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cc65/libsrc/sym1/read.s
2021-06-06 21:28:03 -05:00

51 lines
1.2 KiB
ArmAsm

;
; Wayne Parham (wayne@parhamdata.com)
;
; int 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 hi bit and check for '\r'
cmp #$0D
bne putch
lda #$0A ; Replace with '\n' and set count to zero
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