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cc65/libsrc/sym1/read.s
2022-04-17 16:06:22 +02:00

54 lines
1.4 KiB
ArmAsm

;
; Wayne Parham (wayne@parhamdata.com)
;
; int __fastcall__ read (int fd, void* buf, unsigned count);
;
.include "sym1.inc"
.import popax, popptr1
.importzp ptr1, ptr2, ptr3
.export _read
.proc _read
sta ptr3
stx ptr3+1 ; Count in ptr3
inx
stx ptr2+1 ; Increment and store in ptr2
tax
inx
stx ptr2
jsr popptr1 ; Buffer address in ptr1
jsr popax
begin: dec ptr2
bne getch
dec ptr2+1
beq done ; If buffer full, return
getch: jsr INTCHR ; Get character using Monitor ROM call
jsr OUTCHR ; Echo it
and #$7F ; Clear top bit
cmp #$07 ; Check for '\a'
bne chkcr ; ...if BEL character
jsr BEEP ; Make beep sound
chkcr: cmp #$0D ; Check for '\r'
bne putch ; ...if CR character
lda #$0A ; Replace with '\n'
jsr OUTCHR ; and echo it
putch: ldy #$00 ; Put char into return buffer
sta (ptr1),y
inc ptr1 ; Increment pointer
bne begin
inc ptr1+1
bne begin
done: lda ptr3
ldx ptr3+1
rts ; Return count
.endproc