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NioBlockingSelector.javaAPI DocApache Tomcat 6.0.147932Fri Jul 20 04:20:32 BST 2007org.apache.tomcat.util.net

NioBlockingSelector

public class NioBlockingSelector extends Object

Fields Summary
Constructors Summary
public NioBlockingSelector()
Methods Summary
private static voidcancelKey(NioChannel socket, java.nio.channels.SelectionKey key)

        socket.getPoller().addEvent(
            new Runnable() {
            public void run() {
                key.cancel();
            }
        });
public static intread(java.nio.ByteBuffer buf, NioChannel socket, long readTimeout)
Performs a blocking read using the bytebuffer for data to be read If the selector parameter is null, then it will perform a busy read that could take up a lot of CPU cycles.

param
buf ByteBuffer - the buffer containing the data, we will read as until we have read at least one byte or we timed out
param
socket SocketChannel - the socket to write data to
param
selector Selector - the selector to use for blocking, if null then a busy read will be initiated
param
readTimeout long - the timeout for this read operation in milliseconds, -1 means no timeout
return
int - returns the number of bytes read
throws
EOFException if read returns -1
throws
SocketTimeoutException if the read times out
throws
IOException if an IO Exception occurs in the underlying socket logic

        final SelectionKey key = socket.getIOChannel().keyFor(socket.getPoller().getSelector());
        int read = 0;
        boolean timedout = false;
        int keycount = 1; //assume we can write
        long time = System.currentTimeMillis(); //start the timeout timer
        try {
            while ( (!timedout) && read == 0) {
                if (keycount > 0) { //only read if we were registered for a read
                    int cnt = socket.read(buf);
                    if (cnt == -1)
                        throw new EOFException();
                    read += cnt;
                    if (cnt > 0)
                        break;
                }
                KeyAttachment att = (KeyAttachment) key.attachment();
                try {
                    if ( att.getReadLatch()==null || att.getReadLatch().getCount()==0) att.startReadLatch(1);
                    if ( att.interestOps() == 0) socket.getPoller().add(socket,SelectionKey.OP_READ);
                    att.awaitReadLatch(readTimeout,TimeUnit.MILLISECONDS);
                }catch (InterruptedException ignore) {
                    Thread.interrupted();
                }
                if ( att.getReadLatch()!=null && att.getReadLatch().getCount()> 0) {
                    //we got interrupted, but we haven't received notification from the poller.
                    keycount = 0;
                }else {
                    //latch countdown has happened
                    keycount = 1;
                    att.resetReadLatch();
                }
                if (readTimeout > 0 && (keycount == 0))
                    timedout = (System.currentTimeMillis() - time) >= readTimeout;
            } //while
            if (timedout)
                throw new SocketTimeoutException();
        } finally {
            if (timedout && key != null) {
                cancelKey(socket,key);
            }
        }
        return read;
public static intwrite(java.nio.ByteBuffer buf, NioChannel socket, long writeTimeout)
Performs a blocking write using the bytebuffer for data to be written If the selector parameter is null, then it will perform a busy write that could take up a lot of CPU cycles.

param
buf ByteBuffer - the buffer containing the data, we will write as long as (buf.hasRemaining()==true)
param
socket SocketChannel - the socket to write data to
param
writeTimeout long - the timeout for this write operation in milliseconds, -1 means no timeout
return
int - returns the number of bytes written
throws
EOFException if write returns -1
throws
SocketTimeoutException if the write times out
throws
IOException if an IO Exception occurs in the underlying socket logic

        SelectionKey key = socket.getIOChannel().keyFor(socket.getPoller().getSelector());
        int written = 0;
        boolean timedout = false;
        int keycount = 1; //assume we can write
        long time = System.currentTimeMillis(); //start the timeout timer
        if (socket.getBufHandler().getWriteBuffer() != buf) {
            socket.getBufHandler().getWriteBuffer().put(buf);
            buf = socket.getBufHandler().getWriteBuffer();
        }
        try {
            while ( (!timedout) && buf.hasRemaining()) {
                if (keycount > 0) { //only write if we were registered for a write
                    int cnt = socket.write(buf); //write the data
                    if (cnt == -1)
                        throw new EOFException();
                    written += cnt;
                    if (cnt > 0) {
                        time = System.currentTimeMillis(); //reset our timeout timer
                        continue; //we successfully wrote, try again without a selector
                    }
                }
                if ( key == null ) throw new IOException("Key no longer registered");
                KeyAttachment att = (KeyAttachment) key.attachment();
                try {
                    if ( att.getWriteLatch()==null || att.getWriteLatch().getCount()==0) att.startWriteLatch(1);
                    //only register for write if a write has not yet been issued
                    if ( (att.interestOps() & SelectionKey.OP_WRITE) == 0) socket.getPoller().add(socket,SelectionKey.OP_WRITE);
                    att.awaitWriteLatch(writeTimeout,TimeUnit.MILLISECONDS);
                }catch (InterruptedException ignore) {
                    Thread.interrupted();
                }
                if ( att.getWriteLatch()!=null && att.getWriteLatch().getCount()> 0) {
                    //we got interrupted, but we haven't received notification from the poller.
                    keycount = 0;
                }else {
                    //latch countdown has happened
                    keycount = 1;
                    att.resetWriteLatch();
                }

                if (writeTimeout > 0 && (keycount == 0))
                    timedout = (System.currentTimeMillis() - time) >= writeTimeout;
            } //while
            if (timedout) 
                throw new SocketTimeoutException();
        } finally {
            if (timedout && key != null) {
                cancelKey(socket, key);
            }
        }
        return written;