1 /*

     2  * Copyright (c) 2004, 2012, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.  Oracle designates this

     8  * particular file as subject to the "Classpath" exception as provided

     9  * by Oracle in the LICENSE file that accompanied this code.

    10  *

    11  * This code is distributed in the hope that it will be useful, but WITHOUT

    12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    14  * version 2 for more details (a copy is included in the LICENSE file that

    15  * accompanied this code).

    16  *

    17  * You should have received a copy of the GNU General Public License version

    18  * 2 along with this work; if not, write to the Free Software Foundation,

    19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    20  *

    21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    22  * or visit www.oracle.com if you need additional information or have any

    23  * questions.

    24  */

    25 

    26 package sun.util;

    27 

    28 import java.util.Iterator;

    29 import java.util.Map;

    30 import java.util.Set;

    31 import java.util.AbstractMap;

    32 import java.util.AbstractSet;

    33 import java.util.NoSuchElementException;

    34 

    35 

    36 /**

    37  * A precomputed hash map.

    38  *

    39  * <p> Subclasses of this class are of the following form:

    40  *

    41  * <blockquote><pre>

    42  * class FooMap

    43  *     extends sun.util.PreHashedMap<String>

    44  * {

    45  *

    46  *     private FooMap() {

    47  *         super(ROWS, SIZE, SHIFT, MASK);

    48  *     }

    49  *

    50  *     protected void init(Object[] ht) {

    51  *         ht[0] = new Object[] { "key-1", value_1 };

    52  *         ht[1] = new Object[] { "key-2", value_2,

    53  *                      new Object { "key-3", value_3 } };

    54  *         ...

    55  *     }

    56  *

    57  * }</pre></blockquote>

    58  *

    59  * <p> The <tt>init</tt> method is invoked by the <tt>PreHashedMap</tt>

    60  * constructor with an object array long enough for the map's rows.  The method

    61  * must construct the hash chain for each row and store it in the appropriate

    62  * element of the array.

    63  *

    64  * <p> Each entry in the map is represented by a unique hash-chain node.  The

    65  * final node of a hash chain is a two-element object array whose first element

    66  * is the entry's key and whose second element is the entry's value.  A

    67  * non-final node of a hash chain is a three-element object array whose first

    68  * two elements are the entry's key and value and whose third element is the

    69  * next node in the chain.

    70  *

    71  * <p> Instances of this class are mutable and are not safe for concurrent

    72  * access.  They may be made immutable and thread-safe via the appropriate

    73  * methods in the {@link java.util.Collections} utility class.

    74  *

    75  * <p> In the JDK build, subclasses of this class are typically created via the

    76  * <tt>Hasher</tt> program in the <tt>make/tools/Hasher</tt> directory.

    77  *

    78  * @author Mark Reinhold

    79  * @since 1.5

    80  *

    81  * @see java.util.AbstractMap

    82  */

    83 

    84 public abstract class PreHashedMap<V>

    85     extends AbstractMap<String,V>

    86 {

    87 

    88     private final int rows;

    89     private final int size;

    90     private final int shift;

    91     private final int mask;

    92     private final Object[] ht;

    93 

    94     /**

    95      * Creates a new map.

    96      *

    97      * <p> This constructor invokes the {@link #init init} method, passing it a

    98      * newly-constructed row array that is <tt>rows</tt> elements long.

    99      *

   100      * @param rows

   101      *        The number of rows in the map

   102      * @param size

   103      *        The number of entries in the map

   104      * @param shift

   105      *        The value by which hash codes are right-shifted

   106      * @param mask

   107      *        The value with which hash codes are masked after being shifted

   108      */

   109     protected PreHashedMap(int rows, int size, int shift, int mask) {

   110         this.rows = rows;

   111         this.size = size;

   112         this.shift = shift;

   113         this.mask = mask;

   114         this.ht = new Object[rows];

   115         init(ht);

   116     }

   117 

   118     /**

   119      * Initializes this map.

   120      *

   121      * <p> This method must construct the map's hash chains and store them into

   122      * the appropriate elements of the given hash-table row array.

