org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/pack/PackExt.java

/*
 * Copyright (C) 2013, Google Inc.
 * and other copyright owners as documented in the project's IP log.
 *
 * This program and the accompanying materials are made available
 * under the terms of the Eclipse Distribution License v1.0 which
 * accompanies this distribution, is reproduced below, and is
 * available at http://www.eclipse.org/org/documents/edl-v10.php
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or
 * without modification, are permitted provided that the following
 * conditions are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following
 *   disclaimer in the documentation and/or other materials provided
 *   with the distribution.
 *
 * - Neither the name of the Eclipse Foundation, Inc. nor the
 *   names of its contributors may be used to endorse or promote
 *   products derived from this software without specific prior
 *   written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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 */

package org.eclipse.jgit.internal.storage.pack;

/** A pack file extension. */
public class PackExt {
	private static volatile PackExt[] VALUES = new PackExt[] {};

	/** A pack file extension. */
	public static final PackExt PACK = newPackExt("pack"); //$NON-NLS-1$

	/** A pack index file extension. */
	public static final PackExt INDEX = newPackExt("idx"); //$NON-NLS-1$

	/** A keep pack file extension. */
	public static final PackExt KEEP = newPackExt("keep"); //$NON-NLS-1$

	/** A pack bitmap index file extension. */
	public static final PackExt BITMAP_INDEX = newPackExt("bitmap"); //$NON-NLS-1$

	/** A reftable file. */
	public static final PackExt REFTABLE = newPackExt("ref"); //$NON-NLS-1$

	/** @return all of the PackExt values. */
	public static PackExt[] values() {
		return VALUES;
	}

	/**
	 * Returns a PackExt for the file extension and registers it in the values
	 * array.
	 *
	 * @param ext
	 *            the file extension.
	 * @return the PackExt for the ext
	 */
	public synchronized static PackExt newPackExt(String ext) {
		PackExt[] dst = new PackExt[VALUES.length + 1];
		for (int i = 0; i < VALUES.length; i++) {
			PackExt packExt = VALUES[i];
			if (packExt.getExtension().equals(ext))
				return packExt;
			dst[i] = packExt;
		}
		if (VALUES.length >= 32)
			throw new IllegalStateException(
					"maximum number of pack extensions exceeded"); //$NON-NLS-1$

		PackExt value = new PackExt(ext, VALUES.length);
		dst[VALUES.length] = value;
		VALUES = dst;
		return value;
	}

	private final String ext;

	private final int pos;

	private PackExt(String ext, int pos) {
		this.ext = ext;
		this.pos = pos;
	}

	/** @return the file extension. */
	public String getExtension() {
		return ext;
	}

	/** @return the position of the extension in the values array. */
	public int getPosition() {
		return pos;
	}

	/** @return the bit mask of the extension e.g {@code 1 << getPosition()}. */
	public int getBit() {
		return 1 << getPosition();
	}

	@Override
	public String toString() {
		return String.format("PackExt[%s, bit=0x%s]", getExtension(), //$NON-NLS-1$
				Integer.toHexString(getBit()));
	}
}