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/*
* Copyright (c) 2016-present, RxJava Contributors.
*
* 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.
*/
/*
* Inspired by fastutils' OpenHashSet implementation at
* https://github.com/vigna/fastutil/blob/master/drv/OpenHashSet.drv
*/
package io.reactivex.rxjava3.internal.util;
/**
* A simple open hash set with add, remove and clear capabilities only.
* Doesn't support nor checks for {@code null}s.
*
* @param the element type
*/
public final class OpenHashSet {
private static final int INT_PHI = 0x9E3779B9;
final float loadFactor;
int mask;
int size;
int maxSize;
T[] keys;
public OpenHashSet() {
this(16, 0.75f);
}
/**
* Creates an OpenHashSet with the initial capacity and load factor of 0.75f.
* @param capacity the initial capacity
*/
public OpenHashSet(int capacity) {
this(capacity, 0.75f);
}
@SuppressWarnings("unchecked")
public OpenHashSet(int capacity, float loadFactor) {
this.loadFactor = loadFactor;
int c = Pow2.roundToPowerOfTwo(capacity);
this.mask = c - 1;
this.maxSize = (int)(loadFactor * c);
this.keys = (T[])new Object[c];
}
public boolean add(T value) {
final T[] a = keys;
final int m = mask;
int pos = mix(value.hashCode()) & m;
T curr = a[pos];
if (curr != null) {
if (curr.equals(value)) {
return false;
}
for (;;) {
pos = (pos + 1) & m;
curr = a[pos];
if (curr == null) {
break;
}
if (curr.equals(value)) {
return false;
}
}
}
a[pos] = value;
if (++size >= maxSize) {
rehash();
}
return true;
}
public boolean remove(T value) {
T[] a = keys;
int m = mask;
int pos = mix(value.hashCode()) & m;
T curr = a[pos];
if (curr == null) {
return false;
}
if (curr.equals(value)) {
return removeEntry(pos, a, m);
}
for (;;) {
pos = (pos + 1) & m;
curr = a[pos];
if (curr == null) {
return false;
}
if (curr.equals(value)) {
return removeEntry(pos, a, m);
}
}
}
boolean removeEntry(int pos, T[] a, int m) {
size--;
int last;
int slot;
T curr;
for (;;) {
last = pos;
pos = (pos + 1) & m;
for (;;) {
curr = a[pos];
if (curr == null) {
a[last] = null;
return true;
}
slot = mix(curr.hashCode()) & m;
if (last <= pos ? last >= slot || slot > pos : last >= slot && slot > pos) {
break;
}
pos = (pos + 1) & m;
}
a[last] = curr;
}
}
@SuppressWarnings("unchecked")
void rehash() {
T[] a = keys;
int i = a.length;
int newCap = i << 1;
int m = newCap - 1;
T[] b = (T[])new Object[newCap];
for (int j = size; j-- != 0; ) {
while (a[--i] == null) { } // NOPMD
int pos = mix(a[i].hashCode()) & m;
if (b[pos] != null) {
for (;;) {
pos = (pos + 1) & m;
if (b[pos] == null) {
break;
}
}
}
b[pos] = a[i];
}
this.mask = m;
this.maxSize = (int)(newCap * loadFactor);
this.keys = b;
}
static int mix(int x) {
final int h = x * INT_PHI;
return h ^ (h >>> 16);
}
public Object[] keys() {
return keys; // NOPMD
}
public int size() {
return size;
}
}