1 /*
2 * Copyright (c) 2000, 2019, 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.nio.channels;
27
28 import java.io.IOException;
29 import 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
48 public 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} {@code <=} <i>n</i> {@code <=} <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> {@code +} <i>n</i> {@code -} {@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> {@code +} <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 IllegalArgumentException
94 * If the buffer is read-only
95 *
96 * @throws AsynchronousCloseException
97 * If another thread closes this channel
98 * while the read operation is in progress
99 *
100 * @throws ClosedByInterruptException
101 * If another thread interrupts the current thread
102 * while the read operation is in progress, thereby
103 * closing the channel and setting the current thread's
104 * interrupt status
105 *
106 * @throws IOException
107 * If some other I/O error occurs
108 */
109 public int read(ByteBuffer dst) throws IOException;
110
111 }