1/*
2 * Copyright (c) 2000, 2001, 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.nio.channels;
27
28import java.io.IOException;
29import java.nio.ByteBuffer;
30
31
32/**
33 * A channel that can read bytes.
34 *
35 * <p> Only one read operation upon a readable channel may be in progress at
36 * any given time.  If one thread initiates a read operation upon a channel
37 * then any other thread that attempts to initiate another read operation will
38 * block until the first operation is complete.  Whether or not other kinds of
39 * I/O operations may proceed concurrently with a read operation depends upon
40 * the type of the channel. </p>
41 *
42 *
43 * @author Mark Reinhold
44 * @author JSR-51 Expert Group
45 * @since 1.4
46 */
47
48public interface ReadableByteChannel extends Channel {
49
50    /**
51     * Reads a sequence of bytes from this channel into the given buffer.
52     *
53     * <p> An attempt is made to read up to <i>r</i> bytes from the channel,
54     * where <i>r</i> is the number of bytes remaining in the buffer, that is,
55     * {@code dst.remaining()}, at the moment this method is invoked.
56     *
57     * <p> Suppose that a byte sequence of length <i>n</i> is read, where
58     * {@code 0}&nbsp;{@code <=}&nbsp;<i>n</i>&nbsp;{@code <=}&nbsp;<i>r</i>.
59     * This byte sequence will be transferred into the buffer so that the first
60     * byte in the sequence is at index <i>p</i> and the last byte is at index
61     * <i>p</i>&nbsp;{@code +}&nbsp;<i>n</i>&nbsp;{@code -}&nbsp;{@code 1},
62     * where <i>p</i> is the buffer's position at the moment this method is
63     * invoked.  Upon return the buffer's position will be equal to
64     * <i>p</i>&nbsp;{@code +}&nbsp;<i>n</i>; its limit will not have changed.
65     *
66     * <p> A read operation might not fill the buffer, and in fact it might not
67     * read any bytes at all.  Whether or not it does so depends upon the
68     * nature and state of the channel.  A socket channel in non-blocking mode,
69     * for example, cannot read any more bytes than are immediately available
70     * from the socket's input buffer; similarly, a file channel cannot read
71     * any more bytes than remain in the file.  It is guaranteed, however, that
72     * if a channel is in blocking mode and there is at least one byte
73     * remaining in the buffer then this method will block until at least one
74     * byte is read.
75     *
76     * <p> This method may be invoked at any time.  If another thread has
77     * already initiated a read operation upon this channel, however, then an
78     * invocation of this method will block until the first operation is
79     * complete. </p>
80     *
81     * @param  dst
82     *         The buffer into which bytes are to be transferred
83     *
84     * @return  The number of bytes read, possibly zero, or {@code -1} if the
85     *          channel has reached end-of-stream
86     *
87     * @throws  NonReadableChannelException
88     *          If this channel was not opened for reading
89     *
90     * @throws  ClosedChannelException
91     *          If this channel is closed
92     *
93     * @throws  AsynchronousCloseException
94     *          If another thread closes this channel
95     *          while the read operation is in progress
96     *
97     * @throws  ClosedByInterruptException
98     *          If another thread interrupts the current thread
99     *          while the read operation is in progress, thereby
100     *          closing the channel and setting the current thread's
101     *          interrupt status
102     *
103     * @throws  IOException
104     *          If some other I/O error occurs
105     */
106    public int read(ByteBuffer dst) throws IOException;
107
108}
109