com.cloudhopper.datastore.leveldb.LevelDbDataStoreIterator Maven / Gradle / Ivy

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package com.cloudhopper.datastore.leveldb;

/*
 * #%L
 * ch-datastore
 * %%
 * Copyright (C) 2012 Cloudhopper by Twitter
 * %%
 * 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.
 * #L%
 */

import java.io.IOException;
import java.util.Map.Entry;
import com.cloudhopper.datastore.DataStoreFatalException;
import com.cloudhopper.datastore.DataStoreIterator;
import org.iq80.leveldb.DB;
import org.iq80.leveldb.DBIterator;

/**
 * DateStoreIterator for LevelDB that uses an iterator.
 *
 * @author garth
 */
public class LevelDbDataStoreIterator implements DataStoreIterator {

    private DBIterator cursor;
    private boolean firstNextCall;
    private Entry currentEntry;

    public LevelDbDataStoreIterator(DB db) {
        this.cursor = db.iterator();
        this.firstNextCall = true;
    }

    public boolean next() throws DataStoreFatalException {
        if (this.firstNextCall) {
            this.firstNextCall = false;
	    this.cursor.seekToFirst();
        }
	if (cursor.hasNext()) { 
	    currentEntry = cursor.next();
	    return true;
	} else {
	    return false;
	}
    }

    public boolean jump(byte[] key) throws DataStoreFatalException {
	if (this.firstNextCall) this.firstNextCall = false;
	this.cursor.seek(key);
	if (cursor.hasNext()) { 
	    currentEntry = cursor.next();
	    return true;
	} else {
	    return false;
	}
    }

    public Record getRecord() throws DataStoreFatalException {
        byte[] key = currentEntry.getKey();
        byte[] value = currentEntry.getValue();
        if (key == null || value == null) {
            throw new DataStoreFatalException("Record key or value was null");
        }
        return new Record(key, value);
    }

    public void close() throws DataStoreFatalException {
	try {
	    cursor.close();
	    cursor = null;
	} catch (IOException e) {
	    throw new DataStoreFatalException("Error closing store", e);
	}
    }

}