fix: reimpl handleInterrupt code

passes arm.gba, thumb.gb and armwrestler, fails in actual games
TODO: run FuzzARM debug specific titles

src/Gui.zig

@@ -0,0 +1,193 @@
+const std = @import("std");
+const SDL = @import("sdl2");
+const Self = @This();
+
+const Apu = @import("core/apu.zig").Apu;
+const Arm7tdmi = @import("core/cpu.zig").Arm7tdmi;
+const Scheduler = @import("core/scheduler.zig").Scheduler;
+const FpsTracker = @import("core/util.zig").FpsTracker;
+
+const pitch = @import("core/ppu.zig").framebuf_pitch;
+
+const emu = @import("core/emu.zig");
+const asString = @import("core/util.zig").asString;
+const log = std.log.scoped(.GUI);
+
+const scale = 4;
+const default_title: []const u8 = "ZBA";
+
+window: *SDL.SDL_Window,
+base_title: [12]u8,
+renderer: *SDL.SDL_Renderer,
+texture: *SDL.SDL_Texture,
+audio: ?Audio,
+
+pub fn init(title: [12]u8, width: i32, height: i32) Self {
+    const ret = SDL.SDL_Init(SDL.SDL_INIT_VIDEO | SDL.SDL_INIT_EVENTS | SDL.SDL_INIT_AUDIO | SDL.SDL_INIT_GAMECONTROLLER);
+    if (ret < 0) panic();
+
+    const window = SDL.SDL_CreateWindow(
+        default_title.ptr,
+        SDL.SDL_WINDOWPOS_CENTERED,
+        SDL.SDL_WINDOWPOS_CENTERED,
+        @as(c_int, width * scale),
+        @as(c_int, height * scale),
+        SDL.SDL_WINDOW_SHOWN,
+    ) orelse panic();
+
+    const renderer = SDL.SDL_CreateRenderer(window, -1, SDL.SDL_RENDERER_ACCELERATED | SDL.SDL_RENDERER_PRESENTVSYNC) orelse panic();
+
+    const texture = SDL.SDL_CreateTexture(
+        renderer,
+        SDL.SDL_PIXELFORMAT_RGBA8888,
+        SDL.SDL_TEXTUREACCESS_STREAMING,
+        @as(c_int, width),
+        @as(c_int, height),
+    ) orelse panic();
+
+    return Self{
+        .window = window,
+        .base_title = title,
+        .renderer = renderer,
+        .texture = texture,
+        .audio = null,
+    };
+}
+
+pub fn run(self: *Self, arm7tdmi: *Arm7tdmi, scheduler: *Scheduler) !void {
+    var quit = std.atomic.Atomic(bool).init(false);
+    var frame_rate = FpsTracker.init();
+
+    const thread = try std.Thread.spawn(.{}, emu.run, .{ &quit, &frame_rate, scheduler, arm7tdmi });
+    defer thread.join();
+
+    var title_buf: [0x100]u8 = [_]u8{0} ** 0x100;
+
+    emu_loop: while (true) {
+        var event: SDL.SDL_Event = undefined;
+        while (SDL.SDL_PollEvent(&event) != 0) {
+            switch (event.type) {
+                SDL.SDL_QUIT => break :emu_loop,
+                SDL.SDL_KEYDOWN => {
+                    const io = &arm7tdmi.bus.io;
+                    const key_code = event.key.keysym.sym;
+
+                    switch (key_code) {
+                        SDL.SDLK_UP => io.keyinput.up.unset(),
+                        SDL.SDLK_DOWN => io.keyinput.down.unset(),
+                        SDL.SDLK_LEFT => io.keyinput.left.unset(),
+                        SDL.SDLK_RIGHT => io.keyinput.right.unset(),
+                        SDL.SDLK_x => io.keyinput.a.unset(),
+                        SDL.SDLK_z => io.keyinput.b.unset(),
+                        SDL.SDLK_a => io.keyinput.shoulder_l.unset(),
+                        SDL.SDLK_s => io.keyinput.shoulder_r.unset(),
+                        SDL.SDLK_RETURN => io.keyinput.start.unset(),
+                        SDL.SDLK_RSHIFT => io.keyinput.select.unset(),
+                        else => {},
+                    }
+                },
+                SDL.SDL_KEYUP => {
+                    const io = &arm7tdmi.bus.io;
+                    const key_code = event.key.keysym.sym;
+
+                    switch (key_code) {
+                        SDL.SDLK_UP => io.keyinput.up.set(),
+                        SDL.SDLK_DOWN => io.keyinput.down.set(),
+                        SDL.SDLK_LEFT => io.keyinput.left.set(),
+                        SDL.SDLK_RIGHT => io.keyinput.right.set(),
+                        SDL.SDLK_x => io.keyinput.a.set(),
+                        SDL.SDLK_z => io.keyinput.b.set(),
+                        SDL.SDLK_a => io.keyinput.shoulder_l.set(),
+                        SDL.SDLK_s => io.keyinput.shoulder_r.set(),
+                        SDL.SDLK_RETURN => io.keyinput.start.set(),
+                        SDL.SDLK_RSHIFT => io.keyinput.select.set(),
+                        SDL.SDLK_i => log.err("Sample Count: {}", .{@intCast(u32, SDL.SDL_AudioStreamAvailable(arm7tdmi.bus.apu.stream)) / (2 * @sizeOf(u16))}),
+                        SDL.SDLK_j => log.err("Scheduler Capacity: {} | Scheduler Event Count: {}", .{ scheduler.queue.capacity(), scheduler.queue.count() }),
+                        SDL.SDLK_k => {
+                            // Dump IWRAM to file
+                            log.info("PC: 0x{X:0>8}", .{arm7tdmi.r[15]});
+                            log.info("LR: 0x{X:0>8}", .{arm7tdmi.r[14]});
+                            // const iwram_file = try std.fs.cwd().createFile("iwram.bin", .{});
+                            // defer iwram_file.close();
+
+                            // try iwram_file.writeAll(cpu.bus.iwram.buf);
+                        },
+                        else => {},
+                    }
+                },
+                else => {},
+            }
+        }
+
+        // Emulator has an internal Double Buffer
+        const framebuf = arm7tdmi.bus.ppu.framebuf.get(.Renderer);
+        _ = SDL.SDL_UpdateTexture(self.texture, null, framebuf.ptr, pitch);
+        _ = SDL.SDL_RenderCopy(self.renderer, self.texture, null, null);
+        SDL.SDL_RenderPresent(self.renderer);
+
+        const title = std.fmt.bufPrint(&title_buf, "ZBA | {s} [Emu: {}fps] ", .{ self.base_title, frame_rate.value() }) catch unreachable;
+        SDL.SDL_SetWindowTitle(self.window, title.ptr);
+    }
+
+    quit.store(true, .SeqCst); // Terminate Emulator Thread
+}
+
+pub fn initAudio(self: *Self, apu: *Apu) void {
+    self.audio = Audio.init(apu);
+    self.audio.?.play();
+}
+
+pub fn deinit(self: Self) void {
+    if (self.audio) |aud| aud.deinit();
+    SDL.SDL_DestroyTexture(self.texture);
+    SDL.SDL_DestroyRenderer(self.renderer);
+    SDL.SDL_DestroyWindow(self.window);
+    SDL.SDL_Quit();
+}
+
+const Audio = struct {
+    const This = @This();
+    const sample_rate = @import("core/apu.zig").host_sample_rate;
+
+    device: SDL.SDL_AudioDeviceID,
+
+    fn init(apu: *Apu) This {
+        var have: SDL.SDL_AudioSpec = undefined;
+        var want: SDL.SDL_AudioSpec = std.mem.zeroes(SDL.SDL_AudioSpec);
+        want.freq = sample_rate;
+        want.format = SDL.AUDIO_U16;
+        want.channels = 2;
+        want.samples = 0x100;
+        want.callback = This.callback;
+        want.userdata = apu;
+
+        const device = SDL.SDL_OpenAudioDevice(null, 0, &want, &have, 0);
+        if (device == 0) panic();
+
+        return .{
+            .device = device,
+        };
+    }
+
+    fn deinit(this: This) void {
+        SDL.SDL_CloseAudioDevice(this.device);
+    }
+
+    pub fn play(this: *This) void {
+        SDL.SDL_PauseAudioDevice(this.device, 0);
+    }
+
+    export fn callback(userdata: ?*anyopaque, stream: [*c]u8, len: c_int) void {
+        const apu = @ptrCast(*Apu, @alignCast(@alignOf(*Apu), userdata));
+        const written = SDL.SDL_AudioStreamGet(apu.stream, stream, len);
+
+        // If we don't write anything, play silence otherwise garbage will be played
+        // FIXME: I don't think this hack to remove DC Offset is acceptable :thinking:
+        if (written == 0) std.mem.set(u8, stream[0..@intCast(usize, len)], 0x40);
+    }
+};
+
+fn panic() noreturn {
+    const str = @as(?[*:0]const u8, SDL.SDL_GetError()) orelse "unknown error";
+    @panic(std.mem.sliceTo(str, 0));
+}

src/core/cpu.zig

@@ -6,54 +6,227 @@ const Bit = @import("bitfield").Bit;
 const Bitfield = @import("bitfield").Bitfield;
 const Scheduler = @import("scheduler.zig").Scheduler;
 const FilePaths = @import("util.zig").FilePaths;
+const Logger = @import("util.zig").Logger;
 
-const Allocator = std.mem.Allocator;
 const File = std.fs.File;
 
