org.apache.bookkeeper.util.IteratorUtility Maven / Gradle / Ivy
/**
* Copyright The Apache Software Foundation
*
* 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.bookkeeper.util;
import java.util.Comparator;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.PrimitiveIterator;
import java.util.PrimitiveIterator.OfLong;
import java.util.function.ToLongFunction;
/**
* Utility class to merge iterators.
*/
public class IteratorUtility {
private static final long INVALID_ELEMENT = -1;
/**
* Merges two long primitive sorted iterators and returns merged iterator.
* It expects
* - input iterators to be sorted
* - input iterators to be non-repetitive for merged iterator to be non-repetitive
* It removes duplicates from the input iterators.
*
* @param iter1
* first primitive oflong input iterator
* @param iter2
* second primitive oflong input iterator
* @return merged primitive oflong iterator.
*/
public static OfLong mergePrimitiveLongIterator(OfLong iter1, OfLong iter2) {
return new PrimitiveIterator.OfLong() {
private long curIter1Element = INVALID_ELEMENT;
private long curIter2Element = INVALID_ELEMENT;
private boolean hasToPreFetch = true;
@Override
public boolean hasNext() {
if (hasToPreFetch) {
if (curIter1Element == INVALID_ELEMENT) {
curIter1Element = iter1.hasNext() ? iter1.nextLong() : INVALID_ELEMENT;
}
if (curIter2Element == INVALID_ELEMENT) {
curIter2Element = iter2.hasNext() ? iter2.nextLong() : INVALID_ELEMENT;
}
}
hasToPreFetch = false;
return (curIter1Element != INVALID_ELEMENT || curIter2Element != INVALID_ELEMENT);
}
@Override
public long nextLong() {
if (!hasNext()) {
throw new NoSuchElementException();
}
long returnEntryId = INVALID_ELEMENT;
if (curIter1Element != INVALID_ELEMENT && curIter2Element != INVALID_ELEMENT) {
if (curIter1Element == curIter2Element) {
returnEntryId = curIter1Element;
curIter1Element = INVALID_ELEMENT;
curIter2Element = INVALID_ELEMENT;
} else if (curIter1Element < curIter2Element) {
returnEntryId = curIter1Element;
curIter1Element = INVALID_ELEMENT;
} else {
returnEntryId = curIter2Element;
curIter2Element = INVALID_ELEMENT;
}
} else if (curIter1Element != INVALID_ELEMENT) {
returnEntryId = curIter1Element;
curIter1Element = INVALID_ELEMENT;
} else {
returnEntryId = curIter2Element;
curIter2Element = INVALID_ELEMENT;
}
hasToPreFetch = true;
return returnEntryId;
}
};
}
/**
* Merges two sorted iterators and returns merged iterator sorted using
* comparator. It uses 'function' to convert T type to long, to return long
* iterator.
* It expects
* - input iterators to be sorted
* - input iterators to be non-repetitive for merged iterator to be non-repetitive
* It removes duplicates from the input iterators.
*
* @param iter1
* first iterator of type T
* @param iter2
* second iterator of type T
* @param comparator
* @param function
* @return
*/
public static OfLong mergeIteratorsForPrimitiveLongIterator(Iterator iter1, Iterator iter2,
Comparator comparator, ToLongFunction function) {
return new PrimitiveIterator.OfLong() {
private T curIter1Entry = null;
private T curIter2Entry = null;
private boolean hasToPreFetch = true;
@Override
public boolean hasNext() {
if (hasToPreFetch) {
if (curIter1Entry == null) {
curIter1Entry = iter1.hasNext() ? iter1.next() : null;
}
if (curIter2Entry == null) {
curIter2Entry = iter2.hasNext() ? iter2.next() : null;
}
}
hasToPreFetch = false;
return (curIter1Entry != null || curIter2Entry != null);
}
@Override
public long nextLong() {
if (!hasNext()) {
throw new NoSuchElementException();
}
T returnEntry = null;
if (curIter1Entry != null && curIter2Entry != null) {
int compareValue = comparator.compare(curIter1Entry, curIter2Entry);
if (compareValue == 0) {
returnEntry = curIter1Entry;
curIter1Entry = null;
curIter2Entry = null;
} else if (compareValue < 0) {
returnEntry = curIter1Entry;
curIter1Entry = null;
} else {
returnEntry = curIter2Entry;
curIter2Entry = null;
}
} else if (curIter1Entry != null) {
returnEntry = curIter1Entry;
curIter1Entry = null;
} else {
returnEntry = curIter2Entry;
curIter2Entry = null;
}
hasToPreFetch = true;
return function.applyAsLong(returnEntry);
}
};
}
}