src.it.unimi.dsi.fastutil.chars.CharOpenHashSet Maven / Gradle / Ivy
/* Generic definitions */
/* Assertions (useful to generate conditional code) */
/* Current type and class (and size, if applicable) */
/* Value methods */
/* Interfaces (keys) */
/* Interfaces (values) */
/* Abstract implementations (keys) */
/* Abstract implementations (values) */
/* Static containers (keys) */
/* Static containers (values) */
/* Implementations */
/* Synchronized wrappers */
/* Unmodifiable wrappers */
/* Other wrappers */
/* Methods (keys) */
/* Methods (values) */
/* Methods (keys/values) */
/* Methods that have special names depending on keys (but the special names depend on values) */
/* Equality */
/* Object/Reference-only definitions (keys) */
/* Primitive-type-only definitions (keys) */
/* Object/Reference-only definitions (values) */
/*
* Copyright (C) 2002-2013 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.chars;
import it.unimi.dsi.fastutil.Hash;
import it.unimi.dsi.fastutil.HashCommon;
import it.unimi.dsi.fastutil.booleans.BooleanArrays;
import static it.unimi.dsi.fastutil.HashCommon.arraySize;
import static it.unimi.dsi.fastutil.HashCommon.maxFill;
import java.util.Collection;
import java.util.Iterator;
import java.util.NoSuchElementException;
/** 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
* enlarged as needed by doubling its size when new entries are created, but it is never made
* smaller (even on a {@link #clear()}). 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.
*
*
Warning: The implementation of this class has significantly
* changed in fastutil 6.1.0. Please read the
* comments about this issue in the section “Faster Hash Tables” of the overview.
*
* @see Hash
* @see HashCommon
*/
public class CharOpenHashSet extends AbstractCharSet implements java.io.Serializable, Cloneable, Hash {
private static final long serialVersionUID = 0L;
private static final boolean ASSERTS = false;
/** The array of keys. */
protected transient char key[];
/** The array telling whether a position is used. */
protected transient boolean used[];
/** The acceptable load factor. */
protected final float f;
/** The current table size. */
protected transient int n;
/** Threshold after which we rehash. It must be the table size times {@link #f}. */
protected transient int maxFill;
/** The mask for wrapping a position counter. */
protected transient int mask;
/** Number of entries in the set. */
protected int size;
/** Creates a new hash set.
*
*
The actual table size will be the least power of two greater than expected/f.
*
* @param expected the expected number of elements in the hash set.
* @param f the load factor.
*/
@SuppressWarnings("unchecked")
public CharOpenHashSet( final int expected, final float f ) {
if ( f <= 0 || f > 1 ) throw new IllegalArgumentException( "Load factor must be greater than 0 and smaller than or equal to 1" );
if ( expected < 0 ) throw new IllegalArgumentException( "The expected number of elements must be nonnegative" );
this.f = f;
n = arraySize( expected, f );
mask = n - 1;
maxFill = maxFill( n, f );
key = new char[ n ];
used = new boolean[ n ];
}
/** 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 CharOpenHashSet( 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 CharOpenHashSet() {
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 CharOpenHashSet( 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 CharOpenHashSet( 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 CharOpenHashSet( final CharCollection 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 CharOpenHashSet( final CharCollection 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 CharOpenHashSet( final CharIterator i, final float f ) {
this( DEFAULT_INITIAL_SIZE, f );
while( i.hasNext() ) add( i.nextChar() );
}
/** 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 CharOpenHashSet( final CharIterator i ) {
this( i, DEFAULT_LOAD_FACTOR );
}
/** Creates a new hash set using elements provided by an iterator.
*
* @param i an iterator whose elements will fill the set.
* @param f the load factor.
*/
public CharOpenHashSet( final Iterator i, final float f ) {
this( CharIterators.asCharIterator( i ), f );
}
/** Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor using elements provided by an iterator.
*
* @param i an iterator whose elements will fill the set.
*/
public CharOpenHashSet( final Iterator i ) {
this( CharIterators.asCharIterator( i ) );
}
/** 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 CharOpenHashSet( final char[] a, final int offset, final int length, final float f ) {
this( length < 0 ? 0 : length, f );
CharArrays.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 CharOpenHashSet( final char[] 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 CharOpenHashSet( final char[] 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 CharOpenHashSet( final char[] a ) {
this( a, DEFAULT_LOAD_FACTOR );
}
/*
* The following methods implements some basic building blocks used by
* all accessors. They are (and should be maintained) identical to those used in HashMap.drv.
