collapseos/kernel/mmap.asm
Virgil Dupras ae028e3a86 blockdev: make implementors "random access"
This huge refactoring remove the Seek and Tell routine from blockdev
implementation requirements and change GetC and PutC's API so that they
take an address to read and write (through HL/DE) at each call.

The "PTR" approach in blockdev implementation was very redundant from
device to device and it made more sense to generalize. It's possible
that future device aren't "random access", but we'll be able to add more
device types later.

Another important change in this commit is that the "blockdev handle" is
now opaque. Previously, consumers of the API would happily call routines
directly from one of the 4 offsets. We can't do that any more. This
makes the API more solid for future improvements.

This change forced me to change a lot of things in fs, but overall,
things are now simpler. No more `FS_PTR`: the "device handle" now holds
the active pointer.

Lots, lots of changes, but it also feels a lot cleaner and solid.
2019-06-04 15:36:20 -04:00

37 lines
577 B
NASM

; mmap
;
; Block device that maps to memory.
;
; *** DEFINES ***
; MMAP_START: Memory address where the mmap begins
; Returns absolute addr of memory pointer in HL.
_mmapAddr:
push de
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
; TODO: add bounds check and return Z accordingly.
mmapGetC:
push hl
call _mmapAddr
ld a, (hl)
cp a ; ensure Z
pop hl
ret
mmapPutC:
push hl
call _mmapAddr
ld (hl), a
cp a ; ensure Z
pop hl
ret