// Copyright 2017 JanusGraph Authors
//
// 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 org.janusgraph.diskstorage.util;
import com.google.common.collect.Iterators;
import org.janusgraph.diskstorage.Entry;
import org.janusgraph.diskstorage.EntryList;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
public class EntryArrayList extends ArrayList<Entry> implements EntryList {
public static final int ENTRY_SIZE_ESTIMATE = 256;
public EntryArrayList() {
super();
}
public EntryArrayList(Collection<? extends Entry> c) {
super(c);
}
public static EntryArrayList of(Iterable<? extends Entry> i) {
// This is adapted from Guava's Lists.newArrayList implementation
EntryArrayList result;
if (i instanceof Collection) {
// Let ArrayList's sizing logic work, if possible
result = new EntryArrayList((Collection)i);
} else {
// Unknown size
result = new EntryArrayList();
Iterators.addAll(result, i.iterator());
}
return result;
}
@Override
public Iterator<Entry> reuseIterator() {
return iterator();
}
/**
* This implementation is an inexact estimate.
* It's just the product of a constant ({@link #ENTRY_SIZE_ESTIMATE} times the array size.
* The exact size could be calculated by iterating over the list and summing the remaining
* size of each StaticBuffer in each Entry.
*
* @return crude approximation of actual size
*/
@Override
public int getByteSize() {
return size() * ENTRY_SIZE_ESTIMATE;
}
}