1 /*
2 * Copyright 1996-2005 Sun Microsystems, Inc. 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. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any questions.
24 */
25
26 package java.io;
27
28 import java.nio.charset.Charset;
29 import java.nio.charset.CharsetDecoder;
30 import sun.nio.cs.StreamDecoder;
31
32
33 /**
34 * An InputStreamReader is a bridge from byte streams to character streams: It
35 * reads bytes and decodes them into characters using a specified {@link
36 * java.nio.charset.Charset <code>charset</code>}. The charset that it uses
37 * may be specified by name or may be given explicitly, or the platform's
38 * default charset may be accepted.
39 *
40 * <p> Each invocation of one of an InputStreamReader's read() methods may
41 * cause one or more bytes to be read from the underlying byte-input stream.
42 * To enable the efficient conversion of bytes to characters, more bytes may
43 * be read ahead from the underlying stream than are necessary to satisfy the
44 * current read operation.
45 *
46 * <p> For top efficiency, consider wrapping an InputStreamReader within a
47 * BufferedReader. For example:
48 *
49 * <pre>
50 * BufferedReader in
51 * = new BufferedReader(new InputStreamReader(System.in));
52 * </pre>
53 *
54 * @see BufferedReader
55 * @see InputStream
56 * @see java.nio.charset.Charset
57 *
58 * @author Mark Reinhold
59 * @since JDK1.1
60 */
61
62 public class InputStreamReader extends Reader {
63
64 private final StreamDecoder sd;
65
66 /**
67 * Creates an InputStreamReader that uses the default charset.
68 *
69 * @param in An InputStream
70 */
71 public InputStreamReader(InputStream in) {
72 super(in);
73 try {
74 sd = StreamDecoder.forInputStreamReader(in, this, (String)null); // ## check lock object
75 } catch (UnsupportedEncodingException e) {
76 // The default encoding should always be available
77 throw new Error(e);
78 }
79 }
80
81 /**
82 * Creates an InputStreamReader that uses the named charset.
83 *
84 * @param in
85 * An InputStream
86 *
87 * @param charsetName
88 * The name of a supported
89 * {@link java.nio.charset.Charset </code>charset<code>}
90 *
91 * @exception UnsupportedEncodingException
92 * If the named charset is not supported
93 */
94 public InputStreamReader(InputStream in, String charsetName)
95 throws UnsupportedEncodingException
96 {
97 super(in);
98 if (charsetName == null)
99 throw new NullPointerException("charsetName");
100 sd = StreamDecoder.forInputStreamReader(in, this, charsetName);
101 }
102
103 /**
104 * Creates an InputStreamReader that uses the given charset. </p>
105 *
106 * @param in An InputStream
107 * @param cs A charset
108 *
109 * @since 1.4
110 * @spec JSR-51
111 */
112 public InputStreamReader(InputStream in, Charset cs) {
113 super(in);
114 if (cs == null)
115 throw new NullPointerException("charset");
116 sd = StreamDecoder.forInputStreamReader(in, this, cs);
117 }
118
119 /**
120 * Creates an InputStreamReader that uses the given charset decoder. </p>
121 *
122 * @param in An InputStream
123 * @param dec A charset decoder
124 *
125 * @since 1.4
126 * @spec JSR-51
127 */
128 public InputStreamReader(InputStream in, CharsetDecoder dec) {
129 super(in);
130 if (dec == null)
131 throw new NullPointerException("charset decoder");
132 sd = StreamDecoder.forInputStreamReader(in, this, dec);
133 }
134
135 /**
136 * Returns the name of the character encoding being used by this stream.
137 *
138 * <p> If the encoding has an historical name then that name is returned;
139 * otherwise the encoding's canonical name is returned.
140 *
141 * <p> If this instance was created with the {@link
142 * #InputStreamReader(InputStream, String)} constructor then the returned
143 * name, being unique for the encoding, may differ from the name passed to
144 * the constructor. This method will return <code>null</code> if the
145 * stream has been closed.
146 * </p>
147 * @return The historical name of this encoding, or
148 * <code>null</code> if the stream has been closed
149 *
150 * @see java.nio.charset.Charset
151 *
152 * @revised 1.4
153 * @spec JSR-51
154 */
155 public String getEncoding() {
156 return sd.getEncoding();
157 }
158
159 /**
160 * Reads a single character.
161 *
162 * @return The character read, or -1 if the end of the stream has been
163 * reached
164 *
165 * @exception IOException If an I/O error occurs
166 */
167 public int read() throws IOException {
168 return sd.read();
169 }
170
171 /**
172 * Reads characters into a portion of an array.
173 *
174 * @param cbuf Destination buffer
175 * @param offset Offset at which to start storing characters
176 * @param length Maximum number of characters to read
177 *
178 * @return The number of characters read, or -1 if the end of the
179 * stream has been reached
180 *
181 * @exception IOException If an I/O error occurs
182 */
183 public int read(char cbuf[], int offset, int length) throws IOException {
184 return sd.read(cbuf, offset, length);
185 }
186
187 /**
188 * Tells whether this stream is ready to be read. An InputStreamReader is
189 * ready if its input buffer is not empty, or if bytes are available to be
190 * read from the underlying byte stream.
191 *
192 * @exception IOException If an I/O error occurs
193 */
194 public boolean ready() throws IOException {
195 return sd.ready();
196 }
197
198 public void close() throws IOException {
199 sd.close();
200 }
201 }
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