/*

 * Copyright (c) 2012, 2019, 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.

 *

 * 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 org.graalvm.compiler.serviceprovider;

import java.lang.reflect.Field;

import sun.misc.Unsafe;

/**

 * Access to the {@link Unsafe} capability. Care must be taken not to leak the {@link #UNSAFE} value

 * of out code loaded by the JVMCI class loader or encapsulated in the JVMCI or Graal modules into

 * other code (e.g. via the Polyglot API).

 */

public class GraalUnsafeAccess {

    private static final Unsafe UNSAFE = initUnsafe();

    private static Unsafe initUnsafe() {

        try {

            // Fast path when we are trusted.

            return Unsafe.getUnsafe();

        } catch (SecurityException se) {

            // Slow path when we are not trusted.

            try {

                Field theUnsafe = Unsafe.class.getDeclaredField("theUnsafe");

                theUnsafe.setAccessible(true);

                return (Unsafe) theUnsafe.get(Unsafe.class);

            } catch (Exception e) {

                throw new RuntimeException("exception while trying to get Unsafe", e);

            }

        }

    }

    /**

     * Gets the {@link Unsafe} singleton.

     *

     * @throws SecurityException if a security manager is present and it denies

     *             {@link RuntimePermission}("accessUnsafe")

     */

    public static Unsafe getUnsafe() {

        SecurityManager sm = System.getSecurityManager();

        if (sm != null) {

            sm.checkPermission(new RuntimePermission("accessUnsafe"));

        }

        return UNSAFE;

    }

}