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/*
* Copyright (C) 2007-2024 Sebastiano Vigna
*
* 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 it.unimi.dsi.fastutil.objects;
import java.util.Collection;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.function.Consumer;
/** A simple, brute-force implementation of a set based on a backing array.
*
* The main purpose of this
* implementation is that of wrapping cleanly the brute-force approach to the storage of a very
* small number of items: just put them into an array and scan linearly to find an item.
*/
public class ObjectArraySet extends AbstractObjectSet implements java.io.Serializable, Cloneable {
private static final long serialVersionUID = 1L;
/** The backing array (valid up to {@link #size}, excluded). */
protected transient Object[] a;
/** The number of valid entries in {@link #a}. */
protected int size;
/** Creates a new array set using the given backing array. The resulting set will have as many elements as the array.
*
* It is the responsibility of the caller to ensure that the elements of {@code a} are distinct.
*
* @param a the backing array.
*/
public ObjectArraySet(final Object[] a) {
this.a = a;
size = a.length;
}
/** Creates a new empty array set.
*/
public ObjectArraySet() { this.a = ObjectArrays.EMPTY_ARRAY; }
/** Creates a new empty array set of given initial capacity.
*
* @param capacity the initial capacity.
*/
public ObjectArraySet(final int capacity) { this.a = new Object[capacity]; }
/** Creates a new array set copying the contents of a given collection.
* @param c a collection.
*/
public ObjectArraySet(ObjectCollection c) {
this(c.size());
addAll(c);
}
/** Creates a new array set copying the contents of a given set.
* @param c a collection.
*/
public ObjectArraySet(final Collection c) {
this(c.size());
addAll(c);
}
/** Creates a new array set copying the contents of a given collection.
* @param c a collection.
*/
public ObjectArraySet(ObjectSet c) {
this(c.size());
int i = 0;
for(Object x : c) {
a[i] = x;
i++;
}
size = i;
}
/** Creates a new array set copying the contents of a given set.
* @param c a collection.
*/
public ObjectArraySet(final Set c) {
this(c.size());
int i = 0;
for(K x: c) {
a[i] = (x);
i++;
}
size = i;
}
/** Creates a new array set using the given backing array and the given number of elements of the array.
*
* It is the responsibility of the caller to ensure that the first {@code size} elements of {@code a} are distinct.
*
* @param a the backing array.
* @param size the number of valid elements in {@code a}.
*/
public ObjectArraySet(final Object[] a, final int size) {
this.a = a;
this.size = size;
if (size > a.length) throw new IllegalArgumentException("The provided size (" + size + ") is larger than or equal to the array size (" + a.length + ")");
}
// The 0 and 1 arg overloads allow us to skip the temporary hash set creation.
/** Creates a new empty array set.
*
* @return a new empty array set.
*/
public static ObjectArraySet of() {
return ofUnchecked();
}
/** Creates a new array set using the element given.
*
* @param e the element that the returned set will contain.
* @return a new array set containing {@code e}.
*/
public static ObjectArraySet of(final K e) {
return ofUnchecked(e);
}
/** Creates a new array set using an array of elements.
*
* Unlike the array accepting constructors, this method will throw if duplicate elements
* are encountered. This adds a non-trivial validation burden. Use {@link #ofUnchecked} if you
* know your input has no duplicates, which will skip this validation.
*
* @param a the backing array of the returned array set.
* @throws IllegalArgumentException if there were duplicate entries.
* @return a new array set containing the elements in {@code a}.
*/
@SafeVarargs
public static ObjectArraySet of(final K... a) {
if (a.length == 2) {
if (java.util.Objects.equals(a[0], a[1])) {
throw new IllegalArgumentException("Duplicate element: " + a[1]);
}
} else if (a.length > 2) {
// Will throw on a duplicate entry for us.
ObjectOpenHashSet.of(a);
}
return ofUnchecked(a);
}
/** Creates a new empty array set.
*
* @return a new empty array set.
*/
public static ObjectArraySet ofUnchecked() {
return new ObjectArraySet <>();
}
// No 1 element overload; we want the temporary array constructed for us in the varargs overload
/** Creates a new array set using an array of elements.
*
* It is the responsibility of the caller to ensure that the elements of {@code a} are distinct.
*
* @param a the backing array of the returned array set.
* @return a new array set containing the elements in {@code a}.
*/
@SafeVarargs
public static ObjectArraySet ofUnchecked(final K... a) {
return new ObjectArraySet (a);
}
private int findKey(final Object o) {
final Object[] a = this.a;
for(int i = size; i-- != 0;) if (java.util.Objects.equals(a[i], o)) return i;
return -1;
}
// TODO Maybe make this return a list-iterator like the LinkedXHashSets do?
@Override
@SuppressWarnings("unchecked")
public ObjectIterator iterator() {
return new ObjectIterator () {
int curr = -1, next = 0;
@Override
public boolean hasNext() { return next < size; }
@Override
public K next() {
if (! hasNext()) throw new NoSuchElementException();
return (K) a[curr = next++];
}
@Override
public void remove() {
if (curr == -1) throw new IllegalStateException();
curr = -1;
final int tail = size-- - next--;
System.arraycopy(a, next + 1, a, next, tail);
a[size] = null;
}
@Override
public int skip(int n) {
if (n < 0) throw new IllegalArgumentException("Argument must be nonnegative: " + n);
n = Math.min(n, size - next);
next += n;
if (n != 0) curr = next - 1;
return n;
}
@Override
public void forEachRemaining(final Consumer action) {
final Object a[] = ObjectArraySet.this.a;
while (next < size) action.accept((K) a[next++]);
}
};
}
// If you update this, you will probably want to update ArrayList as well
private final class Spliterator implements ObjectSpliterator {
// Until we split, we will track the size of the set
// Once we split, then we stop updating on structural modifications.
