Source for java.nio.charset.Charset

   1: /* Charset.java -- 
   2:    Copyright (C) 2002, 2004, 2005  Free Software Foundation, Inc.
   3: 
   4: This file is part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2, or (at your option)
   9: any later version.
  10: 
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; see the file COPYING.  If not, write to the
  18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 USA.
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: independent module, the terms and conditions of the license of that
  32: module.  An independent module is a module which is not derived from
  33: or based on this library.  If you modify this library, you may extend
  34: this exception to your version of the library, but you are not
  35: obligated to do so.  If you do not wish to do so, delete this
  36: exception statement from your version. */
  37: 
  38: 
  39: package java.nio.charset;
  40: 
  41: import gnu.classpath.SystemProperties;
  42: 
  43: import gnu.java.nio.charset.Provider;
  44: import gnu.java.nio.charset.iconv.IconvProvider;
  45: 
  46: import java.io.BufferedReader;
  47: import java.io.InputStreamReader;
  48: import java.net.URL;
  49: import java.nio.ByteBuffer;
  50: import java.nio.CharBuffer;
  51: import java.nio.charset.spi.CharsetProvider;
  52: import java.util.Collections;
  53: import java.util.Enumeration;
  54: import java.util.HashSet;
  55: import java.util.Iterator;
  56: import java.util.LinkedHashSet;
  57: import java.util.Locale;
  58: import java.util.Set;
  59: import java.util.SortedMap;
  60: import java.util.TreeMap;
  61: 
  62: /**
  63:  * @author Jesse Rosenstock
  64:  * @since 1.4
  65:  * @status updated to 1.5
  66:  */
  67: public abstract class Charset implements Comparable
  68: {
  69:   private CharsetEncoder cachedEncoder;
  70:   private CharsetDecoder cachedDecoder;
  71:   
  72:   /**
  73:    * Extra Charset providers.
  74:    */
  75:   private static CharsetProvider[] providers;
  76:   
  77:   private final String canonicalName;
  78:   private final String[] aliases;
  79:   
  80:   protected Charset (String canonicalName, String[] aliases)
  81:   {
  82:     checkName (canonicalName);
  83:     if (aliases != null)
  84:       {
  85:         int n = aliases.length;
  86:         for (int i = 0; i < n; ++i)
  87:             checkName (aliases[i]);
  88:       }
  89: 
  90:     cachedEncoder = null;
  91:     cachedDecoder = null;
  92:     this.canonicalName = canonicalName;
  93:     this.aliases = aliases;
  94:   }
  95: 
  96:   /**
  97:    * @throws IllegalCharsetNameException  if the name is illegal
  98:    */
  99:   private static void checkName (String name)
 100:   {
 101:     int n = name.length ();
 102: 
 103:     if (n == 0)
 104:       throw new IllegalCharsetNameException (name);
 105: 
 106:     char ch = name.charAt (0);
 107:     if (!(('A' <= ch && ch <= 'Z')
 108:           || ('a' <= ch && ch <= 'z')
 109:           || ('0' <= ch && ch <= '9')))
 110:       throw new IllegalCharsetNameException (name);
 111: 
 112:     for (int i = 1; i < n; ++i)
 113:       {
 114:         ch = name.charAt (i);
 115:         if (!(('A' <= ch && ch <= 'Z')
 116:               || ('a' <= ch && ch <= 'z')
 117:               || ('0' <= ch && ch <= '9')
 118:               || ch == '-' || ch == '.' || ch == ':' || ch == '_'))
 119:           throw new IllegalCharsetNameException (name);
 120:       }
 121:   }
 122: 
 123:   /**
 124:    * Returns the system default charset.
 125:    *
 126:    * This may be set by the user or VM with the file.encoding
 127:    * property.
 128:    */
 129:   public static Charset defaultCharset()
 130:   {
 131:     String encoding;
 132:     
 133:     try 
 134:       {
 135:     encoding = SystemProperties.getProperty("file.encoding");
 136:       }
 137:     catch(SecurityException e)
 138:       {
 139:     // Use fallback.
 140:     encoding = "ISO-8859-1";
 141:       }
 142:     catch(IllegalArgumentException e)
 143:       {
 144:     // Use fallback.
 145:     encoding = "ISO-8859-1";
 146:       }
 147: 
 148:     try
 149:       {
 150:     return forName(encoding);
 151:       }
 152:     catch(UnsupportedCharsetException e)
 153:       {
 154:     // Ignore.
