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PrimitiveIntCollections.java
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PrimitiveIntCollections.java
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/*
* Copyright (c) 2002-2015 "Neo Technology,"
* Network Engine for Objects in Lund AB [http://neotechnology.com]
*
* This file is part of Neo4j.
*
* Neo4j is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.neo4j.collection.primitive;
import java.util.Collection;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.function.IntFunction;
import java.util.function.IntPredicate;
import org.neo4j.collection.primitive.base.Empty;
import static java.util.Arrays.copyOf;
import static org.neo4j.collection.primitive.PrimitiveCommons.closeSafely;
/**
* Basic and common primitive int collection utils and manipulations.
*
* @see PrimitiveLongCollections
* @see Primitive
*/
public class PrimitiveIntCollections
{
/**
* Base iterator for simpler implementations of {@link PrimitiveIntIterator}s.
*/
public static abstract class PrimitiveIntBaseIterator implements PrimitiveIntIterator
{
private boolean hasNext;
private int next;
@Override
public boolean hasNext()
{
return hasNext ? true : (hasNext = fetchNext());
}
@Override
public int next()
{
if ( !hasNext() )
{
throw new NoSuchElementException( "No more elements in " + this );
}
hasNext = false;
return next;
}
/**
* Fetches the next item in this iterator. Returns whether or not a next item was found. If a next
* item was found, that value must have been set inside the implementation of this method
* using {@link #next(int)}.
*/
protected abstract boolean fetchNext();
/**
* Called from inside an implementation of {@link #fetchNext()} if a next item was found.
* This method returns {@code true} so that it can be used in short-hand conditionals
* (TODO what are they called?), like:
* <pre>
* @Override
* protected boolean fetchNext()
* {
* return source.hasNext() ? next( source.next() ) : false;
* }
* </pre>
* @param nextItem the next item found.
*/
protected boolean next( int nextItem )
{
next = nextItem;
hasNext = true;
return true;
}
}
public static PrimitiveIntIterator iterator( final int... items )
{
return new PrimitiveIntBaseIterator()
{
private int index = -1;
@Override
protected boolean fetchNext()
{
return ++index < items.length ? next( items[index] ) : false;
}
};
}
public static PrimitiveIntIterator reversed( final int... items )
{
return new PrimitiveIntBaseIterator()
{
private int index = items.length;
@Override
protected boolean fetchNext()
{
return --index >= 0 ? next( items[index] ) : false;
}
};
}
public static PrimitiveIntIterator reversed( PrimitiveIntIterator source )
{
int[] items = asArray( source );
return reversed( items );
}
// Concating
public static PrimitiveIntIterator concat( Iterator<PrimitiveIntIterator> iterators )
{
return new PrimitiveIntConcatingIterator( iterators );
}
public static PrimitiveIntIterator prepend( final int item, final PrimitiveIntIterator iterator )
{
return new PrimitiveIntBaseIterator()
{
private boolean singleItemReturned;
@Override
protected boolean fetchNext()
{
if ( !singleItemReturned )
{
singleItemReturned = true;
return next( item );
}
return iterator.hasNext() ? next( iterator.next() ) : false;
}
};
}
public static PrimitiveIntIterator append( final PrimitiveIntIterator iterator, final int item )
{
return new PrimitiveIntBaseIterator()
{
private boolean singleItemReturned;
@Override
protected boolean fetchNext()
{
if ( iterator.hasNext() )
{
return next( iterator.next() );
}
else if ( !singleItemReturned )
{
singleItemReturned = true;
return next( item );
}
return false;
}
};
}
public static class PrimitiveIntConcatingIterator extends PrimitiveIntBaseIterator
{
private final Iterator<PrimitiveIntIterator> iterators;
