001 /* OutputStreamWriter.java -- Writer that converts chars to bytes
002 Copyright (C) 1998, 1999, 2000, 2001, 2003, 2005, 2006 Free Software Foundation, Inc.
003
004 This file is part of GNU Classpath.
005
006 GNU Classpath is free software; you can redistribute it and/or modify
007 it under the terms of the GNU General Public License as published by
008 the Free Software Foundation; either version 2, or (at your option)
009 any later version.
010
011 GNU Classpath is distributed in the hope that it will be useful, but
012 WITHOUT ANY WARRANTY; without even the implied warranty of
013 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
014 General Public License for more details.
015
016 You should have received a copy of the GNU General Public License
017 along with GNU Classpath; see the file COPYING. If not, write to the
018 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019 02110-1301 USA.
020
021 Linking this library statically or dynamically with other modules is
022 making a combined work based on this library. Thus, the terms and
023 conditions of the GNU General Public License cover the whole
024 combination.
025
026 As a special exception, the copyright holders of this library give you
027 permission to link this library with independent modules to produce an
028 executable, regardless of the license terms of these independent
029 modules, and to copy and distribute the resulting executable under
030 terms of your choice, provided that you also meet, for each linked
031 independent module, the terms and conditions of the license of that
032 module. An independent module is a module which is not derived from
033 or based on this library. If you modify this library, you may extend
034 this exception to your version of the library, but you are not
035 obligated to do so. If you do not wish to do so, delete this
036 exception statement from your version. */
037
038
039 package java.io;
040
041 import gnu.gcj.convert.UnicodeToBytes;
042 import gnu.gcj.convert.CharsetToBytesAdaptor;
043 import java.nio.charset.Charset;
044 import java.nio.charset.CharsetEncoder;
045
046 /**
047 * This class writes characters to an output stream that is byte oriented
048 * It converts the chars that are written to bytes using an encoding layer,
049 * which is specific to a particular encoding standard. The desired
050 * encoding can either be specified by name, or if no encoding is specified,
051 * the system default encoding will be used. The system default encoding
052 * name is determined from the system property <code>file.encoding</code>.
053 * The only encodings that are guaranteed to be available are "8859_1"
054 * (the Latin-1 character set) and "UTF8". Unfortunately, Java does not
055 * provide a mechanism for listing the encodings that are supported in
056 * a given implementation.
057 * <p>
058 * Here is a list of standard encoding names that may be available:
059 * <p>
060 * <ul>
061 * <li>8859_1 (ISO-8859-1/Latin-1)
062 * <li>8859_2 (ISO-8859-2/Latin-2)
063 * <li>8859_3 (ISO-8859-3/Latin-3)
064 * <li>8859_4 (ISO-8859-4/Latin-4)
065 * <li>8859_5 (ISO-8859-5/Latin-5)
066 * <li>8859_6 (ISO-8859-6/Latin-6)
067 * <li>8859_7 (ISO-8859-7/Latin-7)
068 * <li>8859_8 (ISO-8859-8/Latin-8)
069 * <li>8859_9 (ISO-8859-9/Latin-9)
070 * <li>ASCII (7-bit ASCII)
071 * <li>UTF8 (UCS Transformation Format-8)
072 * <li>More Later
073 * </ul>
074 *
075 * @author Aaron M. Renn (arenn@urbanophile.com)
076 * @author Per Bothner (bothner@cygnus.com)
077 * @date April 17, 1998.
078 */
079 public class OutputStreamWriter extends Writer
080 {
081 BufferedOutputStream out;
082
083 /**
084 * This is the byte-character encoder class that does the writing and
085 * translation of characters to bytes before writing to the underlying
086 * class.
087 */
088 UnicodeToBytes converter;
089
090 /* Temporary buffer. */
091 private char[] work;
092 private int wcount;
093
094 private OutputStreamWriter(OutputStream out, UnicodeToBytes encoder)
095 {
096 this.out = out instanceof BufferedOutputStream
097 ? (BufferedOutputStream) out
098 : new BufferedOutputStream(out, 250);
099 /* 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