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/*
* Copyright (C) 2002-2022 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 it.unimi.dsi.fastutil.Hash;
import it.unimi.dsi.fastutil.HashCommon;
import static it.unimi.dsi.fastutil.HashCommon.arraySize;
import static it.unimi.dsi.fastutil.HashCommon.maxFill;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.function.Consumer;
import java.util.stream.Collector;
/** A type-specific hash set with with a fast, small-footprint implementation.
*
* Instances of this class use a hash table to represent a set. The table is
* filled up to a specified load factor, and then doubled in size to
* accommodate new entries. If the table is emptied below one fourth
* of the load factor, it is halved in size; however, the table is never reduced to a
* size smaller than that at creation time: this approach makes it
* possible to create sets with a large capacity in which insertions and
* deletions do not cause immediately rehashing. Moreover, halving is
* not performed when deleting entries from an iterator, as it would interfere
* with the iteration process.
*
*
Note that {@link #clear()} does not modify the hash table size.
* Rather, a family of {@linkplain #trim() trimming
* methods} lets you control the size of the table; this is particularly useful
* if you reuse instances of this class.
*
* @see Hash
* @see HashCommon
*/
public class ObjectOpenHashSet extends AbstractObjectSet implements java.io.Serializable, Cloneable, Hash {
private static final long serialVersionUID = 0L;
private static final boolean ASSERTS = false;
/** The array of keys. */
protected transient K[] key;
/** The mask for wrapping a position counter. */
protected transient int mask;
/** Whether this set contains the null key. */
protected transient boolean containsNull;
/** The current table size. Note that an additional element is allocated for storing the null key. */
protected transient int n;
/** Threshold after which we rehash. It must be the table size times {@link #f}. */
protected transient int maxFill;
/** We never resize below this threshold, which is the construction-time {#n}. */
protected final transient int minN;
/** Number of entries in the set (including the null key, if present). */
protected int size;
/** The acceptable load factor. */
protected final float f;
/** Creates a new hash set.
*
* The actual table size will be the least power of two greater than {@code expected}/{@code f}.
*
* @param expected the expected number of elements in the hash set.
* @param f the load factor.
*/
@SuppressWarnings("unchecked")
public ObjectOpenHashSet(final int expected, final float f) {
if (f <= 0 || f >= 1) throw new IllegalArgumentException("Load factor must be greater than 0 and smaller than 1");
if (expected < 0) throw new IllegalArgumentException("The expected number of elements must be nonnegative");
this.f = f;
minN = n = arraySize(expected, f);
mask = n - 1;
maxFill = maxFill(n, f);
key = (K[]) new Object[n + 1];
}
/** Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor.
*
* @param expected the expected number of elements in the hash set.
*/
public ObjectOpenHashSet(final int expected) {
this(expected, DEFAULT_LOAD_FACTOR);
}
/** Creates a new hash set with initial expected {@link Hash#DEFAULT_INITIAL_SIZE} elements
* and {@link Hash#DEFAULT_LOAD_FACTOR} as load factor.
*/
public ObjectOpenHashSet() {
this(DEFAULT_INITIAL_SIZE, DEFAULT_LOAD_FACTOR);
}
/** Creates a new hash set copying a given collection.
*
* @param c a {@link Collection} to be copied into the new hash set.
* @param f the load factor.
*/
public ObjectOpenHashSet(final Collection c, final float f) {
this(c.size(), f);
addAll(c);
}
/** Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor
* copying a given collection.
*
* @param c a {@link Collection} to be copied into the new hash set.
*/
public ObjectOpenHashSet(final Collection c) {
this(c, DEFAULT_LOAD_FACTOR);
}
/** Creates a new hash set copying a given type-specific collection.
*
* @param c a type-specific collection to be copied into the new hash set.
* @param f the load factor.
*/
public ObjectOpenHashSet(final ObjectCollection c, final float f) {
this(c.size(), f);
addAll(c);
}
/** Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor
* copying a given type-specific collection.
