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With inspiration from other libraries
/*
* Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
* Use of this file is governed by the BSD 3-clause license that
* can be found in the LICENSE.txt file in the project root.
*/
package org.antlr.v4.runtime.misc;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Set;
/** {@link Set} implementation with closed hashing (open addressing). */
public class Array2DHashSet implements Set {
public static final int INITAL_CAPACITY = 16; // must be power of 2
public static final int INITAL_BUCKET_CAPACITY = 8;
public static final double LOAD_FACTOR = 0.75;
protected final AbstractEqualityComparator comparator;
protected T[][] buckets;
/** How many elements in set */
protected int n = 0;
protected int threshold = (int)Math.floor(INITAL_CAPACITY * LOAD_FACTOR); // when to expand
protected int currentPrime = 1; // jump by 4 primes each expand or whatever
protected int initialBucketCapacity = INITAL_BUCKET_CAPACITY;
public Array2DHashSet() {
this(null, INITAL_CAPACITY, INITAL_BUCKET_CAPACITY);
}
public Array2DHashSet(AbstractEqualityComparator comparator) {
this(comparator, INITAL_CAPACITY, INITAL_BUCKET_CAPACITY);
}
public Array2DHashSet(AbstractEqualityComparator comparator, int initialCapacity, int initialBucketCapacity) {
if (comparator == null) {
comparator = ObjectEqualityComparator.INSTANCE;
}
this.comparator = comparator;
this.buckets = createBuckets(initialCapacity);
this.initialBucketCapacity = initialBucketCapacity;
}
/**
* Add {@code o} to set if not there; return existing value if already
* there. This method performs the same operation as {@link #add} aside from
* the return value.
*/
public final T getOrAdd(T o) {
if ( n > threshold ) expand();
return getOrAddImpl(o);
}
protected T getOrAddImpl(T o) {
int b = getBucket(o);
T[] bucket = buckets[b];
// NEW BUCKET
if ( bucket==null ) {
bucket = createBucket(initialBucketCapacity);
bucket[0] = o;
buckets[b] = bucket;
n++;
return o;
}
// LOOK FOR IT IN BUCKET
for (int i=0; i other = (Array2DHashSet)o;
if ( other.size() != size() ) return false;
boolean same = this.containsAll(other);
return same;
}
protected void expand() {
T[][] old = buckets;
currentPrime += 4;
int newCapacity = buckets.length * 2;
T[][] newTable = createBuckets(newCapacity);
int[] newBucketLengths = new int[newTable.length];
buckets = newTable;
threshold = (int)(newCapacity * LOAD_FACTOR);
// System.out.println("new size="+newCapacity+", thres="+threshold);
// rehash all existing entries
int oldSize = size();
for (T[] bucket : old) {
if ( bucket==null ) {
continue;
}
for (T o : bucket) {
if ( o==null ) {
break;
}
int b = getBucket(o);
int bucketLength = newBucketLengths[b];
T[] newBucket;
if (bucketLength == 0) {
// new bucket
newBucket = createBucket(initialBucketCapacity);
newTable[b] = newBucket;
}
else {
newBucket = newTable[b];
if (bucketLength == newBucket.length) {
// expand
newBucket = Arrays.copyOf(newBucket, newBucket.length * 2);
newTable[b] = newBucket;
}
}
newBucket[bucketLength] = o;
newBucketLengths[b]++;
}
}
assert n == oldSize;
}
@Override
public final boolean add(T t) {
T existing = getOrAdd(t);
return existing==t;
}
@Override
public final int size() {
return n;
}
@Override
public final boolean isEmpty() {
return n==0;
}
@Override
public final boolean contains(Object o) {
return containsFast(asElementType(o));
}
public boolean containsFast(T obj) {
if (obj == null) {
return false;
}
return get(obj) != null;
}
@Override
public Iterator iterator() {
return new SetIterator(toArray());
}
@Override
public T[] toArray() {
T[] a = createBucket(size());
int i = 0;
for (T[] bucket : buckets) {
if ( bucket==null ) {
continue;
}
for (T o : bucket) {
if ( o==null ) {
break;
}
a[i++] = o;
}
}
return a;
}
@Override
public U[] toArray(U[] a) {
if (a.length < size()) {
a = Arrays.copyOf(a, size());
}
int i = 0;
for (T[] bucket : buckets) {
if ( bucket==null ) {
continue;
}
for (T o : bucket) {
if ( o==null ) {
break;
}
@SuppressWarnings("unchecked") // array store will check this
U targetElement = (U)o;
a[i++] = targetElement;
