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., 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             flush();
 172             out.close();
 173             out = null;
 174           }
 175         work = null;
 176       }
 177   }
 178
 179   /**
 180    * This method returns the name of the character encoding scheme currently
 181    * in use by this stream.  If the stream has been closed, then this method
 182    * may return <code>null</code>.
 183    *
 184    * @return The encoding scheme name
 185    */
 186   public String getEncoding ()
 187   {
 188     return out != null ? converter.getName() : null;
 189   }
 190
 191   /**
 192    * This method flushes any buffered bytes to the underlying output sink.
 193    *
 194    * @exception IOException If an error occurs
 195    */
 196   public void flush () throws IOException
 197   {
 198     synchronized (lock)
 199       {
 200         if (out == null)
 201           throw new IOException("Stream closed");
 202
 203         if (wcount > 0)
 204           {
 205             writeChars(work, 0, wcount);
 206             wcount = 0;
 207           }
 208         out.flush();
 209       }
 210   }
 211
 212   /**
 213    * This method writes <code>count</code> characters from the specified
 214    * array to the output stream starting at position <code>offset</code>
 215    * into the array.
 216    *
 217    * @param buf The array of character to write from
 218    * @param offset The offset into the array to start writing chars from
 219    * @param count The number of chars to write.
 220    *
 221    * @exception IOException If an error occurs
 222    */
 223   public void write (char[] buf, int offset, int count) throws IOException
 224   {
 225     synchronized (lock)
 226       {
 227         if (out == null)
 228           throw new IOException("Stream closed");
 229
 230         if (wcount > 0)
 231           {
 232             writeChars(work, 0, wcount);
 233             wcount = 0;
 234           }
 235         writeChars(buf, offset, count);
 236       }
 237   }
 238
 239   /*
 240    * Writes characters through to the inferior BufferedOutputStream.
 241    * Ignores wcount and the work buffer.
 242    */
 243   private void writeChars(char[] buf, int offset, int count)
 244     throws IOException
 245   {
 246     while (count > 0 || converter.havePendingBytes())
 247       {
 248         // We must flush if out.count == out.buf.length.
 249         // It is probably a good idea to flush if out.buf is almost full.
 250         // This test is an approximation for "almost full".
 251         if (out.count + count >= out.buf.length)
 252           {
 253             out.flush();
 254             if (out.count != 0)
 255               throw new IOException("unable to flush output byte buffer");
 256           }
 257         converter.setOutput(out.buf, out.count);
 258         int converted = converter.write(buf, offset, count);
 259         // Flush if we cannot make progress.
 260         if (converted == 0 && out.count == converter.count)
 261           {
 262             out.flush();
 263             if (out.count != 0)
 264               throw new IOException("unable to flush output byte buffer");
 265           }
 266         offset += converted;
 267         count -= converted;
 268         out.count = converter.count;
 269       }
 270   }
 271
 272   /**
 273    * This method writes <code>count</code> bytes from the specified
 274    * <code>String</code> starting at position <code>offset</code> into the
 275    * <code>String</code>.
 276    *
 277    * @param str The <code>String</code> to write chars from
 278    * @param offset The position in the <code>String</code> to start
 279    * writing chars from
 280    * @param count The number of chars to write
 281    *
 282    * @exception IOException If an error occurs
 283    */
 284   public void write (String str, int offset, int count) throws IOException
 285   {
 286     synchronized (lock)
 287       {
 288         if (out == null)
 289           throw new IOException("Stream closed");
 290
 291         if (work == null)
 292           work = new char[100];
 293         int wlength = work.length;
 294         while (count > 0)
 295           {
 296             int size = count;
 297             if (wcount + size > wlength)
 298               {
 299                 if (2*wcount > wlength)
 300                   {
 301                     writeChars(work, 0, wcount);
 302                     wcount = 0;
 303                   }
 304                 if (wcount + size > wlength)
 305                   size = wlength - wcount;
 306               }
 307             str.getChars(offset, offset+size, work, wcount);
 308             offset += size;
 309             count -= size;
 310             wcount += size;
 311           }
 312       }
 313   }
 314
 315   /**
 316    * This method writes a single character to the output stream.
 317    *
 318    * @param ch The char to write, passed as an int.
 319    *
 320    * @exception IOException If an error occurs
 321    */
 322   public void write (int ch) throws IOException
 323   {
 324     synchronized (lock)
 325       {
 326         if (out == null)
 327           throw new IOException("Stream closed");
 328
 329         if (work == null)
 330           work = new char[100];
 331         if (wcount >= work.length)
 332           {
 333             writeChars(work, 0, wcount);
 334             wcount = 0;
 335           }
 336         work[wcount++] = (char) ch;
 337       }
 338   }
 339
 340 } // class OutputStreamWriter
 341