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chipeightuk.ml
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chipeightuk.ml
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(* todo : fix keys *)
(** Types **)
type bytes = string
type stack = int Stack.t
type opcode = int * int * int * int
type state = { mem : bytes
; v : bytes
; pc_stack : stack
; mutable delay_timer : int
; mutable sound_timer : int
; mutable pc : int
; mutable i : int
; mutable key_pressed : int option
; mutable pressed_since : float
; screen : bool array array
}
type config = { period : float
; ops_per_period : int
; px_mod_bounds : bool
; px_size : int
; px_on : Graphics.color
; px_off : Graphics.color
; sound_freq : int option
; chip8_keys : string
; exec_keys : (char * (unit -> unit)) list
; key_timeout : float
; sprites : string array
; debug : bool
; rom_file : string
}
type precalc = { secs_per_op : float
; period_ms : int
; x_coords : int array
; y_coords : int array
; real_px_size : int
; real_width : int
; real_height : int
}
(** Exceptions **)
exception Escaped
exception End_of_rom
exception Not_implemented of opcode
(** Constants **)
let mem_size = 4096
let reg_size = 16
let mem_start = 0x200
let width = 64
let height = 32
(** Manipulating the [bytes] type **)
(* bytes_make : int -> int -> bytes
[bytes_make n byte] creates a [n]-bytes long
variable with all bytes initialized to [byte]. *)
let bytes_make n byte =
String.make n (Char.chr byte)
(* bytes_get : bytes -> int -> int
[bytes_get bytes i] returns the [i]-th byte of [bytes]. *)
let bytes_get bytes i =
Char.code (String.get bytes i)
(* bytes_set : bytes -> int -> int -> unit
[bytes_set bytes i byte] sets the [i]-th byte of [bytes]
to [byte]. *)
let bytes_set bytes i byte =
String.set bytes i
(Char.chr (byte land 0xFF))
(* bytes_copy : bytes -> int -> string -> unit
[bytes_copy bytes i str] copies every character in [str]
to [bytes], starting at the [i]-th byte of [bytes]. *)
let bytes_copy bytes i str =
String.blit str 0 bytes i
(String.length str)
(* bytes_copy_from_file : bytes -> int -> string -> unit
[bytes_copy bytes i file] copies every byte in [file]
to [bytes], starting at the [i]-th byte of [bytes]. *)
let bytes_copy_from_file bytes i file =
let ic = open_in_bin file in
try really_input ic bytes i
(String.length bytes - i - 1)
with End_of_file -> ();
close_in ic
(** Screen related functions **)
(* open_screen : config -> unit
[open_screen config] opens a window and sets its title. *)
let open_screen config =
let geom = Printf.sprintf "%dx%d"
(config.px_size * width)
(config.px_size * height) in
Graphics.open_graph (match Sys.os_type with
| "Unix" -> " " ^ geom
| _ -> geom);
Graphics.set_window_title ("chipeightuk - "
^ config.rom_file)
(* clear_screen : config -> state -> unit
[clear_screen config state] turns off every pixel,
updating [state]. *)
let clear_screen config precalc state =
Graphics.set_color config.px_off;
Graphics.fill_rect 0 0
precalc.real_width
precalc.real_height;
for y = 0 to height - 1 do
for x = 0 to width - 1 do
state.screen.(y).(x) <- false
done
done
(* flip_pixel : config -> precalc -> state -> int -> int -> bool
[flip_pixel cfg precalc x y value] turns on the pixel at [(x,y)]
if it was off, or turns it off if it was on, returning true if
the pixel was initially on, false otherwise.
