rx.internal.util.OpenHashSet Maven / Gradle / Ivy
/**
* Copyright 2014 Netflix, Inc.
*
* 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.
*
* Modified from http://www.javacodegeeks.com/2013/08/simple-and-lightweight-pool-implementation.html
*/
package rx.internal.util;
import java.util.Arrays;
import rx.functions.Action1;
import rx.internal.util.unsafe.Pow2;
/*
* Inspired by fastutils' OpenHashSet implementation at
* https://github.com/vigna/fastutil/blob/master/drv/OpenHashSet.drv
*/
/**
* 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 {
final float loadFactor;
int mask;
int size;
int maxSize;
T[] keys;
private static final int INT_PHI = 0x9E3779B9;
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;
}
}
public void clear(Action1 clearAction) {
if (size == 0) {
return;
}
T[] a = keys;
int len = a.length;
for (int i = 0; i < len; i++) {
T e = a[i];
if (e != null) {
clearAction.call(e);
}
}
Arrays.fill(a, null);
size = 0;
}
@SuppressWarnings("unchecked")
public void terminate() {
size = 0;
keys = (T[])new Object[0];
}
@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 boolean isEmpty() {
return size == 0;
}
/**
* Returns the raw array of values of this set, watch out for null entires.
* @return the raw array of values of this set
*/
public T[] values() {
return keys; // NOPMD
}
}