WritableByteChannel.java

/*
 * Copyright (c) 2000, 2005, 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
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package java.nio.channels;

import java.io.IOException;
import java.nio.ByteBuffer;

/**
 * A channel that can write bytes.
 *
 * <p> Only one write operation upon a writable channel may be in progress at
 * any given time.  If one thread initiates a write operation upon a channel
 * then any other thread that attempts to initiate another write operation will
 * block until the first operation is complete.  Whether or not other kinds of
 * I/O operations may proceed concurrently with a write operation depends upon
 * the type of the channel. </p>
 *
 * @author Mark Reinhold
 * @author JSR-51 Expert Group
 * @since 1.4
 */
// 可写的字节通道
public interface WritableByteChannel extends Channel {
    
    /**
     * Writes a sequence of bytes to this channel from the given buffer.
     *
     * <p> An attempt is made to write up to <i>r</i> bytes to the channel,
     * where <i>r</i> is the number of bytes remaining in the buffer, that is,
     * {@code src.remaining()}, at the moment this method is invoked.
     *
     * <p> Suppose that a byte sequence of length <i>n</i> is written, where
     * {@code 0}&nbsp;{@code <=}&nbsp;<i>n</i>&nbsp;{@code <=}&nbsp;<i>r</i>.
     * This byte sequence will be transferred from the buffer starting at index
     * <i>p</i>, where <i>p</i> is the buffer's position at the moment this
     * method is invoked; the index of the last byte written will be
     * <i>p</i>&nbsp;{@code +}&nbsp;<i>n</i>&nbsp;{@code -}&nbsp;{@code 1}.
     * Upon return the buffer's position will be equal to
     * <i>p</i>&nbsp;{@code +}&nbsp;<i>n</i>; its limit will not have changed.
     *
     * <p> Unless otherwise specified, a write operation will return only after
     * writing all of the <i>r</i> requested bytes.  Some types of channels,
     * depending upon their state, may write only some of the bytes or possibly
     * none at all.  A socket channel in non-blocking mode, for example, cannot
     * write any more bytes than are free in the socket's output buffer.
     *
     * <p> This method may be invoked at any time.  If another thread has
     * already initiated a write operation upon this channel, however, then an
     * invocation of this method will block until the first operation is
     * complete. </p>
     *
     * @param src The buffer from which bytes are to be retrieved
     *
     * @return The number of bytes written, possibly zero
     *
     * @throws NonWritableChannelException If this channel was not opened for writing
     * @throws ClosedChannelException      If this channel is closed
     * @throws AsynchronousCloseException  If another thread closes this channel
     *                                     while the write operation is in progress
     * @throws ClosedByInterruptException  If another thread interrupts the current thread
     *                                     while the write 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
     */
    // 从src中读取数据，读到的内容向当前通道中写入
    int write(ByteBuffer src) throws IOException;
    
}