text: #include "base64.h"
  #include <iostream>
  
  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);
  
      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 = 0; j < i; 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);
  
      for (j = 0; (j < i - 1); j++) ret += char_array_3[j];
    }
  
    return ret;
  }
  