-// ARM Instruction Groups
-const dataProcessing = @import("cpu/arm/data_processing.zig").dataProcessing;
+// ARM Instructions
+pub const arm = struct {
+    pub const InstrFn = fn (*Arm7tdmi, *Bus, u32) void;
+    const lut: [0x1000]InstrFn = populate();
+
+    const processing = @import("cpu/arm/data_processing.zig").dataProcessing;
     const psrTransfer = @import("cpu/arm/psr_transfer.zig").psrTransfer;
-const singleDataTransfer = @import("cpu/arm/single_data_transfer.zig").singleDataTransfer;
-const halfAndSignedDataTransfer = @import("cpu/arm/half_signed_data_transfer.zig").halfAndSignedDataTransfer;
-const blockDataTransfer = @import("cpu/arm/block_data_transfer.zig").blockDataTransfer;
+    const transfer = @import("cpu/arm/single_data_transfer.zig").singleDataTransfer;
+    const halfSignedTransfer = @import("cpu/arm/half_signed_data_transfer.zig").halfAndSignedDataTransfer;
+    const blockTransfer = @import("cpu/arm/block_data_transfer.zig").blockDataTransfer;
     const branch = @import("cpu/arm/branch.zig").branch;
-const branchAndExchange = @import("cpu/arm/branch.zig").branchAndExchange;
-const armSoftwareInterrupt = @import("cpu/arm/software_interrupt.zig").armSoftwareInterrupt;
-const singleDataSwap = @import("cpu/arm/single_data_swap.zig").singleDataSwap;
+    const branchExchange = @import("cpu/arm/branch.zig").branchAndExchange;
+    const swi = @import("cpu/arm/software_interrupt.zig").armSoftwareInterrupt;
+    const swap = @import("cpu/arm/single_data_swap.zig").singleDataSwap;
 
     const multiply = @import("cpu/arm/multiply.zig").multiply;
     const multiplyLong = @import("cpu/arm/multiply.zig").multiplyLong;
 
-// THUMB Instruction Groups
-const format1 = @import("cpu/thumb/data_processing.zig").format1;
-const format2 = @import("cpu/thumb/data_processing.zig").format2;
-const format3 = @import("cpu/thumb/data_processing.zig").format3;
-const format12 = @import("cpu/thumb/data_processing.zig").format12;
-const format13 = @import("cpu/thumb/data_processing.zig").format13;
+    // Undefined ARM Instruction handler
+    fn und(cpu: *Arm7tdmi, _: *Bus, opcode: u32) void {
+        const id = armIdx(opcode);
+        cpu.panic("[CPU/Decode] ID: 0x{X:0>3} 0x{X:0>8} is an illegal opcode", .{ id, opcode });
+    }
 
-const format4 = @import("cpu/thumb/alu.zig").format4;
-const format5 = @import("cpu/thumb/processing_branch.zig").format5;
+    fn populate() [0x1000]InstrFn {
+        return comptime {
+            @setEvalBranchQuota(0xE000);
+            var ret = [_]InstrFn{und} ** 0x1000;
 
-const format6 = @import("cpu/thumb/data_transfer.zig").format6;
-const format78 = @import("cpu/thumb/data_transfer.zig").format78;
-const format9 = @import("cpu/thumb/data_transfer.zig").format9;
-const format10 = @import("cpu/thumb/data_transfer.zig").format10;
-const format11 = @import("cpu/thumb/data_transfer.zig").format11;
-const format14 = @import("cpu/thumb/block_data_transfer.zig").format14;
-const format15 = @import("cpu/thumb/block_data_transfer.zig").format15;
+            var i: usize = 0;
+            while (i < ret.len) : (i += 1) {
+                ret[i] = switch (@as(u2, i >> 10)) {
+                    0b00 => if (i == 0x121) blk: {
+                        break :blk branchExchange;
+                    } else if (i & 0xFCF == 0x009) blk: {
+                        const A = i >> 5 & 1 == 1;
+                        const S = i >> 4 & 1 == 1;
+                        break :blk multiply(A, S);
+                    } else if (i & 0xFBF == 0x109) blk: {
+                        const B = i >> 6 & 1 == 1;
+                        break :blk swap(B);
+                    } else if (i & 0xF8F == 0x089) blk: {
+                        const U = i >> 6 & 1 == 1;
+                        const A = i >> 5 & 1 == 1;
+                        const S = i >> 4 & 1 == 1;
+                        break :blk multiplyLong(U, A, S);
+                    } else if (i & 0xE49 == 0x009 or i & 0xE49 == 0x049) blk: {
+                        const P = i >> 8 & 1 == 1;
+                        const U = i >> 7 & 1 == 1;
+                        const I = i >> 6 & 1 == 1;
+                        const W = i >> 5 & 1 == 1;
+                        const L = i >> 4 & 1 == 1;
+                        break :blk halfSignedTransfer(P, U, I, W, L);
+                    } else if (i & 0xD90 == 0x100) blk: {
+                        const I = i >> 9 & 1 == 1;
+                        const R = i >> 6 & 1 == 1;
+                        const kind = i >> 4 & 0x3;
+                        break :blk psrTransfer(I, R, kind);
+                    } else blk: {
+                        const I = i >> 9 & 1 == 1;
+                        const S = i >> 4 & 1 == 1;
+                        const instrKind = i >> 5 & 0xF;
+                        break :blk processing(I, S, instrKind);
+                    },
+                    0b01 => if (i >> 9 & 1 == 1 and i & 1 == 1) und else blk: {
+                        const I = i >> 9 & 1 == 1;
+                        const P = i >> 8 & 1 == 1;
+                        const U = i >> 7 & 1 == 1;
+                        const B = i >> 6 & 1 == 1;
+                        const W = i >> 5 & 1 == 1;
+                        const L = i >> 4 & 1 == 1;
+                        break :blk transfer(I, P, U, B, W, L);
+                    },
+                    else => switch (@as(u2, i >> 9 & 0x3)) {
+                        // MSB is guaranteed to be 1
+                        0b00 => blk: {
+                            const P = i >> 8 & 1 == 1;
+                            const U = i >> 7 & 1 == 1;
+                            const S = i >> 6 & 1 == 1;
+                            const W = i >> 5 & 1 == 1;
+                            const L = i >> 4 & 1 == 1;
+                            break :blk blockTransfer(P, U, S, W, L);
+                        },
+                        0b01 => blk: {
+                            const L = i >> 8 & 1 == 1;
+                            break :blk branch(L);
+                        },
+                        0b10 => und, // COP Data Transfer
+                        0b11 => if (i >> 8 & 1 == 1) swi() else und, // COP Data Operation + Register Transfer
+                    },
+                };
+            }
 
-const format16 = @import("cpu/thumb/branch.zig").format16;
-const format18 = @import("cpu/thumb/branch.zig").format18;
-const format19 = @import("cpu/thumb/branch.zig").format19;
+            return ret;
+        };
+    }
+};
 
-const thumbSoftwareInterrupt = @import("cpu/thumb/software_interrupt.zig").thumbSoftwareInterrupt;
+// THUMB Instructions
+pub const thumb = struct {
+    pub const InstrFn = fn (*Arm7tdmi, *Bus, u16) void;
+    const lut: [0x400]InstrFn = populate();
 
-pub const ArmInstrFn = fn (*Arm7tdmi, *Bus, u32) void;
-pub const ThumbInstrFn = fn (*Arm7tdmi, *Bus, u16) void;
-const arm_lut: [0x1000]ArmInstrFn = armPopulate();
-const thumb_lut: [0x400]ThumbInstrFn = thumbPopulate();
+    const processing = @import("cpu/thumb/data_processing.zig");
+    const alu = @import("cpu/thumb/alu.zig").fmt4;
+    const transfer = @import("cpu/thumb/data_transfer.zig");
+    const block_transfer = @import("cpu/thumb/block_data_transfer.zig");
+    const swi = @import("cpu/thumb/software_interrupt.zig").fmt17;
+    const branch = @import("cpu/thumb/branch.zig");
 
