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 {@link * ScatteringByteChannel} interface.
* * * @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()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.
* * @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 srcs.length * * @param length * The maximum number of buffers to be accessed; must be * non-negative and no larger than * srcs.length - offset * * @return The number of bytes written, possibly zero * * @throws IndexOutOfBoundsException * If the preconditions on the offset and 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);