如何将QString转换为binary数据类型！每两个字符转换为一个binary

QString from;

 unsigned char *to;

 int toSize;

  unsigned char *buff; 
  int buffSize;
  int i;
  
  buffSize = toSize*2;                 //此处 *2 为自己工作需要
  if(from.size() != buffSize)
    return -1;
  buff = (unsigned char *)malloc(buffSize);
  if(buff == NULL)
    return -1;
  memcpy(buff, from.toLocal8Bit().constData(), buffSize);    //先将QString 转换为char*
  
  for(i=0; i  {
    if(buff[i]>='0' && buff[i]<='9')            
      buff[i] = buff[i] - '0';                                        
    else if(buff[i]>='a' && buff[i]<='f')
      buff[i] = buff[i] - 'a' + 10;                               //buff[i] -=  'a' - 10;
    else {
      return -1;
      free(buff);
    }
  }
  for(i=0; i    to[i] = buff[i<<1]<<4 + buff[i+1];              //将buf[i<<1]<<       右移四位      
  free(buff);
  return 0;

此处 unsigned char *  等同于binary 数据类型；