/*

 * Copyright (c) 2000, 2001, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

package java.nio.channels;

import java.io.IOException;

import java.nio.ByteBuffer;

/**

 * A channel that can read bytes.

 *

 * <p> Only one read operation upon a readable channel may be in progress at

 * any given time.  If one thread initiates a read operation upon a channel

 * then any other thread that attempts to initiate another read operation will

 * block until the first operation is complete.  Whether or not other kinds of

 * I/O operations may proceed concurrently with a read operation depends upon

 * the type of the channel. </p>

 *

 *

 * @author Mark Reinhold

 * @author JSR-51 Expert Group

 * @since 1.4

 */

public interface ReadableByteChannel extends Channel {

    /**

     * Reads a sequence of bytes from this channel into the given buffer.

     *

     * <p> An attempt is made to read up to <i>r</i> bytes from the channel,

     * where <i>r</i> is the number of bytes remaining in the buffer, that is,

     * <tt>dst.remaining()</tt>, at the moment this method is invoked.

     *

     * <p> Suppose that a byte sequence of length <i>n</i> is read, where

     * <tt>0</tt>&nbsp;<tt>&lt;=</tt>&nbsp;<i>n</i>&nbsp;<tt>&lt;=</tt>&nbsp;<i>r</i>.

     * This byte sequence will be transferred into the buffer so that the first

     * byte in the sequence is at index <i>p</i> and the last byte is at index

     * <i>p</i>&nbsp;<tt>+</tt>&nbsp;<i>n</i>&nbsp;<tt>-</tt>&nbsp;<tt>1</tt>,

     * where <i>p</i> is the buffer's position at the moment this method is

     * invoked.  Upon return the buffer's position will be equal to

     * <i>p</i>&nbsp;<tt>+</tt>&nbsp;<i>n</i>; its limit will not have changed.

     *

     * <p> A read operation might not fill the buffer, and in fact it might not

     * read any bytes at all.  Whether or not it does so depends upon the

     * nature and state of the channel.  A socket channel in non-blocking mode,

     * for example, cannot read any more bytes than are immediately available

     * from the socket's input buffer; similarly, a file channel cannot read

     * any more bytes than remain in the file.  It is guaranteed, however, that

     * if a channel is in blocking mode and there is at least one byte

     * remaining in the buffer then this method will block until at least one

     * byte is read.

     *

     * <p> This method may be invoked at any time.  If another thread has

     * already initiated a read operation upon this channel, however, then an

     * invocation of this method will block until the first operation is

     * complete. </p>

     *

     * @param  dst

     *         The buffer into which bytes are to be transferred

     *

     * @return  The number of bytes read, possibly zero, or <tt>-1</tt> if the

     *          channel has reached end-of-stream

     *

     * @throws  NonReadableChannelException

     *          If this channel was not opened for reading

     *

     * @throws  ClosedChannelException

     *          If this channel is closed

     *

     * @throws  AsynchronousCloseException

     *          If another thread closes this channel

     *          while the read operation is in progress

     *

     * @throws  ClosedByInterruptException

     *          If another thread interrupts the current thread

     *          while the read operation is in progress, thereby

     *          closing the channel and setting the current thread's

     *          interrupt status

     *

     * @throws  IOException

     *          If some other I/O error occurs

     */

    public int read(ByteBuffer dst) throws IOException;

}