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 {@link * GatheringByteChannel} interface.
* * * @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()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.
* * @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 dsts.length * * @param length * The maximum number of buffers to be accessed; must be * non-negative and no larger than * dsts.length - offset * * @return The number of bytes read, possibly zero, * or -1 if the channel has reached end-of-stream * * @throws IndexOutOfBoundsException * If the preconditions on the offset and length * parameters do not hold * * @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);