content: /*
   *  Licensed to the Apache Software Foundation (ASF) under one or more
   *  contributor license agreements.  See the NOTICE file distributed with
   *  this work for additional information regarding copyright ownership.
   *  The ASF licenses this file to You under the Apache License, Version 2.0
   *  (the "License"); you may not use this file except in compliance with
   *  the License.  You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   *  Unless required by applicable law or agreed to in writing, software
   *  distributed under the License is distributed on an "AS IS" BASIS,
   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   *  See the License for the specific language governing permissions and
   *  limitations under the License.
   */
  
  /**
  * @author Alexander Y. Kleymenov
  */
  
  package dev.dworks.apps.anexplorer.libcore.io;
  
  
  
  import dev.dworks.apps.anexplorer.libcore.util.EmptyArray;
  
  
  /**
   * <a href="http://www.ietf.org/rfc/rfc2045.txt">Base64</a> encoder/decoder.
   * In violation of the RFC, this encoder doesn't wrap lines at 76 columns.
   */
  public final class Base64 {
      private Base64() {
      }
  
      public static byte[] decode(byte[] in) {
          return decode(in, in.length);
      }
  
      public static byte[] decode(byte[] in, int len) {
          // approximate output length
          int length = len / 4 * 3;
          // return an empty array on empty or short input without padding
          if (length == 0) {
              return EmptyArray.BYTE;
          }
          // temporary array
          byte[] out = new byte[length];
          // number of padding characters ('=')
          int pad = 0;
          byte chr;
          // compute the number of the padding characters
          // and adjust the length of the input
          for (;;len--) {
              chr = in[len-1];
              // skip the neutral characters
              if ((chr == '\n') || (chr == '\r') ||
                      (chr == ' ') || (chr == '\t')) {
                  continue;
              }
              if (chr == '=') {
                  pad++;
              } else {
                  break;
              }
          }
          // index in the output array
          int outIndex = 0;
          // index in the input array
          int inIndex = 0;
          // holds the value of the input character
          int bits = 0;
          // holds the value of the input quantum
          int quantum = 0;
          for (int i=0; i<len; i++) {
              chr = in[i];
              // skip the neutral characters
              if ((chr == '\n') || (chr == '\r') ||
                      (chr == ' ') || (chr == '\t')) {
                  continue;
              }
              if ((chr >= 'A') && (chr <= 'Z')) {
                  // char ASCII value
                  //  A    65    0
                  //  Z    90    25 (ASCII - 65)
                  bits = chr - 65;
              } else if ((chr >= 'a') && (chr <= 'z')) {
                  // char ASCII value
                  //  a    97    26
                  //  z    122   51 (ASCII - 71)
                  bits = chr - 71;
              } else if ((chr >= '0') && (chr <= '9')) {
                  // char ASCII value
                  //  0    48    52
                  //  9    57    61 (ASCII + 4)
                  bits = chr + 4;
              } else if (chr == '+') {
                  bits = 62;
              } else if (chr == '/') {
                  bits = 63;
              } else {
                  return null;
              }
              // append the value to the quantum
              quantum = (quantum << 6) | (byte) bits;
              if (inIndex%4 == 3) {
                  // 4 characters were read, so make the output:
                  out[outIndex++] = (byte) (quantum >> 16);
                  out[outIndex++] = (byte) (quantum >> 8);
                  out[outIndex++] = (byte) quantum;
              }
              inIndex++;
          }
          if (pad > 0) {
              // adjust the quantum value according to the padding
              quantum = quantum << (6*pad);
              // make output
              out[outIndex++] = (byte) (quantum >> 16);
              if (pad == 1) {
                  out[outIndex++] = (byte) (quantum >> 8);
              }
          }
          // create the resulting array
          byte[] result = new byte[outIndex];
          System.arraycopy(out, 0, result, 0, outIndex);
          return result;
      }
  
      private static final byte[] map = new byte[]
          {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N',
           'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b',
           'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p',
           'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3',
           '4', '5', '6', '7', '8', '9', '+', '/'};
  
      public static String encode(byte[] in) {
          int length = (in.length + 2) * 4 / 3;
          byte[] out = new byte[length];
          int index = 0, end = in.length - in.length % 3;
          for (int i = 0; i < end; i += 3) {
              out[index++] = map[(in[i] & 0xff) >> 2];
              out[index++] = map[((in[i] & 0x03) << 4) | ((in[i+1] & 0xff) >> 4)];
              out[index++] = map[((in[i+1] & 0x0f) << 2) | ((in[i+2] & 0xff) >> 6)];
              out[index++] = map[(in[i+2] & 0x3f)];
          }
          switch (in.length % 3) {
              case 1:
                  out[index++] = map[(in[end] & 0xff) >> 2];
                  out[index++] = map[(in[end] & 0x03) << 4];
                  out[index++] = '=';
                  out[index++] = '=';
                  break;
              case 2:
                  out[index++] = map[(in[end] & 0xff) >> 2];
                  out[index++] = map[((in[end] & 0x03) << 4) | ((in[end+1] & 0xff) >> 4)];
                  out[index++] = map[((in[end+1] & 0x0f) << 2)];
                  out[index++] = '=';
                  break;
          }
          return Strings.construct(out, 0, index, Charsets.US_ASCII);
      }
  }
  