47 lines
736 B
NASM
47 lines
736 B
NASM
; mmap
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;
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; Block device that maps to memory.
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;
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; *** DEFINES ***
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; 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
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; that address).
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.equ MMAP_LEN 0xffff-MMAP_START
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; Returns absolute addr of memory pointer in HL if HL is within bounds.
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; Sets Z on success, unset when out of bounds.
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_mmapAddr:
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push de
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ld de, MMAP_LEN
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call cpHLDE
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jr nc, .outOfBounds ; HL >= DE
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ld de, MMAP_START
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add hl, de
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cp a ; ensure Z
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pop de
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ret
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.outOfBounds:
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pop de
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jp unsetZ
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mmapGetC:
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push hl
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call _mmapAddr
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jr nz, .end
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ld a, (hl)
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; Z already set
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.end:
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pop hl
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ret
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mmapPutC:
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push hl
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call _mmapAddr
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jr nz, .end
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ld (hl), a
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; Z already set
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.end:
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pop hl
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ret
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