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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 skip an initial amount of elements.
*
* @author Brian S O'Neill
* @see LimitCursor
* @since 1.2
*/
public class SkipCursor<S> extends AbstractCursor<S> {
private final Cursor<S> mSource;
private volatile long mSkip;
/**
* @param skip initial amount of elements to skip
* @throws IllegalArgumentException if source is null or skip is negative
*/
public SkipCursor(Cursor<S> source, long skip) {
if (source == null) {
throw new IllegalArgumentException("Source is null");
}
if (skip < 0) {
throw new IllegalArgumentException("Skip is negative: " + skip);
}
mSource = source;
mSkip = skip;
}
public boolean hasNext() throws FetchException {
try {
doSkip();
return mSource.hasNext();
} catch (NoSuchElementException e) {
return false;
}
}
public S next() throws FetchException {
doSkip();
return mSource.next();
}
@Override
public int skipNext(int amount) throws FetchException {
doSkip();
return mSource.skipNext(amount);
}
public void close() throws FetchException {
mSource.close();
}
private void doSkip() throws FetchException {
if (mSkip > 0) {
while (mSkip > Integer.MAX_VALUE) {
mSkip -= mSource.skipNext(Integer.MAX_VALUE);
}
mSource.skipNext((int) mSkip);
mSkip = 0;
}
}
}
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