/*
 * Copyright (c) 2008-2017, Hazelcast, Inc. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.hazelcast.internal.util.hashslot.impl;

import com.hazelcast.internal.memory.MemoryManager;
import com.hazelcast.internal.util.hashslot.HashSlotArray12byteKey;
import com.hazelcast.internal.util.hashslot.HashSlotArray8byteKey;
import com.hazelcast.internal.util.hashslot.HashSlotCursor12byteKey;

import static com.hazelcast.nio.Bits.INT_SIZE_IN_BYTES;
import static com.hazelcast.util.HashUtil.fastIntMix;
import static com.hazelcast.util.HashUtil.fastLongMix;
import static com.hazelcast.util.QuickMath.modPowerOfTwo;

/**
 * Implementation of {@link HashSlotArray8byteKey} as a restriction of {@link HashSlotArrayBase}
 * to a case where just {@code key1} is used.
 * <p>
 * This class uses the first 4 bytes of the value block for the unassigned sentinel.
 * <strong>It is the responsibility of the caller to ensure that the unassigned sentinel
 * is overwritten with a non-sentinel value as soon as a new slot is assigned (after calling
 * {@link #ensure(long, int)} and getting a positive return value).</strong>
 * For the same reason this class must not be instantiated with zero value length. Use
 * {@link HashSlotArray8byteKeyNoValue} as a zero-length key implementation.
 */
public final class HashSlotArray12byteKeyImpl extends HashSlotArrayBase implements HashSlotArray12byteKey {

    private static final int KEY_SIZE = 12;

    public HashSlotArray12byteKeyImpl(int unassignedSentinel, MemoryManager mm, int valueLength,
                                      int initialCapacity, float loadFactor) {
        this(unassignedSentinel, KEY_SIZE, mm, valueLength, initialCapacity, loadFactor);
        assert valueLength > 0 : "Attempted to instantiate HashSlotArrayImpl with zero value length";
    }

    public HashSlotArray12byteKeyImpl(int unassignedSentinel, MemoryManager mm, int valueLength) {
        this(unassignedSentinel, mm, valueLength, CapacityUtil.DEFAULT_CAPACITY, CapacityUtil.DEFAULT_LOAD_FACTOR);
        assert valueLength > 0 : "Attempted to instantiate HashSlotArrayImpl with zero value length";
    }

    private HashSlotArray12byteKeyImpl(int unassignedSentinel, long offsetOfUnassignedSentinel, MemoryManager mm,
                                       int valueLength, int initialCapacity, float loadFactor
    ) {
        super(unassignedSentinel, offsetOfUnassignedSentinel, mm, null, KEY_SIZE, valueLength,
                initialCapacity, loadFactor);
        assert valueLength >= INT_SIZE_IN_BYTES
                && modPowerOfTwo(valueLength - INT_SIZE_IN_BYTES, VALUE_SIZE_GRANULARITY) == 0
                : "Value length must be 4 plus a positive multiple of 8, but was " + valueLength;
    }

    /**
     * {@inheritDoc}
     *
     * Whenever this method returns a positive value, the caller must ensure that the null-sentinel value
     * at the returned address is overwritten with a non-sentinel value.
     */
    @Override public long ensure(long key1, int key2) {
        return super.ensure0(key1, key2);
    }

    @Override public long get(long key1, int key2) {
        return super.get0(key1, key2);
    }

    @Override public boolean remove(long key1, int key2) {
        return super.remove0(key1, key2);
    }

    @Override public HashSlotCursor12byteKey cursor() {
        return new CursorIntKey2();
    }

    @Override protected long key2OfSlot(long baseAddress, long slot) {
        return mem().getInt(slotBase(baseAddress, slot) + KEY_2_OFFSET);
    }

    @Override protected void putKey(long baseAddress, long slot, long key1, long key2) {
        mem().putLong(slotBase(baseAddress, slot) + KEY_1_OFFSET, key1);
        mem().putInt(slotBase(baseAddress, slot) + KEY_2_OFFSET, (int) key2);
    }

    @Override
    protected void markUnassigned(long baseAddress, long slot) {
        mem().putInt(slotBase(baseAddress, slot) + offsetOfUnassignedSentinel, (int) unassignedSentinel);
    }

    @Override
    protected boolean isAssigned(long baseAddress, long slot) {
        return mem().getInt(slotBase(baseAddress, slot) + offsetOfUnassignedSentinel) != unassignedSentinel;
    }

    @Override protected long keyHash(long key1, long key2) {
        return fastLongMix(key1 + fastIntMix((int) key2));
    }
}