/*
 * Copyright (c) 2002-2016, the original author or authors.
 *
 * This software is distributable under the BSD license. See the terms of the
 * BSD license in the documentation provided with this software.
 *
 * http://www.opensource.org/licenses/bsd-license.php
 */
package jdk.internal.org.jline.utils;

import java.lang.reflect.Proxy;
import java.util.Objects;

Signals helpers.
Author:Guillaume Nodet
Since:3.0
/** * Signals helpers. * * @author <a href="mailto:gnodet@gmail.com">Guillaume Nodet</a> * @since 3.0 */
public final class Signals { private Signals() { }
Params:
  • name – the signal, CONT, STOP, etc...
  • handler – the callback to run
Returns:an object that needs to be passed to the unregister(String, Object) method to unregister the handler
/** * * @param name the signal, CONT, STOP, etc... * @param handler the callback to run * * @return an object that needs to be passed to the {@link #unregister(String, Object)} * method to unregister the handler */
public static Object register(String name, Runnable handler) { Objects.requireNonNull(handler); return register(name, handler, handler.getClass().getClassLoader()); } public static Object register(String name, final Runnable handler, ClassLoader loader) { try { Class<?> signalHandlerClass = Class.forName("sun.misc.SignalHandler"); // Implement signal handler Object signalHandler = Proxy.newProxyInstance(loader, new Class<?>[]{signalHandlerClass}, (proxy, method, args) -> { // only method we are proxying is handle() if (method.getDeclaringClass() == Object.class) { if ("toString".equals(method.getName())) { return handler.toString(); } } else if (method.getDeclaringClass() == signalHandlerClass) { Log.trace(() -> "Calling handler " + toString(handler) + " for signal " + name); handler.run(); } return null; }); return doRegister(name, signalHandler); } catch (Exception e) { // Ignore this one too, if the above failed, the signal API is incompatible with what we're expecting Log.debug("Error registering handler for signal ", name, e); return null; } } public static Object registerDefault(String name) { try { Class<?> signalHandlerClass = Class.forName("sun.misc.SignalHandler"); return doRegister(name, signalHandlerClass.getField("SIG_DFL").get(null)); } catch (Exception e) { // Ignore this one too, if the above failed, the signal API is incompatible with what we're expecting Log.debug("Error registering default handler for signal ", name, e); return null; } } public static void unregister(String name, Object previous) { try { // We should make sure the current signal is the one we registered if (previous != null) { doRegister(name, previous); } } catch (Exception e) { // Ignore Log.debug("Error unregistering handler for signal ", name, e); } } private static Object doRegister(String name, Object handler) throws Exception { Log.trace(() -> "Registering signal " + name + " with handler " + toString(handler)); if ("QUIT".equals(name) || "INFO".equals(name) && "9".equals(System.getProperty("java.specification.version"))) { Log.trace(() -> "Ignoring unsupported signal " + name); return null; } Class<?> signalClass = Class.forName("sun.misc.Signal"); Class<?> signalHandlerClass = Class.forName("sun.misc.SignalHandler"); Object signal = signalClass.getConstructor(String.class).newInstance(name); return signalClass.getMethod("handle", signalClass, signalHandlerClass) .invoke(null, signal, handler); } @SuppressWarnings("") private static String toString(Object handler) { try { Class<?> signalHandlerClass = Class.forName("sun.misc.SignalHandler"); if (handler == signalHandlerClass.getField("SIG_DFL").get(null)) { return "SIG_DFL"; } if (handler == signalHandlerClass.getField("SIG_IGN").get(null)) { return "SIG_IGN"; } } catch (Throwable t) { // ignore } return handler != null ? handler.toString() : "null"; } }