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cc65/libsrc/common/_fdesc.s

44 lines
879 B
ArmAsm

;
; Ullrich von Bassewitz, 17.06.1998
;
; int _fdesc (void);
; /* Find a free descriptor slot */
.export __fdesc
.import return0
.include "stdio.inc"
.include "_file.inc"
.proc __fdesc
ldy #0
lda #_FOPEN
Loop: and __filetab + _FILE::f_flags,y ; load flags
beq Found ; jump if closed
.repeat .sizeof(_FILE)
iny
.endrepeat
cpy #(FOPEN_MAX * .sizeof(_FILE)) ; Done?
bne Loop
; File table is full
jmp return0
; Free slot found, get address
Found: tya ; Offset
clc
adc #<__filetab
ldx #>__filetab ; High byte
bcc @L1 ; Jump if no overflow
inx ; Bump high byte
@L1: rts
.endproc