001 /*
002 * Copyright 1996-2005 Sun Microsystems, Inc. All Rights Reserved.
003 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004 *
005 * This code is free software; you can redistribute it and/or modify it
006 * under the terms of the GNU General Public License version 2 only, as
007 * published by the Free Software Foundation. Sun designates this
008 * particular file as subject to the "Classpath" exception as provided
009 * by Sun in the LICENSE file that accompanied this code.
010 *
011 * This code is distributed in the hope that it will be useful, but WITHOUT
012 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
013 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
014 * version 2 for more details (a copy is included in the LICENSE file that
015 * accompanied this code).
016 *
017 * You should have received a copy of the GNU General Public License version
018 * 2 along with this work; if not, write to the Free Software Foundation,
019 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
020 *
021 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
022 * CA 95054 USA or visit www.sun.com if you need additional information or
023 * have any questions.
024 */
025
026 package java.io;
027
028 import java.nio.charset.Charset;
029 import java.nio.charset.CharsetDecoder;
030 import sun.nio.cs.StreamDecoder;
031
032 /**
033 * An InputStreamReader is a bridge from byte streams to character streams: It
034 * reads bytes and decodes them into characters using a specified {@link
035 * java.nio.charset.Charset <code>charset</code>}. The charset that it uses
036 * may be specified by name or may be given explicitly, or the platform's
037 * default charset may be accepted.
038 *
039 * <p> Each invocation of one of an InputStreamReader's read() methods may
040 * cause one or more bytes to be read from the underlying byte-input stream.
041 * To enable the efficient conversion of bytes to characters, more bytes may
042 * be read ahead from the underlying stream than are necessary to satisfy the
043 * current read operation.
044 *
045 * <p> For top efficiency, consider wrapping an InputStreamReader within a
046 * BufferedReader. For example:
047 *
048 * <pre>
049 * BufferedReader in
050 * = new BufferedReader(new InputStreamReader(System.in));
051 * </pre>
052 *
053 * @see BufferedReader
054 * @see InputStream
055 * @see java.nio.charset.Charset
056 *
057 * @version 1.53, 07/05/05
058 * @author Mark Reinhold
059 * @since JDK1.1
060 */
061
062 public class InputStreamReader extends Reader {
063
064 private final StreamDecoder sd;
065
066 /**
067 * Creates an InputStreamReader that uses the default charset.
068 *
069 * @param in An InputStream
070 */
071 public InputStreamReader(InputStream in) {
072 super (in);
073 try {
074 sd = StreamDecoder.forInputStreamReader(in, this ,
075 (String) null); // ## check lock object
076 } catch (UnsupportedEncodingException e) {
077 // The default encoding should always be available
078 throw new Error(e);
079 }
080 }
081
082 /**
083 * Creates an InputStreamReader that uses the named charset.
084 *
085 * @param in
086 * An InputStream
087 *
088 * @param charsetName
089 * The name of a supported
090 * {@link java.nio.charset.Charset </code>charset<code>}
091 *
092 * @exception UnsupportedEncodingException
093 * If the named charset is not supported
094 */
095 public InputStreamReader(InputStream in, String charsetName)
096 throws UnsupportedEncodingException {
097 super (in);
098 if (charsetName == null)
099 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)
184 throws IOException {
185 return sd.read(cbuf, offset, length);
186 }
187
188 /**
189 * Tells whether this stream is ready to be read. An InputStreamReader is
190 * ready if its input buffer is not empty, or if bytes are available to be
191 * read from the underlying byte stream.
192 *
193 * @exception IOException If an I/O error occurs
194 */
195 public boolean ready() throws IOException {
196 return sd.ready();
197 }
198
199 public void close() throws IOException {
200 sd.close();
201 }
202 }
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