(in-package :chip8)
(setf *print-length* 16)
(setf *print-base* 10)
(declaim (optimize (speed 1) (safety 3) (debug 3)))
(declaim (optimize (speed 3) (safety 1) (debug 3)))
;;;; Reference ----------------------------------------------------------------
;;; http://devernay.free.fr/hacks/chip8/C8TECH10.HTM
;;; http://mattmik.com/files/chip8/mastering/chip8.html
;;; https://github.com/AfBu/haxe-chip-8-emulator/wiki/(Super)CHIP-8-Secrets
;;;; Constants ----------------------------------------------------------------
(defconstant +cycles-per-second+ 500)
(defconstant +cycles-before-sleep+ 10)
(defconstant +screen-width+ 64)
(defconstant +screen-height+ 32)
(defconstant +memory-size+ (* 1024 4))
;;;; Types --------------------------------------------------------------------
(deftype int4 () '(unsigned-byte 4))
(deftype int8 () '(unsigned-byte 8))
(deftype int12 () '(unsigned-byte 12))
(deftype int16 () '(unsigned-byte 16))
(deftype x-coord () `(integer 0 (,+screen-width+)))
(deftype y-coord () `(integer 0 (,+screen-height+)))
(deftype basic-array (element-type size)
`(simple-array ,(upgraded-array-element-type element-type) (,size)))
(deftype stack (size)
`(vector ,(upgraded-array-element-type 'int12) ,size))
;;;; Utils --------------------------------------------------------------------
(declaim
(inline not= +_8 -_8 chop cat-bytes get-bit bcd))
(defun make-simple-array (element-type size &rest args)
(apply #'make-array size
:adjustable nil
:fill-pointer nil
:element-type element-type
args))
(defun not= (x y)
(not (= x y)))
(defun chop (size integer)
(ldb (byte size 0) integer))
(defun cat-bytes (high-order low-order)
(dpb high-order (byte 8 8) low-order))
(defun get-bit (position integer)
(ldb (byte 1 position) integer))
(defun +_8 (x y)
(let ((result (+ x y)))
(values (chop 8 result)
(if (> result 255) 1 0))))
(defun -_8 (x y)
(let ((result (- x y)))
(values (chop 8 result)
(if (> x y) 1 0))))
(defun bcd (integer)
(values (-<> integer (floor <> 100) (mod <> 10))
(-<> integer (floor <> 10) (mod <> 10))
(-<> integer (floor <> 1) (mod <> 10))))
(defmacro macro-map ((lambda-list items) &rest body)
(with-gensyms (macro)
`(macrolet ((,macro ,(ensure-list lambda-list) ,@body))
,@(iterate (for item :in items)
(collect `(,macro ,@(ensure-list item)))))))
;;;; Data ---------------------------------------------------------------------
(declaim
(inline chip-flag (setf chip-flag)))
(defstruct debugger
(paused nil :type boolean)
(take-step nil :type boolean)
(print-needed nil :type boolean)
(callbacks-arrived nil :type list))
(defstruct chip
(running t :type boolean)
(memory (make-simple-array 'int8 4096)
:type (basic-array int8 4096)
:read-only t)
(registers (make-simple-array 'int8 16)
:type (basic-array int8 16)
:read-only t)
(keys (make-simple-array 'boolean 16)
:type (basic-array boolean 16)
:read-only t)
(video (make-simple-array 'fixnum (* +screen-height+ +screen-width+))
:type (basic-array fixnum #.(* +screen-height+ +screen-width+))
:read-only t)
(video-dirty t :type boolean)
(index 0 :type int16)
(program-counter #x200 :type int12)
(delay-timer 0 :type int8)
(sound-timer 0 :type int8)
(random-state (make-random-state t)
:type random-state
:read-only t)
(stack (make-array 16
:adjustable nil
:fill-pointer 0
:element-type 'int12)
:type (stack 16)
:read-only t)
(loaded-rom nil :type (or null string))
(debugger (make-debugger) :type debugger :read-only t))
(define-with-macro chip
running