[x] and [y] may be greather than screen boundaries, in which case
the pixel will be either ignored or flipped modulo boundaries,
depending on [cfg]. *)
let flip_pixel cfg precalc state x y =
let x' = x mod width in
let y' = y mod height in
if cfg.px_mod_bounds || (x = x' && y = y') then
begin
let real_x = precalc.x_coords.(x') in
let real_y = precalc.y_coords.(y') in
let was_on = state.screen.(y').(x') in
Graphics.set_color (if was_on then cfg.px_off else cfg.px_on);
Graphics.fill_rect real_x real_y
precalc.real_px_size precalc.real_px_size;
state.screen.(y').(x') <- not was_on;
was_on
end
else
false
(* draw_sprite : config -> precalc -> int -> int -> sprite -> unit
[draw_sprite cfg x y spr] draws the 8-width sprite
represented by [spr]'s eight least significant bits on
the screen at position [(x,y)]. *)
let draw_sprite cfg precalc state x y spr =
let any_was_on = ref false in
for k = 0 to 7 do
if spr land (1 lsl k) <> 0 then
any_was_on := flip_pixel cfg precalc state (x + 7 - k) y
|| !any_was_on
done;
!any_was_on
(** Events related functions **)
(* exec_key : config -> char -> unit
[exec_key config key] calls the custom function bound
to [key], if any. *)
let exec_key config key =
try let f = List.assoc key config.exec_keys in
f ()
with Not_found -> ()
(* poll_key_press : config -> state -> int
[poll_key_press config state] searches the events list for
the latest key press, updating [state] and calling [exec_key]
for each custom key press.
[state] is also updated if the last key press has timed out. *)
let poll_key_press config state =
let new_key = ref None in
while Graphics.key_pressed () do
let pressed_key = Graphics.read_key () in
try new_key := Some (String.index
config.chip8_keys
pressed_key)
with Not_found -> exec_key config pressed_key
done;
match !new_key with
| Some code ->
state.key_pressed <- Some code;
state.pressed_since <- Unix.gettimeofday ()
| None ->
if state.key_pressed <> None then
let pressed_for = (Unix.gettimeofday () -. state.pressed_since) in
if pressed_for > config.key_timeout then
state.key_pressed <- None
(* wait_key : config -> state -> int
[wait_key config state] empties the event list and waits until
a game related key is pressed then updates [state] and returns
the corresponding key code. *)
let rec wait_key config state =
ignore (poll_key_press config state);
let status = Graphics.wait_next_event [Graphics.Key_pressed] in
try let code = String.index config.chip8_keys status.Graphics.key in
state.key_pressed <- Some code;
state.pressed_since <- Unix.gettimeofday ();
code
with Not_found -> exec_key config status.Graphics.key;
wait_key config state
(** Miscellaneous functions used by the main loop **)
(* sleep_for : float -> ()
[sleep_for n] stops program execution for [n] seconds. *)
let sleep_for n =
let until = Unix.gettimeofday() +. n in
let rec delay t =
try ignore (Unix.select [] [] [] t)
with Unix.Unix_error (Unix.EINTR, _, _) ->
let now = Unix.gettimeofday() in
let remaining = until -. now in
if remaining > 0. then
delay remaining
in delay n
(* split_byte : int -> int * int
[split_byte 0xXY] is [(0xX, 0xY)] *)
let split_byte byte =
(byte lsr 4, byte land 0xF)
(* combine_nibbles : int list -> int
[combine_nibbles [X;Y;Z]] is [0xXYZ]. *)
let combine_nibbles l =
List.fold_left (fun acc x -> (acc lsl 4) lor (x land 0xF)) 0 l
(* do_precalc : config -> precalc
[precalc config] does some calculation once and for all *)
let do_precalc config =
let os_dep = match Sys.os_type with
| "Unix" -> (-1)
| _ -> 0
in
{ secs_per_op = config.period /. float_of_int config.ops_per_period
; period_ms = int_of_float (config.period *. 1000.)
; x_coords = Array.init width
(fun x -> x * config.px_size)
; y_coords = Array.init height
(fun y -> (height - y + 1) * config.px_size)
; real_px_size = config.px_size + os_dep
; real_width = width * config.px_size + os_dep
; real_height = height * config.px_size + os_dep
}
(** Processor emulation functions **)
(* init_state : config -> state
[init_state config] return the initial emulator state. *)
let init_state config =
let init_mem = bytes_make mem_size 0 in
bytes_copy init_mem 0 (Array.fold_left (^) "" config.sprites);
{ mem = init_mem
; v = bytes_make reg_size 0
; pc_stack = Stack.create ()
; delay_timer = 0
; sound_timer = 0
; pc = mem_start
; i = 0
; key_pressed = None
; pressed_since = 0.
