/*
    * Copyright (C) 2013, Google Inc. and others
    *
    * This program and the accompanying materials are made available under the
    * terms of the Eclipse Distribution License v. 1.0 which is available at
    * https://www.eclipse.org/org/documents/edl-v10.php.
    *
    * SPDX-License-Identifier: BSD-3-Clause
    */
  
  package org.eclipse.jgit.internal.storage.pack;
  
  /**
   * A pack file extension.
   */
  public class PackExt {
  	private static volatile PackExt/storage/pack/PackExt.html#PackExt">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"); //$NON-NLS-1$
  
  	/**
  	 * Get all of the PackExt values.
  	 *
  	 * @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 static synchronized 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;
  	}
  
  	/**
  	 * Get the file extension.
  	 *
  	 * @return the file extension.
  	 */
  	public String getExtension() {
  		return ext;
  	}
  
  	/**
  	 * Get the position of the extension in the values array.
  	 *
  	 * @return the position of the extension in the values array.
  	 */
  	public int getPosition() {
  		return pos;
  	}
  
  	/**
  	 * Get the bit mask of the extension e.g {@code 1 << getPosition()}.
  	 *
  	 * @return the bit mask of the extension e.g {@code 1 << getPosition()}.
 	 */
 	public int getBit() {
 		return 1 << getPosition();
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	public String toString() {
 		return String.format("PackExt[%s, bit=0x%s]", getExtension(), //$NON-NLS-1$
 				Integer.toHexString(getBit()));
 	}
 }