com.qwazr.database.store.keys.KeyAbstract Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of qwazr-database Show documentation
Database Engine for QWAZR
There is a newer version: 1.5.0
/*
 * Copyright 2015-2016 Emmanuel Keller / QWAZR
 * 
 * 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.qwazr.database.store.keys;

import com.qwazr.database.store.ByteConverter;
import com.qwazr.database.store.KeyIterator;
import com.qwazr.database.store.KeyStore;
import com.qwazr.utils.ArrayUtils;
import com.qwazr.utils.concurrent.BiConsumerEx;

import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.util.Map;

public abstract class KeyAbstract implements KeyInterface {

    private final KeyEnum keyType;

    protected final ByteConverter byteConverter;

    private byte[] keyBytes;

    protected KeyAbstract(final KeyEnum keyType, final ByteConverter byteConverter) {
        this.keyType = keyType;
        this.byteConverter = byteConverter;
        this.keyBytes = null;
    }

    @Override
    public void buildKey(final DataOutputStream output) throws IOException {
        output.writeChar(keyType.id);
    }

    @Override
    public synchronized byte[] getCachedKey() throws IOException {
        if (keyBytes != null) {
            final byte[] kb = new byte[keyBytes.length];
            System.arraycopy(keyBytes, 0, kb, 0, keyBytes.length);
            return kb;
        }
        try (final ByteArrayOutputStream baos = new ByteArrayOutputStream()) {
            try (final DataOutputStream output = new DataOutputStream(baos)) {
                buildKey(output);
                output.flush();
                keyBytes = baos.toByteArray();
                return keyBytes;
            }
        }
    }

    @Override
    final public V getValue(final KeyStore store) throws IOException {
        byte[] bytes = store.get(getCachedKey());
        if (bytes == null)
            return null;
        return byteConverter.toValue(bytes);
    }

    @Override
    final public void setValue(final KeyStore store, final V value) throws IOException {
        store.put(getCachedKey(), byteConverter.toBytes(value));
    }

    @Override
    final public void deleteValue(final KeyStore store) throws IOException {
        store.delete(getCachedKey());
    }

    @Override
    final public void prefixedKeys(final KeyStore store, int start, int rows,
                                   final BiConsumerEx consumer) throws IOException {
        final byte[] prefixKey = getCachedKey();
        try (final KeyIterator iterator = store.iterator(prefixKey)) {
            while (start-- > 0 && iterator.hasNext()) {
                final Map.Entry entry = iterator.next();
                if (!ArrayUtils.startsWith(entry.getKey(), prefixKey))
                    return;
            }
            while (rows-- > 0 && iterator.hasNext()) {
                final Map.Entry entry = iterator.next();
                final byte[] key = entry.getKey();
                if (!ArrayUtils.startsWith(key, prefixKey))
                    return;
                consumer.accept(key, entry.getValue());
            }
        }
    }

}