memory registers
flag
index program-counter
delay-timer sound-timer
random-state
video video-dirty
keys
stack
loaded-rom
debugger)
(define-with-macro debugger
paused take-step print-needed
callbacks-arrived)
(defun chip-flag (chip)
(aref (chip-registers chip) #xF))
(defun (setf chip-flag) (new-value chip)
(setf (aref (chip-registers chip) #xF) new-value))
;;;; Disassembler -------------------------------------------------------------
(defun disassemble-instruction (instruction)
(flet ((v (n) (symb 'v (format nil "~X" n))))
(let ((_x__ (ldb (byte 4 8) instruction))
(__x_ (ldb (byte 4 4) instruction))
(___x (ldb (byte 4 0) instruction))
(__xx (ldb (byte 8 0) instruction))
(_xxx (ldb (byte 12 0) instruction)))
(case (logand #xF000 instruction)
(#x0000 (case instruction
(#x00E0 '(cls))
(#x00EE '(ret))))
(#x1000 `(jp ,_xxx))
(#x2000 `(call ,_xxx))
(#x3000 `(se ,(v _x__) ,__xx))
(#x4000 `(sne ,(v _x__) ,__xx))
(#x5000 (case (logand #x000F instruction)
(#x0 `(se ,(v _x__) ,(v __x_)))))
(#x6000 `(ld ,(v _x__) ,__xx))
(#x7000 `(add ,(v _x__) ,__xx))
(#x8000 (case (logand #x000F instruction)
(#x0 `(ld ,(v _x__) ,(v __x_)))
(#x1 `(or ,(v _x__) ,(v __x_)))
(#x2 `(and ,(v _x__) ,(v __x_)))
(#x3 `(xor ,(v _x__) ,(v __x_)))
(#x4 `(add ,(v _x__) ,(v __x_)))
(#x5 `(sub ,(v _x__) ,(v __x_)))
(#x6 `(shr ,(v _x__) ,(v __x_)))
(#x7 `(subn ,(v _x__) ,(v __x_)))
(#xE `(shl ,(v _x__) ,(v __x_)))))
(#x9000 (case (logand #x000F instruction)
(#x0 `(sne ,(v _x__) ,(v __x_)))))
(#xA000 `(ld i ,_xxx))
(#xB000 `(jp ,(v 0) ,_xxx))
(#xC000 `(rnd ,(v _x__) ,__xx))
(#xD000 `(drw ,(v _x__) ,(v __x_) ,___x))
(#xE000 (case (logand #x00FF instruction)
(#x9E `(skp ,(v _x__)))
(#xA1 `(sknp ,(v _x__)))))
(#xF000 (case (logand #x00FF instruction)
(#x07 `(ld ,(v _x__) dt))
(#x0A `(ld ,(v _x__) k))
(#x15 `(ld dt ,(v _x__)))
(#x18 `(ld st ,(v _x__)))
(#x1E `(add i ,(v _x__)))
(#x29 `(ld f ,(v _x__)))
(#x33 `(ld b ,(v _x__)))
(#x55 `(ld (mem i) ,_x__))
(#x65 `(ld ,_x__ (mem i)))))))))
(defun bit-diagram (integer)
(iterate (for high-bit :from 15 :downto 8)
(for low-bit :from 7 :downto 0)
(for hi = (logbitp high-bit integer))
(for lo = (logbitp low-bit integer))
(collect (cond
((and hi lo) #\full_block)
(hi #\upper_half_block)
(lo #\lower_half_block)
(t #\space))
:result-type 'string)))
(defun retrieve-instruction (array index)
(chip8::cat-bytes (aref array index)
;; ugly hack to handle odd-sized roms
(if (< (1+ index) (length array))
(aref array (1+ index))
0)))
(defun instruction-information (array index)
(let ((instruction (retrieve-instruction array index)))
(list index
instruction
(disassemble-instruction instruction)
(bit-diagram instruction))))
(defun print-disassembled-instruction (array index)
(destructuring-bind (address instruction disassembly bits)
(instruction-information array index)
(format t "~3,'0X: ~4,'0X ~24A ~8A~%"
address
instruction
(or disassembly "")
bits)))
(defun disassemble-instructions (array start)
(iterate
(for i :from start :below (length array) :by 2)
(collect (instruction-information array i) :result-type vector)))
(defun dump-disassembly (array &optional (start 0) (end (length array)))
(iterate
(for i :from start :below end :by 2)
(print-disassembled-instruction array i)
(sleep 0.001)))
;;;; Debugger -----------------------------------------------------------------
(declaim
(ftype (function (debugger) boolean) debugger-should-wait-p))
(defun debugger-pause (debugger)
(with-debugger (debugger)