-const enable_logging = @import("main.zig").enable_logging;
+    /// Undefined THUMB Instruction Handler
+    fn und(cpu: *Arm7tdmi, _: *Bus, opcode: u16) void {
+        const id = thumbIdx(opcode);
+        cpu.panic("[CPU/Decode] ID: 0b{b:0>10} 0x{X:0>2} is an illegal opcode", .{ id, opcode });
+    }
+
+    fn populate() [0x400]InstrFn {
+        return comptime {
+            @setEvalBranchQuota(5025); // This is exact
+            var ret = [_]InstrFn{und} ** 0x400;
+
+            var i: usize = 0;
+            while (i < ret.len) : (i += 1) {
+                ret[i] = switch (@as(u3, i >> 7 & 0x7)) {
+                    0b000 => if (i >> 5 & 0x3 == 0b11) blk: {
+                        const I = i >> 4 & 1 == 1;
+                        const is_sub = i >> 3 & 1 == 1;
+                        const rn = i & 0x7;
+                        break :blk processing.fmt2(I, is_sub, rn);
+                    } else blk: {
+                        const op = i >> 5 & 0x3;
+                        const offset = i & 0x1F;
+                        break :blk processing.fmt1(op, offset);
+                    },
+                    0b001 => blk: {
+                        const op = i >> 5 & 0x3;
+                        const rd = i >> 2 & 0x7;
+                        break :blk processing.fmt3(op, rd);
+                    },
+                    0b010 => switch (@as(u2, i >> 5 & 0x3)) {
+                        0b00 => if (i >> 4 & 1 == 1) blk: {
+                            const op = i >> 2 & 0x3;
+                            const h1 = i >> 1 & 1;
+                            const h2 = i & 1;
+                            break :blk processing.fmt5(op, h1, h2);
+                        } else blk: {
+                            const op = i & 0xF;
+                            break :blk alu(op);
+                        },
+                        0b01 => blk: {
+                            const rd = i >> 2 & 0x7;
+                            break :blk transfer.fmt6(rd);
+                        },
+                        else => blk: {
+                            const op = i >> 4 & 0x3;
+                            const T = i >> 3 & 1 == 1;
+                            break :blk transfer.fmt78(op, T);
+                        },
+                    },
+                    0b011 => blk: {
+                        const B = i >> 6 & 1 == 1;
+                        const L = i >> 5 & 1 == 1;
+                        const offset = i & 0x1F;
+                        break :blk transfer.fmt9(B, L, offset);
+                    },
+                    else => switch (@as(u3, i >> 6 & 0x7)) {
+                        // MSB is guaranteed to be 1
+                        0b000 => blk: {
+                            const L = i >> 5 & 1 == 1;
+                            const offset = i & 0x1F;
+                            break :blk transfer.fmt10(L, offset);
+                        },
+                        0b001 => blk: {
+                            const L = i >> 5 & 1 == 1;
+                            const rd = i >> 2 & 0x7;
+                            break :blk transfer.fmt11(L, rd);
+                        },
+                        0b010 => blk: {
+                            const isSP = i >> 5 & 1 == 1;
+                            const rd = i >> 2 & 0x7;
+                            break :blk processing.fmt12(isSP, rd);
+                        },
+                        0b011 => if (i >> 4 & 1 == 1) blk: {
+                            const L = i >> 5 & 1 == 1;
+                            const R = i >> 2 & 1 == 1;
+                            break :blk block_transfer.fmt14(L, R);
+                        } else blk: {
+                            const S = i >> 1 & 1 == 1;
+                            break :blk processing.fmt13(S);
+                        },
+                        0b100 => blk: {
+                            const L = i >> 5 & 1 == 1;
+                            const rb = i >> 2 & 0x7;
+
+                            break :blk block_transfer.fmt15(L, rb);
+                        },
+                        0b101 => if (i >> 2 & 0xF == 0b1111) blk: {
+                            break :blk thumb.swi();
+                        } else blk: {
+                            const cond = i >> 2 & 0xF;
+                            break :blk branch.fmt16(cond);
+                        },
+                        0b110 => branch.fmt18(),
+                        0b111 => blk: {
+                            const is_low = i >> 5 & 1 == 1;
+                            break :blk branch.fmt19(is_low);
+                        },
+                    },
+                };
+            }
+
+            return ret;
+        };
+    }
+};
+
+const cpu_logging = @import("emu.zig").cpu_logging;
 const log = std.log.scoped(.Arm7Tdmi);
 
 pub const Arm7tdmi = struct {
@@ -62,7 +235,7 @@ pub const Arm7tdmi = struct {
     r: [16]u32,
     pipe: Pipline,
     sched: *Scheduler,
-    bus: Bus,
+    bus: *Bus,
     cpsr: PSR,
     spsr: PSR,
 
@@ -76,34 +249,25 @@ pub const Arm7tdmi = struct {
 
     banked_spsr: [5]PSR,
 
-    log_file: ?*const File,
-    log_buf: [0x100]u8,
-    binary_log: bool,
+    logger: ?Logger,
 
-    pub fn init(alloc: Allocator, sched: *Scheduler, paths: FilePaths) !Self {
+    pub fn init(sched: *Scheduler, bus: *Bus) Self {
         return Self{
             .r = [_]u32{0x00} ** 16,
             .pipe = Pipline.init(),
             .sched = sched,
-            .bus = try Bus.init(alloc, sched, paths),
+            .bus = bus,
             .cpsr = .{ .raw = 0x0000_001F },
             .spsr = .{ .raw = 0x0000_0000 },
             .banked_fiq = [_]u32{0x00} ** 10,
             .banked_r = [_]u32{0x00} ** 12,
             .banked_spsr = [_]PSR{.{ .raw = 0x0000_0000 }} ** 5,
-            .log_file = null,
-            .log_buf = undefined,
-            .binary_log = false,
+            .logger = null,
         };
     }
 
-    pub fn deinit(self: Self) void {
-        self.bus.deinit();
-    }
-
-    pub fn useLogger(self: *Self, file: *const File, is_binary: bool) void {
-        self.log_file = file;
-        self.binary_log = is_binary;
+    pub fn attach(self: *Self, log_file: std.fs.File) void {
+        self.logger = Logger.init(log_file);
     }
 
     inline fn bankedIdx(mode: Mode, kind: BankedKind) usize {
@@ -273,15 +437,16 @@ pub const Arm7tdmi = struct {
     pub fn step(self: *Self) void {
         if (self.cpsr.t.read()) blk: {
             const opcode = @truncate(u16, self.pipe.step(self, u16) orelse break :blk);
-            if (enable_logging) if (self.log_file) |file| self.debug_log(file, opcode);
+            if (cpu_logging) self.logger.?.mgbaLog(self, opcode);
 
-            thumb_lut[thumbIdx(opcode)](self, &self.bus, opcode);
+            thumb.lut[thumbIdx(opcode)](self, self.bus, opcode);
         } else blk: {
             const opcode = self.pipe.step(self, u32) orelse break :blk;
-            if (enable_logging) if (self.log_file) |file| self.debug_log(file, opcode);
+            if (cpu_logging) self.logger.?.mgbaLog(self, opcode);
 
-            if (checkCond(self.cpsr, @truncate(u4, opcode >> 28)))
-                arm_lut[armIdx(opcode)](self, &self.bus, opcode);
+            if (checkCond(self.cpsr, @truncate(u4, opcode >> 28))) {
+                arm.lut[armIdx(opcode)](self, self.bus, opcode);
+            }
         }
 
         if (!self.pipe.flushed) self.r[15] += if (self.cpsr.t.read()) 2 else @as(u32, 4);
@@ -418,25 +583,6 @@ pub const Arm7tdmi = struct {
         };
     }
 
-    fn skyLog(self: *const Self, file: *const File) !void {
-        var buf: [18 * @sizeOf(u32)]u8 = undefined;
-
-        // Write Registers
-        var i: usize = 0;
-        while (i < 0x10) : (i += 1) {
-            skyWrite(&buf, i, self.r[i]);
-        }
-
-        skyWrite(&buf, 0x10, self.cpsr.raw);
-        skyWrite(&buf, 0x11, if (self.hasSPSR()) self.spsr.raw else self.cpsr.raw);
-        _ = try file.writeAll(&buf);
-    }
-
-    fn skyWrite(buf: []u8, i: usize, num: u32) void {
-        const j = @sizeOf(u32) * i;
-        std.mem.writeIntSliceNative(u32, buf[j..(j + @sizeOf(u32))], num);
-    }
-
     fn mgbaLog(self: *const Self, file: *const File, opcode: u32) !void {
         const thumb_fmt = "{X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} cpsr: {X:0>8} | {X:0>4}:\n";
         const arm_fmt = "{X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} cpsr: {X:0>8} | {X:0>8}:\n";
@@ -509,178 +655,6 @@ pub fn checkCond(cpsr: PSR, cond: u4) bool {
     };
 }
 
