/*

 * Copyright (c) 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.

 *

 * 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.jvm.hotspot.gc.z;

import sun.jvm.hotspot.debugger.Address;

import sun.jvm.hotspot.runtime.VM;

import sun.jvm.hotspot.runtime.VMObject;

import sun.jvm.hotspot.types.AddressField;

import sun.jvm.hotspot.types.CIntegerField;

import sun.jvm.hotspot.types.Type;

import sun.jvm.hotspot.types.TypeDataBase;

public class ZForwardingTable extends VMObject {

    private static AddressField tableField;

    private static CIntegerField sizeField;

    static {

        VM.registerVMInitializedObserver((o, d) -> initialize(VM.getVM().getTypeDataBase()));

    }

    static private synchronized void initialize(TypeDataBase db) {

        Type type = db.lookupType("ZForwardingTable");

        tableField = type.getAddressField("_table");

        sizeField = type.getCIntegerField("_size");

    }

    public ZForwardingTable(Address addr) {

        super(addr);

    }

    Address table() {

        return tableField.getAddress(addr);

    }

    long size() {

        return sizeField.getJLong(addr);

    }

    ZForwardingTableEntry at(ZForwardingTableCursor cursor) {

        return new ZForwardingTableEntry(table().getAddressAt(cursor._value * VM.getVM().getBytesPerLong()));

    }

    ZForwardingTableEntry first(long from_index, ZForwardingTableCursor cursor) {

        long mask = size() - 1;

        long hash = ZHash.uint32_to_uint32(from_index);

        cursor._value = hash & mask;

        return at(cursor);

    }

    ZForwardingTableEntry next(ZForwardingTableCursor cursor) {

        long mask = size() - 1;

        cursor._value = (cursor._value + 1) & mask;

        return at(cursor);

    }

    ZForwardingTableEntry find(long from_index, ZForwardingTableCursor cursor) {

        // Reading entries in the table races with the atomic cas done for

        // insertion into the table. This is safe because each entry is at

        // most updated once (from -1 to something else).

        ZForwardingTableEntry entry = first(from_index, cursor);

        while (!entry.is_empty()) {

            if (entry.from_index() == from_index) {

                // Match found, return matching entry

                return entry;

            }

            entry = next(cursor);

        }

        // Match not found, return empty entry

        return entry;

    }

    ZForwardingTableEntry find(long from_index) {

        ZForwardingTableCursor dummy = new ZForwardingTableCursor();

        return find(from_index, dummy);

    }

    void dump() {

        long s = size();

        long count = 0;

        System.out.println("Dumping ZForwardingTable[" + s + "]:");

        ZForwardingTableCursor cursor = new ZForwardingTableCursor();

        for (long i = 0; i < s; i++) {

            cursor._value = i;

            ZForwardingTableEntry entry = at(cursor);

            if (!entry.is_empty()) {

                long hash = ZHash.uint32_to_uint32(entry.from_index());

                System.out.println(i + " " + count + " " + entry + " hash: " + hash + " masked_hash: " + (hash & (s - 1)));

                count++;

            }

        }

    }

}