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collapseos/kernel/stdio.asm
Virgil Dupras 73c3fc7947 shell/stdio: decouple from blkdev (again)
Move load/save to blkdev_cmds and add a new "poke" builtin shell cmd
that is the mirror of "peek" and strictly uses stdio (no blkdev
involved).

This allows us to slim the minimal OS size but, more importantly, change
the behavior of "load" so that we don't expect GetC to block until Z is
set. This way, using "load X" with X being larger than the blkdev size
won't block forever.

This also brings our RC2014 minimal kernel below the 1K mark again.
2019-06-02 11:06:38 -04:00

91 lines
1.3 KiB
NASM

; stdio
;
; Allows other modules to print to "standard out", and get data from "stamdard
; in", that is, the console through which the user is connected in a decoupled
; manner.
;
; *** VARIABLES ***
; Used to store formatted hex values just before printing it.
.equ STDIO_HEX_FMT STDIO_RAMSTART
.equ STDIO_GETC STDIO_HEX_FMT+2
.equ STDIO_PUTC STDIO_GETC+2
.equ STDIO_RAMEND STDIO_PUTC+2
; Sets GetC to the routine where HL points to and PutC to DE.
stdioInit:
ld (STDIO_GETC), hl
ld (STDIO_PUTC), de
ret
stdioGetC:
ld ix, (STDIO_GETC)
jp (ix)
stdioPutC:
ld ix, (STDIO_PUTC)
jp (ix)
; print null-terminated string pointed to by HL
printstr:
push af
push hl
.loop:
ld a, (hl) ; load character to send
or a ; is it zero?
jr z, .end ; if yes, we're finished
call stdioPutC
inc hl
jr .loop
.end:
pop hl
pop af
ret
; print A characters from string that HL points to
printnstr:
push bc
push hl
ld b, a
.loop:
ld a, (hl) ; load character to send
call stdioPutC
inc hl
djnz .loop
.end:
pop hl
pop bc
ret
printcrlf:
ld a, ASCII_CR
call stdioPutC
ld a, ASCII_LF
call stdioPutC
ret
; Print the hex char in A
printHex:
push af
push hl
ld hl, STDIO_HEX_FMT
call fmtHexPair
ld a, 2
call printnstr
pop hl
pop af
ret
; Print the hex pair in HL
printHexPair:
push af
ld a, h
call printHex
ld a, l
call printHex
pop af
ret