int (*f_look)(COMSTACK handle);
int (*f_put)(COMSTACK handle, char *buf, int size);
int (*f_get)(COMSTACK handle, char **buf, int *bufsize);
int (*f_look)(COMSTACK handle);
int (*f_put)(COMSTACK handle, char *buf, int size);
int (*f_get)(COMSTACK handle, char **buf, int *bufsize);