/
GatheringByteChannel.java
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/
GatheringByteChannel.java
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/*
* 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
* 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 from a sequence of buffers.
*
* <p> A <i>gathering</i> write operation writes, in a single invocation, a
* sequence of bytes from one or more of a given sequence of buffers.
* Gathering writes are often useful when implementing network protocols or
* file formats that, for example, group data into segments consisting of one
* or more fixed-length headers followed by a variable-length body. Similar
* <i>scattering</i> read operations are defined in the {@link
* ScatteringByteChannel} interface. </p>
*
* @author Mark Reinhold
* @author JSR-51 Expert Group
* @since 1.4
*/
// 聚集通道，可将多个缓存区的内容发送到单个通道。例如支持批量将多个缓冲区的内容写到文件中
public interface GatheringByteChannel extends WritableByteChannel {
/**
* Writes a sequence of bytes to this channel from a subsequence of the
* given buffers.
*
* <p> An attempt is made to write up to <i>r</i> bytes to this channel,
* where <i>r</i> is the total number of bytes remaining in the specified
* subsequence of the given buffer array, that is,
*
* <blockquote><pre>
* srcs[offset].remaining()
* + srcs[offset+1].remaining()
* + ... + srcs[offset+length-1].remaining()</pre></blockquote>
*
* at the moment that this method is invoked.
*
* <p> Suppose that a byte sequence of length <i>n</i> is written, where
* {@code 0} {@code <=} <i>n</i> {@code <=} <i>r</i>.
* Up to the first {@code srcs[offset].remaining()} bytes of this sequence
* are written from buffer {@code srcs[offset]}, up to the next
* {@code srcs[offset+1].remaining()} bytes are written from buffer
* {@code srcs[offset+1]}, and so forth, until the entire byte sequence is
* written. As many bytes as possible are written from each buffer, hence
* the final position of each updated buffer, except the last updated
* buffer, is guaranteed to be equal to that buffer's limit.
*
* <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 srcs The buffers from which bytes are to be retrieved
* @param offset The offset within the buffer array of the first buffer from
* which bytes are to be retrieved; must be non-negative and no
* larger than {@code srcs.length}
* @param length The maximum number of buffers to be accessed; must be
* non-negative and no larger than
* {@code srcs.length} - {@code offset}
*
* @return The number of bytes written, possibly zero
*
* @throws IndexOutOfBoundsException If the preconditions on the {@code offset} and {@code length}
* parameters do not hold
* @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srcs中offset处起的length个缓冲区读取数据，读到的内容向当前通道中写入
long write(ByteBuffer[] srcs, int offset, int length) throws IOException;
/**
* Writes a sequence of bytes to this channel from the given buffers.
*
* <p> An invocation of this method of the form {@code c.write(srcs)}
* behaves in exactly the same manner as the invocation
*
* <blockquote><pre>
* c.write(srcs, 0, srcs.length);</pre></blockquote>
*
* @param srcs The buffers 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srcs中各个缓冲区读取数据，读到的内容向当前通道中写入
long write(ByteBuffer[] srcs) throws IOException;
}