private PrimitiveIntIterator currentIterator;
public PrimitiveIntConcatingIterator( Iterator<PrimitiveIntIterator> iterators )
{
this.iterators = iterators;
}
@Override
protected boolean fetchNext()
{
if ( currentIterator == null || !currentIterator.hasNext() )
{
while ( iterators.hasNext() )
{
currentIterator = iterators.next();
if ( currentIterator.hasNext() )
{
break;
}
}
}
return currentIterator != null && currentIterator.hasNext() ? next( currentIterator.next() ) : false;
}
protected final PrimitiveIntIterator currentIterator()
{
return currentIterator;
}
}
// Interleave
public static class PrimitiveIntInterleavingIterator extends PrimitiveIntBaseIterator
{
private final Iterable<PrimitiveIntIterator> iterators;
private Iterator<PrimitiveIntIterator> currentRound;
public PrimitiveIntInterleavingIterator( Iterable<PrimitiveIntIterator> iterators )
{
this.iterators = iterators;
}
@Override
protected boolean fetchNext()
{
if ( currentRound == null || !currentRound.hasNext() )
{
currentRound = iterators.iterator();
}
while ( currentRound.hasNext() )
{
PrimitiveIntIterator iterator = currentRound.next();
if ( iterator.hasNext() )
{
return next( iterator.next() );
}
}
currentRound = null;
return false;
}
}
public static PrimitiveIntIterator filter( PrimitiveIntIterator source, final IntPredicate filter )
{
return new PrimitiveIntFilteringIterator( source )
{
@Override
public boolean test( int item )
{
return filter.test( item );
}
};
}
public static PrimitiveIntIterator dedup( PrimitiveIntIterator source )
{
return new PrimitiveIntFilteringIterator( source )
{
private final PrimitiveIntSet visited = Primitive.intSet();
@Override
public boolean test( int testItem )
{
return visited.add( testItem );
}
};
}
public static PrimitiveIntIterator not( PrimitiveIntIterator source, final int disallowedValue )
{
return new PrimitiveIntFilteringIterator( source )
{
@Override
public boolean test( int testItem )
{
return testItem != disallowedValue;
}
};
}
public static PrimitiveIntIterator skip( PrimitiveIntIterator source, final int skipTheFirstNItems )
{
return new PrimitiveIntFilteringIterator( source )
{
private int skipped = 0;
@Override
public boolean test( int item )
{
if ( skipped < skipTheFirstNItems )
{
skipped++;
return false;
}
return true;
}
};
}
public static abstract class PrimitiveIntFilteringIterator extends PrimitiveIntBaseIterator implements IntPredicate
{
private final PrimitiveIntIterator source;
public PrimitiveIntFilteringIterator( PrimitiveIntIterator source )
{
this.source = source;
}
@Override
protected boolean fetchNext()
{
while ( source.hasNext() )
{
int testItem = source.next();
if ( test( testItem ) )
{
return next( testItem );
}
}
return false;
}
@Override
public abstract boolean test( int testItem );
}
// Limitinglic
public static PrimitiveIntIterator limit( final PrimitiveIntIterator source, final int maxItems )
{
return new PrimitiveIntBaseIterator()
{
private int visited;
@Override
protected boolean fetchNext()
{
if ( visited++ < maxItems )
{
if ( source.hasNext() )
{
return next( source.next() );
}
}
return false;
}
};
}
// Range
public static PrimitiveIntIterator range( int end )
{
return range( 0, end );
}
public static PrimitiveIntIterator range( int start, int end )
{
return range( start, end, 1 );
}
public static PrimitiveIntIterator range( int start, int end, int stride )
{
return new PrimitiveIntRangeIterator( start, end, stride );
}
public static class PrimitiveIntRangeIterator extends PrimitiveIntBaseIterator
{
private int current;
private final int end;
private final int stride;
public PrimitiveIntRangeIterator( int start, int end, int stride )
{
this.current = start;
this.end = end;
this.stride = stride;
}
@Override
protected boolean fetchNext()
{
try
{
return current <= end ? next( current ) : false;