*/
public boolean add( final char k ) {
// The starting point.
int pos = ( it.unimi.dsi.fastutil.HashCommon.murmurHash3( (k) ) ) & mask;
// There's always an unused entry.
while( used[ pos ] ) {
if ( ( (key[ pos ]) == (k) ) ) return false;
pos = ( pos + 1 ) & mask;
}
used[ pos ] = true;
key[ pos ] = k;
if ( ++size >= maxFill ) rehash( arraySize( size + 1, f ) );
if ( ASSERTS ) checkTable();
return true;
}
/** Shifts left entries with the specified hash code, starting at the specified position,
* and empties the resulting free entry.
*
* @param pos a starting position.
* @return the position cleared by the shifting process.
*/
protected final int shiftKeys( int pos ) {
// Shift entries with the same hash.
int last, slot;
for(;;) {
pos = ( ( last = pos ) + 1 ) & mask;
while( used[ pos ] ) {
slot = ( it.unimi.dsi.fastutil.HashCommon.murmurHash3( (key[ pos ]) ) ) & mask;
if ( last <= pos ? last >= slot || slot > pos : last >= slot && slot > pos ) break;
pos = ( pos + 1 ) & mask;
}
if ( ! used[ pos ] ) break;
key[ last ] = key[ pos ];
}
used[ last ] = false;
return last;
}
@SuppressWarnings("unchecked")
public boolean remove( final char k ) {
// The starting point.
int pos = ( it.unimi.dsi.fastutil.HashCommon.murmurHash3( (k) ) ) & mask;
// There's always an unused entry.
while( used[ pos ] ) {
if ( ( (key[ pos ]) == (k) ) ) {
size--;
shiftKeys( pos );
if ( ASSERTS ) checkTable();
return true;
}
pos = ( pos + 1 ) & mask;
}
return false;
}
@SuppressWarnings("unchecked")
public boolean contains( final char k ) {
// The starting point.
int pos = ( it.unimi.dsi.fastutil.HashCommon.murmurHash3( (k) ) ) & mask;
// There's always an unused entry.
while( used[ pos ] ) {
if ( ( (key[ pos ]) == (k) ) ) return true;
pos = ( pos + 1 ) & mask;
}
return false;
}
/* 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()}.
*
*/
public void clear() {
if ( size == 0 ) return;
size = 0;
BooleanArrays.fill( used, false );
}
public int size() {
return size;
}
public boolean isEmpty() {
return size == 0;
}
/** A no-op for backward compatibility.
*
* @param growthFactor unused.
* @deprecated Since fastutil 6.1.0, hash tables are doubled when they are too full.
*/
@Deprecated
public void growthFactor( int growthFactor ) {}
/** Gets the growth factor (2).
*
* @return the growth factor of this set, which is fixed (2).
* @see #growthFactor(int)
* @deprecated Since fastutil 6.1.0, hash tables are doubled when they are too full.
*/
@Deprecated
public int growthFactor() {
return 16;
}
/** An iterator over a hash set. */
private class SetIterator extends AbstractCharIterator {
/** The index of the next entry to be returned, if positive or zero. If negative, the next entry to be
returned, if any, is that of index -pos -2 from the {@link #wrapped} list. */
int pos = CharOpenHashSet.this.n;
/** The index of the last entry that has been returned (more precisely, the value of {@link #pos}). 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 lazily allocated list containing elements that have wrapped around the table because of removals; such elements
would not be enumerated (other elements would be usually enumerated twice in their place). */
CharArrayList wrapped;
{
final boolean used[] = CharOpenHashSet.this.used;
if ( c != 0 ) while( ! used[ --pos ] );
}
public boolean hasNext() {
return c != 0;
}
public char nextChar() {
if ( ! hasNext() ) throw new NoSuchElementException();
c--;
// We are just enumerating elements from the wrapped list.
if ( pos < 0 ) return wrapped.getChar( - ( last = --pos ) - 2 );
final char retVal = key[ last = pos ];
//System.err.println( "Count: " + c );
if ( c != 0 ) {
final boolean used[] = CharOpenHashSet.this.used;
while ( pos-- != 0 && !used[ pos ] );
// When here pos < 0 there are no more elements to be enumerated by scanning, but wrapped might be nonempty.
