mirror of
https://github.com/hsoft/collapseos.git
synced 2024-11-21 00:18:06 +11:00
55 lines
774 B
NASM
55 lines
774 B
NASM
|
; mmap
|
||
|
|
;
|
||
|
|
; Block device that maps to memory.
|
||
|
|
;
|
||
|
|
; *** DEFINES ***
|
||
|
|
; MMAP_START: Memory address where the mmap begins
|
||
|
|
|
||
|
|
; *** VARIABLES ***
|
||
|
|
MMAP_PTR .equ MMAP_RAMSTART
|
||
|
|
MMAP_RAMEND .equ MMAP_PTR+2
|
||
|
|
|
||
|
|
; *** CODE ***
|
||
|
|
|
||
|
|
; Increase mem pointer by one
|
||
|
|
_mmapForward:
|
||
|
|
ld hl, (MMAP_PTR)
|
||
|
|
inc hl
|
||
|
|
ld (MMAP_PTR), hl
|
||
|
|
ret
|
||
|
|
|
||
|
|
; Returns absolute addr of memory pointer in HL.
|
||
|
|
_mmapAddr:
|
||
|
|
push de
|
||
|
|
ld hl, (MMAP_PTR)
|
||
|
|
ld de, MMAP_START
|
||
|
|
add hl, de
|
||
|
|
jr nc, .end
|
||
|
|
; we have carry? out of bounds, set to maximum
|
||
|
|
ld hl, 0xffff
|
||
|
|
.end:
|
||
|
|
pop de
|
||
|
|
ret
|
||
|
|
|
||
|
|
; if out of bounds, will continually return the last char
|
||
|
|
mmapGetC:
|
||
|
|
push hl
|
||
|
|
call _mmapAddr
|
||
|
|
ld a, (hl)
|
||
|
|
call _mmapForward
|
||
|
|
pop hl
|
||
|
|
ret
|
||
|
|
|
||
|
|
mmapPutC:
|
||
|
|
push hl
|
||
|
|
call _mmapAddr
|
||
|
|
ld (hl), a
|
||
|
|
call _mmapForward
|
||
|
|
pop hl
|
||
|
|
ret
|
||
|
|
|
||
|
|
mmapSeek:
|
||
|
|
ld (MMAP_PTR), hl
|
||
|
|
ret
|
||
|
|
|