; screen = Array.make_matrix height width false
}
(* read_next_op : config -> state -> opcode
[read_next_op state] reads the two next bytes from the rom,
updating [state] and returning the corresponding opcode.
[config] may be used in a later version. *)
let read_next_op config state =
ignore (config);
let (a, b) = split_byte (bytes_get state.mem state.pc) in
let (c, d) = split_byte (bytes_get state.mem (state.pc + 1)) in
state.pc <- state.pc + 2;
(a, b, c, d)
(* exec_op : config -> precalc -> state -> opcode -> unit
[exec_op config state op] executes operation [op],
updating [state].
[Not_implemented op] exception is raised if [op] is unknown,
for more information please check the following link:
http://en.wikipedia.org/wiki/CHIP-8#Virtual_machine_description *)
let exec_op config precalc state op =
let get_v = bytes_get state.v in
let set_v = bytes_set state.v in
match op with
| (0,0,0,0) -> raise End_of_rom
| (0,0,0xE,0) -> clear_screen config precalc state
| (0,0,0xE,0xE) -> state.pc <- Stack.pop state.pc_stack
| (1,n2,n1,n0) -> state.pc <- combine_nibbles [n2;n1;n0]
| (2,n2,n1,n0) -> Stack.push state.pc state.pc_stack;
state.pc <- combine_nibbles [n2;n1;n0]
| (3,x,n1,n0) -> if get_v x = combine_nibbles [n1;n0] then
state.pc <- state.pc + 2
| (4,x,n1,n0) -> if get_v x <> combine_nibbles [n1;n0] then
state.pc <- state.pc + 2
| (5,x,y,0) -> if get_v x = get_v y then
state.pc <- state.pc + 2
| (6,x,n1,n0) -> set_v x (combine_nibbles [n1;n0])
| (7,x,n1,n0) -> set_v x (get_v x + combine_nibbles [n1;n0])
| (8,x,y,0) -> set_v x (get_v y)
| (8,x,y,1) -> set_v x (get_v x lor get_v y)
| (8,x,y,2) -> set_v x (get_v x land get_v y)
| (8,x,y,3) -> set_v x (get_v x lxor get_v y)
| (8,x,y,4) -> let res = get_v x + get_v y in
set_v x res;
set_v 0xF (res lsr 8)
| (8,x,y,5) -> let res = get_v x - get_v y in
if res >= 0 then
begin
set_v x res;
set_v 0xF 1
end
else
begin
set_v x (res + 256);
set_v 0xF 0
end
| (8,x,y,6) -> let vx = get_v x in
set_v 0xF (vx land 1);
set_v x (vx lsr 1)
| (8,x,y,7) -> let res = get_v y - get_v x in
if res >= 0 then
begin
set_v x res;
set_v 0xF 1
end
else
begin
set_v x (res + 256);
set_v 0xF 0
end
| (8,x,y,0xE) -> let vx = get_v x in
set_v 0xF (vx lsr 7);
set_v x ((vx land 0x7F) lsl 1)
| (9,x,y,0) -> if get_v x <> get_v y then
state.pc <- state.pc + 2
| (0xA,n2,n1,n0) -> state.i <- combine_nibbles [n2;n1;n0]
| (0xB,n2,n1,n0) -> state.pc <- get_v 0 + combine_nibbles [n2;n1;n0]
| (0xC,x,n1,n0) -> set_v x (Random.int (1 + combine_nibbles [n1;n0]))
| (0xD,x,y,n) -> let any_was_on = ref false in
let vx = get_v x in
let vy = get_v y in
for k = 0 to n - 1 do
let was_on = draw_sprite
config
precalc
state
vx (vy + k)
(bytes_get state.mem (state.i + k))
in any_was_on := was_on || !any_was_on
done;
set_v 0xF (if !any_was_on then 1 else 0)
| (0xE,x,0x9,0xE) -> if state.key_pressed = Some (get_v x) then
state.pc <- state.pc + 2
| (0xE,x,0xA,1) -> if state.key_pressed <> Some (get_v x) then
state.pc <- state.pc + 2
