001 /*
002 * Copyright 2000-2001 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.nio.channels;
027
028 import java.io.IOException;
029 import java.nio.ByteBuffer;
030
031 /**
032 * A channel that can read bytes.
033 *
034 * <p> Only one read operation upon a readable channel may be in progress at
035 * any given time. If one thread initiates a read operation upon a channel
036 * then any other thread that attempts to initiate another read operation will
037 * block until the first operation is complete. Whether or not other kinds of
038 * I/O operations may proceed concurrently with a read operation depends upon
039 * the type of the channel. </p>
040 *
041 *
042 * @author Mark Reinhold
043 * @author JSR-51 Expert Group
044 * @version 1.23, 07/05/05
045 * @since 1.4
046 */
047
048 public interface ReadableByteChannel extends Channel {
049
050 /**
051 * Reads a sequence of bytes from this channel into the given buffer.
052 *
053 * <p> An attempt is made to read up to <i>r</i> bytes from the channel,
054 * where <i>r</i> is the number of bytes remaining in the buffer, that is,
055 * <tt>dst.remaining()</tt>, at the moment this method is invoked.
056 *
057 * <p> Suppose that a byte sequence of length <i>n</i> is read, where
058 * <tt>0</tt> <tt><=</tt> <i>n</i> <tt><=</tt> <i>r</i>.
059 * This byte sequence will be transferred into the buffer so that the first
060 * byte in the sequence is at index <i>p</i> and the last byte is at index
061 * <i>p</i> <tt>+</tt> <i>n</i> <tt>-</tt> <tt>1</tt>,
062 * where <i>p</i> is the buffer's position at the moment this method is
063 * invoked. Upon return the buffer's position will be equal to
064 * <i>p</i> <tt>+</tt> <i>n</i>; its limit will not have changed.
065 *
066 * <p> A read operation might not fill the buffer, and in fact it might not
067 * read any bytes at all. Whether or not it does so depends upon the
068 * nature and state of the channel. A socket channel in non-blocking mode,
069 * for example, cannot read any more bytes than are immediately available
070 * from the socket's input buffer; similarly, a file channel cannot read
071 * any more bytes than remain in the file. It is guaranteed, however, that
072 * if a channel is in blocking mode and there is at least one byte
073 * remaining in the buffer then this method will block until at least one
074 * byte is read.
075 *
076 * <p> This method may be invoked at any time. If another thread has
077 * already initiated a read operation upon this channel, however, then an
078 * invocation of this method will block until the first operation is
079 * complete. </p>
080 *
081 * @param dst
082 * The buffer into which bytes are to be transferred
083 *
084 * @return The number of bytes read, possibly zero, or <tt>-1</tt> if the
085 * channel has reached end-of-stream
086 *
087 * @throws NonReadableChannelException
088 * If this channel was not opened for reading
089 *
090 * @throws ClosedChannelException
091 * If this channel is closed
092 *
093 * @throws AsynchronousCloseException
094 * If another thread closes this channel
095 * while the read operation is in progress
096 *
097 * @throws ClosedByInterruptException
098 * If another thread interrupts the current thread
099 * 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 }
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