// Aka, size is late-binding.
boolean hasSplit = false;
int pos, max;
public Spliterator() {
this(0, ObjectArraySet.this.size, false);
}
private Spliterator(int pos, int max, boolean hasSplit) {
assert pos <= max : "pos " + pos + " must be <= max " + max;
this.pos = pos;
this.max = max;
this.hasSplit = hasSplit;
}
private int getWorkingMax() {
return hasSplit ? max : ObjectArraySet.this.size;
}
@Override
public int characteristics() { return ObjectSpliterators.SET_SPLITERATOR_CHARACTERISTICS | java.util.Spliterator.SUBSIZED | java.util.Spliterator.ORDERED; }
@Override
public long estimateSize() { return getWorkingMax() - pos; }
@SuppressWarnings("unchecked")
@Override
public boolean tryAdvance(final Consumer action) {
if (pos >= getWorkingMax()) return false;
action.accept((K) a[pos++]);
return true;
}
@SuppressWarnings("unchecked")
@Override
public void forEachRemaining(final Consumer action) {
final Object[] a = ObjectArraySet.this.a;
for (final int max = getWorkingMax(); pos < max; ++pos) {
action.accept((K) a[pos]);
}
}
@Override
public long skip(long n) {
if (n < 0) throw new IllegalArgumentException("Argument must be nonnegative: " + n);
final int max = getWorkingMax();
if (pos >= max) return 0;
final int remaining = max - pos;
if (n < remaining) {
pos = it.unimi.dsi.fastutil.SafeMath.safeLongToInt(pos + n);
return n;
}
n = remaining;
pos = max;
return n;
}
@Override
public ObjectSpliterator trySplit() {
final int max = getWorkingMax();
int retLen = (max - pos) >> 1;
if (retLen <= 1) return null;
// Update instance max with the last seen list size (if needed) before continuing
this.max = max;
int myNewPos = pos + retLen;
int retMax = myNewPos;
int oldPos = pos;
this.pos = myNewPos;
this.hasSplit = true;
return new Spliterator(oldPos, retMax, true);
}
}
/** {@inheritDoc}
*
* In addition to the usual trait of {@link java.util.Spliterator#DISTINCT DISTINCT} for
* sets, the returned spliterator will also {@linkplain java.util.Spliterator#characteristics() report}
* the trait {@link java.util.Spliterator#ORDERED ORDERED}.
*
*
The returned spliterator is late-binding; it will track structural changes
* after the current item, up until the first {@link java.util.Spliterator#trySplit() trySplit()},
* at which point the maximum index will be fixed.
*
Structural changes before the current item or after the first
* {@link java.util.Spliterator#trySplit() trySplit()} will result in unspecified behavior.
*/
@Override
public ObjectSpliterator spliterator() {
return new Spliterator();
}
@Override
public boolean contains(final Object k) { return findKey(k) != -1; }
@Override
public int size() { return size; }
@Override
public boolean remove(final Object k) {
final int pos = findKey(k);
if (pos == -1) return false;
final int tail = size - pos - 1;
for(int i = 0; i < tail; i++) a[pos + i] = a[pos + i + 1];
size--;
a[size] = null;
return true;
}
@Override
public boolean add(final K k) {
final int pos = findKey(k);
if (pos != -1) return false;
if (size == a.length) {
final Object[] b = new Object[size == 0 ? 2 : size * 2];
for(int i = size; i-- != 0;) b[i] = a[i];
a = b;
}
a[size++] = k;
return true;
}
@Override
public void clear() {
java.util.Arrays.fill(a, 0, size, null);
size = 0;
}
@Override
public boolean isEmpty() { return size == 0; }
@Override
public Object[] toArray() {
final int size = size();
// A subtle part of the spec says the returned array must be Object[] exactly.
if (size == 0) return it.unimi.dsi.fastutil.objects.ObjectArrays.EMPTY_ARRAY;
return java.util.Arrays.copyOf(a, size, Object[].class);
}
@SuppressWarnings("unchecked")
@Override
public T[] toArray(T[] a) {
if (a == null) {
a = (T[]) new Object[size];
} else if (a.length < size) {
a = (T[]) java.lang.reflect.Array.newInstance(a.getClass().getComponentType(), size);
}
System.arraycopy(this.a, 0, a, 0, size);
if (a.length > size) {
a[size] = null;
}
return a;
}
/** Returns a deep copy of this set.
*
* This method performs a deep copy of this array set; the data stored in the
* set, however, is not cloned. Note that this makes a difference only for object keys.
*
* @return a deep copy of this set.
*/
@Override
@SuppressWarnings("unchecked")
public ObjectArraySet clone() {
ObjectArraySet c;
try {
c = (ObjectArraySet )super.clone();
}
catch(CloneNotSupportedException cantHappen) {
throw new InternalError();
}
c.a = a.clone();
return c;
}
private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {
s.defaultWriteObject();
final Object[] a = this.a;
for(int i = 0; i < size; i++) s.writeObject(a[i]);
}
private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException {
s.defaultReadObject();
final Object[] a = this.a = new Object[size];
for(int i = 0; i < size; i++) a[i] = s.readObject();
}
}