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package java.nio.channels;

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



A channel that can read bytes into a sequence of buffers.

 A scattering read operation reads, in a single invocation, a
sequence of bytes into one or more of a given sequence of buffers.
Scattering reads 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
gathering write operations are defined in the GatheringByteChannel interface. 


Author:Mark Reinhold, JSR-51 Expert Group
Since:1.4
/**
 * A channel that can read bytes into a sequence of buffers.
 *
 * <p> A <i>scattering</i> read operation reads, in a single invocation, a
 * sequence of bytes into one or more of a given sequence of buffers.
 * Scattering reads 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>gathering</i> write operations are defined in the {@link
 * GatheringByteChannel} interface.  </p>
 *
 *
 * @author Mark Reinhold
 * @author JSR-51 Expert Group
 * @since 1.4
 */

public interface ScatteringByteChannel
    extends ReadableByteChannel
{

    
Reads a sequence of bytes from this channel into a subsequence of the
given buffers.

 An invocation of this method attempts to read up to r bytes
from this channel, where r is the total number of bytes remaining
the specified subsequence of the given buffer array, that is,

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

at the moment that this method is invoked.

 Suppose that a byte sequence of length n is read, where 0 <= n <= r. Up to the first dsts[offset].remaining() bytes of this sequence are transferred into buffer dsts[offset], up to the next dsts[offset+1].remaining() bytes are transferred into buffer dsts[offset+1], and so forth, until the entire byte sequence is transferred into the given buffers. As many bytes as possible are transferred into 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. 
 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. 


Params:
  • dsts – 
        The buffers into which bytes are to be transferred
  • offset –  The offset within the buffer array of the first buffer into which bytes are to be transferred; must be non-negative and no larger than dsts.length
  • length –  The maximum number of buffers to be accessed; must be non-negative and no larger than dsts.length - offset
Throws:
Returns:The number of bytes read, possibly zero, or -1 if the channel has reached end-of-stream
/**
     * Reads a sequence of bytes from this channel into a subsequence of the
     * given buffers.
     *
     * <p> An invocation of this method attempts to read up to <i>r</i> bytes
     * from this channel, where <i>r</i> is the total number of bytes remaining
     * the specified subsequence of the given buffer array, that is,
     *
     * <blockquote><pre>
     * dsts[offset].remaining()
     *     + dsts[offset+1].remaining()
     *     + ... + dsts[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 read, where
     * {@code 0}&nbsp;{@code <=}&nbsp;<i>n</i>&nbsp;{@code <=}&nbsp;<i>r</i>.
     * Up to the first {@code dsts[offset].remaining()} bytes of this sequence
     * are transferred into buffer {@code dsts[offset]}, up to the next
     * {@code dsts[offset+1].remaining()} bytes are transferred into buffer
     * {@code dsts[offset+1]}, and so forth, until the entire byte sequence
     * is transferred into the given buffers.  As many bytes as possible are
     * transferred into 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> 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  dsts
     *         The buffers into which bytes are to be transferred
     *
     * @param  offset
     *         The offset within the buffer array of the first buffer into
     *         which bytes are to be transferred; must be non-negative and no
     *         larger than {@code dsts.length}
     *
     * @param  length
     *         The maximum number of buffers to be accessed; must be
     *         non-negative and no larger than
     *         {@code dsts.length}&nbsp;-&nbsp;{@code offset}
     *
     * @return The number of bytes read, possibly zero,
     *         or {@code -1} if the channel has reached end-of-stream
     *
     * @throws  IndexOutOfBoundsException
     *          If the preconditions on the {@code offset} and {@code length}
     *          parameters do not hold
     *
     * @throws  IllegalArgumentException
     *          If any of the buffers is read-only
     *
     * @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 long read(ByteBuffer[] dsts, int offset, int length)
        throws IOException;

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

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


Params:
  • dsts – 
        The buffers into which bytes are to be transferred
Throws:
Returns:The number of bytes read, possibly zero, or -1 if the channel has reached end-of-stream
/**
     * Reads a sequence of bytes from this channel into the given buffers.
     *
     * <p> An invocation of this method of the form {@code c.read(dsts)}
     * behaves in exactly the same manner as the invocation
     *
     * <blockquote><pre>
     * c.read(dsts, 0, dsts.length);</pre></blockquote>
     *
     * @param  dsts
     *         The buffers into which bytes are to be transferred
     *
     * @return The number of bytes read, possibly zero,
     *         or {@code -1} if the channel has reached end-of-stream
     *
     * @throws  IllegalArgumentException
     *          If any of the buffers is read-only
     *
     * @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 long read(ByteBuffer[] dsts) throws IOException;

}