(setf paused t print-needed t)))
(defun debugger-unpause (debugger)
(with-debugger (debugger)
(setf paused nil print-needed nil)))
(defun debugger-toggle-pause (debugger)
(if (debugger-paused debugger)
(debugger-unpause debugger)
(debugger-pause debugger)))
(defun debugger-step (debugger)
(with-debugger (debugger)
(setf take-step t)))
(defun debugger-print (debugger chip)
(with-debugger (debugger)
(when (and paused print-needed)
(let ((pc (chip-program-counter chip)))
(setf print-needed nil)
(destructuring-bind (address instruction disassembly bits)
(instruction-information (chip-memory chip) pc)
(format t "~3,'0X: ~4,'0X ~24A ~8A~%"
address
instruction
(or disassembly "")
bits))
(mapc (rcurry #'funcall pc) callbacks-arrived))))
(values))
(defun debugger-paused-p (debugger)
(debugger-paused debugger))
(defun debugger-should-wait-p (debugger)
(with-debugger (debugger)
(if (not paused) ; if we're not paused, we never need to wait
nil
(if take-step
(progn (setf take-step nil ; if we're paused, but are ready to step, go
print-needed t)
nil)
t)))) ; otherwise we're fully paused -- wait
(defun debugger-add-callback-arrived (debugger function)
(push function (debugger-callbacks-arrived debugger))
t)
;;;; Graphics -----------------------------------------------------------------
(declaim
(inline font-location vref (setf vref))
(ftype (function (chip int8 int8 int4) null) draw-sprite))
(defun vref (chip x y)
(aref (chip-video chip) (+ (* +screen-width+ y) x)))
(defun (setf vref) (new-value chip x y)
(setf (aref (chip-video chip) (+ (* +screen-width+ y) x))
new-value))
(defun load-font (chip)
;; Thanks http://www.multigesture.net/articles/how-to-write-an-emulator-chip-8-interpreter/
(replace (chip-memory chip)
(vector #xF0 #x90 #x90 #x90 #xF0 ; 0
#x20 #x60 #x20 #x20 #x70 ; 1
#xF0 #x10 #xF0 #x80 #xF0 ; 2
#xF0 #x10 #xF0 #x10 #xF0 ; 3
#x90 #x90 #xF0 #x10 #x10 ; 4
#xF0 #x80 #xF0 #x10 #xF0 ; 5
#xF0 #x80 #xF0 #x90 #xF0 ; 6
#xF0 #x10 #x20 #x40 #x40 ; 7
#xF0 #x90 #xF0 #x90 #xF0 ; 8
#xF0 #x90 #xF0 #x10 #xF0 ; 9
#xF0 #x90 #xF0 #x90 #x90 ; A
#xE0 #x90 #xE0 #x90 #xE0 ; B
#xF0 #x80 #x80 #x80 #xF0 ; C
#xE0 #x90 #x90 #x90 #xE0 ; D
#xF0 #x80 #xF0 #x80 #xF0 ; E
#xF0 #x80 #xF0 #x80 #x80) ; F
:start1 #x50))
(defun font-location (character)
(+ #x50 (* character 5)))
(defun draw-sprite (chip start-x start-y size)
(with-chip (chip)
(assert (< (+ index size) +memory-size+) (index)
"Sprite data of size ~D starting at #x~4,'0X would be out of bounds"
size index)
(setf flag 0)
(iterate
(repeat size)
(for i :from index)
(for sprite = (aref memory i))
(for y :modulo +screen-height+ :from start-y)
(iterate (for x :modulo +screen-width+ :from start-x)
(for col :from 7 :downto 0)
(for old-pixel = (plusp (vref chip x y)))
(for new-pixel = (plusp (get-bit col sprite)))
(when (and old-pixel new-pixel)
(setf flag 1))
(setf (vref chip x y)
(if (xor old-pixel new-pixel) 255 0))))
(setf video-dirty t))
nil)
;;;; Keyboard -----------------------------------------------------------------
(declaim
(ftype (function (chip (integer 0 (16)))) keydown keyup))
(defun keydown (chip key)
(setf (aref (chip-keys chip) key) t))
(defun keyup (chip key)
(setf (aref (chip-keys chip) key) nil))
;;;; Opcodes ------------------------------------------------------------------
(eval-when (:compile-toplevel :load-toplevel :execute)
(defun parse-opcode-argument-bindings (argument-list)
(flet ((normalize-arg (arg)
