/*
    * Copyright (C) 2020, Michael Dardis. 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.util;
  
  import java.text.MessageFormat;
  
  import org.eclipse.jgit.internal.JGitText;
  
  /**
   * Encodes and decodes to and from hexadecimal notation.
   *
   * @since 5.7
   */
  public final class Hex {
  
  	private static final char[] HEX = "0123456789abcdef".toCharArray(); //$NON-NLS-1$
  
  	/** Defeats instantiation. */
  	private Hex() {
  		// empty
  	}
  
  	/**
  	 * Decode a hexadecimal string to a byte array.
  	 *
  	 * Note this method validates that characters in the given string are valid
  	 * as digits in a hex string.
  	 *
  	 * @param s
  	 *            hexadecimal string
  	 * @return decoded array
  	 */
  	public static byte[] decode(String s) {
  		int len = s.length();
  		byte[] b = new byte[len / 2];
  
  		for (int i = 0; i < len; i += 2) {
  			int left = Character.digit(s.charAt(i), 16);
  			int right = Character.digit(s.charAt(i + 1), 16);
  
  			if (left == -1 || right == -1) {
  				throw new IllegalArgumentException(MessageFormat.format(
  						JGitText.get().invalidHexString,
  						s));
  			}
  
  			b[i / 2] = (byte) (left << 4 | right);
  		}
  		return b;
  	}
  
  	/**
  	 * Encode a byte array to a hexadecimal string.
  	 *
  	 * @param b byte array
  	 * @return hexadecimal string
  	 */
  	public static String toHexString(byte[] b) {
  		char[] c = new char[b.length * 2];
  
  		for (int i = 0; i < b.length; i++) {
  			int v = b[i] & 0xFF;
  
  			c[i * 2] = HEX[v >>> 4];
  			c[i * 2 + 1] = HEX[v & 0x0F];
  		}
  
  		return new String(c);
  	}
  }