/* Copyright 2015 Google Inc. All Rights Reserved.

   https://github.com/google/brotli/blob/master/LICENSE

   Distributed under MIT license.
   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
*/

package net.sourceforge.plantuml.brotli;

import java.nio.ByteBuffer;

/**
 * Collection of static dictionary words.
 *
 * <p>
 * Dictionary content is loaded from binary resource when {@link #getData()} is
 * executed for the first time. Consequently, it saves memory and CPU in case
 * dictionary is not required.
 *
 * <p>
 * One possible drawback is that multiple threads that need dictionary data may
 * be blocked (only once in each classworld). To avoid this, it is enough to
 * call {@link #getData()} proactively.
 */
public final class Dictionary {
	private static volatile ByteBuffer data;

	private static class DataLoader {
		static final boolean OK;

		static {
			boolean ok = true;
			try {
				Class.forName(Dictionary.class.getPackage().getName() + ".DictionaryData");
			} catch (Throwable ex) {
				ok = false;
			}
			OK = ok;
		}
	}

	public static void setData(ByteBuffer data) {
		if (!data.isDirect() || !data.isReadOnly()) {
			throw new BrotliRuntimeException("data must be a direct read-only byte buffer");
		}
		Dictionary.data = data;
	}

	public static ByteBuffer getData() {
		if (data != null) {
			return data;
		}
		if (!DataLoader.OK) {
			throw new BrotliRuntimeException("brotli dictionary is not set");
		}
		/* Might have been set when {@link DictionaryData} was loaded. */
		return data;
	}
}