| (0xF,x,0,7) -> set_v x state.delay_timer
| (0xF,x,0,0xA) -> (match state.key_pressed with
| Some k -> set_v x k
| None -> state.pc <- state.pc - 2)
| (0xF,x,1,5) -> state.delay_timer <- get_v x
| (0xF,x,1,8) -> state.sound_timer <- get_v x
| (0xF,x,1,0xE) -> state.i <- state.i + get_v x
| (0xF,x,2,9) -> state.i <- (get_v x) * 5
| (0xF,x,3,3) -> let n2n1n0 = get_v x in
let (n2n1, n0) = (n2n1n0 / 10, n2n1n0 mod 10) in
let (n2, n1) = (n2n1 / 10, n2n1 mod 10) in
bytes_set state.mem state.i n2;
bytes_set state.mem (state.i + 1) n1;
bytes_set state.mem (state.i + 2) n0
| (0xF,x,5,5) -> for k = 0 to x do
bytes_set state.mem (state.i + k) (get_v k)
done
| (0xF,x,6,5) -> for k = 0 to x do
set_v k (bytes_get state.mem (state.i + k))
done
| _ -> raise (Not_implemented op)
(* loop : config -> state -> float -> int -> unit
[loop config state secs_per_op period_ms] executes
one cycle of operations then updates delay and sound
timers and performs a recursive call. *)
let rec loop config precalc state =
poll_key_press config state;
for i = 1 to config.ops_per_period do
let init_time = Unix.gettimeofday () in
let op = read_next_op config state in
if config.debug then
begin
Printf.printf "I=%03X V=[" state.i;
for k = 0 to 0xF do
Printf.printf "%02X;" (bytes_get state.v k)
done;
Printf.printf "\b]\npc=%03X " state.pc;
let (a,b,c,d) = op in
Printf.printf "%X%X%X%X -> " a b c d;
flush stdout;
ignore (wait_key config state)
end;
exec_op config precalc state op;
let elapsed = Unix.gettimeofday () -. init_time in
let remaining = precalc.secs_per_op -. elapsed in
if remaining > 0. then
sleep_for remaining
(*;if not config.debug then
begin
let (a,b,c,d) = op in
Printf.printf "%X%X%X%X : %f us\n"
a b c d
(elapsed *. 10e6);
flush stdout
end*)
done;
if state.delay_timer > 0 then
state.delay_timer <- state.delay_timer - 1;
if state.sound_timer > 0 then
begin
(match config.sound_freq with
| Some f -> Graphics.sound f (state.sound_timer * precalc.period_ms)
| None -> ());
state.sound_timer <- 0
end;
loop config precalc state
(* power_on : config -> unit
[power_on config] starts the emulator. *)
let power_on config =
Random.self_init ();
open_screen config;
let state = init_state config in
bytes_copy_from_file state.mem 0x200 config.rom_file;
let precalc = do_precalc config in
clear_screen config precalc state;
try loop config precalc state
with End_of_rom | Escaped -> Graphics.close_graph ()
(** Command-line parsing **)
let colors_by_key = [ "black", Graphics.black
; "white", Graphics.white
; "red", Graphics.red
; "green", Graphics.green
; "blue", Graphics.blue
; "yellow", Graphics.yellow
; "cyan", Graphics.cyan
; "magenta", Graphics.magenta
]
let (ckeys, cvalues) = List.split colors_by_key
let colors_by_value = List.combine cvalues ckeys
let color_of_string str =
List.assoc str colors_by_key
let string_of_color color =
try List.assoc color colors_by_value
with Not_found -> Printf.sprintf "0x%06X" color
let base_cfg = { period = 1. /. 60.