}
finally
{
current += stride;
}
}
}
public static PrimitiveIntIterator singleton( final int item )
{
return new PrimitiveIntBaseIterator()
{
private boolean returned;
@Override
protected boolean fetchNext()
{
try
{
return !returned ? next( item ) : false;
}
finally
{
returned = true;
}
}
};
}
public static int first( PrimitiveIntIterator iterator )
{
assertMoreItems( iterator );
return iterator.next();
}
private static void assertMoreItems( PrimitiveIntIterator iterator )
{
if ( !iterator.hasNext() )
{
throw new NoSuchElementException( "No element in " + iterator );
}
}
public static int first( PrimitiveIntIterator iterator, int defaultItem )
{
return iterator.hasNext() ? iterator.next() : defaultItem;
}
public static int last( PrimitiveIntIterator iterator )
{
assertMoreItems( iterator );
return last( iterator, 0 /*will never be used*/ );
}
public static int last( PrimitiveIntIterator iterator, int defaultItem )
{
int result = defaultItem;
while ( iterator.hasNext() )
{
result = iterator.next();
}
return result;
}
public static int single( PrimitiveIntIterator iterator )
{
try
{
assertMoreItems( iterator );
int item = iterator.next();
if ( iterator.hasNext() )
{
throw new NoSuchElementException( "More than one item in " + iterator + ", first:" + item +
", second:" + iterator.next() );
}
closeSafely( iterator );
return item;
}
catch ( NoSuchElementException exception )
{
closeSafely( iterator, exception );
throw exception;
}
}
public static int single( PrimitiveIntIterator iterator, int defaultItem )
{
try
{
if ( !iterator.hasNext() )
{
closeSafely( iterator );
return defaultItem;
}
int item = iterator.next();
if ( iterator.hasNext() )
{
throw new NoSuchElementException( "More than one item in " + iterator + ", first:" + item +
", second:" + iterator.next() );
}
closeSafely( iterator );
return item;
}
catch ( NoSuchElementException exception )
{
closeSafely( iterator, exception );
throw exception;
}
}
public static int itemAt( PrimitiveIntIterator iterator, int index )
{
if ( index >= 0 )
{ // Look forwards
for ( int i = 0; iterator.hasNext() && i < index; i++ )
{
iterator.next();
}
assertMoreItems( iterator );
return iterator.next();
}
// Look backwards
int fromEnd = index * -1;
int[] trail = new int[fromEnd];
int cursor = 0;
for ( ; iterator.hasNext(); cursor++ )
{
trail[cursor%trail.length] = iterator.next();
}
if ( cursor < fromEnd )
{
throw new NoSuchElementException( "Item " + index + " not found in " + iterator );
}
return trail[cursor%fromEnd];
}
public static int itemAt( PrimitiveIntIterator iterator, int index, int defaultItem )
{
if ( index >= 0 )
{ // Look forwards
for ( int i = 0; iterator.hasNext() && i < index; i++ )
{
iterator.next();
}
return iterator.hasNext() ? iterator.next() : defaultItem;
}
// Look backwards
int fromEnd = index * -1;
int[] trail = new int[fromEnd];
int cursor = 0;
for ( ; iterator.hasNext(); cursor++ )
{
trail[cursor%trail.length] = iterator.next();
}
return cursor < fromEnd ? defaultItem : trail[cursor%fromEnd];
}
/**
* Returns the index of the given item in the iterator(zero-based). If no items in {@code iterator}
* equals {@code item} {@code -1} is returned.
*
* @param item the item to look for.
* @param iterator of items.
* @return index of found item or -1 if not found.
*/
public static int indexOf( PrimitiveIntIterator iterator, int item )
{
for ( int i = 0; iterator.hasNext(); i++ )
{
if ( item == iterator.next() )
{
return i;
}
}
return -1;
}
/**
* Validates whether two {@link Iterator}s are equal or not, i.e. if they have contain same number of items
* and each orderly item equals one another.
*
* @param first the {@link Iterator} containing the first items.
* @param other the {@link Iterator} containing the other items.
* @return whether the two iterators are equal or not.