(destructuring-bind (symbol &optional (nibbles 1))
(ensure-list arg)
(list symbol nibbles))))
(iterate
(for (symbol nibbles) :in (mapcar #'normalize-arg argument-list))
(for position :first 3 :then (- position nibbles))
(when (not (eql symbol '_))
(collect `(,symbol (ldb (byte ,(* nibbles 4)
,(* position 4))
opcode))))))))
(defmacro define-opcode (name argument-list &body body)
`(progn
(declaim (ftype (function (chip int16)
(values null &optional))
,name))
(defun ,name (chip opcode)
(declare (ignorable opcode))
(with-chip (chip)
(macrolet ((register (index)
`(aref registers ,index)))
(let ,(parse-opcode-argument-bindings argument-list)
,@body))
nil))))
(macro-map ;; LD ...
((name arglist destination source)
((op-ld-i<imm (_ (value 3)) index value)
(op-ld-reg<imm (_ r (value 2)) (register r) value)
(op-ld-reg<reg (_ rx ry _) (register rx) (register ry))
(op-ld-reg<dt (_ r _ _) (register r) delay-timer)
(op-ld-dt<reg (_ r _ _) delay-timer (register r))
(op-ld-st<reg (_ r _ _) sound-timer (register r))))
`(define-opcode ,name ,arglist
(setf ,destination ,source)))
(define-opcode op-cls () ;; CLS
(fill video 0)
(setf video-dirty t))
(define-opcode op-jp-imm (_ (target 3)) ;; JP addr
(setf program-counter target))
(define-opcode op-jp-imm+reg (_ (target 3)) ;; JP V0 + addr
(setf program-counter (+ target (register 0))))
(define-opcode op-call (_ (target 3)) ;; CALL addr
(vector-push program-counter stack)
(setf program-counter target))
(define-opcode op-ret () ;; RET
(setf program-counter (vector-pop stack)))
(macro-map ;; ADD/SUB (8-bit)
((name op source-arg source-expr)
((op-add-reg<imm +_8 (immediate 2) immediate)
(op-add-reg<reg +_8 (ry 1) (register ry))
(op-sub-reg<reg -_8 (ry 1) (register ry))))
`(define-opcode ,name (_ rx ,source-arg)
(multiple-value-bind (result carry)
(,op (register rx) ,source-expr)
(setf (register rx) result
flag carry))))
(define-opcode op-add-index<reg (_ r) ;; ADD I, Vx (16-bit)
(zapf index (chop 16 (+ % (register r)))))
(define-opcode op-subn-reg<reg (_ rx ry) ;; SUBN
(multiple-value-bind (result carry)
(-_8 (register ry) (register rx)) ; subtraction order is swapped for SUBN
(setf (register rx) result
flag carry)))
(macro-map ;; SE/SNE
((name test x-arg x-form y-arg y-form)
((op-se-reg-imm = (r 1) (register r) (immediate 2) immediate)
(op-sne-reg-imm not= (r 1) (register r) (immediate 2) immediate)
(op-se-reg-reg = (rx 1) (register rx) (ry 1) (register ry))
(op-sne-reg-reg not= (rx 1) (register rx) (ry 1) (register ry))))
`(define-opcode ,name (_ ,x-arg ,y-arg)
(when (,test ,x-form ,y-form)
(incf program-counter 2))))
(macro-map ;; AND/OR/XOR
((name function)
((op-or logior)
(op-and logand)
(op-xor logxor)))
`(define-opcode ,name (_ destination source _)
(zapf (register destination)
(,function % (register source)))))
(define-opcode op-rand (_ r (mask 2)) ;; RND
(setf (register r)
(logand (random 256 random-state) mask)))
(define-opcode op-skp (_ r _ _) ;; SKP
(when (aref keys (register r))
(incf program-counter 2)))
(define-opcode op-sknp (_ r _ _) ;; SKNP
(when (not (aref keys (register r)))
(incf program-counter 2)))
(define-opcode op-ld-mem<regs (_ n _ _) ;; LD [I] < Vn
(replace memory registers :start1 index :end2 (1+ n)))
(define-opcode op-ld-regs<mem (_ n _ _) ;; LD Vn < [I]
(replace registers memory :end1 (1+ n) :start2 index))
(define-opcode op-ld-reg<key (_ r _ _) ;; LD Vx, Key (await)
;; I'm unsure how this instruction is supposed to interact with the timers.
