-BFile bf_open (const char *name, int block_size, int rw);
-int bf_read (BFile bf, int no, void *buf);
-int bf_write (BFile bf, int no, const void *buf);
+BFile bf_open (const char *name, int block_size, int wflag);
+int bf_read (BFile bf, int no, int offset, int num, void *buf);
+int bf_write (BFile bf, int no, int offset, int num, const void *buf);