*
* @param c a type-specific collection to be copied into the new hash set.
*/
public ObjectOpenHashSet(final ObjectCollection c) {
this(c, DEFAULT_LOAD_FACTOR);
}
/** Creates a new hash set using elements provided by a type-specific iterator.
*
* @param i a type-specific iterator whose elements will fill the set.
* @param f the load factor.
*/
public ObjectOpenHashSet(final Iterator i, final float f) {
this(DEFAULT_INITIAL_SIZE, f);
while(i.hasNext()) add(i.next());
}
/** Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor using elements provided by a type-specific iterator.
*
* @param i a type-specific iterator whose elements will fill the set.
*/
public ObjectOpenHashSet(final Iterator i) {
this(i, DEFAULT_LOAD_FACTOR);
}
/** Creates a new hash set and fills it with the elements of a given array.
*
* @param a an array whose elements will be used to fill the set.
* @param offset the first element to use.
* @param length the number of elements to use.
* @param f the load factor.
*/
public ObjectOpenHashSet(final K[] a, final int offset, final int length, final float f) {
this(length < 0 ? 0 : length, f);
ObjectArrays.ensureOffsetLength(a, offset, length);
for(int i = 0; i < length; i++) add(a[offset + i]);
}
/** Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor and fills it with the elements of a given array.
*
* @param a an array whose elements will be used to fill the set.
* @param offset the first element to use.
* @param length the number of elements to use.
*/
public ObjectOpenHashSet(final K[] a, final int offset, final int length) {
this(a, offset, length, DEFAULT_LOAD_FACTOR);
}
/** Creates a new hash set copying the elements of an array.
*
* @param a an array to be copied into the new hash set.
* @param f the load factor.
*/
public ObjectOpenHashSet(final K[] a, final float f) {
this(a, 0, a.length, f);
}
/** Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor
* copying the elements of an array.
*
* @param a an array to be copied into the new hash set.
*/
public ObjectOpenHashSet(final K[] a) {
this(a, DEFAULT_LOAD_FACTOR);
}
/** Creates a new empty hash set.
*
* @return a new empty hash set.
*/
public static ObjectOpenHashSet of() {
return new ObjectOpenHashSet <>();
}
/** Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor
* using the given element.
*
* @param e the element that the returned set will contain.
* @return a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor containing {@code e}.
*/
public static ObjectOpenHashSet of(final K e) {
ObjectOpenHashSet result = new ObjectOpenHashSet <>(1, DEFAULT_LOAD_FACTOR);
result.add(e);
return result;
}
/** Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor
* using the elements given.
*
* @param e0 the first element.
* @param e1 the second element.
* @return a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor containing {@code e0} and {@code e1}.
* @throws IllegalArgumentException if there were duplicate entries.
*/
public static ObjectOpenHashSet of(final K e0, final K e1) {
ObjectOpenHashSet result = new ObjectOpenHashSet <>(2, DEFAULT_LOAD_FACTOR);
result.add(e0);
if (!result.add(e1)) {
throw new IllegalArgumentException("Duplicate element: " + e1);
}
return result;
}
/** Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor
* using the elements given.
*
* @param e0 the first element.
* @param e1 the second element.
* @param e2 the third element.
* @return a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor containing {@code e0}, {@code e1}, and {@code e2}.
* @throws IllegalArgumentException if there were duplicate entries.
*/
public static ObjectOpenHashSet of(final K e0, final K e1, final K e2) {
ObjectOpenHashSet result = new ObjectOpenHashSet <>(3, DEFAULT_LOAD_FACTOR);
result.add(e0);
if (!result.add(e1)) {
throw new IllegalArgumentException("Duplicate element: " + e1);
}
if (!result.add(e2)) {
throw new IllegalArgumentException("Duplicate element: " + e2);
}
return result;
}
/** Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor
* using a list of elements.