}
}
return a;
}
@Override
public final boolean remove(Object o) {
return removeFast(asElementType(o));
}
public boolean removeFast(T obj) {
if (obj == null) {
return false;
}
int b = getBucket(obj);
T[] bucket = buckets[b];
if ( bucket==null ) {
// no bucket
return false;
}
for (int i=0; i collection) {
if ( collection instanceof Array2DHashSet ) {
Array2DHashSet s = (Array2DHashSet)collection;
for (Object[] bucket : s.buckets) {
if ( bucket==null ) continue;
for (Object o : bucket) {
if ( o==null ) break;
if ( !this.containsFast(asElementType(o)) ) return false;
}
}
}
else {
for (Object o : collection) {
if ( !this.containsFast(asElementType(o)) ) return false;
}
}
return true;
}
@Override
public boolean addAll(Collection c) {
boolean changed = false;
for (T o : c) {
T existing = getOrAdd(o);
if ( existing!=o ) changed=true;
}
return changed;
}
@Override
public boolean retainAll(Collection c) {
int newsize = 0;
for (T[] bucket : buckets) {
if (bucket == null) {
continue;
}
int i;
int j;
for (i = 0, j = 0; i < bucket.length; i++) {
if (bucket[i] == null) {
break;
}
if (!c.contains(bucket[i])) {
// removed
continue;
}
// keep
if (i != j) {
bucket[j] = bucket[i];
}
j++;
newsize++;
}
newsize += j;
while (j < i) {
bucket[j] = null;
j++;
}
}
boolean changed = newsize != n;
n = newsize;
return changed;
}
@Override
public boolean removeAll(Collection c) {
boolean changed = false;
for (Object o : c) {
changed |= removeFast(asElementType(o));
}
return changed;
}
@Override
public void clear() {
buckets = createBuckets(INITAL_CAPACITY);
n = 0;
threshold = (int)Math.floor(INITAL_CAPACITY * LOAD_FACTOR);
}
@Override
public String toString() {
if ( size()==0 ) return "{}";
StringBuilder buf = new StringBuilder();
buf.append('{');
boolean first = true;
for (T[] bucket : buckets) {
if ( bucket==null ) continue;
for (T o : bucket) {
if ( o==null ) break;
if ( first ) first=false;
else buf.append(", ");
buf.append(o.toString());
}
}
buf.append('}');
return buf.toString();
}
public String toTableString() {
StringBuilder buf = new StringBuilder();
for (T[] bucket : buckets) {
if ( bucket==null ) {
buf.append("null\n");
continue;
}
buf.append('[');
boolean first = true;
for (T o : bucket) {
if ( first ) first=false;
else buf.append(" ");
if ( o==null ) buf.append("_");
else buf.append(o.toString());
}
buf.append("]\n");
}
return buf.toString();
}
/**
* Return {@code o} as an instance of the element type {@code T}. If
* {@code o} is non-null but known to not be an instance of {@code T}, this
* method returns {@code null}. The base implementation does not perform any
* type checks; override this method to provide strong type checks for the
* {@link #contains} and {@link #remove} methods to ensure the arguments to
* the {@link EqualityComparator} for the set always have the expected
* types.
*
* @param o the object to try and cast to the element type of the set
* @return {@code o} if it could be an instance of {@code T}, otherwise
* {@code null}.
*/
@SuppressWarnings("unchecked")
protected T asElementType(Object o) {
return (T)o;
}
/**
* Return an array of {@code T[]} with length {@code capacity}.
*
* @param capacity the length of the array to return
* @return the newly constructed array
*/
@SuppressWarnings("unchecked")
protected T[][] createBuckets(int capacity) {
return (T[][])new Object[capacity][];
}
/**
* Return an array of {@code T} with length {@code capacity}.
*
* @param capacity the length of the array to return
* @return the newly constructed array
*/
@SuppressWarnings("unchecked")
protected T[] createBucket(int capacity) {
return (T[])new Object[capacity];
}
protected class SetIterator implements Iterator {
final T[] data;
int nextIndex = 0;
boolean removed = true;
public SetIterator(T[] data) {
this.data = data;
}
@Override
public boolean hasNext() {
return nextIndex < data.length;
}
@Override
public T next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
removed = false;
return data[nextIndex++];
}
@Override
public void remove() {
if (removed) {
throw new IllegalStateException();
}
Array2DHashSet.this.remove(data[nextIndex - 1]);
removed = true;
}
}
}