libjava/java/io/OutputStreamWriter.java

   1 /* OutputStreamWriter.java -- Writer that converts chars to bytes
   2    Copyright (C) 1998, 1999, 2000, 2001, 2003, 2005  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., 59 Temple Place, Suite 330, Boston, MA
  19 02111-1307 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
  43 /**
  44  * This class writes characters to an output stream that is byte oriented
  45  * It converts the chars that are written to bytes using an encoding layer,
  46  * which is specific to a particular encoding standard.  The desired
  47  * encoding can either be specified by name, or if no encoding is specified,
  48  * the system default encoding will be used.  The system default encoding
  49  * name is determined from the system property <code>file.encoding</code>.
  50  * The only encodings that are guaranteed to be available are "8859_1"
  51  * (the Latin-1 character set) and "UTF8".  Unfortunately, Java does not
  52  * provide a mechanism for listing the encodings that are supported in
  53  * a given implementation.
  54  * <p>
  55  * Here is a list of standard encoding names that may be available:
  56  * <p>
  57  * <ul>
  58  * <li>8859_1 (ISO-8859-1/Latin-1)
  59  * <li>8859_2 (ISO-8859-2/Latin-2)
  60  * <li>8859_3 (ISO-8859-3/Latin-3)
  61  * <li>8859_4 (ISO-8859-4/Latin-4)
  62  * <li>8859_5 (ISO-8859-5/Latin-5)
  63  * <li>8859_6 (ISO-8859-6/Latin-6)
  64  * <li>8859_7 (ISO-8859-7/Latin-7)
  65  * <li>8859_8 (ISO-8859-8/Latin-8)
  66  * <li>8859_9 (ISO-8859-9/Latin-9)
  67  * <li>ASCII (7-bit ASCII)
  68  * <li>UTF8 (UCS Transformation Format-8)
  69  * <li>More Later
  70  * </ul>
  71  *
  72  * @author Aaron M. Renn (arenn@urbanophile.com)
  73  * @author Per Bothner (bothner@cygnus.com)
  74  * @date April 17, 1998.
  75  */
  76 public class OutputStreamWriter extends Writer
  77 {
  78   BufferedOutputStream out;
  79
  80   /**
  81    * This is the byte-character encoder class that does the writing and
  82    * translation of characters to bytes before writing to the underlying
  83    * class.
  84    */
  85   UnicodeToBytes converter;
  86
  87   /* Temporary buffer. */
  88   private char[] work;
  89   private int wcount;
  90
  91   private OutputStreamWriter(OutputStream out, UnicodeToBytes encoder)
  92   {
  93     this.out = out instanceof BufferedOutputStream
  94                ? (BufferedOutputStream) out
  95                : new BufferedOutputStream(out, 250);
  96     /* Don't need to call super(out) here as long as the lock gets set. */
  97     this.lock = out;
  98     this.converter = encoder;
  99   }
 100
 101   /**
 102    * This method initializes a new instance of <code>OutputStreamWriter</code>
 103    * to write to the specified stream using a caller supplied character
 104    * encoding scheme.  Note that due to a deficiency in the Java language
 105    * design, there is no way to determine which encodings are supported.
 106    *
 107    * @param out The <code>OutputStream</code> to write to
 108    * @param encoding_scheme The name of the encoding scheme to use for
 109    * character to byte translation
 110    *
 111    * @exception UnsupportedEncodingException If the named encoding is
 112    * not available.
 113    */
 114   public OutputStreamWriter (OutputStream out, String encoding_scheme)
 115     throws UnsupportedEncodingException
 116   {
 117     this(out, UnicodeToBytes.getEncoder(encoding_scheme));
 118   }
 119
 120   /**
 121    * This method initializes a new instance of <code>OutputStreamWriter</code>
 122    * to write to the specified stream using the default encoding.
 123    *
 124    * @param out The <code>OutputStream</code> to write to
 125    */
 126   public OutputStreamWriter (OutputStream out)
 127   {
 128     this(out, UnicodeToBytes.getDefaultEncoder());
 129   }
 130
 131   /**
 132    * This method closes this stream, and the underlying
 133    * <code>OutputStream</code>
 134    *
 135    * @exception IOException If an error occurs
 136    */
 137   public void close () throws IOException
 138   {
 139     synchronized (lock)
 140       {
 141         if (out != null)
 142           {
 143             flush();
 144             out.close();
 145             out = null;
 146           }
 147         work = null;
 148       }
 149   }
 150
 151   /**
 152    * This method returns the name of the character encoding scheme currently
 153    * in use by this stream.  If the stream has been closed, then this method
 154    * may return <code>null</code>.
