--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/share/classes/java/nio/channels/package-info.java Sun Aug 31 18:39:01 2008 +0100
@@ -0,0 +1,231 @@
+/*
+ * Copyright 2001-2005 Sun Microsystems, Inc. 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. Sun designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ */
+
+/**
+ * Defines channels, which represent connections to entities that are capable of
+ * performing I/O operations, such as files and sockets; defines selectors, for
+ * multiplexed, non-blocking I/O operations.
+ *
+ * <a name="channels"></a>
+ *
+ * <blockquote><table cellspacing=1 cellpadding=0 summary="Lists channels and their descriptions">
+ * <tr><th><p align="left">Channels</p></th><th><p align="left">Description</p></th></tr>
+ * <tr><td valign=top><tt><i>{@link java.nio.channels.Channel}</i></tt></td>
+ * <td>A nexus for I/O operations</td></tr>
+ * <tr><td valign=top><tt> <i>{@link java.nio.channels.ReadableByteChannel}</i></tt></td>
+ * <td>Can read into a buffer</td></tr>
+ * <tr><td valign=top><tt> <i>{@link java.nio.channels.ScatteringByteChannel} </i></tt></td>
+ * <td>Can read into a sequence of buffers</td></tr>
+ * <tr><td valign=top><tt> <i>{@link java.nio.channels.WritableByteChannel}</i></tt></td>
+ * <td>Can write from a buffer</td></tr>
+ * <tr><td valign=top><tt> <i>{@link java.nio.channels.GatheringByteChannel}</i></tt></td>
+ * <td>Can write from a sequence of buffers</td></tr>
+ * <tr><td valign=top><tt> <i>{@link java.nio.channels.ByteChannel}</i></tt></td>
+ * <td>Can read/write to/from a buffer</td></tr>
+ * <tr><td valign=top><tt> <i>{@link java.nio.channels.SeekableByteChannel}</i></tt></td>
+ * <td>A {@code ByteChannel} connected to an entity that contains a variable-length sequence of bytes</td></tr>
+ * <tr><td valign=top><tt> <i>{@link java.nio.channels.NetworkChannel}</i></tt></td>
+ * <td>A channel to a network socket</td></tr>
+ * <tr><td valign=top><tt> <i>{@link java.nio.channels.MulticastChannel}</i></tt></td>
+ * <td>Can join Internet Protocol (IP) multicast groups</td></tr>
+ * <tr><td valign=top><tt>{@link java.nio.channels.Channels}</tt></td>
+ * <td>Utility methods for channel/stream interoperation</td></tr>
+ * </table></blockquote>
+ *
+ * <p> A <i>channel</i> represents an open connection to an entity such as a
+ * hardware device, a file, a network socket, or a program component that is
+ * capable of performing one or more distinct I/O operations, for example reading
+ * or writing. As specified in the {@link java.nio.channels.Channel} interface,
+ * channels are either open or closed, and they are both <i>asynchronously
+ * closeable</i> and <i>interruptible</i>.
+ *
+ * <p> The {@link java.nio.channels.Channel} interface is extended by several
+ * other interfaces.
+ *
+ * <p> The {@link java.nio.channels.ReadableByteChannel} interface specifies a
+ * {@link java.nio.channels.ReadableByteChannel#read read} method that reads bytes
+ * from the channel into a buffer; similarly, the {@link
+ * java.nio.channels.WritableByteChannel} interface specifies a {@link
+ * java.nio.channels.WritableByteChannel#write write} method that writes bytes
+ * from a buffer to the channel. The {@link java.nio.channels.ByteChannel}
+ * interface unifies these two interfaces for the common case of channels that can
+ * both read and write bytes. The {@link java.nio.channels.SeekableByteChannel}
+ * interface extends the {@code ByteChannel} interface with methods to {@link
+ * java.nio.channels.SeekableByteChannel#position() query} and {@link
+ * java.nio.channels.SeekableByteChannel#position(long) modify} the channel's
+ * current position, and its {@link java.nio.channels.SeekableByteChannel#size
+ * size}.
+ *
+ * <p> The {@link java.nio.channels.ScatteringByteChannel} and {@link
+ * java.nio.channels.GatheringByteChannel} interfaces extend the {@link
+ * java.nio.channels.ReadableByteChannel} and {@link
+ * java.nio.channels.WritableByteChannel} interfaces, respectively, adding {@link
+ * java.nio.channels.ScatteringByteChannel#read read} and {@link
+ * java.nio.channels.GatheringByteChannel#write write} methods that take a
+ * sequence of buffers rather than a single buffer.
