typedef struct FileChrs <Record> {
  int mode; /* rw .. */
  Key *key;
  Ack *ack;
  Record *record;
  Output *reader;
  Data *fileImpl ;
  __code setOutput(Output *output,__code next(...)) ;
  __code Open(Key *key, Output reader, __code next(...)) ;
  __code Ack(Ack *ack, Output reader, __code next(...)) ;
} FileChrs;