cpp_web_tools.cpp

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


static inline bool is_base64(unsigned char c) {
  return (isalnum(c) || (c == '+') || (c == '/'));
}

std::string base64_encode(unsigned char const* bytes_to_encode, unsigned int in_len) {
  std::string ret;
  int i = 0;
  int j = 0;
  unsigned char char_array_3[3];
  unsigned char char_array_4[4];

  while (in_len--) {
    char_array_3[i++] = *(bytes_to_encode++);
    if (i == 3) {
      char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
      char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
      char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
      char_array_4[3] = char_array_3[2] & 0x3f;

      for(i = 0; (i <4) ; i++)
        ret += base64_chars[char_array_4[i]];
      i = 0;
    }
  }

  if (i)
  {
    for(j = i; j < 3; j++)
      char_array_3[j] = '\0';

    char_array_4[0] = ( char_array_3[0] & 0xfc) >> 2;
    char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
    char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
    char_array_4[3] =   char_array_3[2] & 0x3f;

    for (j = 0; (j < i + 1); j++)
      ret += base64_chars[char_array_4[j]];

    while((i++ < 3))
      ret += '=';

  }

  return ret;

}

std::string base64_decode(std::string const& encoded_string) {
  int in_len = 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;

  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] = 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] = 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 charToHex(unsigned char c) {
	short i = c;
	 
	std::stringstream s;
	 
	s << "%" << std::setw(2) << std::setfill('0') << std::hex << i;
	 
	return s.str();
}

unsigned char hexToChar(const std::string &str) {
	short c = 0;
	 
	if(!str.empty()) {
		std::istringstream in(str);
		 
		in >> std::hex >> c;
		 
		if(in.fail()) {
			throw std::runtime_error("stream decode failure");
		}
	}
	 
	return static_cast<unsigned char>(c);
}
    
std::string urlEncode(const std::string &toEncode) {
	std::ostringstream out;

	for(std::string::size_type i=0; i < toEncode.length(); ++i) {
	  short t = toEncode.at(i);

	  if(
		  t == 45 ||          // hyphen
		  (t >= 48 && t <= 57) ||       // 0-9
		  (t >= 65 && t <= 90) ||       // A-Z
		  t == 95 ||          // underscore
		  (t >= 97 && t <= 122) ||  // a-z
		  t == 126            // tilde
	  ) {
		  out << toEncode.at(i);
	  } else {
		  out << charToHex(toEncode.at(i));
	  }
	}

	return out.str();
}

std::string urlDecode(const std::string &toDecode) {
	std::ostringstream out;

	for(std::string::size_type i=0; i < toDecode.length(); ++i) {
	  if(toDecode.at(i) == '%') {
		  std::string str(toDecode.substr(i+1, 2));
		  out << hexToChar(str);
		  i += 2;
	  } else {
		  out << toDecode.at(i);
	  }
	}

	return out.str();
}