+ *
+ * <p> The {@link java.nio.channels.NetworkChannel} interface specifies methods
+ * to {@link java.nio.channels.NetworkChannel#bind bind} the channel's socket,
+ * obtain the address to which the socket is bound, and methods to {@link
+ * java.nio.channels.NetworkChannel#getOption get} and {@link
+ * java.nio.channels.NetworkChannel#setOption set} socket options. The {@link
+ * java.nio.channels.MulticastChannel} interface specifies methods to join
+ * Internet Protocol (IP) multicast groups.
+ *
+ * <p> The {@link java.nio.channels.Channels} utility class defines static methods
+ * that support the interoperation of the stream classes of the <tt>{@link
+ * java.io}</tt> package with the channel classes of this package. An appropriate
+ * channel can be constructed from an {@link java.io.InputStream} or an {@link
+ * java.io.OutputStream}, and conversely an {@link java.io.InputStream} or an
+ * {@link java.io.OutputStream} can be constructed from a channel. A {@link
+ * java.io.Reader} can be constructed that uses a given charset to decode bytes
+ * from a given readable byte channel, and conversely a {@link java.io.Writer} can
+ * be constructed that uses a given charset to encode characters into bytes and
+ * write them to a given writable byte channel.
+ *
+ * <blockquote><table cellspacing=1 cellpadding=0 summary="Lists file channels and their descriptions">
+ * <tr><th><p align="left">File channels</p></th><th><p align="left">Description</p></th></tr>
+ * <tr><td valign=top><tt>{@link java.nio.channels.FileChannel}</tt></td>
+ * <td>Reads, writes, maps, and manipulates files</td></tr>
+ * <tr><td valign=top><tt>{@link java.nio.channels.FileLock}</tt></td>
+ * <td>A lock on a (region of a) file</td></tr>
+ * <tr><td valign=top><tt>{@link java.nio.MappedByteBuffer}/{@link java.nio.MappedBigByteBuffer} </tt></td>
+ * <td>A direct byte buffer or big byte buffer mapped to a region of a file</td></tr>
+ * </table></blockquote>
+ *
+ * <p> The {@link java.nio.channels.FileChannel} class supports the usual
+ * operations of reading bytes from, and writing bytes to, a channel connected to
+ * a file, as well as those of querying and modifying the current file position
+ * and truncating the file to a specific size. It defines methods for acquiring
+ * locks on the whole file or on a specific region of a file; these methods return
+ * instances of the {@link java.nio.channels.FileLock} class. Finally, it defines
+ * methods for forcing updates to the file to be written to the storage device that
+ * contains it, for efficiently transferring bytes between the file and other
+ * channels, and for mapping a region of the file directly into memory.
+ *
+ * <p> A {@code FileChannel} is created by invoking one of its static {@link
+ * java.nio.channels.FileChannel#open open} methods, or by invoking the {@code
+ * getChannel} method of a {@link java.io.FileInputStream}, {@link
+ * java.io.FileOutputStream}, or {@link java.io.RandomAccessFile} to return a
+ * file channel connected to the same underlying file as the <tt>{@link java.io}</tt>
+ * class.
+ *
+ * <a name="multiplex"></a>
+ * <blockquote><table cellspacing=1 cellpadding=0 summary="Lists multiplexed, non-blocking channels and their descriptions">
+ * <tr><th><p align="left">Multiplexed, non-blocking I/O</p></th><th><p align="left">Description</p></th></tr>
+ * <tr><td valign=top><tt>{@link java.nio.channels.SelectableChannel}</tt></td>
+ * <td>A channel that can be multiplexed</td></tr>
+ * <tr><td valign=top><tt> {@link java.nio.channels.DatagramChannel}</tt></td>
+ * <td>A channel to a datagram-oriented socket</td></tr>
+ * <tr><td valign=top><tt> {@link java.nio.channels.Pipe.SinkChannel}</tt></td>
+ * <td>The write end of a pipe</td></tr>
+ * <tr><td valign=top><tt> {@link java.nio.channels.Pipe.SourceChannel}</tt></td>
+ * <td>The read end of a pipe</td></tr>
+ * <tr><td valign=top><tt> {@link java.nio.channels.ServerSocketChannel} </tt></td>
+ * <td>A channel to a stream-oriented listening socket</td></tr>
+ * <tr><td valign=top><tt> {@link java.nio.channels.SocketChannel}</tt></td>
+ * <td>A channel for a stream-oriented connecting socket</td></tr>
+ * <tr><td valign=top><tt>{@link java.nio.channels.Selector}</tt></td>
+ * <td>A multiplexor of selectable channels</td></tr>
+ * <tr><td valign=top><tt>{@link java.nio.channels.SelectionKey}</tt></td>
+ * <td>A token representing the registration <br> of a channel
+ * with a selector</td></tr>
+ * <tr><td valign=top><tt>{@link java.nio.channels.Pipe}</tt></td>
+ * <td>Two channels that form a unidirectional pipe</td></tr>
+ * </table></blockquote>
+ *
+ * <p> Multiplexed, non-blocking I/O, which is much more scalable than
+ * thread-oriented, blocking I/O, is provided by <i>selectors</i>, <i>selectable
+ * channels</i>, and <i>selection keys</i>.
