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- ; mmap
- ;
- ; Block device that maps to memory.
- ;
- ; *** DEFINES ***
- ; MMAP_START: Memory address where the mmap begins
- ; Memory address where the mmap stops, exclusively (we aren't allowed to access
- ; that address).
- .equ MMAP_LEN 0xffff-MMAP_START
-
- ; 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
- ld de, MMAP_LEN
- or a ; reset carry flag
- sbc hl, de
- jr nc, .outOfBounds ; HL >= DE
- add hl, de ; old HL value
- ld de, MMAP_START
- add hl, de
- cp a ; ensure Z
- pop de
- ret
- .outOfBounds:
- pop de
- jp unsetZ
-
- mmapGetB:
- push hl
- call _mmapAddr
- jr nz, .end
- ld a, (hl)
- ; Z already set
- .end:
- pop hl
- ret
-
-
- mmapPutB:
- push hl
- call _mmapAddr
- jr nz, .end
- ld (hl), a
- ; Z already set
- .end:
- pop hl
- ret
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