}
return retVal;
}
/** Shifts left entries with the specified hash code, starting at the specified position,
* and empties the resulting free entry. If any entry wraps around the table, instantiates
* lazily {@link #wrapped} and stores the entry.
*
* @param pos a starting position.
* @return the position cleared by the shifting process.
*/
final int shiftKeys( int pos ) {
// Shift entries with the same hash.
int last, slot;
for(;;) {
pos = ( ( last = pos ) + 1 ) & mask;
while( used[ pos ] ) {
slot = ( it.unimi.dsi.fastutil.HashCommon.murmurHash3( (key[ pos ]) ) ) & mask;
if ( last <= pos ? last >= slot || slot > pos : last >= slot && slot > pos ) break;
pos = ( pos + 1 ) & mask;
}
if ( ! used[ pos ] ) break;
if ( pos < last ) {
// Wrapped entry.
if ( wrapped == null ) wrapped = new CharArrayList ();
wrapped.add( key[ pos ] );
}
key[ last ] = key[ pos ];
}
used[ last ] = false;
return last;
}
@SuppressWarnings("unchecked")
public void remove() {
if ( last == -1 ) throw new IllegalStateException();
if ( pos < -1 ) {
// We're removing wrapped entries.
CharOpenHashSet.this.remove( wrapped.getChar( - pos - 2 ) );
last = -1;
return;
}
size--;
if ( shiftKeys( last ) == pos && c > 0 ) {
c++;
nextChar();
}
last = -1; // You can no longer remove this entry.
if ( ASSERTS ) checkTable();
}
}
public CharIterator iterator() {
return new SetIterator();
}
/** A no-op for backward compatibility. The kind of tables implemented by
* this class never need rehashing.
*
*
If you need to reduce the table size to fit exactly
* this set, use {@link #trim()}.
*
* @return true.
* @see #trim()
* @deprecated A no-op.
*/
@Deprecated
public boolean rehash() {
return true;
}
/** 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() {
final int l = arraySize( size, f );
if ( l >= n ) return true;
try {
rehash( l );
}
catch(OutOfMemoryError cantDoIt) { return false; }
return true;
}
/** 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 ( this.n <= l ) 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 ) {
int i = 0, pos;
final boolean used[] = this.used;
char k;
final char key[] = this.key;
final int newMask = newN - 1;
final char newKey[] = new char[ newN ];
final boolean newUsed[] = new boolean[ newN ];
for( int j = size; j-- != 0; ) {
while( ! used[ i ] ) i++;
k = key[ i ];
pos = ( it.unimi.dsi.fastutil.HashCommon.murmurHash3( (k) ) ) & newMask;
while ( newUsed[ pos ] ) pos = ( pos + 1 ) & newMask;
newUsed[ pos ] = true;
newKey[ pos ] = k;
i++;
}
n = newN;
mask = newMask;
maxFill = maxFill( n, f );
this.key = newKey;
this.used = newUsed;
}
/** 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.
*/
@SuppressWarnings("unchecked")
public CharOpenHashSet clone() {
CharOpenHashSet c;
try {
c = (CharOpenHashSet )super.clone();
}
catch(CloneNotSupportedException cantHappen) {
throw new InternalError();
}
c.key = key.clone();
c.used = used.clone();
return c;
}
/** Returns a hash code for this set.
*
* This method overrides the generic method provided by the superclass.
* Since 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.
*/
public int hashCode() {
int h = 0, i = 0, j = size;
while( j-- != 0 ) {
while( ! used[ i ] ) i++;
h += (key[ i ]);
i++;
}
return h;
}
private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {
final CharIterator i = iterator();
s.defaultWriteObject();
for( int j = size; j-- != 0; ) s.writeChar( i.nextChar() );
}
@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 char key[] = this.key = new char[ n ];
final boolean used[] = this.used = new boolean[ n ];
char k;
for( int i = size, pos = 0; i-- != 0; ) {
k = s.readChar();
pos = ( it.unimi.dsi.fastutil.HashCommon.murmurHash3( (k) ) ) & mask;
while ( used[ pos ] ) pos = ( pos + 1 ) & mask;
used[ pos ] = true;
key[ pos ] = k;
}
if ( ASSERTS ) checkTable();
}
private void checkTable() {}
}