std::string base64_decode(std::string const &encoded_string) {
  int in_len = static_cast<int>(encoded_string.size());
  int i = 0;
  int j = 0;
  int in_ = 0;
  unsigned char char_array_4[4], char_array_3[3];
  std::string ret;

  const std::string base64_chars =
      "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
      "abcdefghijklmnopqrstuvwxyz"
      "0123456789+/";

  while (in_len-- && (encoded_string[in_] != '=') &&
         is_base64(encoded_string[in_])) {
    char_array_4[i++] = encoded_string[in_];
    in_++;
    if (i == 4) {
      for (i = 0; i < 4; i++)
        char_array_4[i] =
            static_cast<unsigned char>(base64_chars.find(char_array_4[i]));

      char_array_3[0] =
          (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
      char_array_3[1] =
          ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
      char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];

      for (i = 0; (i < 3); i++) ret += char_array_3[i];
      i = 0;
    }
  }

  if (i) {
    for (j = i; j < 4; j++) char_array_4[j] = 0;

    for (j = 0; j < 4; j++)
      char_array_4[j] =
          static_cast<unsigned char>(base64_chars.find(char_array_4[j]));

    char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
    char_array_3[1] =
        ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
    char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];

    for (j = 0; (j < i - 1); j++) ret += char_array_3[j];
  }

  return ret;
}
std::string base64_decode(std::string const &encoded_string) {
  int in_len = static_cast<int>(encoded_string.size());
  int i = 0;
  int j = 0;
  int in_ = 0;
  unsigned char char_array_4[4], char_array_3[3];
  std::string ret;

  const std::string base64_chars =
      "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
      "abcdefghijklmnopqrstuvwxyz"
      "0123456789+/";

  while (in_len-- && (encoded_string[in_] != '=') &&
         is_base64(encoded_string[in_])) {
    char_array_4[i++] = encoded_string[in_];
    in_++;
    if (i == 4) {
      for (i = 0; i < 4; i++)
        char_array_4[i] =
            static_cast<unsigned char>(base64_chars.find(char_array_4[i]));

      char_array_3[0] =
          (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
      char_array_3[1] =
          ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
      char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];

      for (i = 0; (i < 3); i++) ret += char_array_3[i];
      i = 0;
    }
  }

  if (i) {
    for (j = i; j < 4; j++) char_array_4[j] = 0;

    for (j = 0; j < 4; j++)
      char_array_4[j] =
          static_cast<unsigned char>(base64_chars.find(char_array_4[j]));

    char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
    char_array_3[1] =
        ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
    char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];

    for (j = 0; (j < i - 1); j++) ret += char_array_3[j];
  }

  return ret;
}