Topic       : TOS - The Operating System
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View Ref-File5.10.27  Fselect                                                   TOS

 Name:         »Fselect« - Enquiry of the file status with timeout.

 Opcode:       285

 Syntax:       int32_t Fselect ( int16_t timeout, int32_t *rfds, 
               int32_t *wfds, ((int32_t) 0) );

 Description:  The function Fselect checks which open files are ready 
               for reading or writing. The parameter rfds points to a 
               LONG bitmap which describes the set of GEMDOS read file 
               descriptors to wait for.

               In this longword, bit n is set when the file descriptor 
               n is to be checked for input. An empty set may also be 
               represented optionally by a NULL-pointer.

               In the same way, wfds points to a set of write file 
               descriptors whose output status is to be checked.

               On return of the function, the handles of the files 
               that are ready for reading or writing respectively and 
               also should be checked are passed in rfds and wfds.

               Note that currently the only BIOS device Fselect works 
               with is the keyboard.

               With timeout one can specify how many milliseconds one 
               should wait before the function returns. A value of 0 
               means in this case that the function waits until one of 
               the specified files is ready for reading or writing.

               Example:

                Fselect (0, 0L, 0L, 0L) waits forever
                Fselect (1, 0L, 0L, 0L) waits for one millisecond

 Return value: The function can return the following results:

                0 :       In the specified time no files were ready 
                          for reading or writing (timeout)
                >0 :      Sum of the set bits of rfds and wfds
                EIHNDL :  At least one of the handles is not assigned 
                          to an open file

 Availability: As of the first in MultiTOS integrated MiNT version 
               1.04.

 Group:        File functions

 See Also:     Binding   Finstat   Foutstat