1 /*
  2  * Copyright (c) 1996, 2021, Oracle and/or its affiliates. All rights reserved.
  3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  4  *
  5  * This code is free software; you can redistribute it and/or modify it
  6  * under the terms of the GNU General Public License version 2 only, as
  7  * published by the Free Software Foundation.  Oracle designates this
  8  * particular file as subject to the "Classpath" exception as provided
  9  * by Oracle in the LICENSE file that accompanied this code.
 10  *
 11  * This code is distributed in the hope that it will be useful, but WITHOUT
 12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 14  * version 2 for more details (a copy is included in the LICENSE file that
 15  * accompanied this code).
 16  *
 17  * You should have received a copy of the GNU General Public License version
 18  * 2 along with this work; if not, write to the Free Software Foundation,
 19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 20  *
 21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 22  * or visit www.oracle.com if you need additional information or have any
 23  * questions.
 24  */
 25 
 26 package java.io;
 27 
 28 import java.nio.CharBuffer;
 29 import java.nio.charset.Charset;
 30 import java.nio.charset.CharsetEncoder;
 31 import sun.nio.cs.StreamEncoder;
 32 
 33 
 34 /**
 35  * An OutputStreamWriter is a bridge from character streams to byte streams:
 36  * Characters written to it are encoded into bytes using a specified {@link
 37  * Charset charset}.  The charset that it uses
 38  * may be specified by name or may be given explicitly, or the
 39  * default charset may be accepted.
 40  *
 41  * <p> Each invocation of a write() method causes the encoding converter to be
 42  * invoked on the given character(s).  The resulting bytes are accumulated in a
 43  * buffer before being written to the underlying output stream.  Note that the
 44  * characters passed to the write() methods are not buffered.
 45  *
 46  * <p> For top efficiency, consider wrapping an OutputStreamWriter within a
 47  * BufferedWriter so as to avoid frequent converter invocations.  For example:
 48  *
 49  * <pre>
 50  * Writer out
 51  *   = new BufferedWriter(new OutputStreamWriter(anOutputStream));
 52  * </pre>
 53  *
 54  * <p> A <i>surrogate pair</i> is a character represented by a sequence of two
 55  * {@code char} values: A <i>high</i> surrogate in the range '&#92;uD800' to
 56  * '&#92;uDBFF' followed by a <i>low</i> surrogate in the range '&#92;uDC00' to
 57  * '&#92;uDFFF'.
 58  *
 59  * <p> A <i>malformed surrogate element</i> is a high surrogate that is not
 60  * followed by a low surrogate or a low surrogate that is not preceded by a
 61  * high surrogate.
 62  *
 63  * <p> This class always replaces malformed surrogate elements and unmappable
 64  * character sequences with the charset's default <i>substitution sequence</i>.
 65  * The {@linkplain CharsetEncoder} class should be used when more
 66  * control over the encoding process is required.
 67  *
 68  * @see BufferedWriter
 69  * @see OutputStream
 70  * @see Charset
 71  *
 72  * @author      Mark Reinhold
 73  * @since       1.1
 74  */
 75 
 76 public class OutputStreamWriter extends Writer {
 77 
 78     private final StreamEncoder se;
 79 
 80     /**
 81      * Creates an OutputStreamWriter that uses the named charset.
 82      *
 83      * @param  out
 84      *         An OutputStream
 85      *
 86      * @param  charsetName
 87      *         The name of a supported {@link Charset charset}
 88      *
 89      * @throws     UnsupportedEncodingException
 90      *             If the named encoding is not supported
 91      */
 92     public OutputStreamWriter(OutputStream out, String charsetName)
 93         throws UnsupportedEncodingException
 94     {
 95         super(out);
 96         if (charsetName == null)
 97             throw new NullPointerException("charsetName");
 98         se = StreamEncoder.forOutputStreamWriter(out, this, charsetName);
 99     }
100 
101     /**
102      * Creates an OutputStreamWriter that uses the default character encoding.
103      *
104      * @param  out  An OutputStream
105      * @see Charset#defaultCharset()
106      */
107     public OutputStreamWriter(OutputStream out) {
108         super(out);
109         se = StreamEncoder.forOutputStreamWriter(out, this,
110                 Charset.defaultCharset());
111     }
112 
113     /**
114      * Creates an OutputStreamWriter that uses the given charset.