-fn thumbPopulate() [0x400]ThumbInstrFn {
-    return comptime {
-        @setEvalBranchQuota(5025); // This is exact
-        var lut = [_]ThumbInstrFn{thumbUndefined} ** 0x400;
-
-        var i: usize = 0;
-        while (i < lut.len) : (i += 1) {
-            lut[i] = switch (@as(u3, i >> 7 & 0x7)) {
-                0b000 => if (i >> 5 & 0x3 == 0b11) blk: {
-                    const I = i >> 4 & 1 == 1;
-                    const is_sub = i >> 3 & 1 == 1;
-                    const rn = i & 0x7;
-                    break :blk format2(I, is_sub, rn);
-                } else blk: {
-                    const op = i >> 5 & 0x3;
-                    const offset = i & 0x1F;
-                    break :blk format1(op, offset);
-                },
-                0b001 => blk: {
-                    const op = i >> 5 & 0x3;
-                    const rd = i >> 2 & 0x7;
-                    break :blk format3(op, rd);
-                },
-                0b010 => switch (@as(u2, i >> 5 & 0x3)) {
-                    0b00 => if (i >> 4 & 1 == 1) blk: {
-                        const op = i >> 2 & 0x3;
-                        const h1 = i >> 1 & 1;
-                        const h2 = i & 1;
-                        break :blk format5(op, h1, h2);
-                    } else blk: {
-                        const op = i & 0xF;
-                        break :blk format4(op);
-                    },
-                    0b01 => blk: {
-                        const rd = i >> 2 & 0x7;
-                        break :blk format6(rd);
-                    },
-                    else => blk: {
-                        const op = i >> 4 & 0x3;
-                        const T = i >> 3 & 1 == 1;
-                        break :blk format78(op, T);
-                    },
-                },
-                0b011 => blk: {
-                    const B = i >> 6 & 1 == 1;
-                    const L = i >> 5 & 1 == 1;
-                    const offset = i & 0x1F;
-                    break :blk format9(B, L, offset);
-                },
-                else => switch (@as(u3, i >> 6 & 0x7)) {
-                    // MSB is guaranteed to be 1
-                    0b000 => blk: {
-                        const L = i >> 5 & 1 == 1;
-                        const offset = i & 0x1F;
-                        break :blk format10(L, offset);
-                    },
-                    0b001 => blk: {
-                        const L = i >> 5 & 1 == 1;
-                        const rd = i >> 2 & 0x7;
-                        break :blk format11(L, rd);
-                    },
-                    0b010 => blk: {
-                        const isSP = i >> 5 & 1 == 1;
-                        const rd = i >> 2 & 0x7;
-                        break :blk format12(isSP, rd);
-                    },
-                    0b011 => if (i >> 4 & 1 == 1) blk: {
-                        const L = i >> 5 & 1 == 1;
-                        const R = i >> 2 & 1 == 1;
-                        break :blk format14(L, R);
-                    } else blk: {
-                        const S = i >> 1 & 1 == 1;
-                        break :blk format13(S);
-                    },
-                    0b100 => blk: {
-                        const L = i >> 5 & 1 == 1;
-                        const rb = i >> 2 & 0x7;
-
-                        break :blk format15(L, rb);
-                    },
-                    0b101 => if (i >> 2 & 0xF == 0b1111) blk: {
-                        break :blk thumbSoftwareInterrupt();
-                    } else blk: {
-                        const cond = i >> 2 & 0xF;
-                        break :blk format16(cond);
-                    },
-                    0b110 => format18(),
-                    0b111 => blk: {
-                        const is_low = i >> 5 & 1 == 1;
-                        break :blk format19(is_low);
-                    },
-                },
-            };
-        }
-
-        return lut;
-    };
-}
-
-fn armPopulate() [0x1000]ArmInstrFn {
-    return comptime {
-        @setEvalBranchQuota(0xE000);
-        var lut = [_]ArmInstrFn{armUndefined} ** 0x1000;
-
-        var i: usize = 0;
-        while (i < lut.len) : (i += 1) {
-            lut[i] = switch (@as(u2, i >> 10)) {
-                0b00 => if (i == 0x121) blk: {
-                    break :blk branchAndExchange;
-                } else if (i & 0xFCF == 0x009) blk: {
-                    const A = i >> 5 & 1 == 1;
-                    const S = i >> 4 & 1 == 1;
-                    break :blk multiply(A, S);
-                } else if (i & 0xFBF == 0x109) blk: {
-                    const B = i >> 6 & 1 == 1;
-                    break :blk singleDataSwap(B);
-                } else if (i & 0xF8F == 0x089) blk: {
-                    const U = i >> 6 & 1 == 1;
-                    const A = i >> 5 & 1 == 1;
-                    const S = i >> 4 & 1 == 1;
-                    break :blk multiplyLong(U, A, S);
-                } else if (i & 0xE49 == 0x009 or i & 0xE49 == 0x049) blk: {
-                    const P = i >> 8 & 1 == 1;
-                    const U = i >> 7 & 1 == 1;
-                    const I = i >> 6 & 1 == 1;
-                    const W = i >> 5 & 1 == 1;
-                    const L = i >> 4 & 1 == 1;
-                    break :blk halfAndSignedDataTransfer(P, U, I, W, L);
-                } else if (i & 0xD90 == 0x100) blk: {
-                    const I = i >> 9 & 1 == 1;
-                    const R = i >> 6 & 1 == 1;
-                    const kind = i >> 4 & 0x3;
-                    break :blk psrTransfer(I, R, kind);
-                } else blk: {
-                    const I = i >> 9 & 1 == 1;
-                    const S = i >> 4 & 1 == 1;
-                    const instrKind = i >> 5 & 0xF;
-                    break :blk dataProcessing(I, S, instrKind);
-                },
-                0b01 => if (i >> 9 & 1 == 1 and i & 1 == 1) armUndefined else blk: {
-                    const I = i >> 9 & 1 == 1;
-                    const P = i >> 8 & 1 == 1;
-                    const U = i >> 7 & 1 == 1;
-                    const B = i >> 6 & 1 == 1;
-                    const W = i >> 5 & 1 == 1;
-                    const L = i >> 4 & 1 == 1;
-                    break :blk singleDataTransfer(I, P, U, B, W, L);
-                },
-                else => switch (@as(u2, i >> 9 & 0x3)) {
-                    // MSB is guaranteed to be 1
-                    0b00 => blk: {
-                        const P = i >> 8 & 1 == 1;
-                        const U = i >> 7 & 1 == 1;
-                        const S = i >> 6 & 1 == 1;
-                        const W = i >> 5 & 1 == 1;
-                        const L = i >> 4 & 1 == 1;
-                        break :blk blockDataTransfer(P, U, S, W, L);
-                    },
-                    0b01 => blk: {
-                        const L = i >> 8 & 1 == 1;
-                        break :blk branch(L);
-                    },
-                    0b10 => armUndefined, // COP Data Transfer
-                    0b11 => if (i >> 8 & 1 == 1) armSoftwareInterrupt() else armUndefined, // COP Data Operation + Register Transfer
-                },
-            };
-        }
-
-        return lut;
-    };
-}
-
 const Pipline = struct {
     const Self = @This();
     stage: [2]?u32,
@@ -757,13 +731,3 @@ fn getMode(bits: u5) ?Mode {
 fn getModeChecked(cpu: *const Arm7tdmi, bits: u5) Mode {
     return getMode(bits) orelse cpu.panic("[CPU/CPSR] 0b{b:0>5} is an invalid CPU mode", .{bits});
 }
-
-fn armUndefined(cpu: *Arm7tdmi, _: *Bus, opcode: u32) void {
-    const id = armIdx(opcode);
-    cpu.panic("[CPU/Decode] ID: 0x{X:0>3} 0x{X:0>8} is an illegal opcode", .{ id, opcode });
-}
-
-fn thumbUndefined(cpu: *Arm7tdmi, _: *Bus, opcode: u16) void {
-    const id = thumbIdx(opcode);
-    cpu.panic("[CPU/Decode] ID: 0b{b:0>10} 0x{X:0>2} is an illegal opcode", .{ id, opcode });
-}

src/core/cpu/arm/block_data_transfer.zig

@@ -1,6 +1,6 @@
 const Bus = @import("../../Bus.zig");
 const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
-const InstrFn = @import("../../cpu.zig").ArmInstrFn;
+const InstrFn = @import("../../cpu.zig").arm.InstrFn;
 
 pub fn blockDataTransfer(comptime P: bool, comptime U: bool, comptime S: bool, comptime W: bool, comptime L: bool) InstrFn {
     return struct {

src/core/cpu/arm/branch.zig

@@ -2,7 +2,7 @@ const std = @import("std");
 
 const Bus = @import("../../Bus.zig");
 const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
-const InstrFn = @import("../../cpu.zig").ArmInstrFn;
+const InstrFn = @import("../../cpu.zig").arm.InstrFn;
 
 const sext = @import("../../util.zig").sext;
 

src/core/cpu/arm/data_processing.zig

@@ -1,6 +1,6 @@
 const Bus = @import("../../Bus.zig");
 const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
-const InstrFn = @import("../../cpu.zig").ArmInstrFn;
+const InstrFn = @import("../../cpu.zig").arm.InstrFn;
 
 const rotateRight = @import("../barrel_shifter.zig").rotateRight;
 const execute = @import("../barrel_shifter.zig").execute;

src/core/cpu/arm/half_signed_data_transfer.zig

@@ -2,7 +2,7 @@ const std = @import("std");
 
 const Bus = @import("../../Bus.zig");
 const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
-const InstrFn = @import("../../cpu.zig").ArmInstrFn;
+const InstrFn = @import("../../cpu.zig").arm.InstrFn;
 
 const sext = @import("../../util.zig").sext;
 const rotr = @import("../../util.zig").rotr;

src/core/cpu/arm/multiply.zig

@@ -1,6 +1,6 @@
 const Bus = @import("../../Bus.zig");
 const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
-const InstrFn = @import("../../cpu.zig").ArmInstrFn;
+const InstrFn = @import("../../cpu.zig").arm.InstrFn;
 
 pub fn multiply(comptime A: bool, comptime S: bool) InstrFn {
     return struct {

src/core/cpu/arm/psr_transfer.zig

@@ -2,7 +2,7 @@ const std = @import("std");
 
 const Bus = @import("../../Bus.zig");
 const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
-const InstrFn = @import("../../cpu.zig").ArmInstrFn;
+const InstrFn = @import("../../cpu.zig").arm.InstrFn;
 const PSR = @import("../../cpu.zig").PSR;
 
 const log = std.log.scoped(.PsrTransfer);

src/core/cpu/arm/single_data_swap.zig

@@ -2,7 +2,7 @@ const std = @import("std");
 
 const Bus = @import("../../Bus.zig");
 const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
-const InstrFn = @import("../../cpu.zig").ArmInstrFn;
+const InstrFn = @import("../../cpu.zig").arm.InstrFn;
 
 const rotr = @import("../../util.zig").rotr;
 

src/core/cpu/arm/single_data_transfer.zig

@@ -4,7 +4,7 @@ const util = @import("../../util.zig");
 const shifter = @import("../barrel_shifter.zig");
 const Bus = @import("../../Bus.zig");
 const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
-const InstrFn = @import("../../cpu.zig").ArmInstrFn;
+const InstrFn = @import("../../cpu.zig").arm.InstrFn;
 
 const rotr = @import("../../util.zig").rotr;
 

src/core/cpu/arm/software_interrupt.zig

@@ -1,6 +1,6 @@
 const Bus = @import("../../Bus.zig");
 const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
-const InstrFn = @import("../../cpu.zig").ArmInstrFn;
+const InstrFn = @import("../../cpu.zig").arm.InstrFn;
 
 pub fn armSoftwareInterrupt() InstrFn {
     return struct {

src/core/cpu/thumb/alu.zig

@@ -1,6 +1,6 @@
 const Bus = @import("../../Bus.zig");
 const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
-const InstrFn = @import("../../cpu.zig").ThumbInstrFn;
+const InstrFn = @import("../../cpu.zig").thumb.InstrFn;
 
 const adc = @import("../arm/data_processing.zig").adc;
 const sbc = @import("../arm/data_processing.zig").sbc;
@@ -15,7 +15,7 @@ const logicalRight = @import("../barrel_shifter.zig").logicalRight;
 const arithmeticRight = @import("../barrel_shifter.zig").arithmeticRight;
 const rotateRight = @import("../barrel_shifter.zig").rotateRight;
 
