/* Copyright (C) 1999  Cygnus Solutions

   This file is part of libgcj.

This software is copyrighted work licensed under the terms of the
Libgcj License.  Please consult the file "LIBGCJ_LICENSE" for
details.  */

package gnu.gcj.convert;

public abstract class BytesToUnicode
{
  /** Buffer to read bytes from.
   * The characters inbuffer[inpos] ... inbuffer[inlength-1] are available. */
  public byte[] inbuffer;
  /** Starting index in buffer to read bytes from. */
  public int inpos;
  /** End of valid bytes in buffer. */
  public int inlength;

  static Class defaultDecodingClass;

  static synchronized void getDefaultDecodingClass()
  {
    // Test (defaultDecodingClass == null) again in case of race condition.
    if (defaultDecodingClass == null)
      {
	String encoding = System.getProperty("file.encoding");
	String className = "gnu.gcj.convert.Input_"+encoding;
	try
	  {
	    defaultDecodingClass = Class.forName(className);
	  }
	catch (ClassNotFoundException ex)
	  {
	    throw new NoClassDefFoundError("missing default encoding "
					   + encoding + " (class "
					   + className + " not found)");
	  }
      }
  }

  public abstract String getName();

  public static BytesToUnicode getDefaultDecoder()
  {
    try
      {
	if (defaultDecodingClass == null)
	  getDefaultDecodingClass();
	return (BytesToUnicode) defaultDecodingClass.newInstance();
      }
    catch (Throwable ex)
      {
	return new Input_8859_1();
      }
  }

  /** Get a byte-stream->char-stream converter given an encoding name. */
  public static BytesToUnicode getDecoder (String encoding)
    throws java.io.UnsupportedEncodingException
  {
    String className = "gnu.gcj.convert.Input_"+encoding;
    Class decodingClass;
    try 
      { 
	decodingClass = Class.forName(className); 
	return (BytesToUnicode) decodingClass.newInstance();
      } 
    catch (Throwable ex) 
      { 
	throw new java.io.UnsupportedEncodingException(encoding
						       + " (" + ex + ')');
      }
  }

  /** Make input bytes available to the conversion.
   * @param buffer source of input bytes
   * @param pos index of first available byte
   * @param length one more than index of last available byte
   */
  public final void setInput(byte[] buffer, int pos, int length)
  {
    inbuffer = buffer;
    inpos = pos;
    inlength = length;
  }

  /** Convert bytes to chars.
   * Input bytes are taken from this.inbuffer.  The available input
   * bytes start at inbuffer[inpos], and end at inbuffer[inlength-1].
   * @param outbuffer buffer for the converted character
   * @param outpos position in buffer to start putting converted characters
   * @param count the maximum number of characters to convert
   * @return number of chars placed in outbuffer.
   * Also, this.inpos is incremented by the number of bytes consumed.
   *
   * (Note the asymmetry in that the input upper bound is inbuffer[inlength-1],
   * while the output upper bound is outbuffer[outpos+count-1].  The
   * justification is that inlength is like the count field of a
   * BufferedInputStream, while the count parameter is like the
   * length parameter of a read request.)  The count parameter is
   * also defined to be <= outbuffer.length - outpos (per the specification
   * of the length parameter for a read request).
   */
  public abstract int read (char[] outbuffer, int outpos, int count);
}