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PrimitiveLongStack.java
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PrimitiveLongStack.java
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/*
* Copyright (c) 2002-2018 "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.NoSuchElementException;
import static java.util.Arrays.copyOf;
/**
* Like a {@code Stack<Long>} but for primitive longs. Virtually GC free in that it has an {@code long[]}
* and merely moves a cursor where to {@link #push(long)} and {@link #poll()} values to and from.
* If many items goes in the stack the {@code long[]} will grow to accomodate all of them, but not shrink again.
*/
public class PrimitiveLongStack implements PrimitiveLongCollection
{
private long[] array;
private int cursor = -1; // where the top most item lives
public PrimitiveLongStack( )
{
this( 16 );
}
public PrimitiveLongStack( int initialSize )
{
this.array = new long[initialSize];
}
@Override
public boolean isEmpty()
{
return cursor == -1;
}
@Override
public void clear()
{
cursor = -1;
}
@Override
public int size()
{
return cursor + 1;
}
@Override
public void close()
{ // Nothing to close
}
@Override
public PrimitiveLongIterator iterator()
{
return new PrimitiveLongIterator()
{
int idx;
@Override
public boolean hasNext()
{
return idx <= cursor;
}
@Override
public long next()
{
if ( !hasNext() )
{
throw new NoSuchElementException();
}
return array[idx++];
}
};
}
@Override
public void visitKeys( PrimitiveLongVisitor visitor )
{
throw new UnsupportedOperationException( "Please implement" );
}
public void push( long value )
{
ensureCapacity();
array[++cursor] = value;
}
private void ensureCapacity()
{
if ( cursor == array.length - 1 )
{
array = copyOf( array, array.length << 1 );
}
}
/**
* @return the top most item, or -1 if stack is empty
*/
public long poll()
{
return cursor == -1 ? -1 : array[cursor--];
}
}