-pub fn format4(comptime op: u4) InstrFn {
+pub fn fmt4(comptime op: u4) InstrFn {
     return struct {
         fn inner(cpu: *Arm7tdmi, _: *Bus, opcode: u16) void {
             const rs = opcode >> 3 & 0x7;

src/core/cpu/thumb/block_data_transfer.zig

@@ -1,8 +1,8 @@
 const Bus = @import("../../Bus.zig");
 const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
-const InstrFn = @import("../../cpu.zig").ThumbInstrFn;
+const InstrFn = @import("../../cpu.zig").thumb.InstrFn;
 
-pub fn format14(comptime L: bool, comptime R: bool) InstrFn {
+pub fn fmt14(comptime L: bool, comptime R: bool) InstrFn {
     return struct {
         fn inner(cpu: *Arm7tdmi, bus: *Bus, opcode: u16) void {
             const count = @boolToInt(R) + countRlist(opcode);
@@ -46,7 +46,7 @@ pub fn format14(comptime L: bool, comptime R: bool) InstrFn {
     }.inner;
 }
 
-pub fn format15(comptime L: bool, comptime rb: u3) InstrFn {
+pub fn fmt15(comptime L: bool, comptime rb: u3) InstrFn {
     return struct {
         fn inner(cpu: *Arm7tdmi, bus: *Bus, opcode: u16) void {
             var address = cpu.r[rb];

src/core/cpu/thumb/branch.zig

@@ -1,11 +1,11 @@
 const Bus = @import("../../Bus.zig");
 const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
-const InstrFn = @import("../../cpu.zig").ThumbInstrFn;
+const InstrFn = @import("../../cpu.zig").thumb.InstrFn;
 
 const checkCond = @import("../../cpu.zig").checkCond;
 const sext = @import("../../util.zig").sext;
 
-pub fn format16(comptime cond: u4) InstrFn {
+pub fn fmt16(comptime cond: u4) InstrFn {
     return struct {
         fn inner(cpu: *Arm7tdmi, _: *Bus, opcode: u16) void {
             // B
@@ -20,7 +20,7 @@ pub fn format16(comptime cond: u4) InstrFn {
     }.inner;
 }
 
-pub fn format18() InstrFn {
+pub fn fmt18() InstrFn {
     return struct {
         // B but conditional
         fn inner(cpu: *Arm7tdmi, _: *Bus, opcode: u16) void {
@@ -30,7 +30,7 @@ pub fn format18() InstrFn {
     }.inner;
 }
 
-pub fn format19(comptime is_low: bool) InstrFn {
+pub fn fmt19(comptime is_low: bool) InstrFn {
     return struct {
         fn inner(cpu: *Arm7tdmi, _: *Bus, opcode: u16) void {
             // BL

src/core/cpu/thumb/data_processing.zig

@@ -2,7 +2,7 @@ const std = @import("std");
 
 const Bus = @import("../../Bus.zig");
 const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
-const InstrFn = @import("../../cpu.zig").ThumbInstrFn;
+const InstrFn = @import("../../cpu.zig").thumb.InstrFn;
 const shifter = @import("../barrel_shifter.zig");
 
 const add = @import("../arm/data_processing.zig").add;
@@ -12,7 +12,7 @@ const setLogicOpFlags = @import("../arm/data_processing.zig").setLogicOpFlags;
 
 const log = std.log.scoped(.Thumb1);
 
-pub fn format1(comptime op: u2, comptime offset: u5) InstrFn {
+pub fn fmt1(comptime op: u2, comptime offset: u5) InstrFn {
     return struct {
         fn inner(cpu: *Arm7tdmi, _: *Bus, opcode: u16) void {
             const rs = opcode >> 3 & 0x7;
@@ -55,7 +55,37 @@ pub fn format1(comptime op: u2, comptime offset: u5) InstrFn {
     }.inner;
 }
 
-pub fn format2(comptime I: bool, is_sub: bool, rn: u3) InstrFn {
+pub fn fmt5(comptime op: u2, comptime h1: u1, comptime h2: u1) InstrFn {
+    return struct {
+        fn inner(cpu: *Arm7tdmi, _: *Bus, opcode: u16) void {
+            const src_idx = @as(u4, h2) << 3 | (opcode >> 3 & 0x7);
+            const dst_idx = @as(u4, h1) << 3 | (opcode & 0x7);
+
+            const src = if (src_idx == 0xF) (cpu.r[src_idx] + 2) & 0xFFFF_FFFE else cpu.r[src_idx];
+            const dst = if (dst_idx == 0xF) (cpu.r[dst_idx] + 2) & 0xFFFF_FFFE else cpu.r[dst_idx];
+
+            switch (op) {
+                0b00 => {
+                    // ADD
+                    const sum = add(false, cpu, dst, src);
+                    cpu.r[dst_idx] = if (dst_idx == 0xF) sum & 0xFFFF_FFFE else sum;
+                },
+                0b01 => cmp(cpu, dst, src), // CMP
+                0b10 => {
+                    // MOV
+                    cpu.r[dst_idx] = if (dst_idx == 0xF) src & 0xFFFF_FFFE else src;
+                },
+                0b11 => {
+                    // BX
+                    cpu.cpsr.t.write(src & 1 == 1);
+                    cpu.r[15] = src & 0xFFFF_FFFE;
+                },
+            }
+        }
+    }.inner;
+}
+
+pub fn fmt2(comptime I: bool, is_sub: bool, rn: u3) InstrFn {
     return struct {
         fn inner(cpu: *Arm7tdmi, _: *Bus, opcode: u16) void {
             const rs = opcode >> 3 & 0x7;
@@ -80,7 +110,7 @@ pub fn format2(comptime I: bool, is_sub: bool, rn: u3) InstrFn {
     }.inner;
 }
 
-pub fn format3(comptime op: u2, comptime rd: u3) InstrFn {
+pub fn fmt3(comptime op: u2, comptime rd: u3) InstrFn {
     return struct {
         fn inner(cpu: *Arm7tdmi, _: *Bus, opcode: u16) void {
             const offset = @truncate(u8, opcode);
@@ -99,18 +129,18 @@ pub fn format3(comptime op: u2, comptime rd: u3) InstrFn {
     }.inner;
 }
 
-pub fn format12(comptime SP: bool, comptime rd: u3) InstrFn {
+pub fn fmt12(comptime isSP: bool, comptime rd: u3) InstrFn {
     return struct {
         fn inner(cpu: *Arm7tdmi, _: *Bus, opcode: u16) void {
             // ADD
-            const left = if (SP) cpu.r[13] else cpu.r[15] & ~@as(u32, 2);
+            const left = if (isSP) cpu.r[13] else cpu.r[15] & ~@as(u32, 2);
             const right = (opcode & 0xFF) << 2;
             cpu.r[rd] = left + right;
         }
     }.inner;
 }
 
-pub fn format13(comptime S: bool) InstrFn {
+pub fn fmt13(comptime S: bool) InstrFn {
     return struct {
         fn inner(cpu: *Arm7tdmi, _: *Bus, opcode: u16) void {
             // ADD

src/core/cpu/thumb/data_transfer.zig

@@ -2,11 +2,11 @@ const std = @import("std");
 
 const Bus = @import("../../Bus.zig");
 const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
-const InstrFn = @import("../../cpu.zig").ThumbInstrFn;
+const InstrFn = @import("../../cpu.zig").thumb.InstrFn;
 
 const rotr = @import("../../util.zig").rotr;
 
-pub fn format6(comptime rd: u3) InstrFn {
+pub fn fmt6(comptime rd: u3) InstrFn {
     return struct {
         fn inner(cpu: *Arm7tdmi, bus: *Bus, opcode: u16) void {
             // LDR
@@ -20,7 +20,7 @@ pub fn format6(comptime rd: u3) InstrFn {
 
 const sext = @import("../../util.zig").sext;
 
-pub fn format78(comptime op: u2, comptime T: bool) InstrFn {
+pub fn fmt78(comptime op: u2, comptime T: bool) InstrFn {
     return struct {
         fn inner(cpu: *Arm7tdmi, bus: *Bus, opcode: u16) void {
             const ro = opcode >> 6 & 0x7;
@@ -80,7 +80,7 @@ pub fn format78(comptime op: u2, comptime T: bool) InstrFn {
     }.inner;
 }
 
