package ch.qos.logback.core.util;

import ch.qos.logback.core.Context;
import ch.qos.logback.core.spi.ContextAwareBase;

/**
 * Allows masking of interrupt flag if previously the flag is already set. Does
 * nothing otherwise.
 * 
 * Typical use:
 * 
 * <pre>
 * InterruptUtil interruptUtil = new InterruptUtil(context);
 * 
 * try {
 *     interruptUtil.maskInterruptFlag();
 *     someOtherThread.join(delay);
 * } catch (InterruptedException e) {
 *     // reachable only if join does not succeed within delay.
 *     // Without the maskInterruptFlag() call, the join() would have returned
 *     // immediately
 *     // had the current thread been interrupted previously, i.e. before entering
 *     // the above block
 * } finally {
 *     interruptUtil.unmaskInterruptFlag();
 * }
 * </pre>
 * 
 * @author Ceki Gulcu
 * @since 1.2.2
 */
public class InterruptUtil extends ContextAwareBase {

    final boolean previouslyInterrupted;

    public InterruptUtil(Context context) {
        super();
        setContext(context);
        previouslyInterrupted = Thread.currentThread().isInterrupted();
    }

    public void maskInterruptFlag() {
        if (previouslyInterrupted) {
            Thread.interrupted();
        }
    }

    public void unmaskInterruptFlag() {
        if (previouslyInterrupted) {
            try {
                Thread.currentThread().interrupt();
            } catch (SecurityException se) {
                addError("Failed to interrupt current thread", se);
            }
        }
    }

}
