1 /*
   2  * Copyright (c) 2000, 2004, 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.nio.cs;
  27 
  28 import java.lang.ref.SoftReference;
  29 import java.nio.charset.Charset;
  30 import java.nio.charset.spi.CharsetProvider;
  31 import java.util.ArrayList;
  32 import java.util.TreeMap;
  33 import java.util.Iterator;
  34 import java.util.Locale;
  35 import java.util.Map;
  36 import sun.misc.ASCIICaseInsensitiveComparator;
  37 
  38 
  39 /**
  40  * Abstract base class for charset providers.
  41  *
  42  * @author Mark Reinhold
  43  */
  44 
  45 public class AbstractCharsetProvider
  46     extends CharsetProvider
  47 {
  48 
  49     /* Maps canonical names to class names
  50      */
  51     private Map<String,String> classMap
  52         = new TreeMap<>(ASCIICaseInsensitiveComparator.CASE_INSENSITIVE_ORDER);
  53 
  54     /* Maps alias names to canonical names
  55      */
  56     private Map<String,String> aliasMap
  57         = new TreeMap<>(ASCIICaseInsensitiveComparator.CASE_INSENSITIVE_ORDER);
  58 
  59     /* Maps canonical names to alias-name arrays
  60      */
  61     private Map<String,String[]> aliasNameMap
  62         = new TreeMap<>(ASCIICaseInsensitiveComparator.CASE_INSENSITIVE_ORDER);
  63 
  64     /* Maps canonical names to soft references that hold cached instances
  65      */
  66     private Map<String,SoftReference<Charset>> cache
  67         = new TreeMap<>(ASCIICaseInsensitiveComparator.CASE_INSENSITIVE_ORDER);
  68 
  69     private String packagePrefix;
  70 
  71     protected AbstractCharsetProvider() {
  72         packagePrefix = "sun.nio.cs";
  73     }
  74 
  75     protected AbstractCharsetProvider(String pkgPrefixName) {
  76         packagePrefix = pkgPrefixName;
  77     }
  78 
  79     /* Add an entry to the given map, but only if no mapping yet exists
  80      * for the given name.
  81      */
  82     private static <K,V> void put(Map<K,V> m, K name, V value) {
  83         if (!m.containsKey(name))
  84             m.put(name, value);
  85     }
  86 
  87     private static <K,V> void remove(Map<K,V> m, K name) {
  88         V x  = m.remove(name);
  89         assert (x != null);
  90     }
  91 
  92     /* Declare support for the given charset
  93      */
  94     protected void charset(String name, String className, String[] aliases) {
  95         synchronized (this) {
  96             put(classMap, name, className);
  97             for (int i = 0; i < aliases.length; i++)
  98                 put(aliasMap, aliases[i], name);
  99             put(aliasNameMap, name, aliases);
 100             cache.clear();
 101         }
 102     }
 103 
 104     protected void deleteCharset(String name, String[] aliases) {
 105         synchronized (this) {
 106             remove(classMap, name);
 107             for (int i = 0; i < aliases.length; i++)
 108                 remove(aliasMap, aliases[i]);
 109             remove(aliasNameMap, name);
 110             cache.clear();
 111         }
 112     }
 113 
 114     /* Late initialization hook, needed by some providers
 115      */
 116     protected void init() { }
 117 
 118     private String canonicalize(String charsetName) {
 119         String acn = aliasMap.get(charsetName);
 120         return (acn != null) ? acn : charsetName;
 121     }
 122 
 123     private Charset lookup(String csn) {
 124 
 125         // Check cache first
 126         SoftReference<Charset> sr = cache.get(csn);
 127         if (sr != null) {
 128             Charset cs = sr.get();
 129             if (cs != null)
 130                 return cs;
 131         }
 132 
 133         // Do we even support this charset?
 134         String cln = classMap.get(csn);
 135 
 136         if (cln == null)
 137             return null;
 138 
 139         // Instantiate the charset and cache it
 140         try {
 141 
 142             Class<?> c = Class.forName(packagePrefix + "." + cln,
 143                                        true,
 144                                        this.getClass().getClassLoader());
 145 
 146             Charset cs = (Charset)c.newInstance();
 147             cache.put(csn, new SoftReference<Charset>(cs));
 148             return cs;
 149         } catch (ClassNotFoundException x) {
 150             return null;
 151         } catch (IllegalAccessException x) {
 152             return null;
 153         } catch (InstantiationException x) {
 154             return null;
 155         }
 156     }
 157 
 158     public final Charset charsetForName(String charsetName) {
 159         synchronized (this) {
 160             init();
 161             return lookup(canonicalize(charsetName));
 162         }
 163     }
 164 
 165     public final Iterator<Charset> charsets() {
 166 
 167         final ArrayList<String> ks;
 168         synchronized (this) {
 169             init();
 170             ks = new ArrayList<>(classMap.keySet());
 171         }
 172 
 173         return new Iterator<Charset>() {
 174                 Iterator<String> i = ks.iterator();
 175 
 176                 public boolean hasNext() {
 177                     return i.hasNext();
 178                 }
 179 
 180                 public Charset next() {
 181                     String csn = i.next();
 182                     return lookup(csn);
 183                 }
 184 
 185                 public void remove() {
 186                     throw new UnsupportedOperationException();
 187                 }
 188             };
 189     }
 190 
 191     public final String[] aliases(String charsetName) {
 192         synchronized (this) {
 193             init();
 194             return aliasNameMap.get(charsetName);
 195         }
 196     }
 197 
 198 }