-pub fn format9(comptime B: bool, comptime L: bool, comptime offset: u5) InstrFn {
+pub fn fmt9(comptime B: bool, comptime L: bool, comptime offset: u5) InstrFn {
     return struct {
         fn inner(cpu: *Arm7tdmi, bus: *Bus, opcode: u16) void {
             const rb = opcode >> 3 & 0x7;
@@ -112,7 +112,7 @@ pub fn format9(comptime B: bool, comptime L: bool, comptime offset: u5) InstrFn
     }.inner;
 }
 
-pub fn format10(comptime L: bool, comptime offset: u5) InstrFn {
+pub fn fmt10(comptime L: bool, comptime offset: u5) InstrFn {
     return struct {
         fn inner(cpu: *Arm7tdmi, bus: *Bus, opcode: u16) void {
             const rb = opcode >> 3 & 0x7;
@@ -132,7 +132,7 @@ pub fn format10(comptime L: bool, comptime offset: u5) InstrFn {
     }.inner;
 }
 
-pub fn format11(comptime L: bool, comptime rd: u3) InstrFn {
+pub fn fmt11(comptime L: bool, comptime rd: u3) InstrFn {
     return struct {
         fn inner(cpu: *Arm7tdmi, bus: *Bus, opcode: u16) void {
             const offset = (opcode & 0xFF) << 2;

src/core/cpu/thumb/software_interrupt.zig

@@ -1,8 +1,8 @@
 const Bus = @import("../../Bus.zig");
 const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
-const InstrFn = @import("../../cpu.zig").ThumbInstrFn;
+const InstrFn = @import("../../cpu.zig").thumb.InstrFn;
 
-pub fn thumbSoftwareInterrupt() InstrFn {
+pub fn fmt17() InstrFn {
     return struct {
         fn inner(cpu: *Arm7tdmi, _: *Bus, _: u16) void {
             // Copy Values from Current Mode

src/core/emu.zig

@@ -5,12 +5,16 @@ const Bus = @import("Bus.zig");
 const Scheduler = @import("scheduler.zig").Scheduler;
 const Arm7tdmi = @import("cpu.zig").Arm7tdmi;
 const FpsTracker = @import("util.zig").FpsTracker;
+const FilePaths = @import("util.zig").FilePaths;
 
 const Timer = std.time.Timer;
 const Thread = std.Thread;
 const Atomic = std.atomic.Atomic;
+const Allocator = std.mem.Allocator;
 
-const audio_sync = true;
+const sync_audio = false;
+const sync_video: RunKind = .UnlimitedFPS;
+pub const cpu_logging = false;
 
 // 228 Lines which consist of 308 dots (which are 4 cycles long)
 const cycles_per_frame: u64 = 228 * (308 * 4); //280896
@@ -35,10 +39,10 @@ const RunKind = enum {
     LimitedBusy,
 };
 
-pub fn run(kind: RunKind, quit: *Atomic(bool), fps: *FpsTracker, sched: *Scheduler, cpu: *Arm7tdmi) void {
-    if (audio_sync) log.info("Audio sync enabled", .{});
+pub fn run(quit: *Atomic(bool), fps: *FpsTracker, sched: *Scheduler, cpu: *Arm7tdmi) void {
+    if (sync_audio) log.info("Audio sync enabled", .{});
 
-    switch (kind) {
+    switch (sync_video) {
         .Unlimited => runUnsynchronized(quit, sched, cpu, null),
         .Limited => runSynchronized(quit, sched, cpu, null),
         .UnlimitedFPS => runUnsynchronized(quit, sched, cpu, fps),
@@ -50,14 +54,17 @@ pub fn run(kind: RunKind, quit: *Atomic(bool), fps: *FpsTracker, sched: *Schedul
 pub fn runFrame(sched: *Scheduler, cpu: *Arm7tdmi) void {
     const frame_end = sched.tick + cycles_per_frame;
 
-    while (true) {
-        while (sched.tick < std.math.min(frame_end, sched.nextTimestamp())) {
-            if (cpu.stepDmaTransfer()) continue; // DMA is blocking, ticks scheduler
-            if (!cpu.isHalted()) cpu.step() else sched.tick += 1;
+    while (sched.tick < frame_end) {
+        if (!cpu.stepDmaTransfer()) {
+            if (cpu.isHalted()) {
+                // Fast-forward to next Event
+                sched.tick = sched.queue.peek().?.tick;
+            } else {
+                cpu.step();
+            }
         }
 
-        if (sched.tick >= frame_end) break;
-        sched.handleEvent(cpu);
+        if (sched.tick >= sched.nextTimestamp()) sched.handleEvent(cpu);
     }
 }
 
@@ -77,14 +84,14 @@ pub fn runUnsynchronized(quit: *Atomic(bool), sched: *Scheduler, cpu: *Arm7tdmi,
 
         while (!quit.load(.SeqCst)) {
             runFrame(sched, cpu);
-            if (audio_sync) syncToAudio(cpu);
+            if (sync_audio) syncToAudio(cpu);
 
             tracker.tick();
         }
     } else {
         while (!quit.load(.SeqCst)) {
             runFrame(sched, cpu);
-            if (audio_sync) syncToAudio(cpu);
+            if (sync_audio) syncToAudio(cpu);
         }
     }
 }
@@ -105,7 +112,7 @@ pub fn runSynchronized(quit: *Atomic(bool), sched: *Scheduler, cpu: *Arm7tdmi, f
             // If we happen to also be syncing to audio, we choose to spin on
             // the amount of time needed for audio to catch up rather than
             // our expected wake-up time
-            if (audio_sync) syncToAudio(cpu) else spinLoop(&timer, wake_time);
+            if (sync_audio) syncToAudio(cpu) else spinLoop(&timer, wake_time);
             wake_time = new_wake_time;
 
             tracker.tick();
@@ -115,7 +122,7 @@ pub fn runSynchronized(quit: *Atomic(bool), sched: *Scheduler, cpu: *Arm7tdmi, f
             runFrame(sched, cpu);
             const new_wake_time = syncToVideo(&timer, wake_time);
             // see above comment
-            if (audio_sync) syncToAudio(cpu) else spinLoop(&timer, wake_time);
+            if (sync_audio) syncToAudio(cpu) else spinLoop(&timer, wake_time);
 
             wake_time = new_wake_time;
         }

src/core/ppu.zig

@@ -573,7 +573,7 @@ pub const Ppu = struct {
         // See if HBlank DMA is present and not enabled
 
         if (!self.dispstat.vblank.read())
-            pollBlankingDma(&cpu.bus, .HBlank);
+            pollBlankingDma(cpu.bus, .HBlank);
 
         self.dispstat.hblank.set();
         self.sched.push(.HBlank, 68 * 4 -| late);
@@ -615,7 +615,7 @@ pub const Ppu = struct {
                 self.aff_bg[1].latchRefPoints();
 
                 // See if Vblank DMA is present and not enabled
-                pollBlankingDma(&cpu.bus, .VBlank);
+                pollBlankingDma(cpu.bus, .VBlank);
             }
 
             if (scanline == 227) self.dispstat.vblank.unset();

src/core/util.zig

@@ -1,6 +1,7 @@
 const std = @import("std");
 const builtin = @import("builtin");
 const Log2Int = std.math.Log2Int;
+const Arm7tdmi = @import("cpu.zig").Arm7tdmi;
 
 // Sign-Extend value of type `T` to type `U`
 pub fn sext(comptime T: type, comptime U: type, value: T) T {
@@ -112,3 +113,64 @@ pub fn writeUndefined(log: anytype, comptime format: []const u8, args: anytype)
     log.warn(format, args);
     if (builtin.mode == .Debug) std.debug.panic("TODO: Implement I/O Register", .{});
 }
+
+pub const Logger = struct {
+    const Self = @This();
+
+    buf: std.io.BufferedWriter(4096 << 2, std.fs.File.Writer),
+
+    pub fn init(file: std.fs.File) Self {
+        return .{
+            .buf = .{ .unbuffered_writer = file.writer() },
+        };
+    }
+
+    pub fn print(self: *Self, comptime format: []const u8, args: anytype) !void {
+        try self.buf.writer().print(format, args);
+    }
+
+    pub fn mgbaLog(self: *Self, arm7tdmi: *const Arm7tdmi, opcode: u32) void {
+        const fmt_base = "{X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} {X:0>8} cpsr: {X:0>8} | ";
+        const thumb_fmt = fmt_base ++ "{X:0>4}:\n";
+        const arm_fmt = fmt_base ++ "{X:0>8}:\n";
+
+        if (arm7tdmi.cpsr.t.read()) {
+            if (opcode >> 11 == 0x1E) {
+                // Instruction 1 of a BL Opcode, print in ARM mode
+                const low = arm7tdmi.bus.debugRead(u16, arm7tdmi.r[15]);
+                const bl_opcode = @as(u32, opcode) << 16 | low;
+
+                self.print(arm_fmt, Self.fmtArgs(arm7tdmi, bl_opcode)) catch @panic("failed to write to log file");
+            } else {
+                self.print(thumb_fmt, Self.fmtArgs(arm7tdmi, opcode)) catch @panic("failed to write to log file");
+            }
+        } else {
+            self.print(arm_fmt, Self.fmtArgs(arm7tdmi, opcode)) catch @panic("failed to write to log file");
+        }
+    }
+
+    fn fmtArgs(arm7tdmi: *const Arm7tdmi, opcode: u32) FmtArgTuple {
+        return .{
+            arm7tdmi.r[0],
+            arm7tdmi.r[1],
+            arm7tdmi.r[2],
+            arm7tdmi.r[3],
+            arm7tdmi.r[4],
+            arm7tdmi.r[5],
+            arm7tdmi.r[6],
+            arm7tdmi.r[7],
+            arm7tdmi.r[8],
+            arm7tdmi.r[9],
+            arm7tdmi.r[10],
+            arm7tdmi.r[11],
+            arm7tdmi.r[12],
+            arm7tdmi.r[13],
+            arm7tdmi.r[14],
+            arm7tdmi.r[15] - 4,
+            arm7tdmi.cpsr.raw,
+            opcode,
+        };
+    }
+};
+
+const FmtArgTuple = std.meta.Tuple(&.{ u32, u32, u32, u32, u32, u32, u32, u32, u32, u32, u32, u32, u32, u32, u32, u32, u32, u32 });