;;
;; Either the timers should continue to count down while we wait for a key, or
;; they should pause while waiting, but I can't find anything in the docs that
;; spells it out.
;;
;; This implementation chooses the former (timers keep running) for now.
(let ((key (position t keys)))
(if key
(setf (register r) key)
;; If we don't have a key, just execute this instruction again next time.
(decf program-counter 2))))
(define-opcode op-shr (_ r _ _) ;; SHR
(let ((value (register r)))
(setf flag (get-bit 0 value)
(register r) (ash value -1))))
(define-opcode op-shl (_ r _ _) ;; SHL
(let ((value (register r)))
(setf flag (get-bit 7 value)
(register r) (chop 8 (ash value 1)))))
(define-opcode op-ld-font<vx (_ r _ _) ;; LD F, Vx
(setf index (font-location (register r))))
(define-opcode op-ld-bcd<vx (_ r _ _) ;; LD B, Vx
(multiple-value-bind (hundreds tens ones)
(bcd (register r))
(setf (aref memory (+ index 0)) hundreds
(aref memory (+ index 1)) tens
(aref memory (+ index 2)) ones)))
(define-opcode op-draw (_ rx ry size) ;; DRW Vx, Vy, size
(draw-sprite chip (register rx) (register ry) size))
;;;; Sound --------------------------------------------------------------------
(defconstant +pi+ (float pi 1.0))
(defconstant +tau+ (* 2 +pi+))
(defconstant +sample-rate+ 44100d0)
(defconstant +audio-buffer-size+ 512)
(defconstant +audio-buffer-time+ (* +audio-buffer-size+ (/ +sample-rate+)))
(defun square (angle)
(if (< (mod angle +tau+) +pi+)
1.0
-1.0))
(defun saw (angle)
(let ((a (mod angle +tau+)))
(if (< a +pi+)
(map-range 0 +pi+
1.0 -1.0
a)
(map-range +pi+ +tau+
-1.0 1.0
a))))
(defun make-audio-buffer ()
(make-simple-array 'single-float +audio-buffer-size+ :initial-element 0.0))
(defun fill-buffer (buffer function rate start)
(iterate
(for i :index-of-vector buffer)
(for angle :from start :by rate)
(setf (aref buffer i) (funcall function angle))
(finally (return (mod angle +tau+)))))
(defun fill-square (buffer rate start)
(fill-buffer buffer #'square rate start))
(defun fill-sine (buffer rate start)
(fill-buffer buffer #'sin rate start))
(defun fill-sawtooth (buffer rate start)
(fill-buffer buffer #'saw rate start))
(defun audio-rate (frequency)
(float (* (/ +tau+ +sample-rate+) frequency) 1.0))
(defun run-sound (chip)
(portaudio:with-audio
(portaudio:with-default-audio-stream
(audio-stream 0 1
:sample-format :float
:sample-rate +sample-rate+
:frames-per-buffer +audio-buffer-size+)
(with-chip (chip)
(iterate (with buffer = (make-audio-buffer))
(with angle = 0.0)
(with rate = (audio-rate 440))
(while running)
(if (and (plusp sound-timer)
(not (debugger-paused-p debugger)))
(progn
(setf angle (fill-sawtooth buffer rate angle))
(portaudio:write-stream audio-stream buffer))
(sleep +audio-buffer-time+)))))))
;;;; Timers -------------------------------------------------------------------
(declaim
(ftype (function (chip) null) decrement-timers run-timers))
(defun decrement-timers (chip)
(flet ((decrement (i)
(if (plusp i)
(1- i)
0)))
(with-chip (chip)
(sb-ext:atomic-update delay-timer #'decrement)
