//////////////////////license & copyright header/////////////////////////
//                                                                     //
//    Base64 - encode/decode data using the Base64 encoding scheme     //
//                                                                     //
//                Copyright (c) 1998 by Kevin Kelley                   //
//                                                                     //
// This library is free software; you can redistribute it and/or       //
// modify it under the terms of the GNU Lesser General Public          //
// License as published by the Free Software Foundation; either        //
// version 2.1 of the License, or (at your option) any later version.  //
//                                                                     //
// This library is distributed in the hope that it will be useful,     //
// but WITHOUT ANY WARRANTY; without even the implied warranty of      //
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the       //
// GNU Lesser General Public License for more details.                 //
//                                                                     //
// You should have received a copy of the GNU Lesser General Public    //
// License along with this library; if not, write to the Free Software //
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA           //
// 02111-1307, USA, or contact the author:                             //
//                                                                     //
// Kevin Kelley <kelley@ruralnet.net> - 30718 Rd. 28, La Junta, CO,    //
// 81050  USA.                                                         //
//                                                                     //
////////////////////end license & copyright header///////////////////////

package soot.tagkit;

import java.util.Arrays;

/*-
 * #%L
 * Soot - a J*va Optimization Framework
 * %%
 * Copyright (C) 1997 - 2018 Raja Vallée-Rai and others
 * %%
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation, either version 2.1 of the
 * License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Lesser Public License for more details.
 * 
 * You should have received a copy of the GNU General Lesser Public
 * License along with this program.  If not, see
 * <http://www.gnu.org/licenses/lgpl-2.1.html>.
 * #L%
 */

/**
 * Provides encoding of raw bytes to base64-encoded characters, and decoding of base64 characters to raw bytes.
 *
 * @author Kevin Kelley (kelley@ruralnet.net)
 * @version 1.3
 * @date 06 August 1998
 * @modified 14 February 2000
 * @modified 22 September 2000
 */
public class Base64 {

  //
  // code characters for values 0..63
  //
  private static final char[] alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=".toCharArray();

  //
  // lookup table for converting base64 characters to value in range 0..63
  //
  private static final byte[] codes = new byte[256];

  static {
    for (int i = 0; i < 256; i++) {
      codes[i] = -1;
    }
    for (int i = 'A'; i <= 'Z'; i++) {
      codes[i] = (byte) (i - 'A');
    }
    for (int i = 'a'; i <= 'z'; i++) {
      codes[i] = (byte) (26 + i - 'a');
    }
    for (int i = '0'; i <= '9'; i++) {
      codes[i] = (byte) (52 + i - '0');
    }
    codes['+'] = 62;
    codes['/'] = 63;
  }

  /**
   * returns an array of base64-encoded characters to represent the passed data array.
   *
   * @param data
   *          the array of bytes to encode
   * @return base64-coded character array.
   */
  public static char[] encode(byte[] data) {
    char[] out = new char[((data.length + 2) / 3) * 4];

    //
    // 3 bytes encode to 4 chars. Output is always an even
    // multiple of 4 characters.
    //
    for (int i = 0, index = 0; i < data.length; i += 3, index += 4) {
      boolean quad = false;
      boolean trip = false;

      int val = (0xFF & data[i]);
      val <<= 8;
      if ((i + 1) < data.length) {
        val |= (0xFF & data[i + 1]);
        trip = true;
      }
      val <<= 8;
      if ((i + 2) < data.length) {
        val |= (0xFF & data[i + 2]);
        quad = true;
      }
      out[index + 3] = alphabet[(quad ? (val & 0x3F) : 64)];
      val >>= 6;
      out[index + 2] = alphabet[(trip ? (val & 0x3F) : 64)];
      val >>= 6;
      out[index + 1] = alphabet[val & 0x3F];
      val >>= 6;
      out[index + 0] = alphabet[val & 0x3F];
    }
    return out;
  }

  /**
   * Decodes a BASE-64 encoded stream to recover the original data. White space before and after will be trimmed away, but no
   * other manipulation of the input will be performed.
   *
   * As of version 1.2 this method will properly handle input containing junk characters (newlines and the like) rather than
   * throwing an error. It does this by pre-parsing the input and generating from that a count of VALID input characters.
   **/
  public static byte[] decode(char[] data) {
    // as our input could contain non-BASE64 data (newlines,
    // whitespace of any sort, whatever) we must first adjust
    // our count of USABLE data so that...
    // (a) we don't misallocate the output array, and
    // (b) think that we miscalculated our data length
    // just because of extraneous throw-away junk

    int tempLen = data.length;
    for (char element : data) {
      if ((element > 255) || codes[element] < 0) {
        --tempLen; // ignore non-valid chars and padding
      }
    }
    // calculate required length:
    // -- 3 bytes for every 4 valid base64 chars
    // -- plus 2 bytes if there are 3 extra base64 chars,
    // or plus 1 byte if there are 2 extra.

    int len = (tempLen / 4) * 3;
    if ((tempLen % 4) == 3) {
      len += 2;
    }
    if ((tempLen % 4) == 2) {
      len += 1;
    }

    byte[] out = new byte[len];

    int shift = 0; // # of excess bits stored in accum
    int accum = 0; // excess bits
    int index = 0;

    for (char element : data) {
      int value = (element > 255) ? -1 : codes[element];

      if (value >= 0) // skip over non-code
      {
        accum <<= 6; // bits shift up by 6 each time thru
        shift += 6; // loop, with new bits being put in
        accum |= value; // at the bottom.
        if (shift >= 8) // whenever there are 8 or more shifted in,
        {
          shift -= 8; // write them out (from the top, leaving any
          out[index++] = // excess at the bottom for next iteration.
              (byte) ((accum >> shift) & 0xff);
        }
      }
      // we will also have skipped processing a padding null byte ('=') here;
      // these are used ONLY for padding to an even length and do not legally
      // occur as encoded data. for this reason we can ignore the fact that
      // no index++ operation occurs in that special case: the out[] array is
      // initialized to all-zero bytes to start with and that works to our
      // advantage in this combination.
    }

    // if there is STILL something wrong we just have to throw up now!
    if (index != out.length) {
      throw new Error("Miscalculated data length (wrote " + index + " instead of " + out.length + ")");
    }

    return out;
  }
}
