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| 1 | +/* | |
| 2 | + * Copyright (c) 1998, 2007, Oracle and/or its affiliates. All rights reserved. | |
| 3 | + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | |
| 4 | + * | |
| 5 | + * This code is free software; you can redistribute it and/or modify it | |
| 6 | + * under the terms of the GNU General Public License version 2 only, as | |
| 7 | + * published by the Free Software Foundation. Oracle designates this | |
| 8 | + * particular file as subject to the "Classpath" exception as provided | |
| 9 | + * by Oracle in the LICENSE file that accompanied this code. | |
| 10 | + * | |
| 11 | + * This code is distributed in the hope that it will be useful, but WITHOUT | |
| 12 | + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
| 13 | + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
| 14 | + * version 2 for more details (a copy is included in the LICENSE file that | |
| 15 | + * accompanied this code). | |
| 16 | + * | |
| 17 | + * You should have received a copy of the GNU General Public License version | |
| 18 | + * 2 along with this work; if not, write to the Free Software Foundation, | |
| 19 | + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | |
| 20 | + * | |
| 21 | + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | |
| 22 | + * or visit www.oracle.com if you need additional information or have any | |
| 23 | + * questions. | |
| 24 | + */ | |
| 25 | + | |
| 26 | +package sun.misc; | |
| 27 | +import java.util.Hashtable; | |
| 28 | + | |
| 29 | +/** | |
| 30 | + * This class provides ANSI/ISO C signal support. A Java program can register | |
| 31 | + * signal handlers for the current process. There are two restrictions: | |
| 32 | + * <ul> | |
| 33 | + * <li> | |
| 34 | + * Java code cannot register a handler for signals that are already used | |
| 35 | + * by the Java VM implementation. The <code>Signal.handle</code> | |
| 36 | + * function raises an <code>IllegalArgumentException</code> if such an attempt | |
| 37 | + * is made. | |
| 38 | + * <li> | |
| 39 | + * When <code>Signal.handle</code> is called, the VM internally registers a | |
| 40 | + * special C signal handler. There is no way to force the Java signal handler | |
| 41 | + * to run synchronously before the C signal handler returns. Instead, when the | |
| 42 | + * VM receives a signal, the special C signal handler creates a new thread | |
| 43 | + * (at priority <code>Thread.MAX_PRIORITY</code>) to | |
| 44 | + * run the registered Java signal handler. The C signal handler immediately | |
| 45 | + * returns. Note that because the Java signal handler runs in a newly created | |
| 46 | + * thread, it may not actually be executed until some time after the C signal | |
| 47 | + * handler returns. | |
| 48 | + * </ul> | |
| 49 | + * <p> | |
| 50 | + * Signal objects are created based on their names. For example: | |
| 51 | + * <blockquote><pre> | |
| 52 | + * new Signal("INT"); | |
| 53 | + * </blockquote></pre> | |
| 54 | + * constructs a signal object corresponding to <code>SIGINT</code>, which is | |
| 55 | + * typically produced when the user presses <code>Ctrl-C</code> at the command line. | |
| 56 | + * The <code>Signal</code> constructor throws <code>IllegalArgumentException</code> | |
| 57 | + * when it is passed an unknown signal. | |
| 58 | + * <p> | |
| 59 | + * This is an example of how Java code handles <code>SIGINT</code>: | |
| 60 | + * <blockquote><pre> | |
| 61 | + * SignalHandler handler = new SignalHandler () { | |
| 62 | + * public void handle(Signal sig) { | |
| 63 | + * ... // handle SIGINT | |
| 64 | + * } | |
| 65 | + * }; | |
| 66 | + * Signal.handle(new Signal("INT"), handler); | |
| 67 | + * </blockquote></pre> | |
| 68 | + * | |
| 69 | + * @author Sheng Liang | |
| 70 | + * @author Bill Shannon | |
| 71 | + * @see sun.misc.SignalHandler | |
| 72 | + * @since 1.2 | |
| 73 | + */ | |
| 74 | +public final class Signal { | |
| 75 | + private static Hashtable handlers = new Hashtable(4); | |
| 76 | + private static Hashtable signals = new Hashtable(4); | |
| 77 | + | |
| 78 | + private int number; | |
| 79 | + private String name; | |
| 80 | + | |
| 81 | + /* Returns the signal number */ | |
| 82 | + public int getNumber() { | |
| 83 | + return number; | |
| 84 | + } | |
| 85 | + | |
| 86 | + /** | |
| 87 | + * Returns the signal name. | |
| 88 | + * | |
| 89 | + * @return the name of the signal. | |
| 90 | + * @see sun.misc.Signal#Signal(String name) | |
| 91 | + */ | |
| 92 | + public String getName() { | |
| 93 | + return name; | |
| 94 | + } | |
| 95 | + | |
| 96 | + /** | |
| 97 | + * Compares the equality of two <code>Signal</code> objects. | |
| 98 | + * | |
| 99 | + * @param other the object to compare with. | |
| 100 | + * @return whether two <code>Signal</code> objects are equal. | |
| 101 | + */ | |
| 102 | + public boolean equals(Object other) { | |
| 103 | + if (this == other) { | |
| 104 | + return true; | |
| 105 | + } | |
| 106 | + if (other == null || !(other instanceof Signal)) { | |
| 107 | + return false; | |
