UnsharedNameTable.java revision 2571:10fc81ac75b4 
1/*
2 * Copyright (c) 1999, 2013, 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
26package com.sun.tools.javac.util;
27
28import java.lang.ref.WeakReference;
29
30/**
31 * Implementation of Name.Table that stores names in individual arrays
32 * using weak references. It is recommended for use when a single shared
33 * byte array is unsuitable.
34 *
35 *  <p><b>This is NOT part of any supported API.
36 *  If you write code that depends on this, you do so at your own risk.
37 *  This code and its internal interfaces are subject to change or
38 *  deletion without notice.</b>
39 */
40public class UnsharedNameTable extends Name.Table {
41    static public Name.Table create(Names names) {
42        return new UnsharedNameTable(names);
43    }
44
45    static class HashEntry extends WeakReference<NameImpl> {
46        HashEntry next;
47        HashEntry(NameImpl referent) {
48            super(referent);
49        }
50    }
51
52    /** The hash table for names.
53     */
54    private HashEntry[] hashes = null;
55
56    /** The mask to be used for hashing
57     */
58    private int hashMask;
59
60    /** Index counter for names in this table.
61     */
62    public int index;
63
64    /** Allocator
65     *  @param names The main name table
66     *  @param hashSize the (constant) size to be used for the hash table
67     *                  needs to be a power of two.
68     */
69    public UnsharedNameTable(Names names, int hashSize) {
70        super(names);
71        hashMask = hashSize - 1;
72        hashes = new HashEntry[hashSize];
73    }
74
75    public UnsharedNameTable(Names names) {
76        this(names, 0x8000);
77    }
78
79
80    @Override
81    public Name fromChars(char[] cs, int start, int len) {
82        byte[] name = new byte[len * 3];
83        int nbytes = Convert.chars2utf(cs, start, name, 0, len);
84        return fromUtf(name, 0, nbytes);
85    }
86
87    @Override
88    public Name fromUtf(byte[] cs, int start, int len) {
89        int h = hashValue(cs, start, len) & hashMask;
90
91        HashEntry element = hashes[h];
92
93        NameImpl n = null;
94
95        HashEntry previousNonNullTableEntry = null;
96        HashEntry firstTableEntry = element;
97
98        while (element != null) {
99            if (element == null) {
100                break;
101            }
102
103            n = element.get();
104
105            if (n == null) {
106                if (firstTableEntry == element) {
107                    hashes[h] = firstTableEntry = element.next;
108                }
109                else {
110                    Assert.checkNonNull(previousNonNullTableEntry, "previousNonNullTableEntry cannot be null here.");
111                    previousNonNullTableEntry.next = element.next;
112                }
113            }
114            else {
115                if (n.getByteLength() == len && equals(n.bytes, 0, cs, start, len)) {
116                    return n;
117                }
118                previousNonNullTableEntry = element;
119            }
120
121            element = element.next;
122        }
123
124        byte[] bytes = new byte[len];
125        System.arraycopy(cs, start, bytes, 0, len);
126        n = new NameImpl(this, bytes, index++);
127
128        HashEntry newEntry = new HashEntry(n);
129
130        if (previousNonNullTableEntry == null) { // We are not the first name with that hashCode.
131            hashes[h] = newEntry;
132        }
133        else {
134            Assert.checkNull(previousNonNullTableEntry.next, "previousNonNullTableEntry.next must be null.");
135            previousNonNullTableEntry.next = newEntry;
136        }
137
138        return n;
139    }
140
141    @Override
142    public void dispose() {
143        hashes = null;
144    }
145
146    static class NameImpl extends Name {
147        NameImpl(UnsharedNameTable table, byte[] bytes, int index) {
148            super(table);
149            this.bytes = bytes;
150            this.index = index;
151        }
152
153        final byte[] bytes;
154        final int index;
155
156        @Override
157        public int getIndex() {
158            return index;
159        }
160
161        @Override
162        public int getByteLength() {
163            return bytes.length;
164        }
165
166        @Override
167        public byte getByteAt(int i) {
168            return bytes[i];
169        }
170
171        @Override
172        public byte[] getByteArray() {
173            return bytes;
174        }
175
176        @Override
177        public int getByteOffset() {
178            return 0;
179        }
180
181    }
182
183}
184