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jaredpar/SelectorWrapper.java

Forked from anonymous/SelectorWrapper.java
Created February 14, 2014 21:29
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Revisions

  1. @invalid-email-address Anonymous created this gist Feb 14, 2014.
    98 changes: 98 additions & 0 deletions SelectorWrapper.java
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,98 @@
    package com.koushikdutta.async;

    import java.io.IOException;
    import java.nio.channels.SelectionKey;
    import java.nio.channels.Selector;
    import java.util.Set;
    import java.util.concurrent.Semaphore;
    import java.util.concurrent.TimeUnit;

    /**
    * Created by koush on 2/13/14.
    */
    public class SelectorWrapper {
    private Selector selector;
    boolean isWaking;
    Semaphore semaphore = new Semaphore(0);
    public Selector getSelector() {
    return selector;
    }

    public SelectorWrapper(Selector selector) {
    this.selector = selector;
    }

    public int selectNow() throws IOException {
    return selector.selectNow();
    }

    public void select() throws IOException {
    select(0);
    }

    public void select(long timeout) throws IOException {
    try {
    semaphore.drainPermits();
    selector.select(timeout);
    }
    finally {
    semaphore.release(Integer.MAX_VALUE);
    }
    }

    public Set<SelectionKey> keys() {
    return selector.keys();
    }

    public Set<SelectionKey> selectedKeys() {
    return selector.selectedKeys();
    }

    public void close() throws IOException {
    selector.close();
    }

    public boolean isOpen() {
    return selector.isOpen();
    }

    public void wakeupOnce() {
    // see if it is selecting, ie, can't acquire a permit
    boolean selecting = !semaphore.tryAcquire();
    selector.wakeup();
    // if it was selecting, then the wakeup definitely worked.
    if (selecting)
    return;

    // now, we NEED to wait for the select to start to forcibly wake it.
    synchronized (this) {
    // check if another thread is already waiting
    if (isWaking) {
    // System.out.println("race wakeup already progressing");
    return;
    }
    isWaking = true;
    }

    try {
    // System.out.println("performing race wakup");
    // try to wake up 10 times
    for (int i = 0; i < 100; i++) {
    try {
    if (semaphore.tryAcquire(10, TimeUnit.MILLISECONDS)) {
    // System.out.println("race wakeup success");
    return;
    }
    }
    catch (InterruptedException e) {
    }
    selector.wakeup();
    }
    }
    finally {
    synchronized (this) {
    isWaking = false;
    }
    }
    }
    }