   123      *

   124      * @param rows

   125      *        The row array to be initialized

   126      */

   127     protected abstract void init(Object[] ht);

   128 

   129     @SuppressWarnings("unchecked")

   130     private V toV(Object x) {

   131         return (V)x;

   132     }

   133 

   134     public V get(Object k) {

   135         int h = (k.hashCode() >> shift) & mask;

   136         Object[] a = (Object[])ht[h];

   137         if (a == null) return null;

   138         for (;;) {

   139             if (a[0].equals(k))

   140                 return toV(a[1]);

   141             if (a.length < 3)

   142                 return null;

   143             a = (Object[])a[2];

   144         }

   145     }

   146 

   147     /**

   148      * @throws UnsupportedOperationException

   149      *         If the given key is not part of this map's initial key set

   150      */

   151     public V put(String k, V v) {

   152         int h = (k.hashCode() >> shift) & mask;

   153         Object[] a = (Object[])ht[h];

   154         if (a == null)

   155             throw new UnsupportedOperationException(k);

   156         for (;;) {

   157             if (a[0].equals(k)) {

   158                 V ov = toV(a[1]);

   159                 a[1] = v;

   160                 return ov;

   161             }

   162             if (a.length < 3)

   163                 throw new UnsupportedOperationException(k);

   164             a = (Object[])a[2];

   165         }

   166     }

   167 

   168     public Set<String> keySet() {

   169         return new AbstractSet<String> () {

   170 

   171             public int size() {

   172                 return size;

   173             }

   174 

   175             public Iterator<String> iterator() {

   176                 return new Iterator<String>() {

   177                     private int i = -1;

   178                     Object[] a = null;

   179                     String cur = null;

   180 

   181                     private boolean findNext() {

   182                         if (a != null) {

   183                             if (a.length == 3) {

   184                                 a = (Object[])a[2];

   185                                 cur = (String)a[0];

   186                                 return true;

   187                             }

   188                             i++;

   189                             a = null;

   190                         }

   191                         cur = null;

   192                         if (i >= rows)

   193                             return false;

   194                         if (i < 0 || ht[i] == null) {

   195                             do {

   196                                 if (++i >= rows)

   197                                     return false;

   198                             } while (ht[i] == null);

   199                         }

   200                         a = (Object[])ht[i];

   201                         cur = (String)a[0];

   202                         return true;

   203                     }

   204 

   205                     public boolean hasNext() {

   206                         if (cur != null)

   207                             return true;

   208                         return findNext();

   209                     }

   210 

   211                     public String next() {

   212                         if (cur == null) {

   213                             if (!findNext())

   214                                 throw new NoSuchElementException();

   215                         }

   216                         String s = cur;

   217                         cur = null;

   218                         return s;

   219                     }

   220 

   221                     public void remove() {

   222                         throw new UnsupportedOperationException();

   223                     }

   224 

   225                 };

   226             }

   227         };

   228     }

   229 

   230     public Set<Map.Entry<String,V>> entrySet() {

   231         return new AbstractSet<Map.Entry<String,V>> () {

   232 

   233             public int size() {

   234                 return size;

   235             }

   236 

   237             public Iterator<Map.Entry<String,V>> iterator() {

   238                 return new Iterator<Map.Entry<String,V>>() {

   239                     final Iterator<String> i = keySet().iterator();

   240 

   241                     public boolean hasNext() {

   242                         return i.hasNext();

   243                     }

   244 

   245                     public Map.Entry<String,V> next() {

   246                         return new Map.Entry<String,V>() {

   247                             String k = i.next();

   248                             public String getKey() { return k; }

   249                             public V getValue() { return get(k); }

   250                             public int hashCode() {

   251                                 V v = get(k);

   252                                 return (k.hashCode()

   253                                         + (v == null

   254                                            ? 0

   255                                            : v.hashCode()));

   256                             }

   257                             public boolean equals(Object ob) {

   258                                 if (ob == this)

   259                                     return true;

   260                                 if (!(ob instanceof Map.Entry))

   261                                     return false;

   262                                 Map.Entry<?,?> that = (Map.Entry<?,?>)ob;

   263                                 return ((this.getKey() == null

   264                                          ? that.getKey() == null

   265                                          : this.getKey()

   266                                                .equals(that.getKey()))

   267                                         &&

   268                                         (this.getValue() == null

   269                                          ? that.getValue() == null

   270                                          : this.getValue()

   271                                                .equals(that.getValue())));

   272                             }

   273                             public V setValue(V v) {

   274                                 throw new UnsupportedOperationException();

   275                             }

   276                         };

   277                     }

   278 

   279                     public void remove() {

   280                         throw new UnsupportedOperationException();

   281                     }

   282 

   283                 };

   284             }

   285         };

   286     }

   287 

   288 }