(sb-ext:atomic-update sound-timer #'decrement)))
nil)
(defun run-timers (chip)
(with-chip (chip)
(iterate
(while running)
(when (not (debugger-paused-p debugger))
(decrement-timers chip))
(sleep 1/60))))
;;;; CPU ----------------------------------------------------------------------
(declaim
(ftype (function (chip) null) run-cpu emulate-cycle)
(ftype (function (chip int16) null) dispatch-instruction))
(defparameter *c* nil)
(defun reset (chip)
(with-chip (chip)
(fill memory 0)
(fill registers 0)
(fill keys nil)
(fill video 0)
(load-font chip)
(replace memory (read-file-into-byte-vector loaded-rom)
:start1 #x200)
(setf running t
video-dirty t
program-counter #x200
delay-timer 0
sound-timer 0
(fill-pointer stack) 0))
(values))
(defun load-rom (chip filename)
(setf (chip-loaded-rom chip) filename)
(reset chip))
(defun dispatch-instruction (chip instruction)
(macrolet ((call (name) `(,name chip instruction)))
(ecase (logand #xF000 instruction)
(#x0000 (ecase instruction
(#x00E0 (call op-cls))
(#x00EE (call op-ret))))
(#x1000 (call op-jp-imm))
(#x2000 (call op-call))
(#x3000 (call op-se-reg-imm))
(#x4000 (call op-sne-reg-imm))
(#x5000 (ecase (logand #x000F instruction)
(#x0 (call op-se-reg-reg))))
(#x6000 (call op-ld-reg<imm))
(#x7000 (call op-add-reg<imm))
(#x8000 (ecase (logand #x000F instruction)
(#x0 (call op-ld-reg<reg))
(#x1 (call op-or))
(#x2 (call op-and))
(#x3 (call op-xor))
(#x4 (call op-add-reg<reg))
(#x5 (call op-sub-reg<reg))
(#x6 (call op-shr))
(#x7 (call op-subn-reg<reg))
(#xE (call op-shl))))
(#x9000 (ecase (logand #x000F instruction)
(#x0 (call op-sne-reg-reg))))
(#xA000 (call op-ld-i<imm))
(#xB000 (call op-jp-imm+reg))
(#xC000 (call op-rand))
(#xD000 (call op-draw))
(#xE000 (ecase (logand #x00FF instruction)
(#x9E (call op-skp))
(#xA1 (call op-sknp))))
(#xF000 (ecase (logand #x00FF instruction)
(#x07 (call op-ld-reg<dt))
(#x0A (call op-ld-reg<key))
(#x15 (call op-ld-dt<reg))
(#x18 (call op-ld-st<reg))
(#x1E (call op-add-index<reg))
(#x29 (call op-ld-font<vx))
(#x33 (call op-ld-bcd<vx))
(#x55 (call op-ld-mem<regs))
(#x65 (call op-ld-regs<mem)))))))
(defun emulate-cycle (chip)
(with-chip (chip)
(debugger-print debugger chip)
(if (debugger-should-wait-p debugger)
(sleep 10/1000)
(let ((instruction (cat-bytes (aref memory program-counter)
(aref memory (1+ program-counter)))))
(zapf program-counter (chop 12 (+ % 2)))
(dispatch-instruction chip instruction)))
nil))
(defun run-cpu (chip)
(iterate
(while (chip-running chip))
(emulate-cycle chip)
(for tick :every-nth +cycles-before-sleep+ :do
(sleep (/ +cycles-before-sleep+ +cycles-per-second+)))))
;;;; Main ---------------------------------------------------------------------
(defun run (rom-filename)
(let ((chip (make-chip)))
(setf *c* chip)
(load-rom chip rom-filename)
(chip8.gui::run-gui
chip
(lambda ()
;; Really it's just the sound that needs to be here...
(bt:make-thread (curry #'run-cpu chip))
(bt:make-thread (curry #'run-timers chip))
(bt:make-thread (curry #'run-sound chip))))))