src/jdk.jfr/share/classes/jdk/jfr/internal/handlers/EventHandler.java

/*
 * Copyright (c) 2016, 2018, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package jdk.jfr.internal.handlers;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;

import jdk.jfr.EventType;
import jdk.jfr.internal.EventControl;
import jdk.jfr.internal.JVM;
import jdk.jfr.internal.PlatformEventType;
import jdk.jfr.internal.PrivateAccess;
import jdk.jfr.internal.StringPool;

// Users should not be subclass for security reasons.
public abstract class EventHandler {
    // Accessed by generated sub class
    protected final PlatformEventType platformEventType;

    private final EventType eventType;
    private final EventControl eventControl;

    // Accessed by generated sub class
    EventHandler(boolean registered, EventType eventType, EventControl eventControl) {
        this.eventType = eventType;
        this.platformEventType = PrivateAccess.getInstance().getPlatformEventType(eventType);
        this.eventControl = eventControl;
        platformEventType.setRegistered(registered);
    }

    final protected StringPool createStringFieldWriter() {
        return new StringPool();
    }

    // Accessed by generated code in event class
    public final boolean shouldCommit(long duration) {
        return isEnabled() && duration >= platformEventType.getThresholdTicks();
    }

    // Accessed by generated code in event class
    // Accessed by generated sub class
    public final boolean isEnabled() {
        return platformEventType.isCommitable();
    }

    public final EventType getEventType() {
        return eventType;
    }

    public final PlatformEventType getPlatformEventType() {
        return platformEventType;
    }

    public final EventControl getEventControl() {
        return eventControl;
    }

    public static long timestamp() {
        return JVM.counterTime();
    }

    public static long duration(long startTime) {
        if (startTime == 0) {
            // User forgot to invoke begin, or instrumentation was
            // added after the user invoked begin.
            // Returning 0 will make it an instant event
            return 0;
        }
        return timestamp() - startTime;
    }

    // Prevent a malicious user from instantiating a generated event handlers.
    @Override
    public final Object clone() throws java.lang.CloneNotSupportedException {
        throw new CloneNotSupportedException();
    }

    private final void writeObject(ObjectOutputStream out) throws IOException {
        throw new IOException("Object cannot be serialized");
    }

    private final void readObject(ObjectInputStream in) throws IOException {
        throw new IOException("Class cannot be deserialized");
    }

    public boolean isRegistered() {
        return platformEventType.isRegistered();
    }

    public boolean setRegistered(boolean registered) {
       return platformEventType.setRegistered(registered);
    }
}