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collapseos/apps/zasm/io.asm
2019-05-14 16:45:56 -04:00

81 lines
1.5 KiB
NASM

; *** Consts ***
.equ IO_MAX_LINELEN 0xff
; *** Variables ***
.equ IO_IN_GETC IO_RAMSTART
.equ IO_IN_PUTC IO_IN_GETC+2
.equ IO_IN_SEEK IO_IN_PUTC+2
.equ IO_IN_TELL IO_IN_SEEK+2
.equ IO_OUT_GETC IO_IN_TELL+2
.equ IO_OUT_PUTC IO_OUT_GETC+2
.equ IO_OUT_SEEK IO_OUT_PUTC+2
.equ IO_OUT_TELL IO_OUT_SEEK+2
.equ IO_LINEBUF IO_OUT_TELL+2
.equ IO_RAMEND IO_LINEBUF+IO_MAX_LINELEN+1
; *** Code ***
ioGetC:
ld ix, (IO_IN_GETC)
jp (ix)
ioPutC:
ld ix, (IO_OUT_PUTC)
jp (ix)
ioRewind:
ld hl, 0
ld ix, (IO_IN_SEEK)
jp (ix)
; Sets Z is A is CR, LF, or null.
isLineEnd:
or a ; same as cp 0
ret z
cp 0x0d
ret z
cp 0x0a
ret z
cp '\'
ret
; Read a single line from ioGetCPtr and place it in IO_LINEBUF.
; Returns number of chars read in A. 0 means we're at the end of our input
; stream, which happens when GetC unsets Z. Make HL point to IO_LINEBUF.
; We ignore empty lines and pass through them like butter.
; A null char is written at the end of the line.
ioReadLine:
push bc
; consume ioGetC as long as it yields a line end char.
.loop1:
call ioGetC
jr nz, .eof ; GetC unsets Z? We don't have a line to read,
; we have EOF.
call isLineEnd
jr z, .loop1
; A contains the first char of our line.
ld c, 1
ld (IO_LINEBUF), a
ld hl, IO_LINEBUF+1
.loop2:
call ioGetC
call isLineEnd
jr z, .success ; We have end of line
ld (hl), a
inc hl
inc c
jr .loop2
.success:
; write null char at HL before we return
xor a
ld (hl), a
ld a, c
ld hl, IO_LINEBUF
jr .end
.eof:
xor a
.end:
pop bc
ret