C++ char转十六进制

int hexCharToInt(char c)  {           if (c >= '0' && c <= '9') return (c - '0');          if (c >= 'A' && c <= 'F') return (c - 'A' + 10);          if (c >= 'a' && c <= 'f') return (c - 'a' + 10);          return 0;  }    char* hexstringToBytes(string s)  {                   int sz = s.length();          char *ret = new char[sz/2];          for (int i=0 ; i <sz ; i+=2) {              ret[i/2] = (char) ((hexCharToInt(s.at(i)) << 4)                                  | hexCharToInt(s.at(i+1)));          }          return ret;  }    string bytestohexstring(char* bytes,int bytelength)  {    string str("");    string str2("0123456789abcdef");      for (int i=0;i<bytelength;i++) {       int b;       b = 0x0f&(bytes[i]>>4);       char s1 = str2.at(b);       str.append(1,str2.at(b));                 b = 0x0f & bytes[i];       str.append(1,str2.at(b));       char s2 = str2.at(b);     }     return str;  }    int main()  {          char s[3] ={'a','b','c'};  

        std::string result;

        result = bytestohexstring(s,strlen(s));  

        for(int i=0;i<3;i++)
        {
            printf("%02x", s[i]&0xFF);
        }

        printf("\n%s\n",result.data());

        system("pause");}