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
26package java.io;
27
28import java.nio.charset.Charset;
29import java.nio.charset.CharsetDecoder;
30import 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       1.1
60 */
61
62public 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     * @exception  IndexOutOfBoundsException {@inheritDoc}
183     */
184    public int read(char cbuf[], int offset, int length) 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}
203