OutputStreamWriter.java

/* OutputStreamWriter.java -- Writer that converts chars to bytes
   Copyright (C) 1998, 1999, 2000, 2001, 2003, 2005, 2006  Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
 
GNU Classpath is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
conditions of the GNU General Public License cover the whole
combination.

As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
modules, and to copy and distribute the resulting executable under
terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
module.  An independent module is a module which is not derived from
or based on this library.  If you modify this library, you may extend
this exception to your version of the library, but you are not
obligated to do so.  If you do not wish to do so, delete this
exception statement from your version. */


package java.io;

import gnu.gcj.convert.UnicodeToBytes;
import gnu.gcj.convert.CharsetToBytesAdaptor;
import java.nio.charset.Charset;
import java.nio.charset.CharsetEncoder;

/**
 * This class writes characters to an output stream that is byte oriented
 * It converts the chars that are written to bytes using an encoding layer,
 * which is specific to a particular encoding standard.  The desired
 * encoding can either be specified by name, or if no encoding is specified,
 * the system default encoding will be used.  The system default encoding
 * name is determined from the system property <code>file.encoding</code>.
 * The only encodings that are guaranteed to be available are "8859_1"
 * (the Latin-1 character set) and "UTF8".  Unfortunately, Java does not
 * provide a mechanism for listing the encodings that are supported in
 * a given implementation.
 * <p>
 * Here is a list of standard encoding names that may be available:
 * <p>
 * <ul>
 * <li>8859_1 (ISO-8859-1/Latin-1)
 * <li>8859_2 (ISO-8859-2/Latin-2)
 * <li>8859_3 (ISO-8859-3/Latin-3)
 * <li>8859_4 (ISO-8859-4/Latin-4)
 * <li>8859_5 (ISO-8859-5/Latin-5)
 * <li>8859_6 (ISO-8859-6/Latin-6)
 * <li>8859_7 (ISO-8859-7/Latin-7)
 * <li>8859_8 (ISO-8859-8/Latin-8)
 * <li>8859_9 (ISO-8859-9/Latin-9)
 * <li>ASCII (7-bit ASCII)
 * <li>UTF8 (UCS Transformation Format-8)
 * <li>More Later
 * </ul>
 *
 * @author Aaron M. Renn (arenn@urbanophile.com)
 * @author Per Bothner (bothner@cygnus.com)
 * @date April 17, 1998.  
 */
public class OutputStreamWriter extends Writer
{
  BufferedOutputStream out;

  /**
   * This is the byte-character encoder class that does the writing and
   * translation of characters to bytes before writing to the underlying
   * class.
   */
  UnicodeToBytes converter;

  /* Temporary buffer. */
  private char[] work;
  private int wcount;

  private OutputStreamWriter(OutputStream out, UnicodeToBytes encoder)
  {
    this.out = out instanceof BufferedOutputStream 
	       ? (BufferedOutputStream) out
	       : new BufferedOutputStream(out, 250);
    /* Don't need to call super(out) here as long as the lock gets set. */
    this.lock = out;
    this.converter = encoder;
  }

  /**
   * This method initializes a new instance of <code>OutputStreamWriter</code>
   * to write to the specified stream using a caller supplied character
   * encoding scheme.  Note that due to a deficiency in the Java language
   * design, there is no way to determine which encodings are supported.
   *
   * @param out The <code>OutputStream</code> to write to
   * @param encoding_scheme The name of the encoding scheme to use for 
   * character to byte translation
   *
   * @exception UnsupportedEncodingException If the named encoding is 
   * not available.
   */
  public OutputStreamWriter (OutputStream out, String encoding_scheme) 
    throws UnsupportedEncodingException
  {
    this(out, UnicodeToBytes.getEncoder(encoding_scheme));
  }

  /**
   * This method initializes a new instance of <code>OutputStreamWriter</code>
   * to write to the specified stream using the default encoding.
   *
   * @param out The <code>OutputStream</code> to write to
   */
  public OutputStreamWriter (OutputStream out)
  {
    this(out, UnicodeToBytes.getDefaultEncoder());
  }

  /**
   * This method initializes a new instance of <code>OutputStreamWriter</code>
   * to write to the specified stream using a given <code>Charset</code>.
   *
   * @param out The <code>OutputStream</code> to write to
   * @param cs The <code>Charset</code> of the encoding to use
   */
  public OutputStreamWriter(OutputStream out, Charset cs)
  {
    this(out, new CharsetToBytesAdaptor(cs));
  }