*
* @param a a list of elements that will be used to initialize the new hash set.
* @return a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor containing the elements of {@code a}.
* @throws IllegalArgumentException if a duplicate entry was encountered.
*/
@SafeVarargs
public static ObjectOpenHashSet of(final K... a) {
ObjectOpenHashSet result = new ObjectOpenHashSet <>(a.length, DEFAULT_LOAD_FACTOR);
for (K element : a) {
if (!result.add(element)) {
throw new IllegalArgumentException("Duplicate element " + element);
}
}
return result;
}
// Collector wants a function that returns the collection being added to.
private ObjectOpenHashSet combine(ObjectOpenHashSet toAddFrom) {
addAll(toAddFrom);
return this;
}
private static final Collector> TO_SET_COLLECTOR =
Collector.of(
ObjectOpenHashSet::new,
ObjectOpenHashSet::add,
ObjectOpenHashSet::combine
, Collector.Characteristics.UNORDERED
);
/** Returns a {@link Collector} that collects a {@code Stream}'s elements into a new hash set. */
@SuppressWarnings({"unchecked","rawtypes"})
public static Collector > toSet() {
return (Collector) TO_SET_COLLECTOR;
}
/** Returns a {@link Collector} that collects a {@code Stream}'s elements into a new hash set, potentially pre-allocated to handle the given size. */
public static Collector > toSetWithExpectedSize(int expectedSize) {
if (expectedSize <= Hash.DEFAULT_INITIAL_SIZE) {
// Already below default capacity. Just use all default construction instead of fiddling with atomics in SizeDecreasingSupplier
return toSet();
}
return Collector.of(
new ObjectCollections.SizeDecreasingSupplier<
K,
ObjectOpenHashSet >(
expectedSize, (int size) ->
size <= Hash.DEFAULT_INITIAL_SIZE ? new ObjectOpenHashSet () : new ObjectOpenHashSet (size)),
ObjectOpenHashSet::add,
ObjectOpenHashSet::combine
, Collector.Characteristics.UNORDERED
);
}
private int realSize() {
return containsNull ? size - 1 : size;
}
/** Ensures that this set can hold a certain number of elements without rehashing.
*
* @param capacity a number of elements; there will be no rehashing unless
* the set {@linkplain #size() size} exceeds this number.
*/
public void ensureCapacity(final int capacity) {
final int needed = arraySize(capacity, f);
if (needed > n) rehash(needed);
}
private void tryCapacity(final long capacity) {
final int needed = (int)Math.min(1 << 30, Math.max(2, HashCommon.nextPowerOfTwo((long)Math.ceil(capacity / f))));
if (needed > n) rehash(needed);
}
@Override
public boolean addAll(Collection c) {
// The resulting collection will be at least c.size() big
if (f <= .5) ensureCapacity(c.size()); // The resulting collection will be sized for c.size() elements
else tryCapacity(size() + c.size()); // The resulting collection will be tentatively sized for size() + c.size() elements
return super.addAll(c);
}
@Override
public boolean add(final K k) {
int pos;
if (( (k) == null )) {
if (containsNull) return false;
containsNull = true;
}
else {
K curr;
final K[] key = this.key;
// The starting point.
if (! ( (curr = key[pos = ( it.unimi.dsi.fastutil.HashCommon.mix( (k).hashCode() ) ) & mask]) == null )) {
if (( (curr).equals(k) )) return false;
while(! ( (curr = key[pos = (pos + 1) & mask]) == null ))
if (( (curr).equals(k) )) return false;
}
key[pos] = k;
}
if (size++ >= maxFill) rehash(arraySize(size + 1, f));
if (ASSERTS) checkTable();
return true;
}
/** Add a random element if not present, get the existing value if already present.
