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1   /*
2    * Copyright (c) 1996, 2013, 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.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 charset}.  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 charset}
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.
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.
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 }