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

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 *
 *  Copyright (c) 2014-2019 Appsicle
 *  Copyright (c) 2019-2023 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.
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package io.questdb.std;

public class LowerCaseCharSequenceHashSet extends AbstractLowerCaseCharSequenceHashSet {

    private static final int MIN_INITIAL_CAPACITY = 16;

    public LowerCaseCharSequenceHashSet() {
        this(MIN_INITIAL_CAPACITY);
    }

    private LowerCaseCharSequenceHashSet(int initialCapacity) {
        this(initialCapacity, 0.4);
    }

    private LowerCaseCharSequenceHashSet(int initialCapacity, double loadFactor) {
        super(initialCapacity, loadFactor);
        clear();
    }

    /**
     * Adds key to hash set preserving key uniqueness.
     *
     * @param key immutable sequence of characters.
     * @return false if key is already in the set and true otherwise.
     */
    public boolean add(CharSequence key) {
        int index = keyIndex(key);
        if (index < 0) {
            return false;
        }

        addAt(index, key);
        return true;
    }

    public void addAt(int index, CharSequence key) {
        keys[index] = key;
        if (--free < 1) {
            rehash();
        }
    }

    public boolean contains(CharSequence key) {
        return keyIndex(key) < 0;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        LowerCaseCharSequenceHashSet that = (LowerCaseCharSequenceHashSet) o;
        if (size() != that.size()) {
            return false;
        }
        for (CharSequence key : keys) {
            if (key != null && that.excludes(key)) {
                return false;
            }
        }
        return true;
    }

    @Override
    public int hashCode() {
        int hashCode = 0;
        for (int i = 0, n = keys.length; i < n; i++) {
            if (keys[i] != noEntryKey) {
                hashCode += Chars.hashCode(keys[i]);
            }
        }
        return hashCode;
    }

    public CharSequence keyAt(int index) {
        return keys[-index - 1];
    }

    private void rehash() {
        int newCapacity = capacity * 2;
        final int size = size();
        free = capacity = newCapacity;
        int len = Numbers.ceilPow2((int) (newCapacity / loadFactor));
        CharSequence[] newKeys = new CharSequence[len];
        CharSequence[] oldKeys = keys;
        mask = len - 1;
        this.keys = newKeys;
        free -= size;
        for (int i = 0, n = oldKeys.length; i < n; i++) {
            CharSequence key = oldKeys[i];
            if (key != null) {
                keys[keyIndex(key)] = key;
            }
        }
    }

    @Override
    protected void erase(int index) {
        keys[index] = noEntryKey;
    }

    @Override
    protected void move(int from, int to) {
        keys[to] = keys[from];
        erase(from);
    }
}