*/
public static boolean equals( PrimitiveIntIterator first, PrimitiveIntIterator other )
{
boolean firstHasNext, otherHasNext;
// single | so that both iterator's hasNext() gets evaluated.
while ( (firstHasNext = first.hasNext()) | (otherHasNext = other.hasNext()) )
{
if ( firstHasNext != otherHasNext || first.next() != other.next() )
{
return false;
}
}
return true;
}
public static PrimitiveIntSet asSet( PrimitiveIntIterator iterator )
{
PrimitiveIntSet set = Primitive.intSet();
while ( iterator.hasNext() )
{
int next = iterator.next();
if ( !set.add( next ) )
{
throw new IllegalStateException( "Duplicate " + next + " from " + iterator );
}
}
return set;
}
public static PrimitiveIntSet asSetAllowDuplicates( PrimitiveIntIterator iterator )
{
PrimitiveIntSet set = Primitive.intSet();
while ( iterator.hasNext() )
{
set.add( iterator.next() );
}
return set;
}
public static int count( PrimitiveIntIterator iterator )
{
int count = 0;
for ( ; iterator.hasNext(); iterator.next(), count++ )
{ // Just loop through this
}
return count;
}
public static int[] asArray( PrimitiveIntIterator iterator )
{
int[] array = new int[8];
int i = 0;
for ( ; iterator.hasNext(); i++ )
{
if ( i >= array.length )
{
array = copyOf( array, i << 1 );
}
array[i] = iterator.next();
}
if ( i < array.length )
{
array = copyOf( array, i );
}
return array;
}
public static int[] asArray( Collection<Integer> values )
{
int[] array = new int[values.size()];
int i = 0;
for ( int value : values )
{
array[i++] = value;
}
return array;
}
private static final PrimitiveIntIterator EMPTY = new PrimitiveIntBaseIterator()
{
@Override
protected boolean fetchNext()
{
return false;
}
};
public static PrimitiveIntIterator emptyIterator()
{
return EMPTY;
}
public static PrimitiveIntSet emptySet()
{
return Empty.EMPTY_PRIMITIVE_INT_SET;
}
public static PrimitiveIntIterator toPrimitiveIterator( final Iterator<Integer> iterator )
{
return new PrimitiveIntBaseIterator()
{
@Override
protected boolean fetchNext()
{
if ( iterator.hasNext() )
{
Integer nextValue = iterator.next();
if ( null == nextValue )
{
throw new IllegalArgumentException( "Cannot convert null Integer to primitive int" );
}
return next( nextValue.intValue() );
}
return false;
}
};
}
public static PrimitiveIntIterator flatten( final Iterator<PrimitiveIntIterator> source )
{
return new PrimitiveIntBaseIterator()
{
private PrimitiveIntIterator current;
@Override
protected boolean fetchNext()
{
while ( current == null || !current.hasNext() )
{
if ( !source.hasNext() )
{
return false;
}
current = source.next();
}
return source.hasNext() ? next( current.next() ) : false;
}
};
}
public static <T> Iterator<T> map( final IntFunction<T> mapFunction, final PrimitiveIntIterator source )
{
return new Iterator<T>()
{
@Override
public boolean hasNext()
{
return source.hasNext();
}
@Override
public T next()
{
return mapFunction.apply( source.next() );
}
@Override
public void remove()
{
throw new UnsupportedOperationException();
}
};
}
private static final PrimitiveIntPredicate TRUE = new PrimitiveIntPredicate()
{
@Override
public boolean accept( int value )
{
return true;
}
};
/**
* @deprecated use {@link IntPredicates#alwaysTrue()} instead
*/
@Deprecated
public static PrimitiveIntPredicate alwaysTrue()
{
return TRUE;
}
public static PrimitiveIntIterator constant( final int value )
{
return new PrimitiveIntBaseIterator()
{
@Override
protected boolean fetchNext()
{
return next( value );
}
};
}
public static PrimitiveIntSet asSet( int[] values )
{
PrimitiveIntSet set = Primitive.intSet( values.length );
for ( int value : values )
{
set.add( value );
}
return set;
}
}