/*

 * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.

 * Copyright (c) 2019, Red Hat Inc. 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.internal.misc;

/**

 * A class used to expose details of the underlying hardware that

 * configure the operation of class Unsafe.  This class is

 * package-private as the only intended client is class Unsafe.

 * All fields in this class must be static final constants.

 *

 * @since 13

 *

 * @implNote

 *

 * The JVM injects hardware-specific values into all the static fields

 * of this class during JVM initialization. The static initialization

 * block is executed when the class is initialized then JVM injection

 * updates the fields with the correct constants. The static block

 * is required to prevent the fields from being considered constant

 * variables, so the field values will be not be compiled directly into

 * any class that uses them.

 */

final class UnsafeConstants {

    /**

     * This constructor is private because the class is not meant to

     * be instantiated.

     */

    private UnsafeConstants() {}

    /**

     * The size in bytes of a native pointer, as stored via {@link

     * #putAddress}.  This value will be either 4 or 8.  Note that the

     * sizes of other primitive types (as stored in native memory

     * blocks) is determined fully by their information content.

     *

     * @implNote

     * The actual value for this field is injected by the JVM.

     */

    static final int ADDRESS_SIZE0;

    /**

     * The size in bytes of a native memory page (whatever that is).

     * This value will always be a power of two.

     *

     * @implNote

     * The actual value for this field is injected by the JVM.

     */

    static final int PAGE_SIZE;

    /**

     * Flag whose value is true if and only if the native endianness

     * of this platform is big.

     *

     * @implNote

     * The actual value for this field is injected by the JVM.

     */

    static final boolean BIG_ENDIAN;

    /**

     * Flag whose value is true if and only if the platform can

     * perform unaligned accesses

     *

     * @implNote

     * The actual value for this field is injected by the JVM.

     */

    static final boolean UNALIGNED_ACCESS;

    /**

     * The size of an L1 data cache line which will be either a power

     * of two or zero.

     *

     * <p>A non-zero value indicates that writeback to memory is

     * enabled for the current processor. The value defines the

     * natural alignment and size of any data cache line committed to

     * memory by a single writeback operation. If data cache line

     * writeback is not enabled for the current hardware the field

     * will have value 0.

     *

     * @implNote

     * The actual value for this field is injected by the JVM.

     */

    static final int DATA_CACHE_LINE_FLUSH_SIZE;

    static {

        ADDRESS_SIZE0 = 0;

        PAGE_SIZE = 0;

        BIG_ENDIAN = false;

        UNALIGNED_ACCESS = false;

        DATA_CACHE_LINE_FLUSH_SIZE = 0;

    }

}