1 /*
   2  * Copyright (c) 2005, 2010, 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 com.sun.xml.internal.rngom.binary;
  27 
  28 final class PatternInterner {
  29     private static final int INIT_SIZE = 256;
  30     private static final float LOAD_FACTOR = 0.3f;
  31     private Pattern[] table;
  32     private int used;
  33     private int usedLimit;
  34 
  35     PatternInterner() {
  36         table = null;
  37         used = 0;
  38         usedLimit = 0;
  39     }
  40 
  41     PatternInterner(PatternInterner parent) {
  42         table = parent.table;
  43         if (table != null)
  44             table = (Pattern[]) table.clone();
  45         used = parent.used;
  46         usedLimit = parent.usedLimit;
  47     }
  48 
  49     Pattern intern(Pattern p) {
  50         int h;
  51 
  52         if (table == null) {
  53             table = new Pattern[INIT_SIZE];
  54             usedLimit = (int) (INIT_SIZE * LOAD_FACTOR);
  55             h = firstIndex(p);
  56         } else {
  57             for (h = firstIndex(p); table[h] != null; h = nextIndex(h)) {
  58                 if (p.samePattern(table[h]))
  59                     return table[h];
  60             }
  61         }
  62         if (used >= usedLimit) {
  63             // rehash
  64             Pattern[] oldTable = table;
  65             table = new Pattern[table.length << 1];
  66             for (int i = oldTable.length; i > 0;) {
  67                 --i;
  68                 if (oldTable[i] != null) {
  69                     int j;
  70                     for (j = firstIndex(oldTable[i]);
  71                         table[j] != null;
  72                         j = nextIndex(j));
  73                     table[j] = oldTable[i];
  74                 }
  75             }
  76             for (h = firstIndex(p); table[h] != null; h = nextIndex(h));
  77             usedLimit = (int) (table.length * LOAD_FACTOR);
  78         }
  79         used++;
  80         table[h] = p;
  81         return p;
  82     }
  83 
  84     private int firstIndex(Pattern p) {
  85         return p.patternHashCode() & (table.length - 1);
  86     }
  87 
  88     private int nextIndex(int i) {
  89         return i == 0 ? table.length - 1 : i - 1;
  90     }
  91 }