| 108 | + } | |
| 109 | + Signal other1 = (Signal)other; | |
| 110 | + return name.equals(other1.name) && (number == other1.number); | |
| 111 | + } | |
| 112 | + | |
| 113 | + /** | |
| 114 | + * Returns a hashcode for this Signal. | |
| 115 | + * | |
| 116 | + * @return a hash code value for this object. | |
| 117 | + */ | |
| 118 | + public int hashCode() { | |
| 119 | + return number; | |
| 120 | + } | |
| 121 | + | |
| 122 | + /** | |
| 123 | + * Returns a string representation of this signal. For example, "SIGINT" | |
| 124 | + * for an object constructed using <code>new Signal ("INT")</code>. | |
| 125 | + * | |
| 126 | + * @return a string representation of the signal | |
| 127 | + */ | |
| 128 | + public String toString() { | |
| 129 | + return "SIG" + name; | |
| 130 | + } | |
| 131 | + | |
| 132 | + /** | |
| 133 | + * Constructs a signal from its name. | |
| 134 | + * | |
| 135 | + * @param name the name of the signal. | |
| 136 | + * @exception IllegalArgumentException unknown signal | |
| 137 | + * @see sun.misc.Signal#getName() | |
| 138 | + */ | |
| 139 | + public Signal(String name) { | |
| 140 | + number = findSignal(name); | |
| 141 | + this.name = name; | |
| 142 | + if (number < 0) { | |
| 143 | + throw new IllegalArgumentException("Unknown signal: " + name); | |
| 144 | + } | |
| 145 | + } | |
| 146 | + | |
| 147 | + /** | |
| 148 | + * Registers a signal handler. | |
| 149 | + * | |
| 150 | + * @param sig a signal | |
| 151 | + * @param handler the handler to be registered with the given signal. | |
| 152 | + * @result the old handler | |
| 153 | + * @exception IllegalArgumentException the signal is in use by the VM | |
| 154 | + * @see sun.misc.Signal#raise(Signal sig) | |
| 155 | + * @see sun.misc.SignalHandler | |
| 156 | + * @see sun.misc.SignalHandler#SIG_DFL | |
| 157 | + * @see sun.misc.SignalHandler#SIG_IGN | |
| 158 | + */ | |
| 159 | + public static synchronized SignalHandler handle(Signal sig, | |
| 160 | + SignalHandler handler) | |
| 161 | + throws IllegalArgumentException { | |
| 162 | + long newH = (handler instanceof NativeSignalHandler) ? | |
| 163 | + ((NativeSignalHandler)handler).getHandler() : 2; | |
| 164 | + long oldH = handle0(sig.number, newH); | |
| 165 | + if (oldH == -1) { | |
| 166 | + throw new IllegalArgumentException | |
| 167 | + ("Signal already used by VM or OS: " + sig); | |
| 168 | + } | |
| 169 | + signals.put(new Integer(sig.number), sig); | |
| 170 | + synchronized (handlers) { | |
| 171 | + SignalHandler oldHandler = (SignalHandler)handlers.get(sig); | |
| 172 | + handlers.remove(sig); | |
| 173 | + if (newH == 2) { | |
| 174 | + handlers.put(sig, handler); | |
| 175 | + } | |
| 176 | + if (oldH == 0) { | |
| 177 | + return SignalHandler.SIG_DFL; | |
| 178 | + } else if (oldH == 1) { | |
| 179 | + return SignalHandler.SIG_IGN; | |
| 180 | + } else if (oldH == 2) { | |
| 181 | + return oldHandler; | |
| 182 | + } else { | |
| 183 | + return new NativeSignalHandler(oldH); | |
| 184 | + } | |
| 185 | + } | |
| 186 | + } | |
| 187 | + | |
| 188 | + /** | |
| 189 | + * Raises a signal in the current process. | |
| 190 | + * | |
| 191 | + * @param sig a signal | |
| 192 | + * @see sun.misc.Signal#handle(Signal sig, SignalHandler handler) | |
| 193 | + */ | |
| 194 | + public static void raise(Signal sig) throws IllegalArgumentException { | |
| 195 | + if (handlers.get(sig) == null) { | |
| 196 | + throw new IllegalArgumentException("Unhandled signal: " + sig); | |
| 197 | + } | |
| 198 | + raise0(sig.number); | |
| 199 | + } | |
| 200 | + | |
| 201 | + /* Called by the VM to execute Java signal handlers. */ | |
| 202 | + private static void dispatch(final int number) { | |
| 203 | + final Signal sig = (Signal)signals.get(new Integer(number)); | |
| 204 | + final SignalHandler handler = (SignalHandler)handlers.get(sig); | |
| 205 | + | |
| 206 | + Runnable runnable = new Runnable () { | |
| 207 | + public void run() { | |
| 208 | + // Don't bother to reset the priority. Signal handler will | |
| 209 | + // run at maximum priority inherited from the VM signal | |
| 210 | + // dispatch thread. | |
| 211 | + // Thread.currentThread().setPriority(Thread.NORM_PRIORITY); | |
| 212 | + handler.handle(sig); | |
| 213 | + } | |
| 214 | + }; | |
| 215 | + if (handler != null) { | |
| 216 | + new Thread(runnable, sig + " handler").start(); | |
| 217 | + } | |
| 218 | + } | |
| 219 | + | |
| 220 | + /* Find the signal number, given a name. Returns -1 for unknown signals. */ | |
| 221 | + private static native int findSignal(String sigName); | |
| 222 | + /* Registers a native signal handler, and returns the old handler. | |
| 223 | + * Handler values: | |
| 224 | + * 0 default handler | |
| 225 | + * 1 ignore the signal | |
| 226 | + * 2 call back to Signal.dispatch | |
| 227 | + * other arbitrary native signal handlers | |
| 228 | + */ | |
| 229 | + private static native long handle0(int sig, long nativeH); | |
| 230 | + /* Raise a given signal number */ | |
| 231 | + private static native void raise0(int sig); | |
| 232 | +} | |