Java example source code file (SourceChannelImpl.java)

This example Java source code file (SourceChannelImpl.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

error, filedescriptor, indexoutofboundsexception, ioexception, nativedispatcher, nio, object, pollnval, selchimpl, selectionkeyimpl, sourcechannelimpl, st_inuse, st_killed, st_uninitialized

The SourceChannelImpl.java Java example source code

/*
 * Copyright (c) 2000, 2013, Oracle and/or its affiliates. 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.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package sun.nio.ch;

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


class SourceChannelImpl
    extends Pipe.SourceChannel
    implements SelChImpl
{

    // Used to make native read and write calls
    private static final NativeDispatcher nd = new FileDispatcherImpl();

    // The file descriptor associated with this channel
    FileDescriptor fd;

    // fd value needed for dev/poll. This value will remain valid
    // even after the value in the file descriptor object has been set to -1
    int fdVal;

    // ID of native thread doing read, for signalling
    private volatile long thread = 0;

    // Lock held by current reading thread
    private final Object lock = new Object();

    // Lock held by any thread that modifies the state fields declared below
    // DO NOT invoke a blocking I/O operation while holding this lock!
    private final Object stateLock = new Object();

    // -- The following fields are protected by stateLock

    // Channel state
    private static final int ST_UNINITIALIZED = -1;
    private static final int ST_INUSE = 0;
    private static final int ST_KILLED = 1;
    private volatile int state = ST_UNINITIALIZED;

    // -- End of fields protected by stateLock


    public FileDescriptor getFD() {
        return fd;
    }

    public int getFDVal() {
        return fdVal;
    }

    SourceChannelImpl(SelectorProvider sp, FileDescriptor fd) {
        super(sp);
        this.fd = fd;
        this.fdVal = IOUtil.fdVal(fd);
        this.state = ST_INUSE;
    }

    protected void implCloseSelectableChannel() throws IOException {
        synchronized (stateLock) {
            if (state != ST_KILLED)
                nd.preClose(fd);
            long th = thread;
            if (th != 0)
                NativeThread.signal(th);
            if (!isRegistered())
                kill();
        }
    }

    public void kill() throws IOException {
        synchronized (stateLock) {
            if (state == ST_KILLED)
                return;
            if (state == ST_UNINITIALIZED) {
                state = ST_KILLED;
                return;
            }
            assert !isOpen() && !isRegistered();
            nd.close(fd);
            state = ST_KILLED;
        }
    }

    protected void implConfigureBlocking(boolean block) throws IOException {
        IOUtil.configureBlocking(fd, block);
    }

    public boolean translateReadyOps(int ops, int initialOps,
                                     SelectionKeyImpl sk) {
        int intOps = sk.nioInterestOps(); // Do this just once, it synchronizes
        int oldOps = sk.nioReadyOps();
        int newOps = initialOps;

        if ((ops & PollArrayWrapper.POLLNVAL) != 0)
            throw new Error("POLLNVAL detected");

        if ((ops & (PollArrayWrapper.POLLERR
                    | PollArrayWrapper.POLLHUP)) != 0) {
            newOps = intOps;
            sk.nioReadyOps(newOps);
            return (newOps & ~oldOps) != 0;
        }

        if (((ops & PollArrayWrapper.POLLIN) != 0) &&
            ((intOps & SelectionKey.OP_READ) != 0))
            newOps |= SelectionKey.OP_READ;

        sk.nioReadyOps(newOps);
        return (newOps & ~oldOps) != 0;
    }

    public boolean translateAndUpdateReadyOps(int ops, SelectionKeyImpl sk) {
        return translateReadyOps(ops, sk.nioReadyOps(), sk);
    }

    public boolean translateAndSetReadyOps(int ops, SelectionKeyImpl sk) {
        return translateReadyOps(ops, 0, sk);
    }

    public void translateAndSetInterestOps(int ops, SelectionKeyImpl sk) {
        if (ops == SelectionKey.OP_READ)
            ops = PollArrayWrapper.POLLIN;
        sk.selector.putEventOps(sk, ops);
    }

    private void ensureOpen() throws IOException {
        if (!isOpen())
            throw new ClosedChannelException();
    }

    public int read(ByteBuffer dst) throws IOException {
        ensureOpen();
        synchronized (lock) {
            int n = 0;
            try {
                begin();
                if (!isOpen())
                    return 0;
                thread = NativeThread.current();
                do {
                    n = IOUtil.read(fd, dst, -1, nd);
                } while ((n == IOStatus.INTERRUPTED) && isOpen());
                return IOStatus.normalize(n);
            } finally {
                thread = 0;
                end((n > 0) || (n == IOStatus.UNAVAILABLE));
                assert IOStatus.check(n);
            }
        }
    }

    public long read(ByteBuffer[] dsts, int offset, int length)
        throws IOException
    {
        if ((offset < 0) || (length < 0) || (offset > dsts.length - length))
           throw new IndexOutOfBoundsException();
        return read(Util.subsequence(dsts, offset, length));
    }

    public long read(ByteBuffer[] dsts) throws IOException {
        if (dsts == null)
            throw new NullPointerException();
        ensureOpen();
        synchronized (lock) {
            long n = 0;
            try {
                begin();
                if (!isOpen())
                    return 0;
                thread = NativeThread.current();
                do {
                    n = IOUtil.read(fd, dsts, nd);
                } while ((n == IOStatus.INTERRUPTED) && isOpen());
                return IOStatus.normalize(n);
            } finally {
                thread = 0;
                end((n > 0) || (n == IOStatus.UNAVAILABLE));
                assert IOStatus.check(n);
            }
        }
    }
}