gomp-20050608-branch/libjava/gnu/gcj/convert/BytesToUnicode.java

   1 /* Copyright (C) 1999, 2000, 2001, 2005  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 import java.nio.charset.Charset;
  12
  13 public abstract class BytesToUnicode extends IOConverter
  14 {
  15   /** Buffer to read bytes from.
  16    * The characters inbuffer[inpos] ... inbuffer[inlength-1] are available. */
  17   public byte[] inbuffer;
  18   /** Starting index in buffer to read bytes from. */
  19   public int inpos;
  20   /** End of valid bytes in buffer. */
  21   public int inlength;
  22
  23   // The name of the default encoding.
  24   static String defaultEncoding;
  25
  26   /* These keep a small cache of decoders for reuse.  The array holds
  27      the actual decoders.  The currCachePos is the next value we are
  28      going to replace in the cache.  We don't just throw the data away
  29      if the cache is full, because if the cache filled up with stuff
  30      we don't need then the cache would be worthless.  We instead
  31      circulate through the cache the implement kind of an LRU
  32      algorithm. */
  33   private static final int CACHE_SIZE = 4;  // A power of 2 for speed
  34   private static BytesToUnicode[] decoderCache
  35     = new BytesToUnicode[CACHE_SIZE];
  36   private static int currCachePos = 0;
  37
  38   public abstract String getName();
  39
  40   public static BytesToUnicode getDefaultDecoder()
  41   {
  42     try
  43       {
  44         synchronized (BytesToUnicode.class)
  45           {
  46             if (defaultEncoding == null)
  47               {
  48                 String encoding
  49                   = canonicalize (System.getProperty("file.encoding",
  50                                                      "8859_1"));
  51                 String className = "gnu.gcj.convert.Input_" + encoding;
  52                 try
  53                   {
  54                     Class defaultDecodingClass = Class.forName(className);
  55                     defaultEncoding = encoding;
  56                   }
  57                 catch (ClassNotFoundException ex)
  58                   {
  59                     throw new NoClassDefFoundError("missing default encoding "
  60                                                    + encoding + " (class "
  61                                                    + className
  62                                                    + " not found)");
  63                   }
  64               }
  65           }
  66         return getDecoder (defaultEncoding);
  67       }
  68     catch (Throwable ex)
  69       {
  70         return new Input_8859_1();
  71       }
  72   }
  73
  74   /** Get a byte-stream->char-stream converter given an encoding name. */
  75   public static BytesToUnicode getDecoder (String encoding)
  76     throws java.io.UnsupportedEncodingException
  77   {
  78     /* First hunt in our cache to see if we have a decoder that is
  79        already allocated. */
  80     String canonicalEncoding = canonicalize(encoding);
  81     synchronized (BytesToUnicode.class)
  82       {
  83         int i;
  84         for (i = 0; i < decoderCache.length; ++i)
  85           {
  86             if (decoderCache[i] != null
  87                 && canonicalEncoding.equals(decoderCache[i].getName ()))
  88               {
  89                 BytesToUnicode rv = decoderCache[i];
  90                 decoderCache[i] = null;
  91                 return rv;
  92             }
  93           }
  94       }
  95
  96     // It's not in the cache, so now we have to do real work.
  97     String className = "gnu.gcj.convert.Input_" + canonicalEncoding;
  98     Class decodingClass;
  99     try
 100       {
 101         decodingClass = Class.forName(className);
 102         return (BytesToUnicode) decodingClass.newInstance();
 103       }
 104     catch (Throwable ex)
 105       {
 106         try
 107           {
 108             // We pass the original name to iconv and let it handle
 109             // its own aliasing.  Note that we intentionally prefer
 110             // iconv over nio.
 111             return new Input_iconv (encoding);
 112           }
 113         catch (Throwable _)
 114           {
 115             // Ignore, and try the next method.
 116           }
 117         try
 118           {
 119             return new BytesToCharsetAdaptor(Charset.forName(encoding));
 120           }
 121         catch (Throwable _)
 122           {
 123             throw new java.io.UnsupportedEncodingException(encoding
 124                                                            + " (" + ex + ')');
 125           }
 126       }
 127   }
 128
 129   /** Make input bytes available to the conversion.
 130    * @param buffer source of input bytes
 131    * @param pos index of first available byte
 132    * @param length one more than index of last available byte
 133    */
 134   public final void setInput(byte[] buffer, int pos, int length)
 135   {
 136     inbuffer = buffer;
 137     inpos = pos;
 138     inlength = length;
 139   }
 140
 141   /** Convert bytes to chars.
 142    * Input bytes are taken from this.inbuffer.  The available input
 143    * bytes start at inbuffer[inpos], and end at inbuffer[inlength-1].
 144    * @param outbuffer buffer for the converted character
 145    * @param outpos position in buffer to start putting converted characters
 146    * @param count the maximum number of characters to convert
 147    * @return number of chars placed in outbuffer.
 148    * Also, this.inpos is incremented by the number of bytes consumed.
 149    *
 150    * (Note the asymmetry in that the input upper bound is inbuffer[inlength-1],
 151    * while the output upper bound is outbuffer[outpos+count-1].  The
 152    * justification is that inlength is like the count field of a
 153    * BufferedInputStream, while the count parameter is like the
 154    * length parameter of a read request.)  The count parameter is
 155    * also defined to be <= outbuffer.length - outpos (per the specification
 156    * of the length parameter for a read request).
 157    */
 158   public abstract int read (char[] outbuffer, int outpos, int count);
 159
 160   /** Indicate that the converter is resuable.
 161    * This class keeps track of converters on a per-encoding basis.
 162    * When done with an encoder you may call this method to indicate
 163    * that it can be reused later.
 164    */
 165   public void done ()
 166   {
 167     synchronized (BytesToUnicode.class)
 168       {
 169         this.inbuffer = null;
 170         this.inpos = 0;
 171         this.inlength = 0;
 172
 173         decoderCache[currCachePos] = this;
 174         currCachePos = (currCachePos + 1) % CACHE_SIZE;
 175       }
 176   }
 177 }