///////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2001, Eric D. Friedman All Rights Reserved.
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library 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 Lesser General Public
// License along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
///////////////////////////////////////////////////////////////////////////////
package gnu.trove.impl.hash;
import gnu.trove.iterator.TIterator;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.NoSuchElementException;
/**
* Implements all iterator functions for the hashed object set.
* Subclasses may override objectAtIndex to vary the object
* returned by calls to next() (e.g. for values, and Map.Entry
* objects).
* <p/>
* <p> Note that iteration is fastest if you forego the calls to
* <tt>hasNext</tt> in favor of checking the size of the structure
* yourself and then call next() that many times:
* <p/>
* <pre>
* Iterator i = collection.iterator();
* for (int size = collection.size(); size-- > 0;) {
* Object o = i.next();
* }
* </pre>
* <p/>
* <p>You may, of course, use the hasNext(), next() idiom too if
* you aren't in a performance critical spot.</p>
*/
public abstract class THashIterator<V> implements TIterator, Iterator<V> {
private final TObjectHash<V> _object_hash;
/** the data structure this iterator traverses */
protected final THash _hash;
/**
* the number of elements this iterator believes are in the
* data structure it accesses.
*/
protected int _expectedSize;
/** the index used for iteration. */
protected int _index;
/**
* Create an instance of THashIterator over the values of the TObjectHash
*
* @param hash the object
*/
protected THashIterator( TObjectHash<V> hash ) {
_hash = hash;
_expectedSize = _hash.size();
_index = _hash.capacity();
_object_hash = hash;
}
/**
* Moves the iterator to the next Object and returns it.
*
* @return an <code>Object</code> value
* @throws ConcurrentModificationException
* if the structure
* was changed using a method that isn't on this iterator.
* @throws NoSuchElementException if this is called on an
* exhausted iterator.
*/
public V next() {
moveToNextIndex();
return objectAtIndex( _index );
}
/**
* Returns true if the iterator can be advanced past its current
* location.
*
* @return a <code>boolean</code> value
*/
public boolean hasNext() {
return nextIndex() >= 0;
}
/**
* Removes the last entry returned by the iterator.
* Invoking this method more than once for a single entry
* will leave the underlying data structure in a confused
* state.
*/
public void remove() {
if ( _expectedSize != _hash.size() ) {
throw new ConcurrentModificationException();
}
// Disable auto compaction during the remove. This is a workaround for bug 1642768.
try {
_hash.tempDisableAutoCompaction();
_hash.removeAt( _index );
}
finally {
_hash.reenableAutoCompaction( false );
}
_expectedSize--;
}
/**
* Sets the internal <tt>index</tt> so that the `next' object
* can be returned.
*/
protected final void moveToNextIndex() {
// doing the assignment && < 0 in one line shaves
// 3 opcodes...
if ( ( _index = nextIndex() ) < 0 ) {
throw new NoSuchElementException();
}
}
/**
* Returns the index of the next value in the data structure
* or a negative value if the iterator is exhausted.
*
* @return an <code>int</code> value
* @throws ConcurrentModificationException
* if the underlying
* collection's size has been modified since the iterator was
* created.
*/
protected final int nextIndex() {
if ( _expectedSize != _hash.size() ) {
throw new ConcurrentModificationException();
}
Object[] set = _object_hash._set;
int i = _index;
while ( i-- > 0 && ( set[i] == TObjectHash.FREE || set[i] == TObjectHash.REMOVED ) ) {
;
}
return i;
}
/**
* Returns the object at the specified index. Subclasses should
* implement this to return the appropriate object for the given
* index.
*
* @param index the index of the value to return.
* @return an <code>Object</code> value
*/
abstract protected V objectAtIndex( int index );
} // THashIterator