*
* This is equivalent to (but faster than) doing a:
*
* K exist = set.get(k);
* if (exist == null) {
* set.add(k);
* exist = k;
* }
*
*/
public K addOrGet(final K k) {
int pos;
if (( (k) == null )) {
if (containsNull) return key [n];
containsNull = true;
}
else {
K curr;
final K[] key = this.key;
// The starting point.
if (! ( (curr = key[pos = ( it.unimi.dsi.fastutil.HashCommon.mix( (k).hashCode() ) ) & mask]) == null )) {
if (( (curr).equals(k) )) return curr;
while(! ( (curr = key[pos = (pos + 1) & mask]) == null ))
if (( (curr).equals(k) )) return curr;
}
key[pos] = k;
}
if (size++ >= maxFill) rehash(arraySize(size + 1, f));
if (ASSERTS) checkTable();
return k;
}
/** Shifts left entries with the specified hash code, starting at the specified position,
* and empties the resulting free entry.
*
* @param pos a starting position.
*/
protected final void shiftKeys(int pos) {
// Shift entries with the same hash.
int last, slot;
K curr;
final K[] key = this.key;
for(;;) {
pos = ((last = pos) + 1) & mask;
for(;;) {
if (( (curr = key[pos]) == null )) {
key[last] = (null);
return;
}
slot = ( it.unimi.dsi.fastutil.HashCommon.mix( (curr).hashCode() ) ) & mask;
if (last <= pos ? last >= slot || slot > pos : last >= slot && slot > pos) break;
pos = (pos + 1) & mask;
}
key[last] = curr;
}
}
private boolean removeEntry(final int pos) {
size--;
shiftKeys(pos);
if (n > minN && size < maxFill / 4 && n > DEFAULT_INITIAL_SIZE) rehash(n / 2);
return true;
}
private boolean removeNullEntry() {
containsNull = false;
key[n] = (null);
size--;
if (n > minN && size < maxFill / 4 && n > DEFAULT_INITIAL_SIZE) rehash(n / 2);
return true;
}
@SuppressWarnings("unchecked")
@Override
public boolean remove(final Object k) {
if (( ((K) k) == null )) {
if (containsNull) return removeNullEntry();
return false;
}
K curr;
final K[] key = this.key;
int pos;
// The starting point.
if (( (curr = key[pos = ( it.unimi.dsi.fastutil.HashCommon.mix( (k).hashCode() ) ) & mask]) == null )) return false;
if (( (k).equals(curr) )) return removeEntry(pos);
while(true) {
if (( (curr = key[pos = (pos + 1) & mask]) == null )) return false;
if (( (k).equals(curr) )) return removeEntry(pos);
}
}
@SuppressWarnings("unchecked")
@Override
public boolean contains(final Object k) {
if (( ((K) k) == null )) return containsNull;
K curr;
final K[] key = this.key;
int pos;
// The starting point.
if (( (curr = key[pos = ( it.unimi.dsi.fastutil.HashCommon.mix( (k).hashCode() ) ) & mask]) == null )) return false;
if (( (k).equals(curr) )) return true;
while(true) {
if (( (curr = key[pos = (pos + 1) & mask]) == null )) return false;
if (( (k).equals(curr) )) return true;
}
}
/** Returns the element of this set that is equal to the given key, or {@code null}.
* @return the element of this set that is equal to the given key, or {@code null}.
*/
@SuppressWarnings("unchecked")
public K get(final Object k) {
if (( ((K) k) == null )) return key[n]; // This is correct independently of the value of containsNull and of the set being custom
K curr;
final K[] key = this.key;
int pos;
// The starting point.
if (( (curr = key[pos = ( it.unimi.dsi.fastutil.HashCommon.mix( (k).hashCode() ) ) & mask]) == null )) return null;
if (( (k).equals(curr) )) return curr;
// There's always an unused entry.
while(true) {
if (( (curr = key[pos = (pos + 1) & mask]) == null )) return null;
if (( (k).equals(curr) )) return curr;
}
}
/* Removes all elements from this set.
