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package java.nio.channels;

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



A channel that can write bytes from a sequence of buffers.

 A gathering 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
scattering read operations are defined in the ScatteringByteChannel interface. 


Author:Mark Reinhold, JSR-51 Expert Group
Since:1.4
/**
 * 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
 */

public interface GatheringByteChannel
    extends WritableByteChannel
{

    
Writes a sequence of bytes to this channel from a subsequence of the
given buffers.

 An attempt is made to write up to r bytes to this channel,
where r is the total number of bytes remaining in the specified
subsequence of the given buffer array, that is,

srcs[offset].remaining()
    + srcs[offset+1].remaining()
    + ... + srcs[offset+length-1].remaining()

at the moment that this method is invoked.

 Suppose that a byte sequence of length n is written, where 0 <= n <= r. Up to the first srcs[offset].remaining() bytes of this sequence are written from buffer srcs[offset], up to the next srcs[offset+1].remaining() bytes are written from buffer 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. 
 Unless otherwise specified, a write operation will return only after
writing all of the r 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.

 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. 


Params:
  • srcs – 
        The buffers from which bytes are to be retrieved
  • 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 srcs.length
  • length –  The maximum number of buffers to be accessed; must be non-negative and no larger than srcs.length - offset
Throws:
Returns: The number of bytes written, possibly zero
/**
     * 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}&nbsp;{@code <=}&nbsp;<i>n</i>&nbsp;{@code <=}&nbsp;<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}&nbsp;-&nbsp;{@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
     */
    public long write(ByteBuffer[] srcs, int offset, int length)
        throws IOException;


    
Writes a sequence of bytes to this channel from the given buffers.

 An invocation of this method of the form c.write(srcs) behaves in exactly the same manner as the invocation 
c.write(srcs, 0, srcs.length);


Params:
  • srcs – 
        The buffers from which bytes are to be retrieved
Throws:
Returns: The number of bytes written, possibly zero
/**
     * 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
     */
    public long write(ByteBuffer[] srcs) throws IOException;

}