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/*
* Copyright (C) 2002-2021 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>(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;
}
private 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() {
}
}