*
* To increase object reuse, this method does not change the table size.
* If you want to reduce the table size, you must use {@link #trim()}.
*
*/
@Override
public void clear() {
if (size == 0) return;
size = 0;
containsNull = false;
Arrays.fill(key, (null));
}
@Override
public int size() {
return size;
}
@Override
public boolean isEmpty() {
return size == 0;
}
/** An iterator over a hash set. */
private final class SetIterator implements ObjectIterator {
/** The index of the last entry returned, if positive or zero; initially, {@link #n}. If negative, the last
element returned was that of index {@code - pos - 1} from the {@link #wrapped} list. */
int pos = n;
/** The index of the last entry that has been returned (more precisely, the value of {@link #pos} if {@link #pos} is positive,
or {@link Integer#MIN_VALUE} if {@link #pos} is negative). It is -1 if either
we did not return an entry yet, or the last returned entry has been removed. */
int last = -1;
/** A downward counter measuring how many entries must still be returned. */
int c = size;
/** A boolean telling us whether we should return the null key. */
boolean mustReturnNull = ObjectOpenHashSet.this.containsNull;
/** A lazily allocated list containing elements that have wrapped around the table because of removals. */
ObjectArrayList wrapped;
@Override
public boolean hasNext() {
return c != 0;
}
@Override
public K next() {
if (! hasNext()) throw new NoSuchElementException();
c--;
if (mustReturnNull) {
mustReturnNull = false;
last = n;
return key[n];
}
final K key[] = ObjectOpenHashSet.this.key;
for(;;) {
if (--pos < 0) {
// We are just enumerating elements from the wrapped list.
last = Integer.MIN_VALUE;
return wrapped.get(- pos - 1);
}
if (! ( (key[pos]) == null )) return key[last = pos];
}
}
/** Shifts left entries with the specified hash code, starting at the specified position,
* and empties the resulting free entry.
*
* @param pos a starting position.
*/
private final void shiftKeys(int pos) {
// Shift entries with the same hash.
int last, slot;
K curr;
final K[] key = ObjectOpenHashSet.this.key;
for(;;) {
pos = ((last = pos) + 1) & mask;
for(;;) {
if (( (curr = key[pos]) == null )) {
key[last] = (null);
return;
}
slot = ( it.unimi.dsi.fastutil.HashCommon.mix( (curr).hashCode() ) ) & mask;
if (last <= pos ? last >= slot || slot > pos : last >= slot && slot > pos) break;
pos = (pos + 1) & mask;
}
if (pos < last) { // Wrapped entry.
if (wrapped == null) wrapped = new ObjectArrayList <>(2);
wrapped.add(key[pos]);
}
key[last] = curr;
}
}
@Override
public void remove() {
if (last == -1) throw new IllegalStateException();
if (last == n) {
ObjectOpenHashSet.this.containsNull = false;
ObjectOpenHashSet.this.key[n] = (null);
}
else if (pos >= 0) shiftKeys(last);
else {
// We're removing wrapped entries.
ObjectOpenHashSet.this.remove(wrapped.set(- pos - 1, null));
last = -1; // Note that we must not decrement size
return;
}
size--;
last = -1; // You can no longer remove this entry.
if (ASSERTS) checkTable();
}
@Override
public void forEachRemaining(final Consumer action) {
final K key[] = ObjectOpenHashSet.this.key;
if (mustReturnNull) {
mustReturnNull = false;
last = n;
action.accept(key[n]);
c--;
}
while(c != 0) {
if (--pos < 0) {
// We are just enumerating elements from the wrapped list.
last = Integer.MIN_VALUE;
action.accept(wrapped.get(- pos - 1));
c--;
} else if (! ( (key[pos]) == null )) {
action.accept(key[last = pos]);
c--;
}
}
}
}
@Override
public ObjectIterator iterator() {
return new SetIterator();
}
private final class SetSpliterator implements ObjectSpliterator {
private static final int POST_SPLIT_CHARACTERISTICS = ObjectSpliterators.SET_SPLITERATOR_CHARACTERISTICS & ~java.util.Spliterator.SIZED;
/** The index (which bucket) of the next item to give to the action.
