/*

 * Copyright (c) 2016, 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 sun.hotspot.gc;

import java.util.ArrayList;

import java.util.List;

import sun.hotspot.WhiteBox;

/**

 * API to obtain information about selected and supported Garbage Collectors

 * retrieved from the VM with the WhiteBox API.

 */

public enum GC {

    Serial(1),

    Parallel(2),

    ConcMarkSweep(4),

    G1(8);

    private static final GC CURRENT_GC;

    private static final int ALL_GC_CODES;

    private static final boolean IS_BY_ERGO;

    static {

        WhiteBox WB = WhiteBox.getWhiteBox();

        ALL_GC_CODES = WB.allSupportedGC();

        IS_BY_ERGO = WB.gcSelectedByErgo();

        int currentCode = WB.currentGC();

        GC tmp = null;

        for (GC gc: GC.values()) {

            if (gc.code == currentCode) {

                tmp = gc;

                break;

            }

        }

        if (tmp == null) {

            throw new Error("Unknown current GC code " + currentCode);

        }

        CURRENT_GC = tmp;

    }

    private final int code;

    private GC(int code) {

        this.code = code;

    }

    /**

     * @return true if the collector is supported by the VM, false otherwise.

     */

    public boolean isSupported() {

        return (ALL_GC_CODES & code) != 0;

    }

    /**

     * @return the current collector used by VM.

     */

    public static GC current() {

        return CURRENT_GC;

    }

    /**

     * @return true if GC was selected by ergonomic, false if specified

     * explicitly by the command line flag.

     */

    public static boolean currentSetByErgo() {

        return IS_BY_ERGO;

    }

    /**

     * @return List of collectors supported by the VM.

     */

    public static List<GC> allSupported() {

        List<GC> list = new ArrayList<>();

        for (GC gc: GC.values()) {

            if (gc.isSupported()) {

                list.add(gc);

            }

        }

        return list;

    }

}