src/cpu/thumb/processing_branch.zig

@@ -1,42 +0,0 @@
-const Bus = @import("../../Bus.zig");
-const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
-const InstrFn = @import("../../cpu.zig").ThumbInstrFn;
-
-const cmp = @import("../arm/data_processing.zig").cmp;
-const add = @import("../arm/data_processing.zig").add;
-
-pub fn format5(comptime op: u2, comptime h1: u1, comptime h2: u1) InstrFn {
-    return struct {
-        fn inner(cpu: *Arm7tdmi, _: *Bus, opcode: u16) void {
-            const src_idx = @as(u4, h2) << 3 | (opcode >> 3 & 0x7);
-            const dst_idx = @as(u4, h1) << 3 | (opcode & 0x7);
-
-            const src_mask = if (src_idx == 0xF) ~@as(u32, 1) else ~@as(u32, 0);
-            const dst_mask = if (dst_idx == 0xF) ~@as(u32, 1) else ~@as(u32, 0);
-
-            const src = cpu.r[src_idx] & src_mask;
-            const dst = cpu.r[dst_idx] & dst_mask;
-
-            switch (op) {
-                0b00 => {
-                    // ADD
-                    const sum = add(false, cpu, dst, src);
-                    cpu.r[dst_idx] = sum & dst_mask;
-                },
-                0b01 => cmp(cpu, dst, src), // CMP
-                0b10 => {
-                    // MOV
-                    cpu.r[dst_idx] = src & dst_mask;
-                },
-                0b11 => {
-                    // BX
-                    cpu.cpsr.t.write(src & 1 == 1);
-                    cpu.r[15] = src & ~@as(u32, 1);
-                    cpu.pipe.flush();
-                },
-            }
-
-            if (dst_idx == 0xF) cpu.pipe.flush();
-        }
-    }.inner;
-}

src/main.zig

@@ -1,35 +1,23 @@
 const std = @import("std");
 const builtin = @import("builtin");
-const SDL = @import("sdl2");
-const clap = @import("clap");
+
 const known_folders = @import("known_folders");
+const clap = @import("clap");
 
-const emu = @import("emu.zig");
-const Bus = @import("Bus.zig");
-const Apu = @import("apu.zig").Apu;
-const Arm7tdmi = @import("cpu.zig").Arm7tdmi;
-const Scheduler = @import("scheduler.zig").Scheduler;
-const FpsTracker = @import("util.zig").FpsTracker;
+const Gui = @import("Gui.zig");
+const Bus = @import("core/Bus.zig");
+const Arm7tdmi = @import("core/cpu.zig").Arm7tdmi;
+const Scheduler = @import("core/scheduler.zig").Scheduler;
+const FilePaths = @import("core/util.zig").FilePaths;
 
-const Timer = std.time.Timer;
-const Thread = std.Thread;
-const Atomic = std.atomic.Atomic;
-const File = std.fs.File;
-
-const window_scale = 4;
-const gba_width = @import("ppu.zig").width;
-const gba_height = @import("ppu.zig").height;
-const framebuf_pitch = @import("ppu.zig").framebuf_pitch;
-const expected_rate = @import("emu.zig").frame_rate;
-
-const sample_rate = @import("apu.zig").host_sample_rate;
-
-pub const enable_logging: bool = true;
-const is_binary: bool = false;
-const log = std.log.scoped(.GUI);
+const Allocator = std.mem.Allocator;
+const log = std.log.scoped(.CLI);
+const width = @import("core/ppu.zig").width;
+const height = @import("core/ppu.zig").height;
+const arm7tdmi_logging = @import("core/emu.zig").cpu_logging;
 pub const log_level = if (builtin.mode != .Debug) .info else std.log.default_level;
 
-const asString = @import("util.zig").asString;
+// TODO: Reimpl Logging
 
 // CLI Arguments + Help Text
 const params = clap.parseParamsComptime(
@@ -40,251 +28,78 @@ const params = clap.parseParamsComptime(
 );
 
 pub fn main() anyerror!void {
-    // Allocator for Emulator + CLI
+    // Main Allocator for ZBA
     var gpa = std.heap.GeneralPurposeAllocator(.{}){};
     defer std.debug.assert(!gpa.deinit());
-    const alloc = gpa.allocator();
+    const allocator = gpa.allocator();
 
-    // Setup CLI using zig-clap
-    var res = try clap.parse(clap.Help, &params, clap.parsers.default, .{});
-    defer res.deinit();
+    // Handle CLI Input
+    const result = try clap.parse(clap.Help, &params, clap.parsers.default, .{});
+    defer result.deinit();
 
-    const stderr = std.io.getStdErr();
-    defer stderr.close();
+    const paths = try handleArguments(allocator, &result);
+    defer if (paths.save) |path| allocator.free(path);
 
-    // Display Help, if requested
-    // Grab ROM and BIOS paths if provided
-    if (res.args.help) return clap.help(stderr.writer(), clap.Help, &params, .{});
-    const rom_path = try getRomPath(res, stderr);
-    const bios_path: ?[]const u8 = if (res.args.bios) |p| p else null;
-
-    // Determine Save Directory
-    const save_dir = try getSavePath(alloc);
-    defer if (save_dir) |path| alloc.free(path);
-    log.info("Found save directory: {s}", .{save_dir});
-
-    // Initialize Scheduler and ARM7TDMI Emulator
-    // Provide GBA Bus (initialized with ARM7TDMI) with a valid ptr to ARM7TDMI
-    var scheduler = Scheduler.init(alloc);
+    // TODO: Take Emulator Init Code out of main.zig
+    var scheduler = Scheduler.init(allocator);
     defer scheduler.deinit();
 
-    const paths = .{ .bios = bios_path, .rom = rom_path, .save = save_dir };
-    var cpu = try Arm7tdmi.init(alloc, &scheduler, paths);
-    defer cpu.deinit();
-    cpu.bus.attach(&cpu);
-    cpu.fastBoot(); // Uncomment to skip BIOS
+    var bus = try Bus.init(allocator, &scheduler, paths);
+    defer bus.deinit();
 
-    // Copy ROM title while Emulator still belongs to this thread
-    const title = cpu.bus.pak.title;
+    var arm7tdmi = Arm7tdmi.init(&scheduler, &bus);
 
-    // Initialize SDL2
-    initSdl2();
-    defer SDL.SDL_Quit();
-
-    const dev = initAudio(&cpu.bus.apu);
-    defer SDL.SDL_CloseAudioDevice(dev);
-
-    // TODO: Refactor or delete this Logging code
-    // I probably still need logging in some form though (e.g. Golden Sun IIRC)
-    const log_file: ?File = if (enable_logging) blk: {
-        const file = try std.fs.cwd().createFile(if (is_binary) "zba.bin" else "zba.log", .{});
-        cpu.useLogger(&file, is_binary);
-        break :blk file;
-    } else null;
+    const log_file: ?std.fs.File = if (arm7tdmi_logging) try std.fs.cwd().createFile("zba.log", .{}) else null;
     defer if (log_file) |file| file.close();
 
-    var quit = Atomic(bool).init(false);
-    var emu_rate = FpsTracker.init();
+    if (log_file) |file| arm7tdmi.attach(file);
+    bus.attach(&arm7tdmi); // TODO: Shrink Surface (only CPSR and  r15?)
+    if (paths.bios == null) arm7tdmi.fastBoot();
 
-    // Run Emulator in it's separate thread
-    // From this point on, interacting with Arm7tdmi or Scheduler
-    // be justified, as it will require to be thread-afe
-    const emu_thread = try Thread.spawn(.{}, emu.run, .{ .LimitedFPS, &quit, &emu_rate, &scheduler, &cpu });
-    defer emu_thread.join();
+    var gui = Gui.init(bus.pak.title, width, height);
+    gui.initAudio(&bus.apu);
+    defer gui.deinit();
 
