libjava/java/io/OutputStreamWriter.java

   1 /* OutputStreamWriter.java -- Writer that converts chars to bytes
   2    Copyright (C) 1998, 1999, 2000, 2001, 2003, 2005, 2006  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.io;
  40
  41 import gnu.gcj.convert.UnicodeToBytes;
  42 import gnu.gcj.convert.CharsetToBytesAdaptor;
  43 import java.nio.charset.Charset;
  44 import java.nio.charset.CharsetEncoder;
  45
  46 /**
  47  * This class writes characters to an output stream that is byte oriented
  48  * It converts the chars that are written to bytes using an encoding layer,
  49  * which is specific to a particular encoding standard.  The desired
  50  * encoding can either be specified by name, or if no encoding is specified,
  51  * the system default encoding will be used.  The system default encoding
  52  * name is determined from the system property <code>file.encoding</code>.
  53  * The only encodings that are guaranteed to be available are "8859_1"
  54  * (the Latin-1 character set) and "UTF8".  Unfortunately, Java does not
  55  * provide a mechanism for listing the encodings that are supported in
  56  * a given implementation.
  57  * <p>
  58  * Here is a list of standard encoding names that may be available:
  59  * <p>
  60  * <ul>
  61  * <li>8859_1 (ISO-8859-1/Latin-1)
  62  * <li>8859_2 (ISO-8859-2/Latin-2)
  63  * <li>8859_3 (ISO-8859-3/Latin-3)
  64  * <li>8859_4 (ISO-8859-4/Latin-4)
  65  * <li>8859_5 (ISO-8859-5/Latin-5)
  66  * <li>8859_6 (ISO-8859-6/Latin-6)
  67  * <li>8859_7 (ISO-8859-7/Latin-7)
  68  * <li>8859_8 (ISO-8859-8/Latin-8)
  69  * <li>8859_9 (ISO-8859-9/Latin-9)
  70  * <li>ASCII (7-bit ASCII)
  71  * <li>UTF8 (UCS Transformation Format-8)
  72  * <li>More Later
  73  * </ul>
  74  *
  75  * @author Aaron M. Renn (arenn@urbanophile.com)
  76  * @author Per Bothner (bothner@cygnus.com)
  77  * @date April 17, 1998.
  78  */
  79 public class OutputStreamWriter extends Writer
  80 {
  81   BufferedOutputStream out;
  82
  83   /**
  84    * This is the byte-character encoder class that does the writing and
  85    * translation of characters to bytes before writing to the underlying
  86    * class.
  87    */
  88   UnicodeToBytes converter;
  89
  90   /* Temporary buffer. */
  91   private char[] work;
  92   private int wcount;
  93
  94   private OutputStreamWriter(OutputStream out, UnicodeToBytes encoder)
  95   {
  96     this.out = out instanceof BufferedOutputStream
  97                ? (BufferedOutputStream) out
  98                : new BufferedOutputStream(out, 250);
  99     /* Don't need to call super(out) here as long as the lock gets set. */
 100     this.lock = out;
 101     this.converter = encoder;
 102   }
 103
 104   /**
 105    * This method initializes a new instance of <code>OutputStreamWriter</code>
 106    * to write to the specified stream using a caller supplied character
 107    * encoding scheme.  Note that due to a deficiency in the Java language
 108    * design, there is no way to determine which encodings are supported.
 109    *
 110    * @param out The <code>OutputStream</code> to write to
 111    * @param encoding_scheme The name of the encoding scheme to use for
 112    * character to byte translation
 113    *
 114    * @exception UnsupportedEncodingException If the named encoding is
 115    * not available.
 116    */
 117   public OutputStreamWriter (OutputStream out, String encoding_scheme)
 118     throws UnsupportedEncodingException
 119   {
 120     this(out, UnicodeToBytes.getEncoder(encoding_scheme));
 121   }
 122
 123   /**
 124    * This method initializes a new instance of <code>OutputStreamWriter</code>
 125    * to write to the specified stream using the default encoding.
 126    *
 127    * @param out The <code>OutputStream</code> to write to
 128    */
 129   public OutputStreamWriter (OutputStream out)
 130   {
 131     this(out, UnicodeToBytes.getDefaultEncoder());
 132   }
 133
 134   /**
 135    * This method initializes a new instance of <code>OutputStreamWriter</code>
 136    * to write to the specified stream using a given <code>Charset</code>.
 137    *
 138    * @param out The <code>OutputStream</code> to write to
 139    * @param cs The <code>Charset</code> of the encoding to use
 140    */
 141   public OutputStreamWriter(OutputStream out, Charset cs)
 142   {
 143     this(out, new CharsetToBytesAdaptor(cs));
 144   }
 145
 146   /**
 147    * This method initializes a new instance of <code>OutputStreamWriter</code>
 148    * to write to the specified stream using a given
 149    * <code>CharsetEncoder</code>.