* Unlike {@link SetIterator}, this counts up instead of down.
*/
int pos = 0;
/** The maximum bucket (exclusive) to iterate to */
int max = n;
/** An upwards counter counting how many we have given */
int c = 0;
/** A boolean telling us whether we should return the null key. */
boolean mustReturnNull = ObjectOpenHashSet.this.containsNull;
boolean hasSplit = false;
SetSpliterator() {}
SetSpliterator(int pos, int max, boolean mustReturnNull, boolean hasSplit) {
this.pos = pos;
this.max = max;
this.mustReturnNull = mustReturnNull;
this.hasSplit = hasSplit;
}
@Override
public boolean tryAdvance(final Consumer action) {
if (mustReturnNull) {
mustReturnNull = false;
++c;
action.accept(key[n]);
return true;
}
final K key[] = ObjectOpenHashSet.this.key;
while (pos < max) {
if (! ( (key[pos]) == null )) {
++c;
action.accept(key[pos++]);
return true;
} else {
++pos;
}
}
return false;
}
@Override
public void forEachRemaining(final Consumer action) {
final K key[] = ObjectOpenHashSet.this.key;
if (mustReturnNull) {
mustReturnNull = false;
action.accept(key[n]);
++c;
}
while (pos < max) {
if (! ( (key[pos]) == null )) {
action.accept(key[pos]);
++c;
}
++pos;
}
}
@Override
public int characteristics() {
return hasSplit ? POST_SPLIT_CHARACTERISTICS : ObjectSpliterators.SET_SPLITERATOR_CHARACTERISTICS;
}
@Override
public long estimateSize() {
if (!hasSplit) {
// Root spliterator; we know how many are remaining.
return size - c;
} else {
// After we split, we can no longer know exactly how many we have (or at least not efficiently).
// (size / n) * (max - pos) aka currentTableDensity * numberOfBucketsLeft seems like a good estimate.
return Math.min(size - c, (long)(((double)realSize() / n) * (max - pos)) + (mustReturnNull ? 1 : 0));
}
}
@Override
public SetSpliterator trySplit() {
if (pos >= max - 1) return null;
int retLen = (max - pos) >> 1;
if (retLen <= 1) return null;
int myNewPos = pos + retLen;
int retPos = pos;
int retMax = myNewPos;
// Since null is returned first, and the convention is that the returned split is the prefix of elements,
// the split will take care of returning null (if needed), and we won't return it anymore.
SetSpliterator split = new SetSpliterator(retPos, retMax, mustReturnNull, true);
this.pos = myNewPos;
this.mustReturnNull = false;
this.hasSplit = true;
return split;
}
@Override
public long skip(long n) {
if (n < 0) throw new IllegalArgumentException("Argument must be nonnegative: " + n);
if (n == 0) return 0;
long skipped = 0;
if (mustReturnNull) {
mustReturnNull = false;
++skipped;
--n;
}
final K key[] = ObjectOpenHashSet.this.key;
while (pos < max && n > 0) {
if (! ( (key[pos++]) == null )) {
++skipped;
--n;
}
}
return skipped;
}
}
@Override
public ObjectSpliterator spliterator() {
return new SetSpliterator();
}
@Override
public void forEach(final Consumer action) {
if (containsNull) action.accept(key[n]);
final K key[] = this.key;
for(int pos = n; pos-- != 0; ) if (! ( (key[pos]) == null )) action.accept(key[pos]);
}
/** Rehashes this set, making the table as small as possible.
*
* This method rehashes the table to the smallest size satisfying the
* load factor. It can be used when the set will not be changed anymore, so
* to optimize access speed and size.
*
*
If the table size is already the minimum possible, this method
* does nothing.