115      *
116      * @param  out
117      *         An OutputStream
118      *
119      * @param  cs
120      *         A charset
121      *
122      * @since 1.4
123      */
124     public OutputStreamWriter(OutputStream out, Charset cs) {
125         super(out);
126         if (cs == null)
127             throw new NullPointerException("charset");
128         se = StreamEncoder.forOutputStreamWriter(out, this, cs);
129     }
130 
131     /**
132      * Creates an OutputStreamWriter that uses the given charset encoder.
133      *
134      * @param  out
135      *         An OutputStream
136      *
137      * @param  enc
138      *         A charset encoder
139      *
140      * @since 1.4
141      */
142     public OutputStreamWriter(OutputStream out, CharsetEncoder enc) {
143         super(out);
144         if (enc == null)
145             throw new NullPointerException("charset encoder");
146         se = StreamEncoder.forOutputStreamWriter(out, this, enc);
147     }
148 
149     /**
150      * Returns the name of the character encoding being used by this stream.
151      *
152      * <p> If the encoding has an historical name then that name is returned;
153      * otherwise the encoding's canonical name is returned.
154      *
155      * <p> If this instance was created with the {@link
156      * #OutputStreamWriter(OutputStream, String)} constructor then the returned
157      * name, being unique for the encoding, may differ from the name passed to
158      * the constructor.  This method may return {@code null} if the stream has
159      * been closed. </p>
160      *
161      * @return The historical name of this encoding, or possibly
162      *         {@code null} if the stream has been closed
163      *
164      * @see Charset
165      *
166      * @revised 1.4
167      */
168     public String getEncoding() {
169         return se.getEncoding();
170     }
171 
172     /**
173      * Flushes the output buffer to the underlying byte stream, without flushing
174      * the byte stream itself.  This method is non-private only so that it may
175      * be invoked by PrintStream.
176      */
177     void flushBuffer() throws IOException {
178         se.flushBuffer();
179     }
180 
181     /**
182      * Writes a single character.
183      *
184      * @throws     IOException  If an I/O error occurs
185      */
186     public void write(int c) throws IOException {
187         se.write(c);
188     }
189 
190     /**
191      * Writes a portion of an array of characters.
192      *
193      * @param  cbuf  Buffer of characters
194      * @param  off   Offset from which to start writing characters
195      * @param  len   Number of characters to write
196      *
197      * @throws  IndexOutOfBoundsException
198      *          If {@code off} is negative, or {@code len} is negative,
199      *          or {@code off + len} is negative or greater than the length
200      *          of the given array
201      *
202      * @throws  IOException  If an I/O error occurs
203      */
204     public void write(char[] cbuf, int off, int len) throws IOException {
205         se.write(cbuf, off, len);
206     }
207 
208     /**
209      * Writes a portion of a string.
210      *
211      * @param  str  A String
212      * @param  off  Offset from which to start writing characters
213      * @param  len  Number of characters to write
214      *
215      * @throws  IndexOutOfBoundsException
216      *          If {@code off} is negative, or {@code len} is negative,
217      *          or {@code off + len} is negative or greater than the length
218      *          of the given string
219      *
220      * @throws  IOException  If an I/O error occurs
221      */
222     public void write(String str, int off, int len) throws IOException {
223         se.write(str, off, len);
224     }
225 
226     @Override
227     public Writer append(CharSequence csq, int start, int end) throws IOException {
228         if (csq == null) csq = "null";
229         return append(csq.subSequence(start, end));
230     }
231 
232     @Override
233     public Writer append(CharSequence csq) throws IOException {
234         if (csq instanceof CharBuffer) {
235             se.write((CharBuffer) csq);
236         } else {
237             se.write(String.valueOf(csq));
238         }
239         return this;
240     }
241 
242     /**
243      * Flushes the stream.
244      *
245      * @throws     IOException  If an I/O error occurs
246      */
247     public void flush() throws IOException {
248         se.flush();
249     }
250 
251     public void close() throws IOException {
252         se.close();
253     }
254 }