A Chip-8 Emulator written in PowerShell

chip8.ps1

param(
	[string]$rom,
	[int]$cpulimit = 0,
	[switch]$nowrap = $false,
	[switch]$noclear = $false
)
if ($rom -eq "") {
	"PowerShell Chip-8 Emulator 1.0`n"+
	"  by SuperLlama ([email protected])`n"+
	"-"*48+"`n"+
	"  .\chip8.ps1 -rom C:\Path\To\ROM [-cpulimit SpeedInHz] [-nowrap] [-noclear]"
	return
}
#initialize vram and ram using a rom
$scr = (new-object uInt16[] (32*4))
$ram = [byte[]](
	#hex font
	0xF0,0x90,0x90,0x90,0xF0,0x20,0x60,0x20,0x20,0x70,
	0xF0,0x10,0xF0,0x80,0xF0,0xF0,0x10,0xF0,0x10,0xF0,
	0x90,0x90,0xF0,0x10,0x10,0xF0,0x80,0xF0,0x10,0xF0,
	0xF0,0x80,0xF0,0x90,0xF0,0xF0,0x10,0x20,0x40,0x40,
	0xF0,0x90,0xF0,0x90,0xF0,0xF0,0x90,0xF0,0x10,0xF0,
	0xF0,0x90,0xF0,0x90,0x90,0xE0,0x90,0xE0,0x90,0xE0,
	0xF0,0x80,0x80,0x80,0xF0,0xE0,0x90,0x90,0x90,0xE0,
	0xF0,0x80,0xF0,0x80,0xF0,0xF0,0x80,0xF0,0x80,0x80
)
$ram += (new-object byte[] (0x200 - $ram.length)) #pad to 200
$ram += Get-Content $rom -Encoding byte #load cartridge
$ram += (new-object byte[] (0x1000 - $ram.length)) #pad to 1000

#initialize registers
$pc = 0x200
$V = (new-object byte[] 0x16)
$call_stack = (new-object int16[] 0x16)
$stack_ptr = 0
$I = 0
$delay = 0
$sound = 0

#keyboard bindings
$keybind = ('X','1','2','3','Q','W','E','A','S','D','Z','C','4','R','F','V')
$o_keystate = 0
$keystate = 0

#screen drawing routine
$title = "PowerShell Chip-8 Emulator"
$title_bar = ("═"*((64-$title.Length)/2))
$frame_top = "╔"+$title_bar+$title+$title_bar+"╗"
$frame_bottom = "╚"+("═"*64)+"╝`n" +
" "*14+"┌─────────┒              ┌─────────┒`n"+
" "*14+"│  Chip8  ┃              │ Windows ┃`n"+
" "*14+"│ 1 2 3 C ┃    ━━━━━━    │ 1 2 3 4 ┃`n"+
" "*14+"│ 4 5 6 D ┃              ┃ Q W E R ┃`n"+
" "*14+"│ 7 8 9 E ┃    ━━━━━━    ┃ A S D F ┃`n"+
" "*14+"│ A 0 B F ┃              ┃ Z X C V ┃`n"+
" "*14+"┕━━━━━━━━━┛              ┕━━━━━━━━━┛`n"

$draw = {
	$frame = "$frame_top`n"
	for ($i = 0; $i -lt (32*4); $i+=8) {
		$frame += "║"
		for ($j = 0; $j -lt 4; $j++) {
			$frame += (
			[int64][Convert]::ToString($scr[$i+$j],2) +
			2*[int64][Convert]::ToString($scr[$i+$j+4],2)
			).ToString().PadLeft(16,"0").Replace(0," ").Replace(1,"▀").Replace(2,"▄").Replace(3,"█")
		}
		$frame += "║`n"
	}
	$frame += $frame_bottom
	if (!$noclear) {
		Clear
	}
	$frame
}

