collapseos/kernel/mmap.asm

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; mmap
;
; Block device that maps to memory.
;
; *** DEFINES ***
; MMAP_START: Memory address where the mmap begins
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; Memory address where the mmap stops, exclusively (we aren't allowed to access
; that address).
.equ MMAP_LEN 0xffff-MMAP_START
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; Returns absolute addr of memory pointer in HL if HL is within bounds.
; Sets Z on success, unset when out of bounds.
_mmapAddr:
push de
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ld de, MMAP_LEN
call cpHLDE
jr nc, .outOfBounds ; HL >= DE
ld de, MMAP_START
add hl, de
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cp a ; ensure Z
pop de
ret
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.outOfBounds:
pop de
jp unsetZ
mmapGetB:
push hl
call _mmapAddr
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jr nz, .end
ld a, (hl)
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; Z already set
.end:
pop hl
ret
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mmapPutB:
push hl
call _mmapAddr
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jr nz, .end
ld (hl), a
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; Z already set
.end:
pop hl
ret