strangedb/src/main/java/org/warp/jcwdb/EntryReference.java

package org.warp.jcwdb;

import java.io.IOException;

/**
 * You must have only a maximum of 1 reference for each index
 * @param <T>
 */
public class EntryReference<T> implements Castable, AutoCloseable {
	private final JCWDatabase db;
	private final long entryIndex;
	private final DBTypeParser<T> parser;
	public T value;
	private volatile boolean closed;
	private final Object closeLock = new Object();

	public EntryReference(JCWDatabase db, long entryId, DBTypeParser<T> parser) throws IOException {
		this.db = db;
		this.entryIndex = entryId;
		this.parser = parser;
		this.value = db.indices.get(entryId, parser.getReader());
	}

	public DBTypeParser<T> getParser() {
		return parser;
	}

	public long getIndex() {
		return entryIndex;
	}

	public void save() throws IOException {
		if (!closed) {
			db.indices.set(entryIndex, parser.getWriter(value));
		}
	}

	@Override
	public <T> T cast() {
		return (T) this;
	}

	@Override
	public void close() throws IOException {
		if (closed) {
			return;
		}
		synchronized (closeLock) {
			if (closed) {
				return;
			}

			db.removeEntryReference(entryIndex);
			save();

			closed = true;
		}
	}
}