63 lines
2.1 KiB
NASM
63 lines
2.1 KiB
NASM
SECTION "Tools", ROM0
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; Memory copier
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; @param de - Address source to start of data to be copied
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; @param hl - Address destomatopm where to copy the data to
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; @param bc - The total amount of bytes to copy
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; @return a = Zero
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; @return bc = Zero
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; @return de = Address Source to the byte after the last byte from source (garbage)
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; @return hl = Address Target to the byte after the last byte on the target (garbage)
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Memcpy:
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ld a, [de] ; Load the value at [de] to accumilator
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ld [hli], a ; Load the value from accumilator to the destination address and increment it by one
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inc de ; Increment de to point to next byte to copy
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dec bc ; Decrement bc the total amount of bytes to copy
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ld a, b ; Load the first half of total amount of bytes to write to accumilator
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or c ; OR together the second half of total amount with the first half
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jr nz, Memcpy ; Loop back to Memcpy if not zero
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ret
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Memfill:
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; Fill an area in memory at position hl with value a for b amount of times
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;
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; @param hl - Starting address in memory to fill
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; @param a - The value to fill said address space with
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; @param b - How many bytes we should fill starting from said address space
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; @return a - garbage
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; @return b - PosX on where to draw text
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; @return c - PosY on where to draw text
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; @return hl - Workram position for text pointer
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; @return de - Memory address to source string
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.repeatFill
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ld [hli], a
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dec b
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jr nz, .repeatFill
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ret
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Memfill16:
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; Fill an area in memory at position hl with value a for bc amount of times
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;
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; @param hl - Starting address in memory to fill
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; @param a - The value to fill said address space with
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; @param b - How many bytes we should fill starting from said address space
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; @return a - garbage
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; @return b - PosX on where to draw text
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; @return c - PosY on where to draw text
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; @return hl - Workram position for text pointer
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; @return de - Memory address to source string
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.repeatFill
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ld [hli], a
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dec bc
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jr nz, .repeatFill
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ret
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;;
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; Waits for the vblank ISR to increment the count of vertical blanks.
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; Will lock up if DI, vblank IRQ off, or LCD off.
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; Clobbers A, HL
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WaitVBlank:
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.wait
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halt
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ret
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