#include <string>
#include <cctype>
#include <iostream>
using std::cout;
using std::endl;
using std::string;
 
const string b64_chars = 
             "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
             "abcdefghijklmnopqrstuvwxyz"
             "0123456789+/";
 
inline bool is_b64(unsigned char c) 
{
  return (isalnum(c) || (c == '+') || (c == '/'));
}
 
 
string b64_encode(const string bytes_to_encode) 
{
  unsigned int in_len = bytes_to_encode.size(); 
  string ret;
  int i = 0;
  int j = 0;
  int n = 0;
  unsigned char char_array_3[3];
  unsigned char char_array_4[4];
 
  while (in_len--) 
  {
    char_array_3[i++] = bytes_to_encode[n++];
    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 += b64_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 += b64_chars[char_array_4[j]];
 
    while((i++ < 3))
      ret += '=';
  }
 
  return ret;
}
 
//................................................................. 
 
string b64_decode(const string &encoded_string) 
{
  unsigned int in_len = encoded_string.size();
  int i = 0;
  int j = 0;
  int in_ = 0;
  unsigned char char_array_4[4];
  unsigned char char_array_3[3];
  string ret;
 
  while (in_len-- && ( encoded_string[in_] != '=') && is_b64(encoded_string[in_])) 
  {
    char_array_4[i++] = encoded_string[in_]; 
    in_++;
    if (i ==4) 
    {
      for (i = 0; i <4; i++)
        char_array_4[i] = b64_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] = b64_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;
}
 
int main(int argc, char * argv[])
{
    char const * str = "qazwsx12вася3@mail.ru";
    std::string res = b64_encode( str );
    
    std::cout << res << std::endl; 
}

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