WOL Apgar routine in CPP (RenegadeProjects.com)

apgar.cpp

std::string apgar(std::string input) {  
  std::string lookup = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
  std::string out = "";
  int i = 0;
  while (i < 8) {
    unsigned char left = input[i];
    unsigned char right = input[input.length() - i];

    unsigned char x = left & 1 ? ((left << 1) ^ (left & 1)) & right : left ^ right;

    out += lookup[x & 63];
    i++;
  }
  return out;
}