; ops_per_period = 4
; debug = false
; px_mod_bounds = true
; px_size = 8
; px_on = Graphics.rgb 0xFF 0xcc 0x00
; px_off = Graphics.rgb 00 00 0x77
; sound_freq = Some 220
; chip8_keys = "0123456789/*-+\r." (* 0123456789ABCDEF *)
; exec_keys = [('\x1B', fun () -> raise Escaped)]
; key_timeout = 0.300
; sprites = [| "\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 *)
|]
; rom_file = ""
}
let _ =
let usage = "\nUsage: chipeightuk <options> <file-list>\n\n"
^ "chipeightuk, a CHIP-8 emulator written in OCaml\n\n"
^ "Options are:" in
let cfg = ref base_cfg in
let rom_files = Queue.create () in
let fun_anon_args x = Queue.push x rom_files in
let specs =
[ "-d"
, Arg.Symbol
( ["on";"off"]
, (fun str -> cfg := {!cfg with debug = (str = "on")})
)
, " Set debug mode "
^ (Printf.sprintf "(default %s)"
(if base_cfg.debug then "on" else "off"))
;
"-pmb"
, Arg.Symbol
( ["on";"off"]
, (fun str -> cfg := {!cfg with px_mod_bounds = (str = "on")})
)
, " Set pixels modulo boundaries mode "
^ (Printf.sprintf "(default %s)"
(if base_cfg.px_mod_bounds then "on" else "off"))
;
"-tf"
, Arg.Float (fun f -> cfg := {!cfg with period = 1. /. f})
, "<frequency> Set timers frequency in Hertz "
^ (Printf.sprintf "(default %.2f)" (1. /. base_cfg.period))
;
"-tp"
, Arg.Float (fun p -> cfg := {!cfg with period = p /. 1000.})
, "<period> Set timers period in milliseconds "
^ (Printf.sprintf "(default %.2f)" (base_cfg.period *. 1000.))
;
"-oc"
, Arg.Int (fun oc -> cfg := {!cfg with ops_per_period = oc})
, "<count> Set number of opcodes executed during one period "
^ (Printf.sprintf "(default %d)" base_cfg.ops_per_period)
;
"-km"
, Arg.String (fun keys -> cfg := {!cfg with chip8_keys = keys})
, "<keys> Set whole 0123456789ABCDEF keymap "
^ (Printf.sprintf "(default %S)" base_cfg.chip8_keys)
;
"-kt"
, Arg.Float (fun t -> cfg := {!cfg with key_timeout = t /. 1000.})
, "<time> Set key-press timeout in milliseconds "
^ (Printf.sprintf " (default %.2f)" (base_cfg.key_timeout *. 1000.))
;
"-sf"
, Arg.Int (fun f -> cfg := {!cfg with sound_freq = Some f})
, "<frequency> Set sound output frequency in Hertz "
^ (Printf.sprintf "(default %d)"
(match base_cfg.sound_freq with
| Some f -> f
| None -> (-1)))
;
"-mute"
, Arg.Unit (fun () -> cfg := {!cfg with sound_freq = None})
, " Disable sound output "
^ (Printf.sprintf "(default %s)"
(match base_cfg.sound_freq with
| Some _ -> "enabled"
| None -> "disabled"))
;
"-px"
, Arg.Int (fun size -> cfg := {!cfg with px_size = size})
, "<size> Set on-screen size-per-pixel "
^ (Printf.sprintf "(default %d)" base_cfg.px_size)
;
"-pxon"
, Arg.Symbol
( ckeys
, fun c -> cfg := {!cfg with px_on = color_of_string c}
)
, " Set color for enabled pixels "
^ (Printf.sprintf "(default %s)" (string_of_color base_cfg.px_on))
;
"-pxoff"
, Arg.Symbol
( ckeys
, fun c -> cfg := {!cfg with px_off = color_of_string c}
)
, " Set color for disabled pixels "
^ (Printf.sprintf "(default %s)" (string_of_color base_cfg.px_off))
;
"-"
, Arg.String fun_anon_args
, "<file> Load a rom file with filename starting with a -"
] in
Arg.parse specs fun_anon_args usage;
try Queue.iter (fun file ->
power_on {!cfg with rom_file = file};
if (!cfg).debug then
print_newline ())
rom_files
with Graphics.Graphic_failure _ -> if (!cfg).debug then
print_newline ()