  /**
   * This method initializes a new instance of <code>OutputStreamWriter</code>
   * to write to the specified stream using a given
   * <code>CharsetEncoder</code>.
   *
   * @param out The <code>OutputStream</code> to write to
   * @param enc The <code>CharsetEncoder</code> to encode the output with
   */
  public OutputStreamWriter(OutputStream out, CharsetEncoder enc)
  {
    this(out, new CharsetToBytesAdaptor(enc));
  }

  /**
   * This method closes this stream, and the underlying 
   * <code>OutputStream</code>
   *
   * @exception IOException If an error occurs
   */
  public void close () throws IOException
  {
    synchronized (lock)
      {
	if (out != null)
	  {
	    converter.setFinished();
	    flush();
	    out.close();
	    out = null;
	  }
	work = null;
      }
  }

  /**
   * This method returns the name of the character encoding scheme currently
   * in use by this stream.  If the stream has been closed, then this method
   * may return <code>null</code>.
   *
   * @return The encoding scheme name
   */
  public String getEncoding ()
  {
    return out != null ? converter.getName() : null;
  }

  /**
   * This method flushes any buffered bytes to the underlying output sink.
   *
   * @exception IOException If an error occurs
   */
  public void flush () throws IOException
  {
    synchronized (lock)
      {
	if (out == null)
	  throw new IOException("Stream closed");

	// Always write -- if we are close()ing then we want to make
	// sure the converter is flushed.
	if (work == null)
	  work = new char[100];
	writeChars(work, 0, wcount);
	wcount = 0;

	out.flush();
      }
  }

  /**
   * This method writes <code>count</code> characters from the specified
   * array to the output stream starting at position <code>offset</code>
   * into the array.
   *
   * @param buf The array of character to write from
   * @param offset The offset into the array to start writing chars from
   * @param count The number of chars to write.
   *
   * @exception IOException If an error occurs
   */
  public void write (char[] buf, int offset, int count) throws IOException
  {
    synchronized (lock)
      {
	if (out == null)
	  throw new IOException("Stream closed");

	if (wcount > 0)
	  {
	    writeChars(work, 0, wcount);
	    wcount = 0;
	  }
	writeChars(buf, offset, count);
      }
  }

  /*
   * Writes characters through to the inferior BufferedOutputStream.
   * Ignores wcount and the work buffer.
   */
  private void writeChars(char[] buf, int offset, int count)
    throws IOException
  {
    do
      {
	// We must flush if out.count == out.buf.length.
	// It is probably a good idea to flush if out.buf is almost full.
	// This test is an approximation for "almost full".
	if (out.count + count >= out.buf.length)
	  {
	    out.flush();
	    if (out.count != 0)
	      throw new IOException("unable to flush output byte buffer");
	  }
	converter.setOutput(out.buf, out.count);
	int converted = converter.write(buf, offset, count);
	// Must set this before we flush the output stream, because
	// flushing will reset 'out.count'.
	out.count = converter.count;
	// Flush if we cannot make progress.
	if (converted == 0 && out.count == converter.count)
	  {
	    out.flush();
	    if (out.count != 0)
	      throw new IOException("unable to flush output byte buffer");
	  }
	offset += converted;
	count -= converted;
      }
    while (count > 0 || converter.havePendingBytes());
  }

  /**
   * This method writes <code>count</code> bytes from the specified 
   * <code>String</code> starting at position <code>offset</code> into the
   * <code>String</code>.
   *
   * @param str The <code>String</code> to write chars from
   * @param offset The position in the <code>String</code> to start 
   * writing chars from
   * @param count The number of chars to write
   *
   * @exception IOException If an error occurs
   */
  public void write (String str, int offset, int count) throws IOException
  {
    synchronized (lock)
      {
	if (out == null)
	  throw new IOException("Stream closed");

	if (work == null)
	  work = new char[100];
	int wlength = work.length;
	while (count > 0)
	  {
	    int size = count;
	    if (wcount + size > wlength)
	      {
		if (2*wcount > wlength)
		  {
		    writeChars(work, 0, wcount);
		    wcount = 0;
		  }
		if (wcount + size > wlength)
		  size = wlength - wcount;
	      }
	    str.getChars(offset, offset+size, work, wcount);
	    offset += size;
	    count -= size;
	    wcount += size;
	  }
      }
  }

  /**
   * This method writes a single character to the output stream.
   *
   * @param ch The char to write, passed as an int.
   *
   * @exception IOException If an error occurs
   */
  public void write (int ch) throws IOException
  {
    synchronized (lock)
      {
	if (out == null)
	  throw new IOException("Stream closed");

	if (work == null)
	  work = new char[100];
	if (wcount >= work.length)
	  {
	    writeChars(work, 0, wcount);
	    wcount = 0;
	  }
	work[wcount++] = (char) ch;
      }
  }

} // class OutputStreamWriter