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	/*
	* 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
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/
	package jdk.jfr.internal;

	import java.io.IOException;

	/**
	* Checks if the running VM supports Flight Recorder.
	*
	* Purpose of this helper class is to detect early and cleanly if the VM has
	* support for Flight Recorder, i.e. not throw {@link UnsatisfiedLinkError} in
	* unexpected places.
	* <p>
	* This is needed so a disabled-jfr.jar can be built for non Oracle JDKs.
	*/
	public final class JVMSupport {

	private static final String UNSUPPORTED_VM_MESSAGE = "Flight Recorder is not supported on this VM";
	private static final boolean notAvailable = !checkAvailability();

	private static boolean checkAvailability() {
	// set jfr.unsupported.vm to true to test API on an unsupported VM
	try {
	if (SecuritySupport.getBooleanProperty("jfr.unsupported.vm")) {
	return false;
	}
	} catch (NoClassDefFoundError cnfe) {
	return false;
	}
	try {
	// Will typically throw UnsatisfiedLinkError if
	// there is no native implementation
	JVM.getJVM().isAvailable();
	return true;
	} catch (Throwable t) {
	return false;
	}
	}

	public static void ensureWithInternalError() {
	if (notAvailable) {
	throw new InternalError(UNSUPPORTED_VM_MESSAGE);
	}
	}

	public static void ensureWithIOException() throws IOException {
	if (notAvailable) {
	throw new IOException(UNSUPPORTED_VM_MESSAGE);
	}
	}

	public static void ensureWithIllegalStateException() {
	if (notAvailable) {
	throw new IllegalStateException(UNSUPPORTED_VM_MESSAGE);
	}
	}

	public static boolean isNotAvailable() {
	return notAvailable;
	}

	public static void tryToInitializeJVM() {
	}
	}

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