 155:       }
 156:     catch(IllegalCharsetNameException e)
 157:       {
 158:     // Ignore.
 159:       }
 160:     catch(IllegalArgumentException e)
 161:       {
 162:     // Ignore.
 163:       }
 164:     
 165:     throw new IllegalStateException("Can't get default charset!");
 166:   }
 167: 
 168:   public static boolean isSupported (String charsetName)
 169:   {
 170:     return charsetForName (charsetName) != null;
 171:   }
 172: 
 173:   /**
 174:    * Returns the Charset instance for the charset of the given name.
 175:    * 
 176:    * @param charsetName
 177:    * @return
 178:    * @throws UnsupportedCharsetException if this VM does not support
 179:    * the charset of the given name.
 180:    * @throws IllegalCharsetNameException if the given charset name is
 181:    * legal.
 182:    * @throws IllegalArgumentException if <code>charsetName</code> is null.
 183:    */
 184:   public static Charset forName (String charsetName)
 185:   {
 186:     // Throws IllegalArgumentException as the JDK does.
 187:     if(charsetName == null)
 188:         throw new IllegalArgumentException("Charset name must not be null.");
 189:     
 190:     Charset cs = charsetForName (charsetName);
 191:     if (cs == null)
 192:       throw new UnsupportedCharsetException (charsetName);
 193:     return cs;
 194:   }
 195: 
 196:   /**
 197:    * Retrieves a charset for the given charset name.
 198:    *
 199:    * @return A charset object for the charset with the specified name, or
 200:    * <code>null</code> if no such charset exists.
 201:    *
 202:    * @throws IllegalCharsetNameException  if the name is illegal
 203:    */
 204:   private static Charset charsetForName(String charsetName)
 205:   {
 206:     checkName (charsetName);
 207:     // Try the default provider first
 208:     // (so we don't need to load external providers unless really necessary)
 209:     // if it is an exotic charset try loading the external providers.
 210:     Charset cs = provider().charsetForName(charsetName);
 211:     if (cs == null)
 212:       {
 213:     CharsetProvider[] providers = providers2();
 214:     for (int i = 0; i < providers.length; i++)
 215:       {
 216:         cs = providers[i].charsetForName(charsetName);
 217:         if (cs != null)
 218:           break;
 219:       }
 220:       }
 221:     return cs;
 222:   }
 223: 
 224:   public static SortedMap availableCharsets()
 225:   {
 226:     TreeMap charsets = new TreeMap(String.CASE_INSENSITIVE_ORDER);
 227:     for (Iterator i = provider().charsets(); i.hasNext(); )
 228:       {
 229:     Charset cs = (Charset) i.next();
 230:     charsets.put(cs.name(), cs);
 231:       }
 232: 
 233:     CharsetProvider[] providers = providers2();
 234:     for (int j = 0; j < providers.length; j++)
 235:       {
 236:         for (Iterator i = providers[j].charsets(); i.hasNext(); )
 237:           {
 238:             Charset cs = (Charset) i.next();
 239:             charsets.put(cs.name(), cs);
 240:           }
 241:       }
 242: 
 243:     return Collections.unmodifiableSortedMap(charsets);
 244:   }
 245: 
 246:   private static CharsetProvider provider()
 247:   {
 248:     String useIconv = SystemProperties.getProperty
 249:       ("gnu.classpath.nio.charset.provider.iconv");
 250: 
 251:     if (useIconv != null)
 252:       return IconvProvider.provider();
 253: 
 254:     return Provider.provider();
 255:   }
 256: 
 257:   /**
 258:    * We need to support multiple providers, reading them from
 259:    * java.nio.charset.spi.CharsetProvider in the resource directory
 260:    * META-INF/services. This returns the "extra" charset providers.
