001/* CollationKey.java -- Precomputed collation value
002   Copyright (C) 1998, 1999, 2000, 2003, 2005  Free Software Foundation, Inc.
003
004This file is part of GNU Classpath.
005
006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
008the Free Software Foundation; either version 2, or (at your option)
009any later version.
010
011GNU Classpath is distributed in the hope that it will be useful, but
012WITHOUT ANY WARRANTY; without even the implied warranty of
013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014General Public License for more details.
015
016You should have received a copy of the GNU General Public License
017along with GNU Classpath; see the file COPYING.  If not, write to the
018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
028executable, regardless of the license terms of these independent
029modules, and to copy and distribute the resulting executable under
030terms of your choice, provided that you also meet, for each linked
031independent module, the terms and conditions of the license of that
032module.  An independent module is a module which is not derived from
033or based on this library.  If you modify this library, you may extend
034this exception to your version of the library, but you are not
035obligated to do so.  If you do not wish to do so, delete this
036exception statement from your version. */
037
038
039package java.text;
040
041import java.util.Arrays;
042
043/* Written using "Java Class Libraries", 2nd edition, plus online
044 * API docs for JDK 1.2 from http://www.javasoft.com.
045 * Status: Believed complete and correct.
046 */
047
048/**
049 * This class represents a pre-computed series of bits representing a
050 * <code>String</code> for under a particular <code>Collator</code>.  This
051 * value may be compared bitwise against another <code>CollationKey</code>
052 * representing a different <code>String</code> under the same
053 * <code>Collator</code> in a manner than is usually more efficient than
054 * using the raw <code>Collator</code> compare methods.  There is overhead
055 * associated with calculating this value, so it is generally not
056 * advisable to compute <code>CollationKey</code>'s unless multiple
057 * comparisons against a <code>String</code> will be done.  (For example,
058 * in a sort routine).
059 * <p>
060 * This class cannot be instantiated directly.  Instead, a
061 * <code>CollationKey</code> is created by calling the
062 * <code>getCollationKey</code> method on an instance of <code>Collator</code>.
063 *
064 * @author Aaron M. Renn (arenn@urbanophile.com)
065 * @author Tom Tromey (tromey@cygnus.com)
066 * @date March 25, 1999
067 */
068public class CollationKey implements Comparable<CollationKey>
069{
070  /**
071   * This is the <code>Collator</code> this object was created from.
072   */
073  private Collator collator;
074
075  /**
076   * This is the <code>String</code> this object represents.
077   */
078  private String originalText;
079
080  /**
081   * This is the bit value for this key.
082   */
083  private byte[] key;
084
085  CollationKey (Collator collator, String originalText, byte[] key)
086  {
087    this.collator = collator;
088    this.originalText = originalText;
089    this.key = key;
090  }
091
092  /**
093   * This method compares the specified object to this one.  An integer is
094   * returned which indicates whether the specified object is less than,
095   * greater than, or equal to this object.
096   *
097   * @param ck The <code>CollationKey</code> to compare against this one.
098   *
099   * @return A negative integer if this object is less than the specified object, 0 if it is equal or a positive integer if it is greater than the specified object.
100   */
101  public int compareTo (CollationKey ck)
102  {
103    int max = Math.min (key.length, ck.key.length);
104
105    for (int i = 0; i < max; ++i)
106      {
107        if (key[i] != ck.key[i])
108          return key[i] - ck.key[i];
109      }
110
111    return key.length - ck.key.length;
112  }
113
114  /**
115   * This method tests the specified <code>Object</code> for equality with
116   * this object.  This will be true if and only if:
117   * <p>
118   * <ul>
119   * <li>The specified object must not be <code>null</code></li>
120   * <li>The specified object is an instance of <code>CollationKey</code>.</li>
121   * <li>The specified object was created from the same <code>Collator</code>
122   * as this object.</li>
123   * <li>The specified object has the same source string and bit key as
124   * this object.</li>
125   * </ul>
126   *
127   * @param obj The <code>Object</code> to test for equality.
128   *
129   * @return <code>true</code> if the specified object is equal to this one, <code>false</code> otherwise.
130   */
131  public boolean equals (Object obj)
132  {
133    if (! (obj instanceof CollationKey))
134      return false;
135
136    CollationKey ck = (CollationKey) obj;
137
138    if (ck.collator != collator)
139      return false;
140
141    if (!ck.getSourceString ().equals (getSourceString ()))
142      return false;
143
144    if (! Arrays.equals (ck.toByteArray (), toByteArray ()))
145      return false;
146
147    return true;
148  }
149
150  /**
151   * This method returns the <code>String</code> that this object was created
152   * from.
153   *
154   * @return The source <code>String</code> for this object.
155   */
156  public String getSourceString()
157  {
158    return originalText;
159  }
160
161  /**
162   * This method returns a hash value for this object.  The hash value
163   * returned will be the hash code of the bit key so that identical bit
164   * keys will return the same value.
165   *
166   * @return A hash value for this object.
167   */
168  public int hashCode()
169  {
170    // We just follow BitSet instead of thinking up something new.
171    long h = originalText.hashCode();
172    for (int i = key.length - 1; i >= 0; --i)
173      h ^= key[i] * (i + 1);
174    return (int) ((h >> 32) ^ h);
175  }
176
177  /**
178   * This method returns the collation bit sequence as a byte array.
179   *
180   * @return A byte array containing the collation bit sequence.
181   */
182  public byte[] toByteArray()
183  {
184    return key;
185  }
186}