170 lines
3.8 KiB
Fennel
170 lines
3.8 KiB
Fennel
(local lume (require :lib.lume))
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(local asm (require :asm.asm))
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(local VM (require :asm.vm))
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(local tile (require :game.tiles))
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(local link (require :link))
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(local {: lo : hi} (require :lib.util))
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(local prg (asm.new))
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; (prg:debug-to "test.dbg")
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(local tiles (prg:org 0x6100))
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(local vm (VM.new prg))
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(local code1 vm.code)
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(local mon {
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:hexout :0xfdda
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:putchar :0xfded
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:bell :0xff3a
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})
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(fn achar [c] (bit.bor (string.byte c) 0x80))
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(fn astr [s]
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(-> [(string.byte s 1 -1)]
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(lume.map #(bit.bor $1 0x80))
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(-> (table.unpack) (string.char))))
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; a handful of debugging words
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(vm:def :.
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[:lda vm.TOPH :x]
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[:jsr mon.hexout]
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[:lda vm.TOP :x]
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[:jsr mon.hexout]
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[:lda (achar " ")]
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[:jsr mon.putchar]
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(vm:drop))
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(vm:def :stacklen
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(vm:reserve)
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[:txa] [:lsr :a] [:sta vm.TOP :x]
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[:lda 0] [:sta vm.TOPH :x])
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(vm:word :.s
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:stacklen (prg:parse-addr vm.TOP) :swap
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(vm:for :dup :get :. :inc :inc) :drop)
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; Graphics routines
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(vm:def :hires
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[:sta :0xc050]
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[:sta :0xc057]
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[:sta :0xc052])
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(vm:def :mixed [:sta :0xc051])
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; starting address:
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; 0x2000 + (x*2) + (y%4 * 0x100) + ((y/4) * 0x28)
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; x between 0-19
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; y between 0-12
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; yx - 16-bit value, low byte x, high byte y
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(code1:append :screeny-lookup [:bytes "\0\040\080"])
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(vm:def :tile>screen ; yx -- p
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[:lda vm.TOPH :x] ; a=y
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[:lsr :a] [:lsr :a] ; a=y/4
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[:tay] ; y=y/4
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[:lda 0x03]
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[:and vm.TOPH :x] ; a=y%4
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[:ora 0x20] ; a=0x20 + y%4
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[:sta vm.TOPH :x] ; high byte is set (and y is wiped)
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[:lda vm.TOP :x] ; a=x
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[:asl :a] ; a = x*2
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[:clc]
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[:adc :screeny-lookup :y] ; a=x*2 + (y/4)*0x28
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[:sta vm.TOP :x] ; low byte is set
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)
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; note: the graphical tile data must not cross a page boundary
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; (this happens automatically because each tile is 32 bytes and we
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; start them on a page; this lets lookup-tile be fast)
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(fn draw-block []
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[:block
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[:clc]
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[:ldy 8]
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:loop
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[:lda [vm.TOP :x]]
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[:sta [vm.ST1 :x]]
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[:inc vm.TOP :x]
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[:lda vm.ST1H :x]
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[:adc 4]
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[:sta vm.ST1H :x]
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[:dey]
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[:bne :loop]])
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(fn draw-vertical-block []
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[:block
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(draw-block)
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[:lda vm.ST1H :x]
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[:sbc 31] ; with carry clear this is 32
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[:sta vm.ST1H :x]
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[:lda vm.ST1 :x]
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[:ora 0x80]
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[:sta vm.ST1 :x]
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(draw-block)])
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(vm:def :drawtile ; p gfx --
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(draw-vertical-block)
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[:lda vm.ST1H :x]
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[:sbc 31]
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[:sta vm.ST1H :x]
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[:lda vm.ST1 :x]
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[:sbc 0x7f]
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[:sta vm.ST1 :x]
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(draw-vertical-block)
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(vm:drop) (vm:drop))
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(vm:def :cleargfx
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(vm:push 0x4000)
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[:block :page
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[:dec vm.TOPH :x]
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[:lda 0]
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[:block :start
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[:sta [vm.TOP :x]]
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[:inc vm.TOP :x]
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[:bne :start]]
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[:lda vm.TOPH :x]
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[:cmp 0x20]
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[:bne :page]]
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(vm:drop))
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(vm:word :drawmaprow ; pscreen pmap -- pmap
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20 (vm:for
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:2dup :bget :lookup-tile :drawtile
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:inc :swap :inc :inc :swap) :swap :drop)
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(vm:word :drawmap
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:lit :map 0x0c00 (vm:until 0x100 :-
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:dup :tile>screen ; pmap yx pscreen
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:<rot :drawmaprow :swap ; pmap yx
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:dup :not) :drop :drop)
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(vm:def :lookup-tile ; itile -- ptile
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; each tile is 32 bytes; 2^5
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; we save some cycles by storing the indices as lllhhhhh, so we don't need to shift them'
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[:lda vm.TOP :x] [:tay]
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[:and 0x1f]
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[:clc] [:adc #(hi tiles.org)]
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[:sta vm.TOPH :x]
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[:tya] [:and 0xe0]
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[:sta vm.TOP :x])
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(tile.appendtiles (tile.loadtiles) tiles)
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; thought:
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; hotswap-safe debug stub at root of call stack
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; but REPL debug stub should be very available as a task
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; 20x12 means full map is 240 bytes - we have an extra 16 bytes at the end to mess with?
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(tile.appendmaps (prg:org 0x6800))
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(code1:append :main
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[:jsr :reset]
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[:jsr :interpret]
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[:vm :hires ; :mixed
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:cleargfx ; :drawmap
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(vm:forever
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(vm:hotswap-sync) :drawmap
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)
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; 0x0000 :tile>screen 0 :lookup-tile :drawtile
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:quit])
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(prg:assemble)
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