb.append((char) ('a' + d1 - 10));

      if (d2 < 10)
        sb.append((char) ('0' + d2));
      else
        sb.append((char) ('a' + d2 - 10));
    }

    return sb.toString();
  }

  /**
   * Calculates the key's hash
   */
  @Override
  public int hashCode()
  {
    int hash = 37;

    byte []buf = _hash;
    int len = buf.length;
    
    for (int i = 0; i < len; i++) {
      hash = 65521 * hash + buf[i];
    }

    return hash;
  }

  /**
   * Check for equality
   */
  @Override
  public boolean equals(Object o)
  {
    if (this == o)
      return true;
    else if (! (o instanceof HashKey))
      return false;

    HashKey key = (HashKey) o;

    byte []hashA = _hash;
    byte []hashB = key._hash;

    int len = hashA.length;

    if (len != hashB.length)
      return false;

    for (int i = 0; i < len; i++) {
      if (hashA[i] != hashB[i])
        return false;
    }

    return true;
  }

  public int compareTo(HashKey key)
  {
    if (key == null)
      return 1;

    byte []hashA = _hash;
    byte []hashB = key._hash;

    int len = hashA.length;

    for (int i = 0; i < len; i++) {
      int delta = hashA[i] - hashB[i];

      if (delta != 0)
        return delta;
    }

    return 0;
  }

  @Override
  public String toString()
  {
    return getClass().getSimpleName() + "[" + toString(_hash, 4) + "]";
  }
}