*
* @return true if there was enough memory to trim the set.
* @see #trim(int)
*/
public boolean trim() {
return trim(size);
}
/** Rehashes this set if the table is too large.
*
*
Let N be the smallest table size that can hold
* max(n,{@link #size()}) entries, still satisfying the load factor. If the current
* table size is smaller than or equal to N, this method does
* nothing. Otherwise, it rehashes this set in a table of size
* N.
*
*
This method is useful when reusing sets. {@linkplain #clear() Clearing a
* set} leaves the table size untouched. If you are reusing a set
* many times, you can call this method with a typical
* size to avoid keeping around a very large table just
* because of a few large transient sets.
*
* @param n the threshold for the trimming.
* @return true if there was enough memory to trim the set.
* @see #trim()
*/
public boolean trim(final int n) {
final int l = HashCommon.nextPowerOfTwo((int)Math.ceil(n / f));
if (l >= this.n || size > maxFill(l, f)) return true;
try {
rehash(l);
}
catch(OutOfMemoryError cantDoIt) { return false; }
return true;
}
/** Rehashes the set.
*
*
This method implements the basic rehashing strategy, and may be
* overriden by subclasses implementing different rehashing strategies (e.g.,
* disk-based rehashing). However, you should not override this method
* unless you understand the internal workings of this class.
*
* @param newN the new size
*/
@SuppressWarnings("unchecked")
protected void rehash(final int newN) {
final K key[] = this.key;
final int mask = newN - 1; // Note that this is used by the hashing macro
final K newKey[] = (K[]) new Object[newN + 1];
int i = n, pos;
for(int j = realSize(); j-- != 0;) {
while(( (key[--i]) == null ));
if (! ( (newKey[pos = ( it.unimi.dsi.fastutil.HashCommon.mix( (key[i]).hashCode() ) ) & mask]) == null ))
while (! ( (newKey[pos = (pos + 1) & mask]) == null ));
newKey[pos] = key[i];
}
n = newN;
this.mask = mask;
maxFill = maxFill(n, f);
this.key = newKey;
}
/** Returns a deep copy of this set.
*
*
This method performs a deep copy of this hash 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 ObjectOpenHashSet clone() {
ObjectOpenHashSet c;
try {
c = (ObjectOpenHashSet )super.clone();
}
catch(CloneNotSupportedException cantHappen) {
throw new InternalError();
}
c.key = key.clone();
c.containsNull = containsNull;
return c;
}
/** Returns a hash code for this set.
*
* This method overrides the generic method provided by the superclass.
* Since {@code equals()} is not overriden, it is important
* that the value returned by this method is the same value as
* the one returned by the overriden method.
*
* @return a hash code for this set.
*/
@Override
public int hashCode() {
int h = 0;
for(int j = realSize(), i = 0; j-- != 0;) {
while(( (key[i]) == null )) i++;
if (this != key[i])
h += ( (key[i]).hashCode() );
i++;
}
// Zero / null have hash zero.
return h;
}
private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {
final ObjectIterator i = iterator();
s.defaultWriteObject();
for(int j = size; j-- != 0;) s.writeObject(i.next());
}
@SuppressWarnings("unchecked")
private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException {
s.defaultReadObject();
n = arraySize(size, f);
maxFill = maxFill(n, f);
mask = n - 1;
final K key[] = this.key = (K[]) new Object[n + 1];
K k;
for(int i = size, pos; i-- != 0;) {
k = (K) s.readObject();
if (( (k) == null )) {
pos = n;
containsNull = true;
}
else {
if (! ( (key[pos = ( it.unimi.dsi.fastutil.HashCommon.mix( (k).hashCode() ) ) & mask]) == null ))
while (! ( (key[pos = (pos + 1) & mask]) == null ));
}
key[pos] = k;
}
if (ASSERTS) checkTable();
}
private void checkTable() {}
}