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/*
* Copyright 2008-2012 Amazon Technologies, Inc. or its affiliates.
* Amazon, Amazon.com and Carbonado are trademarks or registered trademarks
* of Amazon Technologies, Inc. or its affiliates. All rights reserved.
*
* 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 com.amazon.carbonado.cursor;
import java.util.NoSuchElementException;
import com.amazon.carbonado.Cursor;
import com.amazon.carbonado.FetchException;
/**
* Wraps another cursor to limit the amount of elements.
*
* @author Brian S O'Neill
* @see SkipCursor
* @since 1.2
*/
public class LimitCursor<S> extends AbstractCursor<S> {
private final Cursor<S> mSource;
private volatile long mRemaining;
/**
* @param limit maximum amount of elements
* @throws IllegalArgumentException if source is null or limit is negative
*/
public LimitCursor(Cursor<S> source, long limit) {
if (source == null) {
throw new IllegalArgumentException("Source is null");
}
if (limit < 0) {
throw new IllegalArgumentException("Limit is negative: " + limit);
}
mSource = source;
mRemaining = limit;
}
public boolean hasNext() throws FetchException {
try {
if (mSource.hasNext()) {
if (mRemaining > 0) {
return true;
}
mSource.close();
}
} catch (NoSuchElementException e) {
}
return false;
}
public S next() throws FetchException {
if (mRemaining <= 0) {
throw new NoSuchElementException();
}
S next = mSource.next();
if (--mRemaining <= 0) {
mSource.close();
}
return next;
}
@Override
public int skipNext(int amount) throws FetchException {
if (mRemaining <= 0) {
return 0;
}
if (amount > mRemaining) {
amount = (int) mRemaining;
}
amount = mSource.skipNext(amount);
if ((mRemaining -= amount) <= 0) {
mSource.close();
}
return amount;
}
public void close() throws FetchException {
mSource.close();
}
}
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