/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 org.apache.jackrabbit.rmi.remote;
import java.io.Serializable;
import java.rmi.RemoteException;
import java.util.NoSuchElementException;
/**
* A buffered remote iterator. Used to transfer a remote iterator reference
* along with a buffer of the first few iterator elements in one network
* transmission.
*/
public class BufferIterator implements RemoteIterator, Serializable {
/** The element buffer. Set to <code>null</code> when the iterator ends. */
private Object[] buffer;
/** Cached size of the iterator. */
private final long size;
/** Remote iterator reference. */
private final RemoteIterator remote;
/**
* Creates a new buffered remote iterator.
*
* @param buffer first elements in the iterator
* @param size total iterator size
* @param remote reference to the remaining iterator
*/
public BufferIterator(Object[] buffer, long size, RemoteIterator remote) {
this.buffer = buffer;
this.size = size;
this.remote = remote;
}
/**
* Returns the cached size of the iterator.
*
* @return iterator size, or <code>-1</code> if unknown
* @see RemoteIterator#getSize()
*/
public long getSize() {
return size;
}
/**
* Skips the given number of elements. First discards elements from the
* element buffer and only then contacts the remote iterator.
*
* @param items number of items to skip
* @throws IllegalArgumentException if <code>items</code> is negative
* @throws NoSuchElementException if skipped past the last element
* @throws RemoteException on RMI errors
* @see RemoteIterator#skip(long)
*/
public void skip(long items)
throws IllegalArgumentException, NoSuchElementException,
RemoteException {
if (items < 0) {
throw new IllegalArgumentException("Negative skip is not allowed");
} else if (buffer == null && items > 0) {
throw new NoSuchElementException("Skipped past the last element");
} else if (items > buffer.length) {
remote.skip(items - buffer.length);
buffer = remote.nextObjects();
} else {
Object[] tmp = new Object[buffer.length - (int) items];
System.arraycopy(buffer, (int) items, tmp, 0, tmp.length);
buffer = tmp;
}
}
/**
* Returns the currently buffered elements and fills in the buffer
* with next elements.
*
* @return buffered elements, or <code>null</code> if the iterator has ended
* @throws RemoteException on RMI errors
* @see RemoteIterator#nextObjects()
*/
public Object[] nextObjects() throws RemoteException {
if (buffer == null) {
return null;
} else {
Object[] tmp = buffer;
buffer = remote.nextObjects();
return tmp;
}
}
}