org.iq80.leveldb.impl.MemTable Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of SWBTripleStoreLevelDB Show documentation
TripleStore implementation for SemanticWebBuilder using LevelDB
The newest version!
/**
 * Copyright (C) 2011 the original author or authors.
 * See the notice.md file distributed with this work for additional
 * information regarding copyright ownership.
 *
 * 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.iq80.leveldb.impl;

import com.google.common.base.Preconditions;
import com.google.common.collect.Iterators;
import com.google.common.collect.PeekingIterator;
import org.iq80.leveldb.util.InternalIterator;
import org.iq80.leveldb.util.Slice;

import java.util.Map.Entry;
import java.util.concurrent.ConcurrentSkipListMap;
import java.util.concurrent.atomic.AtomicLong;

import static org.iq80.leveldb.util.SizeOf.SIZE_OF_LONG;

public class MemTable implements SeekingIterable
{
    private final ConcurrentSkipListMap table;
    private final AtomicLong approximateMemoryUsage = new AtomicLong();

    public MemTable(InternalKeyComparator internalKeyComparator)
    {
        table = new ConcurrentSkipListMap(internalKeyComparator);
    }

    public boolean isEmpty()
    {
        return table.isEmpty();
    }

    public long approximateMemoryUsage()
    {
        return approximateMemoryUsage.get();
    }

    public void add(long sequenceNumber, ValueType valueType, Slice key, Slice value)
    {
        Preconditions.checkNotNull(valueType, "valueType is null");
        Preconditions.checkNotNull(key, "key is null");
        Preconditions.checkNotNull(valueType, "valueType is null");

        InternalKey internalKey = new InternalKey(key, sequenceNumber, valueType);
        table.put(internalKey, value);

        approximateMemoryUsage.addAndGet(key.length() + SIZE_OF_LONG + value.length());
    }

    public LookupResult get(LookupKey key)
    {
        Preconditions.checkNotNull(key, "key is null");

        InternalKey internalKey = key.getInternalKey();
        Entry entry = table.ceilingEntry(internalKey);
        if (entry == null) {
            return null;
        }

        InternalKey entryKey = entry.getKey();
        if (entryKey.getUserKey().equals(key.getUserKey())) {
            if (entryKey.getValueType() == ValueType.DELETION) {
                return LookupResult.deleted(key);
            } else {
                return LookupResult.ok(key, entry.getValue());
            }
        }
        return null;
    }

    @Override
    public MemTableIterator iterator()
    {
        return new MemTableIterator();
    }

    public class MemTableIterator implements InternalIterator
    {

        private PeekingIterator> iterator;

        public MemTableIterator()
        {
            iterator = Iterators.peekingIterator(table.entrySet().iterator());
        }

        @Override
        public boolean hasNext()
        {
            return iterator.hasNext();
        }

        @Override
        public void seekToFirst()
        {
            iterator = Iterators.peekingIterator(table.entrySet().iterator());
        }

        @Override
        public void seek(InternalKey targetKey)
        {
            iterator = Iterators.peekingIterator(table.tailMap(targetKey).entrySet().iterator());
        }

        @Override
        public InternalEntry peek()
        {
            Entry entry = iterator.peek();
            return new InternalEntry(entry.getKey(), entry.getValue());
        }

        @Override
        public InternalEntry next()
        {
            Entry entry = iterator.next();
            return new InternalEntry(entry.getKey(), entry.getValue());
        }

        @Override
        public void remove()
        {
            throw new UnsupportedOperationException();
        }
    }
}