001    /* Writer.java -- Base class for character output streams
002       Copyright (C) 1998, 1999, 2001, 2003, 2004, 2005  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    /* Written using "Java Class Libraries", 2nd edition, plus online
042     * API docs for JDK 1.2 beta from http://www.javasoft.com.
043     * Status:  Believed complete and correct.
044     */
045    
046    /**
047     * This abstract class forms the base of the hierarchy of classes that
048     * write output as a stream of chars.  It provides a common set of methods
049     * for writing chars to stream.  Subclasses implement and/or extend these
050     * methods to write chars in a particular manner or to a particular
051     * destination such as a file on disk or network connection.
052     *
053     * @author Aaron M. Renn (arenn@urbanophile.com)
054     * @author Per Bothner (bothner@cygnus.com)
055     */
056    public abstract class Writer implements Appendable, Closeable, Flushable
057    {
058      /**
059       * This is the object used to synchronize criticial code sections for
060       * thread safety.  Subclasses should use this field instead of using
061       * synchronized methods or explicity synchronizations on <code>this</code>
062       */
063      protected Object lock;
064    
065      /**
066       * This is the default no-argument constructor for this class.  This method
067       * will set up the class to synchronize criticial sections on itself.
068       */
069      protected Writer()
070      {
071        lock = this;
072      }
073    
074      /**
075       * This method initializes a <code>Writer</code> that will synchronize
076       * on the specified <code>Object</code>.
077       *
078       * @param lock The <code>Object</code> to use for synchronizing critical
079       *             sections. Must not be null.
080       */
081      protected Writer(Object lock)
082      {
083        if (lock == null)
084          throw new NullPointerException();
085    
086        this.lock = lock;
087      }
088    
089      /**
090       * This method forces any data that may have been buffered to be written
091       * to the underlying output device.  Please note that the host environment
092       * might perform its own buffering unbeknowst to Java.  In that case, a
093       * write made (for example, to a disk drive) might be cached in OS
094       * buffers instead of actually being written to disk.
095       *
096       * @exception IOException If an error occurs
097       */
098      public abstract void flush() throws IOException;
099    
100      /**
101       * This method closes the stream.  Any internal or native resources
102       * associated
103       * with this stream are freed.  Any subsequent attempt to access the stream
104       * might throw an exception.
105       * <p>
106       * This method in this class does nothing.
107       *
108       * @exception IOException If an error occurs
109       */
110      public abstract void close() throws IOException;
111    
112      /**
113       * This method writes a single char to the output stream.
114       *
115       * @param b The char to be written to the output stream, passed as an int
116       *
117       * @exception IOException If an error occurs
118       */
119      public void write(int b) throws IOException
120      {
121        char[] buf = new char[1];
122    
123        buf[0] = (char)b;
124        write(buf, 0, buf.length);
125      }
126    
127      /**
128       * This method all the writes char from the passed array to the output
129       * stream. This method is equivalent to
130       * <code>write(buf, 0, buf.length)</code> which
131       * is exactly how it is implemented in this class.
132       *
133       * @param buf The array of char to write
134       *
135       * @exception IOException If an error occurs
136       */
137      public void write(char[] buf) throws IOException
138      {
139        write(buf, 0, buf.length);
140      }
141    
142      /**
143       * This method writes <code>len</code> char from the specified array
144       * <code>buf</code> starting at index <code>offset</code> into the array.
145       * <p>
146       * Subclasses must provide an implementation of this abstract method.
147       *
148       * @param buf The array of char to write from
149       * @param offset The index into the array to start writing from
150       * @param len The number of char to write
151       *
152       * @exception IOException If an error occurs
153       */
154      public abstract void write(char[] buf, int offset, int len)
155        throws IOException;
156    
157      /**
158       * This method writes all the characters in a <code>String</code> to the
159       * output.
160       *
161       * @param str The <code>String</code> whose chars are to be written.
162       *
163       * @exception IOException If an error occurs
164       */
165      public void write(String str) throws IOException
166      {
167        write(str, 0, str.length());
168      }
169    
170      /**
171       * This method writes <code>len</code> chars from the <code>String</code>
172       * starting at position <code>offset</code>.
173       *
174       * @param str The <code>String</code> that is to be written
175       * @param offset The character offset into the <code>String</code> to start
176       *               writing from
177       * @param len The number of chars to write
178       *
179       * @exception IOException If an error occurs
180       */
181      public void write(String str, int offset, int len) throws IOException
182      {
183        // FIXME - for libgcj re-write using native code to not require
184        // copied buffer.
185        char[] buf = new char[len];
186    
187        str.getChars(offset, offset + len, buf, 0);
188        write(buf, 0, len);
189      }
190    
191      /** @since 1.5 */
192      public Writer append(char c) throws IOException
193      {
194        write(c);
195        return this;
196      }
197    
198      /** @since 1.5 */
199      public Writer append(CharSequence cs) throws IOException
200      {
201        write(cs == null ? "null" : cs.toString());
202        return this;
203      }
204    
205      /** @since 1.5 */
206      public Writer append(CharSequence cs, int start, int end) throws IOException
207      {
208        write(cs == null ? "null" : cs.subSequence(start, end).toString());
209        return this;
210      }
211    }