old-autovect-branch/libjava/gnu/gcj/convert/BytesToUnicode.java

   1 /* Copyright (C) 1999, 2000, 2001  Free Software Foundation
   2
   3    This file is part of libgcj.
   4
   5 This software is copyrighted work licensed under the terms of the
   6 Libgcj License.  Please consult the file "LIBGCJ_LICENSE" for
   7 details.  */
   8
   9 package gnu.gcj.convert;
  10
  11 public abstract class BytesToUnicode extends IOConverter
  12 {
  13   /** Buffer to read bytes from.
  14    * The characters inbuffer[inpos] ... inbuffer[inlength-1] are available. */
  15   public byte[] inbuffer;
  16   /** Starting index in buffer to read bytes from. */
  17   public int inpos;
  18   /** End of valid bytes in buffer. */
  19   public int inlength;
  20
  21   // The name of the default encoding.
  22   static String defaultEncoding;
  23
  24   /* These keep a small cache of decoders for reuse.  The array holds
  25      the actual decoders.  The currCachePos is the next value we are
  26      going to replace in the cache.  We don't just throw the data away
  27      if the cache is full, because if the cache filled up with stuff
  28      we don't need then the cache would be worthless.  We instead
  29      circulate through the cache the implement kind of an LRU
  30      algorithm. */
  31   private static final int CACHE_SIZE = 4;  // A power of 2 for speed
  32   private static BytesToUnicode[] decoderCache
  33     = new BytesToUnicode[CACHE_SIZE];
  34   private static int currCachePos = 0;
  35
  36   public abstract String getName();
  37
  38   public static BytesToUnicode getDefaultDecoder()
  39   {
  40     try
  41       {
  42         synchronized (BytesToUnicode.class)
  43           {
  44             if (defaultEncoding == null)
  45               {
  46                 String encoding
  47                   = canonicalize (System.getProperty("file.encoding",
  48                                                      "8859_1"));
  49                 String className = "gnu.gcj.convert.Input_" + encoding;
  50                 try
  51                   {
  52                     Class defaultDecodingClass = Class.forName(className);
  53                     defaultEncoding = encoding;
  54                   }
  55                 catch (ClassNotFoundException ex)
  56                   {
  57                     throw new NoClassDefFoundError("missing default encoding "
  58                                                    + encoding + " (class "
  59                                                    + className
  60                                                    + " not found)");
  61                   }
  62               }
  63           }
  64         return getDecoder (defaultEncoding);
  65       }
  66     catch (Throwable ex)
  67       {
  68         return new Input_8859_1();
  69       }
  70   }
  71
  72   /** Get a byte-stream->char-stream converter given an encoding name. */
  73   public static BytesToUnicode getDecoder (String encoding)
  74     throws java.io.UnsupportedEncodingException
  75   {
  76     /* First hunt in our cache to see if we have a decoder that is
  77        already allocated. */
  78     String canonicalEncoding = canonicalize(encoding);
  79     synchronized (BytesToUnicode.class)
  80       {
  81         int i;
  82         for (i = 0; i < decoderCache.length; ++i)
  83           {
  84             if (decoderCache[i] != null
  85                 && canonicalEncoding.equals(decoderCache[i].getName ()))
  86               {
  87                 BytesToUnicode rv = decoderCache[i];
  88                 decoderCache[i] = null;
  89                 return rv;
  90             }
  91           }
  92       }
  93
  94     // It's not in the cache, so now we have to do real work.
  95     String className = "gnu.gcj.convert.Input_" + canonicalEncoding;
  96     Class decodingClass;
  97     try
  98       {
  99         decodingClass = Class.forName(className);
 100         return (BytesToUnicode) decodingClass.newInstance();
 101       }
 102     catch (Throwable ex)
 103       {
 104         try
 105           {
 106             // We pass the original name to iconv and let it handle
 107             // its own aliasing.
 108             return new Input_iconv (encoding);
 109           }
 110         catch (Throwable _)
 111           {
 112             throw new java.io.UnsupportedEncodingException(encoding
 113                                                            + " (" + ex + ')');
 114           }
 115       }
 116   }
 117
 118   /** Make input bytes available to the conversion.
 119    * @param buffer source of input bytes
 120    * @param pos index of first available byte
 121    * @param length one more than index of last available byte
 122    */
 123   public final void setInput(byte[] buffer, int pos, int length)
 124   {
 125     inbuffer = buffer;
 126     inpos = pos;
 127     inlength = length;
 128   }
 129
 130   /** Convert bytes to chars.
 131    * Input bytes are taken from this.inbuffer.  The available input
 132    * bytes start at inbuffer[inpos], and end at inbuffer[inlength-1].
 133    * @param outbuffer buffer for the converted character
 134    * @param outpos position in buffer to start putting converted characters
 135    * @param count the maximum number of characters to convert
 136    * @return number of chars placed in outbuffer.
 137    * Also, this.inpos is incremented by the number of bytes consumed.
 138    *
 139    * (Note the asymmetry in that the input upper bound is inbuffer[inlength-1],
 140    * while the output upper bound is outbuffer[outpos+count-1].  The
 141    * justification is that inlength is like the count field of a
 142    * BufferedInputStream, while the count parameter is like the
 143    * length parameter of a read request.)  The count parameter is
 144    * also defined to be <= outbuffer.length - outpos (per the specification
 145    * of the length parameter for a read request).
 146    */
 147   public abstract int read (char[] outbuffer, int outpos, int count);
 148
 149   /** Indicate that the converter is resuable.
 150    * This class keeps track of converters on a per-encoding basis.
 151    * When done with an encoder you may call this method to indicate
 152    * that it can be reused later.
 153    */
 154   public void done ()
 155   {
 156     synchronized (BytesToUnicode.class)
 157       {
 158         this.inbuffer = null;
 159         this.inpos = 0;
 160         this.inlength = 0;
 161
 162         decoderCache[currCachePos] = this;
 163         currCachePos = (currCachePos + 1) % CACHE_SIZE;
 164       }
 165   }
 166 }