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        "_file.inc"
  12
  13 .proc   __fdesc
  14
  15         ldy     #0
  16         lda     #_FOPEN
  17 Loop:   and     __filetab + _FILE_f_flags,y     ; load flags
  18         beq     Found                           ; jump if closed
  19 .repeat ::_FILE_size
  20         iny
  21 .endrepeat
  22         cpy     #(FOPEN_MAX * _FILE_size)       ; Done?
  23         bne     Loop
  24
  25 ; File table is full
  26
  27         jmp     return0
  28
  29 ; Free slot found, get address
  30
  31 Found:  tya                     ; Offset
  32         clc
  33         adc     #<__filetab
  34         ldx     #>__filetab     ; High byte
  35         bcc     @L1             ; Jump if no overflow
  36         inx                     ; Bump high byte
  37 @L1:    rts
  38
  39 .endproc
  40
  41
  42