io.questdb.std.LongIntHashMap Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of core Show documentation
QuestDB is High Performance Time Series Database
There is a newer version: 5.0.1
/*******************************************************************************
 *     ___                  _   ____  ____
 *    / _ \ _   _  ___  ___| |_|  _ \| __ )
 *   | | | | | | |/ _ \/ __| __| | | |  _ \
 *   | |_| | |_| |  __/\__ \ |_| |_| | |_) |
 *    \__\_\\__,_|\___||___/\__|____/|____/
 *
 *  Copyright (c) 2014-2019 Appsicle
 *  Copyright (c) 2019-2020 QuestDB
 *
 *  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 io.questdb.std;

import java.util.Arrays;


public class LongIntHashMap implements Mutable {

    private static final int MIN_INITIAL_CAPACITY = 16;
    private static final int noEntryValue = -1;
    private final double loadFactor;
    private int[] values;
    private long[] keys;
    private int free;
    private int mask;

    public LongIntHashMap() {
        this(8);
    }

    private LongIntHashMap(int initialCapacity) {
        this(initialCapacity, 0.5f);
    }

    private LongIntHashMap(int initialCapacity, double loadFactor) {
        if (loadFactor <= 0d || loadFactor >= 1d) {
            throw new IllegalArgumentException("0 < loadFactor < 1");
        }
        int capacity = Math.max(initialCapacity, (int) (initialCapacity / loadFactor));
        capacity = capacity < MIN_INITIAL_CAPACITY ? MIN_INITIAL_CAPACITY : Numbers.ceilPow2(capacity);
        this.loadFactor = loadFactor;
        values = new int[capacity];
        keys = new long[capacity];
        free = initialCapacity;
        mask = capacity - 1;
        clear();
    }

    public final void clear() {
        Arrays.fill(values, noEntryValue);
    }

    public int get(long key) {
        int index = (int) key & mask;
        if (values[index] == noEntryValue || keys[index] == key) {
            return values[index];
        }
        return probe(key, index);
    }

    public void put(long key, int value) {
        insertKey(key, value);
        if (free == 0) {
            rehash();
        }
    }

    private void insertKey(long key, int value) {
        int index = (int) key & mask;
        if (values[index] == noEntryValue) {
            Unsafe.arrayPut(keys, index, key);
            Unsafe.arrayPut(values, index, value);
            free--;
            return;
        }

        if (keys[index] == key) {
            Unsafe.arrayPut(values, index, value);
            return;
        }

        probeInsert(key, index, value);
    }

    private int probe(long key, int index) {
        do {
            index = (index + 1) & mask;
            if (values[index] == noEntryValue || keys[index] == key) {
                return values[index];
            }
        } while (true);
    }

    private void probeInsert(long key, int index, int value) {
        do {
            index = (index + 1) & mask;
            if (values[index] == noEntryValue) {
                Unsafe.arrayPut(keys, index, key);
                Unsafe.arrayPut(values, index, value);
                free--;
                return;
            }

            if (key == keys[index]) {
                Unsafe.arrayPut(values, index, value);
                return;
            }
        } while (true);
    }

    private void rehash() {
        int newCapacity = values.length << 1;
        mask = newCapacity - 1;
        free = (int) (newCapacity * loadFactor);
        int[] oldValues = values;
        long[] oldKeys = keys;
        this.keys = new long[newCapacity];
        this.values = new int[newCapacity];
        Arrays.fill(values, noEntryValue);

        for (int i = oldKeys.length; i-- > 0; ) {
            int val = oldValues[i];
            if (val != noEntryValue) {
                insertKey(oldKeys[i], val);
            }
        }
    }
}