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/*******************************************************************************
* ___ _ ____ ____
* / _ \ _ _ ___ ___| |_| _ \| __ )
* | | | | | | |/ _ \/ __| __| | | | _ \
* | |_| | |_| | __/\__ \ |_| |_| | |_) |
* \__\_\\__,_|\___||___/\__|____/|____/
*
* 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 org.jetbrains.annotations.NotNull;
import java.util.AbstractSet;
import java.util.Arrays;
import java.util.Iterator;
public class ObjHashSet extends AbstractSet implements Mutable {
private static final int MIN_INITIAL_CAPACITY = 16;
private static final Object noEntryKey = new Object();
private final double loadFactor;
private final ObjList list;
private T[] keys;
private int free;
private int capacity;
private int mask;
public ObjHashSet() {
this(MIN_INITIAL_CAPACITY);
}
public ObjHashSet(int initialCapacity) {
this(initialCapacity, 0.4f, 0.3f);
}
@SuppressWarnings("unchecked")
private ObjHashSet(int initialCapacity, double loadFactor, double hashFactor) {
if (loadFactor <= 0d || loadFactor >= 1d) {
throw new IllegalArgumentException("0 < loadFactor < 1");
}
if (hashFactor <= 0d || hashFactor >= 1d) {
throw new IllegalArgumentException("0 < hashFactor < 1");
}
initialCapacity = (int) (initialCapacity * (1 + hashFactor));
int capacity = Math.max(initialCapacity, (int) (initialCapacity / loadFactor));
this.loadFactor = loadFactor;
keys = (T[]) new Object[capacity < MIN_INITIAL_CAPACITY ? MIN_INITIAL_CAPACITY : Numbers.ceilPow2(capacity)];
mask = keys.length - 1;
free = this.capacity = initialCapacity;
this.list = new ObjList<>(free);
clear();
}
public void addAll(ObjHashSet that) {
for (int i = 0, n = that.size(); i < n; i++) {
this.add(that.get(i));
}
}
public boolean addAt(int index, T key) {
if (addAt0(index, key)) {
list.add(key);
return true;
}
return false;
}
public T get(int index) {
return list.getQuick(index);
}
@Override
@NotNull
public Iterator iterator() {
throw new UnsupportedOperationException();
}
public int size() {
return capacity - free;
}
@SuppressWarnings("unchecked")
@Override
public boolean contains(Object o) {
return keyIndex((T) o) < 0;
}
public boolean add(T key) {
return addAt(keyIndex(key), key);
}
public int keyIndex(T key) {
int index = idx(key);
T kv = keys[index];
if (kv == noEntryKey) {
return index;
}
if (kv == key || key.equals(kv)) {
return -index - 1;
}
return probe(key, index);
}
@Override
@SuppressWarnings("unchecked")
public boolean remove(Object key) {
int keyIndex = keyIndex((T) key);
if (keyIndex < 0) {
list.remove(keys[-keyIndex - 1]);
removeAt(keyIndex);
return true;
}
return false;
}
public final void clear() {
free = capacity;
Arrays.fill(keys, noEntryKey);
list.clear();
}
@Override
public String toString() {
return list.toString();
}
private boolean addAt0(int index, T key) {
if (index > -1) {
keys[index] = key;
if (--free == 0) {
rehash();
}
return true;
}
return false;
}
private void erase(int index) {
((Object[]) keys)[index] = noEntryKey;
}
private int idx(T key) {
return key == null ? 0 : (Hash.spread(key.hashCode()) & mask);
}
private void move(int from, int to) {
keys[to] = keys[from];
erase(from);
}
private int probe(T key, int index) {
do {
index = (index + 1) & mask;
final T kv = keys[index];
if (kv == noEntryKey) {
return index;
}
if (kv == key || key.equals(kv)) {
return -index - 1;
}
} while (true);
}
@SuppressWarnings({"unchecked"})
private void rehash() {
int newCapacity = keys.length << 1;
mask = newCapacity - 1;
free = capacity = (int) (newCapacity * loadFactor);
T[] oldKeys = keys;
this.keys = (T[]) new Object[newCapacity];
Arrays.fill(keys, noEntryKey);
for (int i = oldKeys.length; i-- > 0; ) {
T key = oldKeys[i];
if (key != noEntryKey) {
addAt0(keyIndex(key), key);
}
}
}
private void removeAt(int index) {
if (index < 0) {
int from = -index - 1;
erase(from);
free++;
// after we have freed up a slot
// consider non-empty keys directly below
// they may have been a direct hit but because
// directly hit slot wasn't empty these keys would
// have moved.
//
// After slot if freed these keys require re-hash
from = (from + 1) & mask;
for (
T key = keys[from];
key != noEntryKey;
from = (from + 1) & mask, key = keys[from]
) {
int idealHit = Hash.spread(key.hashCode()) & mask;
if (idealHit != from) {
int to;
if (keys[idealHit] != noEntryKey) {
to = probe(key, idealHit);
} else {
to = idealHit;
}
if (to > -1) {
move(from, to);
}
}
}
}
}
}