Add-Type -AssemblyName PresentationFramework

$last_tick = (Get-Date).Ticks

while ($true) {
	$x = ($ram[$pc] -band 0xF) #_x__
	$y = ($ram[$pc+1] -shr 4) #__y_
	$nn = $ram[$pc+1] #__nn
	$nnn = $ram[$pc+1] -bor ($x -shl 8) #_nnn
	#[Convert]::ToString($ram[$pc],16).PadLeft(2,"0")+[Convert]::ToString($ram[$pc+1],16).PadLeft(2,"0") + " -> $I"
	switch ($ram[$pc] -shr 4) {
		0x0 {
			switch ($ram[$pc+1]) {
				0xE0 { #clear screen
					for ($n = 0; $n -lt (32*4); $n++) {
						$scr[$n] = 0;
					}
					&$draw
				}
				0xEE { #return
					$stack_ptr--
					$pc = $call_stack[$stack_ptr]
				}
			}
		}
		0x1 { #jump
			$pc = $nnn - 2
		}
		0x2 { #call
			$call_stack[$stack_ptr] = $pc
			$stack_ptr++
			$pc = $nnn - 2
		}
		0x3 { #se
			if ($V[$x] -eq $nn) {
				$pc += 2
			}
		}
		0x4 { #sne
			if ($V[$x] -ne $nn) {
				$pc += 2
			}
		}
		0x5 { #ser
			if ($V[$x] -eq $V[$y]) {
				$pc += 2
			}
		}
		0x6 { #ld
			$V[$x] = $nn
		}
		0x7 { #add
			$V[$x] = ($V[$x] + $nn) -band 0xFF
		}
		0x8 {
			switch ($nn -band 0xF) {
				0 {
					$V[$x] = $V[$y]
				}
				1 {
					$V[$x] = $V[$x] -bor $V[$y]
				}
				2 {
					$V[$x] = $V[$x] -band $V[$y]
				}
				3 {
					$V[$x] = $V[$x] -bxor $V[$y]
				}
				4 {
					$new_val = $V[$x] + $V[$y]
					$V[$x] = $new_val -band 0xFF
					if ($new_val -gt 0xFF) {
						$V[0xF] = 1
					} else {
						$V[0xF] = 0
					}
				}
				5 {
					if ($V[$x] -gt $V[$y]) {
						$V[0xF] = 1
					} else {
						$V[0xF] = 0
					}
					$V[$x] = (256 + $V[$x] - $V[$y]) % 256
				}
				6 {
					$V[0xF] = $V[$x] -band 1
					$V[$x] = $V[$x] -shr 1
				}
				7 {
					if ($V[$y] -gt $V[$x]) {
						$V[0xF] = 1
					} else {
						$V[0xF] = 0
					}
					$V[$x] = (256 + $V[$y] - $V[$x]) % 256
				}
				0xE {
					$V[0xF] = $V[$x] -band 1
					$V[$x] = $V[$x] -shl 1
				}
			}
		}
		0x9 { #sner
			if ($V[$x] -ne $V[$y]) {
				$pc += 2
			}
		}
		0xA { #addr
			$I = $nnn
		}
		0xB { #jmp offset
			$pc = $nnn + $V[0] - 2
		}
		0xC {
			$V[$x] = (Get-Random) -band $nn
		}
		0xD {
			$x = $V[$x]
			$y = $V[$y]
			
			if (!$nowrap) {
				$x = $x % 64
				$y = $y % 64
			}
			
			$V[0xF] = 0
			
			for ($n = 0; $n -lt ($nn -band 0xF); $n++) {
				$spr_line = ([uInt16]$ram[$I+$n] -shl 8)
				$c = (($y+$n)%32)*4+[Math]::Floor($x/16)
				
				if ($nowrap -and (($y+$n -ge 32) -or ($y+$n) -lt 0)) {
					continue
				}
				
				$sub_line = ($spr_line -shr ($x % 16))
				if ($scr[$c] -band $sub_line) {
					$V[0xF] = 1
				}
				$scr[$c] = $scr[$c] -bxor $sub_line
				
				if ($x % 16 -gt 8) {
					$c++
					if ($x -gt 64-16) {
						$c-=4
						if ($nowrap) {
							continue
						}
					}
					$sub_line = ($spr_line -shl (16 - ($x % 16)))
					if ($scr[$c] -band $sub_line) {
						$V[0xF] = 1
					}
					$scr[$c] = $scr[$c] -bxor $sub_line
				}
			}
			&$draw
		}
		0xE {
			switch ($nn) {
				0x9E {
					if ([System.Windows.Input.Keyboard]::IsKeyDown($keybind[$V[$x]])) {
						$pc += 2
					}
				}
				0xA1 {
					if (![System.Windows.Input.Keyboard]::IsKeyDown($keybind[$V[$x]])) {
						$pc += 2
					}
				}
			}
		}
		0xF {
			switch ($nn) {
				0x07 {
					$V[$x] = $delay
				}
				0x0A {
					$wait = $true
					for ($k = 0; $k -lt 0xF; $k++) {
						$bit = (1 -shl $k)
						if ([System.Windows.Input.Keyboard]::IsKeyDown($keybind[$k])) {
							$keystate = ($keystate -bor $bit)
							if (($o_keystate -band $bit) -eq 0) {
								$V[$x] = $k
								$wait = $false
							}
						} else {
							$keystate = ($keystate -band (-bnot $bit))
						}
					}
					if ($wait) {
						$pc -= 2
					} else {
						$V[$x]
					}
				}
				0x15 {
					$delay = $V[$x]
				}
				0x18 {
					$sound = $V[$x]
				}
				0x1E {
					$I += $V[$x]
				}
				0x29 {
					$I = $V[$x]*5
				}
				0x33 {
					$ram[$I] = [Math]::Floor($V[$x]/100)
					$ram[$I+1] = [Math]::Floor($V[$x]/10)%10
					$ram[$I+2] = $V[$x]%10
				}
				0x55 {
					for ($n = 0; $n -le $x; $n++) {
						$ram[$I+$n] = $V[$n]
					}
				}
				0x65 {
					for ($n = 0; $n -le $x; $n++) {
						$V[$n] = $ram[$I+$n]
					}
				}
			}
		}
	}
	$pc += 2
	do {
		$tick = (Get-Date).Ticks
	} while ($cpulimit -ne 0 -and ($tick - $last_tick) -lt (10000000/$cpulimit))
	$rate = 60*($tick - $last_tick)/10000000
	$last_tick = $tick
	$delay -= $rate
	if ($delay -lt 0) { $delay = 0 }
	$sound -= $rate
	if ($sound -lt 0) { $sound = 0 }
	$o_keystate = $keystate
}