git.sur5r.net Git - cc65/blob - libsrc/common/_fdesc.s

   1 ;
   2 ; Ullrich von Bassewitz, 17.06.1998
   3 ;
   4 ; int _fdesc (void);
   5 ; /* Find a free descriptor slot */
   6
   7
   8         .export         __fdesc
   9         .import         return0
  10
  11         .include        "stdio.inc"
  12         .include        "_file.inc"
  13
  14 .proc   __fdesc
  15
  16         ldy     #0
  17         lda     #_FOPEN
  18 Loop:   and     __filetab + _FILE::f_flags,y    ; load flags
  19         beq     Found                           ; jump if closed
  20 .repeat .sizeof(_FILE)
  21         iny
  22 .endrepeat
  23         cpy     #(FOPEN_MAX * .sizeof(_FILE))   ; Done?
  24         bne     Loop
  25
  26 ; File table is full
  27
  28         jmp     return0
  29
  30 ; Free slot found, get address
  31
  32 Found:  tya                     ; Offset
  33         clc
  34         adc     #<__filetab
  35         ldx     #>__filetab     ; High byte
  36         bcc     @L1             ; Jump if no overflow
  37         inx                     ; Bump high byte
  38 @L1:    rts
  39
  40 .endproc
  41
  42
  43