-    var title_buf: [0x20]u8 = std.mem.zeroes([0x20]u8);
-    const window_title = try std.fmt.bufPrint(&title_buf, "ZBA | {s}", .{asString(title)});
-
-    const window = createWindow(window_title, gba_width, gba_height);
-    defer SDL.SDL_DestroyWindow(window);
-
-    const renderer = createRenderer(window);
-    defer SDL.SDL_DestroyRenderer(renderer);
-
-    const texture = createTexture(renderer, gba_width, gba_height);
-    defer SDL.SDL_DestroyTexture(texture);
-
-    // Init FPS Timer
-    var dyn_title_buf: [0x100]u8 = [_]u8{0x00} ** 0x100;
-
-    emu_loop: while (true) {
-        var event: SDL.SDL_Event = undefined;
-        while (SDL.SDL_PollEvent(&event) != 0) {
-            switch (event.type) {
-                SDL.SDL_QUIT => break :emu_loop,
-                SDL.SDL_KEYDOWN => {
-                    const io = &cpu.bus.io;
-                    const key_code = event.key.keysym.sym;
-
-                    switch (key_code) {
-                        SDL.SDLK_UP => io.keyinput.up.unset(),
-                        SDL.SDLK_DOWN => io.keyinput.down.unset(),
-                        SDL.SDLK_LEFT => io.keyinput.left.unset(),
-                        SDL.SDLK_RIGHT => io.keyinput.right.unset(),
-                        SDL.SDLK_x => io.keyinput.a.unset(),
-                        SDL.SDLK_z => io.keyinput.b.unset(),
-                        SDL.SDLK_a => io.keyinput.shoulder_l.unset(),
-                        SDL.SDLK_s => io.keyinput.shoulder_r.unset(),
-                        SDL.SDLK_RETURN => io.keyinput.start.unset(),
-                        SDL.SDLK_RSHIFT => io.keyinput.select.unset(),
-                        else => {},
-                    }
-                },
-                SDL.SDL_KEYUP => {
-                    const io = &cpu.bus.io;
-                    const key_code = event.key.keysym.sym;
-
-                    switch (key_code) {
-                        SDL.SDLK_UP => io.keyinput.up.set(),
-                        SDL.SDLK_DOWN => io.keyinput.down.set(),
-                        SDL.SDLK_LEFT => io.keyinput.left.set(),
-                        SDL.SDLK_RIGHT => io.keyinput.right.set(),
-                        SDL.SDLK_x => io.keyinput.a.set(),
-                        SDL.SDLK_z => io.keyinput.b.set(),
-                        SDL.SDLK_a => io.keyinput.shoulder_l.set(),
-                        SDL.SDLK_s => io.keyinput.shoulder_r.set(),
-                        SDL.SDLK_RETURN => io.keyinput.start.set(),
-                        SDL.SDLK_RSHIFT => io.keyinput.select.set(),
-                        SDL.SDLK_i => log.err("Sample Count: {}", .{@intCast(u32, SDL.SDL_AudioStreamAvailable(cpu.bus.apu.stream)) / (2 * @sizeOf(u16))}),
-                        SDL.SDLK_j => log.err("Scheduler Capacity: {} | Scheduler Event Count: {}", .{ scheduler.queue.capacity(), scheduler.queue.count() }),
-                        SDL.SDLK_k => {
-                            // Dump IWRAM to file
-                            log.info("PC: 0x{X:0>8}", .{cpu.r[15]});
-                            log.info("LR: 0x{X:0>8}", .{cpu.r[14]});
-                            // const iwram_file = try std.fs.cwd().createFile("iwram.bin", .{});
-                            // defer iwram_file.close();
-
-                            // try iwram_file.writeAll(cpu.bus.iwram.buf);
-                        },
-                        else => {},
-                    }
-                },
-                else => {},
-            }
+    try gui.run(&arm7tdmi, &scheduler);
 }
 
-        // Emulator has an internal Double Buffer
-        const buf_ptr = cpu.bus.ppu.framebuf.get(.Renderer).ptr;
-        _ = SDL.SDL_UpdateTexture(texture, null, buf_ptr, framebuf_pitch);
-        _ = SDL.SDL_RenderCopy(renderer, texture, null, null);
-        SDL.SDL_RenderPresent(renderer);
-
-        const dyn_title = std.fmt.bufPrint(&dyn_title_buf, "{s} [Emu: {}fps] ", .{ window_title, emu_rate.value() }) catch unreachable;
-        SDL.SDL_SetWindowTitle(window, dyn_title.ptr);
-    }
-
-    quit.store(true, .SeqCst); // Terminate Emulator Thread
-}
-
-const CliError = error{
-    InsufficientOptions,
-    UnneededOptions,
-};
-
-fn sdlPanic() noreturn {
-    const str = @as(?[*:0]const u8, SDL.SDL_GetError()) orelse "unknown error";
-    @panic(std.mem.sliceTo(str, 0));
-}
-
-fn initSdl2() void {
-    const status = SDL.SDL_Init(SDL.SDL_INIT_VIDEO | SDL.SDL_INIT_EVENTS | SDL.SDL_INIT_AUDIO | SDL.SDL_INIT_GAMECONTROLLER);
-    if (status < 0) sdlPanic();
-}
-
-fn createWindow(title: []u8, width: c_int, height: c_int) *SDL.SDL_Window {
-    return SDL.SDL_CreateWindow(
-        title.ptr,
-        SDL.SDL_WINDOWPOS_CENTERED,
-        SDL.SDL_WINDOWPOS_CENTERED,
-        width * window_scale,
-        height * window_scale,
-        SDL.SDL_WINDOW_SHOWN,
-    ) orelse sdlPanic();
-}
-
-fn createRenderer(window: *SDL.SDL_Window) *SDL.SDL_Renderer {
-    return SDL.SDL_CreateRenderer(window, -1, SDL.SDL_RENDERER_ACCELERATED | SDL.SDL_RENDERER_PRESENTVSYNC) orelse sdlPanic();
-}
-
-fn createTexture(renderer: *SDL.SDL_Renderer, width: c_int, height: c_int) *SDL.SDL_Texture {
-    return SDL.SDL_CreateTexture(
-        renderer,
-        SDL.SDL_PIXELFORMAT_RGBA8888,
-        SDL.SDL_TEXTUREACCESS_STREAMING,
-        width,
-        height,
-    ) orelse sdlPanic();
-}
-
-fn initAudio(apu: *Apu) SDL.SDL_AudioDeviceID {
-    var have: SDL.SDL_AudioSpec = undefined;
-    var want: SDL.SDL_AudioSpec = .{
-        .freq = sample_rate,
-        .format = SDL.AUDIO_U16,
-        .channels = 2,
-        .samples = 0x100,
-        .callback = audioCallback,
-        .userdata = apu,
-        .silence = undefined,
-        .size = undefined,
-        .padding = undefined,
-    };
-
-    const dev = SDL.SDL_OpenAudioDevice(null, 0, &want, &have, 0);
-    if (dev == 0) sdlPanic();
-
-    // Start Playback on the Audio device
-    SDL.SDL_PauseAudioDevice(dev, 0);
-    return dev;
-}
-
-export fn audioCallback(userdata: ?*anyopaque, stream: [*c]u8, len: c_int) void {
-    const apu = @ptrCast(*Apu, @alignCast(8, userdata));
-    const written = SDL.SDL_AudioStreamGet(apu.stream, stream, len);
-
-    // If we don't write anything, play silence otherwise garbage will be played
-    // FIXME: I don't think this hack to remove DC Offset is acceptable :thinking:
-    if (written == 0) std.mem.set(u8, stream[0..@intCast(usize, len)], 0x40);
-}
-
-fn getSavePath(alloc: std.mem.Allocator) !?[]const u8 {
+fn getSavePath(allocator: Allocator) !?[]const u8 {
     const save_subpath = "zba" ++ [_]u8{std.fs.path.sep} ++ "save";
 
-    const maybe_data_path = try known_folders.getPath(alloc, .data);
-    defer if (maybe_data_path) |path| alloc.free(path);
+    const maybe_data_path = try known_folders.getPath(allocator, .data);
+    defer if (maybe_data_path) |path| allocator.free(path);
 
-    const save_path = if (maybe_data_path) |base| try std.fs.path.join(alloc, &[_][]const u8{ base, "zba", "save" }) else null;
+    const save_path = if (maybe_data_path) |base| try std.fs.path.join(allocator, &[_][]const u8{ base, "zba", "save" }) else null;
 
     if (save_path) |_| {
         // If we've determined what our save path should be, ensure the prereq directories
         // are present so that we can successfully write to the path when necessary
-        const maybe_data_dir = try known_folders.open(alloc, .data, .{});
+        const maybe_data_dir = try known_folders.open(allocator, .data, .{});
         if (maybe_data_dir) |data_dir| try data_dir.makePath(save_subpath);
     }
 
     return save_path;
 }
 
-fn getRomPath(res: clap.Result(clap.Help, &params, clap.parsers.default), stderr: std.fs.File) ![]const u8 {
-    return switch (res.positionals.len) {
-        1 => res.positionals[0],
-        0 => {
-            try stderr.writeAll("ZBA requires a positional path to a GamePak ROM.\n");
-            return CliError.InsufficientOptions;
-        },
-        else => {
-            try stderr.writeAll("ZBA received too many arguments.\n");
-            return CliError.UnneededOptions;
-        },
+fn getRomPath(result: *const clap.Result(clap.Help, &params, clap.parsers.default)) ![]const u8 {
+    return switch (result.positionals.len) {
+        1 => result.positionals[0],
+        0 => std.debug.panic("ZBA requires a positional path to a GamePak ROM.\n", .{}),
+        else => std.debug.panic("ZBA received too many arguments.\n", .{}),
+    };
+}
+
+pub fn handleArguments(allocator: Allocator, result: *const clap.Result(clap.Help, &params, clap.parsers.default)) !FilePaths {
+    const rom_path = try getRomPath(result);
+    log.info("ROM path: {s}", .{rom_path});
+    const bios_path = result.args.bios;
+    if (bios_path) |path| log.info("BIOS path: {s}", .{path}) else log.info("No BIOS provided", .{});
+    const save_path = try getSavePath(allocator);
+    if (save_path) |path| log.info("Save path: {s}", .{path});
+
+    return FilePaths{
+        .rom = rom_path,
+        .bios = bios_path,
+        .save = save_path,
     };
 }