 155    *
 156    * @return The encoding scheme name
 157    */
 158   public String getEncoding ()
 159   {
 160     return out != null ? converter.getName() : null;
 161   }
 162
 163   /**
 164    * This method flushes any buffered bytes to the underlying output sink.
 165    *
 166    * @exception IOException If an error occurs
 167    */
 168   public void flush () throws IOException
 169   {
 170     synchronized (lock)
 171       {
 172         if (out == null)
 173           throw new IOException("Stream closed");
 174
 175         if (wcount > 0)
 176           {
 177             writeChars(work, 0, wcount);
 178             wcount = 0;
 179           }
 180         out.flush();
 181       }
 182   }
 183
 184   /**
 185    * This method writes <code>count</code> characters from the specified
 186    * array to the output stream starting at position <code>offset</code>
 187    * into the array.
 188    *
 189    * @param buf The array of character to write from
 190    * @param offset The offset into the array to start writing chars from
 191    * @param count The number of chars to write.
 192    *
 193    * @exception IOException If an error occurs
 194    */
 195   public void write (char[] buf, int offset, int count) throws IOException
 196   {
 197     synchronized (lock)
 198       {
 199         if (out == null)
 200           throw new IOException("Stream closed");
 201
 202         if (wcount > 0)
 203           {
 204             writeChars(work, 0, wcount);
 205             wcount = 0;
 206           }
 207         writeChars(buf, offset, count);
 208       }
 209   }
 210
 211   /*
 212    * Writes characters through to the inferior BufferedOutputStream.
 213    * Ignores wcount and the work buffer.
 214    */
 215   private void writeChars(char[] buf, int offset, int count)
 216     throws IOException
 217   {
 218     while (count > 0 || converter.havePendingBytes())
 219       {
 220         // We must flush if out.count == out.buf.length.
 221         // It is probably a good idea to flush if out.buf is almost full.
 222         // This test is an approximation for "almost full".
 223         if (out.count + count >= out.buf.length)
 224           {
 225             out.flush();
 226             if (out.count != 0)
 227               throw new IOException("unable to flush output byte buffer");
 228           }
 229         converter.setOutput(out.buf, out.count);
 230         int converted = converter.write(buf, offset, count);
 231         // Flush if we cannot make progress.
 232         if (converted == 0 && out.count == converter.count)
 233           {
 234             out.flush();
 235             if (out.count != 0)
 236               throw new IOException("unable to flush output byte buffer");
 237           }
 238         offset += converted;
 239         count -= converted;
 240         out.count = converter.count;
 241       }
 242   }
 243
 244   /**
 245    * This method writes <code>count</code> bytes from the specified
 246    * <code>String</code> starting at position <code>offset</code> into the
 247    * <code>String</code>.
 248    *
 249    * @param str The <code>String</code> to write chars from
 250    * @param offset The position in the <code>String</code> to start
 251    * writing chars from
 252    * @param count The number of chars to write
 253    *
 254    * @exception IOException If an error occurs
 255    */
 256   public void write (String str, int offset, int count) throws IOException
 257   {
 258     synchronized (lock)
 259       {
 260         if (out == null)
 261           throw new IOException("Stream closed");
 262
 263         if (work == null)
 264           work = new char[100];
 265         int wlength = work.length;
 266         while (count > 0)
 267           {
 268             int size = count;
 269             if (wcount + size > wlength)
 270               {
 271                 if (2*wcount > wlength)
 272                   {
 273                     writeChars(work, 0, wcount);
 274                     wcount = 0;
 275                   }
 276                 if (wcount + size > wlength)
 277                   size = wlength - wcount;
 278               }
 279             str.getChars(offset, offset+size, work, wcount);
 280             offset += size;
 281             count -= size;
 282             wcount += size;
 283           }
 284       }
 285   }
 286
 287   /**
 288    * This method writes a single character to the output stream.
 289    *
 290    * @param ch The char to write, passed as an int.
 291    *
 292    * @exception IOException If an error occurs
 293    */
 294   public void write (int ch) throws IOException
 295   {
 296     synchronized (lock)
 297       {
 298         if (out == null)
 299           throw new IOException("Stream closed");
 300
 301         if (work == null)
 302           work = new char[100];
 303         if (wcount >= work.length)
 304           {
 305             writeChars(work, 0, wcount);
 306             wcount = 0;
 307           }
 308         work[wcount++] = (char) ch;
 309       }
 310   }
 311
 312 } // class OutputStreamWriter
 313