 150    *
 151    * @param out The <code>OutputStream</code> to write to
 152    * @param enc The <code>CharsetEncoder</code> to encode the output with
 153    */
 154   public OutputStreamWriter(OutputStream out, CharsetEncoder enc)
 155   {
 156     this(out, new CharsetToBytesAdaptor(enc));
 157   }
 158
 159   /**
 160    * This method closes this stream, and the underlying
 161    * <code>OutputStream</code>
 162    *
 163    * @exception IOException If an error occurs
 164    */
 165   public void close () throws IOException
 166   {
 167     synchronized (lock)
 168       {
 169         if (out != null)
 170           {
 171             converter.setFinished();
 172             flush();
 173             out.close();
 174             out = null;
 175           }
 176         work = null;
 177       }
 178   }
 179
 180   /**
 181    * This method returns the name of the character encoding scheme currently
 182    * in use by this stream.  If the stream has been closed, then this method
 183    * may return <code>null</code>.
 184    *
 185    * @return The encoding scheme name
 186    */
 187   public String getEncoding ()
 188   {
 189     return out != null ? converter.getName() : null;
 190   }
 191
 192   /**
 193    * This method flushes any buffered bytes to the underlying output sink.
 194    *
 195    * @exception IOException If an error occurs
 196    */
 197   public void flush () throws IOException
 198   {
 199     synchronized (lock)
 200       {
 201         if (out == null)
 202           throw new IOException("Stream closed");
 203
 204         // Always write -- if we are close()ing then we want to make
 205         // sure the converter is flushed.
 206         if (work == null)
 207           work = new char[100];
 208         writeChars(work, 0, wcount);
 209         wcount = 0;
 210
 211         out.flush();
 212       }
 213   }
 214
 215   /**
 216    * This method writes <code>count</code> characters from the specified
 217    * array to the output stream starting at position <code>offset</code>
 218    * into the array.
 219    *
 220    * @param buf The array of character to write from
 221    * @param offset The offset into the array to start writing chars from
 222    * @param count The number of chars to write.
 223    *
 224    * @exception IOException If an error occurs
 225    */
 226   public void write (char[] buf, int offset, int count) throws IOException
 227   {
 228     synchronized (lock)
 229       {
 230         if (out == null)
 231           throw new IOException("Stream closed");
 232
 233         if (wcount > 0)
 234           {
 235             writeChars(work, 0, wcount);
 236             wcount = 0;
 237           }
 238         writeChars(buf, offset, count);
 239       }
 240   }
 241
 242   /*
 243    * Writes characters through to the inferior BufferedOutputStream.
 244    * Ignores wcount and the work buffer.
 245    */
 246   private void writeChars(char[] buf, int offset, int count)
 247     throws IOException
 248   {
 249     do
 250       {
 251         // We must flush if out.count == out.buf.length.
 252         // It is probably a good idea to flush if out.buf is almost full.
 253         // This test is an approximation for "almost full".
 254         if (out.count + count >= out.buf.length)
 255           {
 256             out.flush();
 257             if (out.count != 0)
 258               throw new IOException("unable to flush output byte buffer");
 259           }
 260         converter.setOutput(out.buf, out.count);
 261         int converted = converter.write(buf, offset, count);
 262         // Must set this before we flush the output stream, because
 263         // flushing will reset 'out.count'.
 264         out.count = converter.count;
 265         // Flush if we cannot make progress.
 266         if (converted == 0 && out.count == converter.count)
 267           {
 268             out.flush();
 269             if (out.count != 0)
 270               throw new IOException("unable to flush output byte buffer");
 271           }
 272         offset += converted;
 273         count -= converted;
 274       }
 275     while (count > 0 || converter.havePendingBytes());
 276   }
 277
 278   /**
 279    * This method writes <code>count</code> bytes from the specified
 280    * <code>String</code> starting at position <code>offset</code> into the
 281    * <code>String</code>.
 282    *
 283    * @param str The <code>String</code> to write chars from
 284    * @param offset The position in the <code>String</code> to start
 285    * writing chars from
 286    * @param count The number of chars to write
 287    *
 288    * @exception IOException If an error occurs
 289    */
 290   public void write (String str, int offset, int count) throws IOException
 291   {
 292     synchronized (lock)
 293       {
 294         if (out == null)
 295           throw new IOException("Stream closed");
 296
 297         if (work == null)
 298           work = new char[100];
 299         int wlength = work.length;
 300         while (count > 0)
 301           {
 302             int size = count;
 303             if (wcount + size > wlength)
 304               {
 305                 if (2*wcount > wlength)
 306                   {
 307                     writeChars(work, 0, wcount);
 308                     wcount = 0;
 309                   }
 310                 if (wcount + size > wlength)
 311                   size = wlength - wcount;
 312               }
 313             str.getChars(offset, offset+size, work, wcount);
 314             offset += size;
 315             count -= size;
 316             wcount += size;
 317           }
 318       }
 319   }
 320
 321   /**
 322    * This method writes a single character to the output stream.
 323    *
 324    * @param ch The char to write, passed as an int.
 325    *
 326    * @exception IOException If an error occurs
 327    */
 328   public void write (int ch) throws IOException
 329   {
 330     synchronized (lock)
 331       {
 332         if (out == null)
 333           throw new IOException("Stream closed");
 334
 335         if (work == null)
 336           work = new char[100];
 337         if (wcount >= work.length)
 338           {
 339             writeChars(work, 0, wcount);
 340             wcount = 0;
 341           }
 342         work[wcount++] = (char) ch;
 343       }
 344   }
 345
 346 } // class OutputStreamWriter
 347