 261:    */
 262:   private static CharsetProvider[] providers2()
 263:   {
 264:     if (providers == null)
 265:       {
 266:         try
 267:           {
 268:             Enumeration en = ClassLoader.getSystemResources
 269:           ("META-INF/services/java.nio.charset.spi.CharsetProvider");
 270:             LinkedHashSet set = new LinkedHashSet();
 271:             while (en.hasMoreElements())
 272:               {
 273:                 BufferedReader rdr = new BufferedReader(new InputStreamReader
 274:                   (((URL) (en.nextElement())).openStream()));
 275:                 while (true)
 276:                   {
 277:                     String s = rdr.readLine();
 278:                     if (s == null)
 279:               break;
 280:                     CharsetProvider p =
 281:               (CharsetProvider) ((Class.forName(s)).newInstance());
 282:                     set.add(p);
 283:                   }
 284:                }
 285: 
 286:             providers = new CharsetProvider[set.size()];
 287:             set.toArray(providers);
 288:           }
 289:         catch (Exception e)
 290:           {
 291:             throw new RuntimeException(e);
 292:           }
 293:       }
 294:     return providers;
 295:   }
 296: 
 297:   public final String name ()
 298:   {
 299:     return canonicalName;
 300:   }
 301: 
 302:   public final Set aliases ()
 303:   {
 304:     if (aliases == null)
 305:       return Collections.EMPTY_SET;
 306: 
 307:     // should we cache the aliasSet instead?
 308:     int n = aliases.length;
 309:     HashSet aliasSet = new HashSet (n);
 310:     for (int i = 0; i < n; ++i)
 311:         aliasSet.add (aliases[i]);
 312:     return Collections.unmodifiableSet (aliasSet);
 313:   }
 314: 
 315:   public String displayName ()
 316:   {
 317:     return canonicalName;
 318:   }
 319: 
 320:   public String displayName (Locale locale)
 321:   {
 322:     return canonicalName;
 323:   }
 324: 
 325:   public final boolean isRegistered ()
 326:   {
 327:     return (!canonicalName.startsWith ("x-")
 328:             && !canonicalName.startsWith ("X-"));
 329:   }
 330: 
 331:   public abstract boolean contains (Charset cs);
 332: 
 333:   public abstract CharsetDecoder newDecoder ();
 334: 
 335:   public abstract CharsetEncoder newEncoder ();
 336: 
 337:   public boolean canEncode ()
 338:   {
 339:     return true;
 340:   }
 341: 
 342:   // NB: This implementation serializes different threads calling
 343:   // Charset.encode(), a potential performance problem.  It might
 344:   // be better to remove the cache, or use ThreadLocal to cache on
 345:   // a per-thread basis.
 346:   public final synchronized ByteBuffer encode (CharBuffer cb)
 347:   {
 348:     try
 349:       {
 350:     if (cachedEncoder == null)
 351:       {
 352:         cachedEncoder = newEncoder ()
 353:           .onMalformedInput (CodingErrorAction.REPLACE)
 354:           .onUnmappableCharacter (CodingErrorAction.REPLACE);
 355:       } else
 356:       cachedEncoder.reset();
 357:     return cachedEncoder.encode (cb);
 358:       }
 359:     catch (CharacterCodingException e)
 360:       {
 361:         throw new AssertionError (e);
 362:       }
 363:   }
 364:   
 365:   public final ByteBuffer encode (String str)
 366:   {
 367:     return encode (CharBuffer.wrap (str));
 368:   }
 369: 
 370:   // NB: This implementation serializes different threads calling
 371:   // Charset.decode(), a potential performance problem.  It might
 372:   // be better to remove the cache, or use ThreadLocal to cache on
 373:   // a per-thread basis.
 374:   public final synchronized CharBuffer decode (ByteBuffer bb)
 375:   {
 376:     try
 377:       {
 378:     if (cachedDecoder == null)
 379:       {
 380:         cachedDecoder = newDecoder ()
 381:           .onMalformedInput (CodingErrorAction.REPLACE)
 382:           .onUnmappableCharacter (CodingErrorAction.REPLACE);
 383:       } else
 384:       cachedDecoder.reset();
 385: 
 386:     return cachedDecoder.decode (bb);
 387:       }
 388:     catch (CharacterCodingException e)
 389:       {
 390:         throw new AssertionError (e);
 391:       }
 392:   }
 393: 
 394:   public final int compareTo (Object ob)
 395:   {
 396:     return canonicalName.compareToIgnoreCase (((Charset) ob).canonicalName);
 397:   }
 398: 
 399:   public final int hashCode ()
 400:   {
 401:     return canonicalName.hashCode ();
 402:   }
 403: 
 404:   public final boolean equals (Object ob)
 405:   {
 406:     if (ob instanceof Charset)
 407:       return canonicalName.equalsIgnoreCase (((Charset) ob).canonicalName);
 408:     else
 409:       return false;
 410:   }
 411: 
 412:   public final String toString ()
 413:   {
 414:     return canonicalName;
 415:   }
 416: }