+ *
+ * <p> A <a href="Selector.html"><i>selector</i></a> is a multiplexor of <a
+ * href="SelectableChannel.html"><i>selectable channels</i></a>, which in turn are
+ * a special type of channel that can be put into <a
+ * href="SelectableChannel.html#bm"><i>non-blocking mode</i></a>. To perform
+ * multiplexed I/O operations, one or more selectable channels are first created,
+ * put into non-blocking mode, and {@link
+ * java.nio.channels.SelectableChannel#register <i>registered</i>}
+ * with a selector. Registering a channel specifies the set of I/O operations
+ * that will be tested for readiness by the selector, and returns a <a
+ * href="SelectionKey.html"><i>selection key</i></a> that represents the
+ * registration.
+ *
+ * <p> Once some channels have been registered with a selector, a <a
+ * href="Selector.html#selop"><i>selection operation</i></a> can be performed in
+ * order to discover which channels, if any, have become ready to perform one or
+ * more of the operations in which interest was previously declared. If a channel
+ * is ready then the key returned when it was registered will be added to the
+ * selector's <i>selected-key set</i>. The key set, and the keys within it, can
+ * be examined in order to determine the operations for which each channel is
+ * ready. From each key one can retrieve the corresponding channel in order to
+ * perform whatever I/O operations are required.
+ *
+ * <p> That a selection key indicates that its channel is ready for some operation
+ * is a hint, but not a guarantee, that such an operation can be performed by a
+ * thread without causing the thread to block. It is imperative that code that
+ * performs multiplexed I/O be written so as to ignore these hints when they prove
+ * to be incorrect.
+ *
+ * <p> This package defines selectable-channel classes corresponding to the {@link
+ * java.net.DatagramSocket}, {@link java.net.ServerSocket}, and {@link
+ * java.net.Socket} classes defined in the <tt>{@link java.net}</tt> package.
+ * Minor changes to these classes have been made in order to support sockets that
+ * are associated with channels. This package also defines a simple class that
+ * implements unidirectional pipes. In all cases, a new selectable channel is
+ * created by invoking the static <tt>open</tt> method of the corresponding class.
+ * If a channel needs an associated socket then a socket will be created as a side
+ * effect of this operation.
+ *
+ * <p> The implementation of selectors, selectable channels, and selection keys
+ * can be replaced by "plugging in" an alternative definition or instance of the
+ * {@link java.nio.channels.spi.SelectorProvider} class defined in the <tt>{@link
+ * java.nio.channels.spi}</tt> package. It is not expected that many developers
+ * will actually make use of this facility; it is provided primarily so that
+ * sophisticated users can take advantage of operating-system-specific
+ * I/O-multiplexing mechanisms when very high performance is required.
+ *
+ * <p> Much of the bookkeeping and synchronization required to implement the
+ * multiplexed-I/O abstractions is performed by the {@link
+ * java.nio.channels.spi.AbstractInterruptibleChannel}, {@link
+ * java.nio.channels.spi.AbstractSelectableChannel}, {@link
+ * java.nio.channels.spi.AbstractSelectionKey}, and {@link
+ * java.nio.channels.spi.AbstractSelector} classes in the <tt>{@link
+ * java.nio.channels.spi}</tt> package. When defining a custom selector provider,
+ * only the {@link java.nio.channels.spi.AbstractSelector} and {@link
+ * java.nio.channels.spi.AbstractSelectionKey} classes should be subclassed
+ * directly; custom channel classes should extend the appropriate {@link
+ * java.nio.channels.SelectableChannel} subclasses defined in this package.
+ *
+ * <hr width="80%">
+ * <p> Unless otherwise noted, passing a <tt>null</tt> argument to a constructor
+ * or method in any class or interface in this package will cause a {@link
+ * java.lang.NullPointerException NullPointerException} to be thrown.
+ *
+ * @since 1.4
+ * @author Mark Reinhold
+ * @author JSR-51 Expert Group
+ */
+
+package java.nio.channels;