channelio.java

来自「一个小公司要求给写的很简单的任务管理系统。」· Java 代码 · 共 187 行

/*
 * @(#)ChannelIO.java	1.3 05/11/17
 * 
 * Copyright (c) 2006 Sun Microsystems, Inc. All Rights Reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 
 * -Redistribution of source code must retain the above copyright notice, this
 *  list of conditions and the following disclaimer.
 * 
 * -Redistribution in binary form must reproduce the above copyright notice, 
 *  this list of conditions and the following disclaimer in the documentation
 *  and/or other materials provided with the distribution.
 * 
 * Neither the name of Sun Microsystems, Inc. or the names of contributors may 
 * be used to endorse or promote products derived from this software without 
 * specific prior written permission.
 * 
 * This software is provided "AS IS," without a warranty of any kind. ALL 
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
 * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
 * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MIDROSYSTEMS, INC. ("SUN")
 * AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
 * AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
 * DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST 
 * REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL, 
 * INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY 
 * OF LIABILITY, ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE, 
 * EVEN IF SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
 * 
 * You acknowledge that this software is not designed, licensed or intended
 * for use in the design, construction, operation or maintenance of any
 * nuclear facility.
 */

import java.io.*;
import java.nio.*;
import java.nio.channels.*;

/**
 * A helper class for properly sizing inbound byte buffers and
 * redirecting I/O calls to the proper SocketChannel call.
 * <P>
 * Many of these calls may seem unnecessary until you consider
 * that they are placeholders for the secure variant, which is much
 * more involved.  See ChannelIOSecure for more information.
 *
 * @author Brad R. Wetmore
 * @author Mark Reinhold
 * @version 1.3, 05/11/17
 */
class ChannelIO {

    protected SocketChannel sc;

    /*
     * All of the inbound request data lives here until we determine
     * that we've read everything, then we pass that data back to the
     * caller.
     */
    protected ByteBuffer requestBB;
    static private int requestBBSize = 4096;

    protected ChannelIO(SocketChannel sc, boolean blocking)
	    throws IOException {
	this.sc = sc;
	sc.configureBlocking(blocking);
    }

    static ChannelIO getInstance(SocketChannel sc, boolean blocking)
	    throws IOException {
	ChannelIO cio = new ChannelIO(sc, blocking);
	cio.requestBB = ByteBuffer.allocate(requestBBSize);

	return cio;
    }

    SocketChannel getSocketChannel() {
	return sc;
    }

    /*
     * Return a ByteBuffer with "remaining" space to work.  If you have to
     * reallocate the ByteBuffer, copy the existing info into the new buffer.
     */
    protected void resizeRequestBB(int remaining) {
	if (requestBB.remaining() < remaining) {
	    // Expand buffer for large request
	    ByteBuffer bb = ByteBuffer.allocate(requestBB.capacity() * 2);
	    requestBB.flip();
	    bb.put(requestBB);
	    requestBB = bb;
	}
    }

    /*
     * Perform any handshaking processing.
     * <P>
     * This variant is for Servers without SelectionKeys (e.g.
     * blocking).
     * <P>
     * return true when we're done with handshaking.
     */
    boolean doHandshake() throws IOException {
	return true;
    }

    /*
     * Perform any handshaking processing.
     * <P>
     * This variant is for Servers with SelectionKeys, so that
     * we can register for selectable operations (e.g. selectable
     * non-blocking).
     * <P>
     * return true when we're done with handshaking.
     */
    boolean doHandshake(SelectionKey sk) throws IOException {
	return true;
    }

    /*
     * Resize (if necessary) the inbound data buffer, and then read more
     * data into the read buffer.
     */
    int read() throws IOException {
	/*
	 * Allocate more space if less than 5% remains
	 */
	resizeRequestBB(requestBBSize/20);
	return sc.read(requestBB);
    }

    /*
     * All data has been read, pass back the request in one buffer.
     */
    ByteBuffer getReadBuf() {
	return requestBB;
    }

    /*
     * Write the src buffer into the socket channel.
     */
    int write(ByteBuffer src) throws IOException {
	return sc.write(src);
    }

    /*
     * Perform a FileChannel.TransferTo on the socket channel.
     */
    long transferTo(FileChannel fc, long pos, long len) throws IOException {
	return fc.transferTo(pos, len, sc);
    }

    /*
     * Flush any outstanding data to the network if possible.
     * <P>
     * This isn't really necessary for the insecure variant, but needed
     * for the secure one where intermediate buffering must take place.
     * <P>
     * Return true if successful.
     */
    boolean dataFlush() throws IOException {
	return true;
    }

    /*
     * Start any connection shutdown processing.
     * <P>
     * This isn't really necessary for the insecure variant, but needed
     * for the secure one where intermediate buffering must take place.
     * <P>
     * Return true if successful, and the data has been flushed.
     */
    boolean shutdown() throws IOException {
	return true;
    }

    /*
     * Close the underlying connection.
     */
    void close() throws IOException {
	sc.close();
    }

}