Initial commit

src/chip8.zig

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+const std = @import("std");
+const structure = @import("stack.zig");
+const sdl3 = @import("sdl3");
+const str = @import("structs.zig");
+
+pub const Emulator = struct {
+    const Self = @This();
+
+    const w_pixels = 64;
+    const h_pixels = 32;
+    const scale = 25;
+
+    const memory_size = 4096;
+    const StackType = structure.Stack(u16, 32);
+
+    const program_start = 0x200;
+    const font_start = 0x050;
+
+    display: [h_pixels][w_pixels]u1,
+    memory: [memory_size]u8, // programs start at 0x200 address
+    pc: u16,
+    i: u16,
+    // Each call to the stack pushes 2B, and stack should be 64B big
+    // 2B x 32 = 64B
+    stack: StackType,
+    timers: struct {
+        delay: u8,
+        sound: u8,
+    },
+    registers: [16]u8,
+
+    pub fn init(allocator: std.mem.Allocator) !Self {
+        return .{
+            .display = std.mem.zeroes([h_pixels][w_pixels]u1),
+            .memory = try initMemory(allocator),
+            .pc = 0,
+            .i = 0,
+            // stack init
+            .stack = StackType.init(),
+            .timers = .{
+                // u8 max
+                .delay = 0xFF,
+                .sound = 0xFF,
+            },
+            .registers = std.mem.zeroes([16]u8),
+        };
+    }
+
+    pub fn destroy(self: *Self) void {
+        self.stack.destroy();
+    }
+
+    fn initMemory(allocator: std.mem.Allocator) ![memory_size]u8 {
+        var memory = std.mem.zeroes([memory_size]u8);
+
+        const font_data = [_]u8{
+            0xF0, 0x90, 0x90, 0x90, 0xF0, // 0
+            0x20, 0x60, 0x20, 0x20, 0x70, // 1
+            0xF0, 0x10, 0xF0, 0x80, 0xF0, // 2
+            0xF0, 0x10, 0xF0, 0x10, 0xF0, // 3
+            0x90, 0x90, 0xF0, 0x10, 0x10, // 4
+            0xF0, 0x80, 0xF0, 0x10, 0xF0, // 5
+            0xF0, 0x80, 0xF0, 0x90, 0xF0, // 6
+            0xF0, 0x10, 0x20, 0x40, 0x40, // 7
+            0xF0, 0x90, 0xF0, 0x90, 0xF0, // 8
+            0xF0, 0x90, 0xF0, 0x10, 0xF0, // 9
+            0xF0, 0x90, 0xF0, 0x90, 0x90, // A
+            0xE0, 0x90, 0xE0, 0x90, 0xE0, // B
+            0xF0, 0x80, 0x80, 0x80, 0xF0, // C
+            0xE0, 0x90, 0x90, 0x90, 0xE0, // D
+            0xF0, 0x80, 0xF0, 0x80, 0xF0, // E
+            0xF0, 0x80, 0xF0, 0x80, 0x80, // F
+        };
+
+        // loading font data into the memory
+        for (font_data, font_start..) |value, i| {
+            memory[i] = value;
+        }
+
+        // reading game data
+        const filename = getFileName(allocator) catch |err| {
+            std.debug.print("Failed to parse the game filename: {}\n", .{err});
+            return err;
+        };
+
+        const file = readFile(allocator, filename) catch |err| {
+            std.debug.print("Failed to read the file '{s}: {}\n", .{ filename, err });
+            return err;
+        };
+        defer allocator.free(file);
+
+        // loading game data into the memory
+        for (file, program_start..) |value, i| {
+            memory[i] = value;
+        }
+
+        return memory;
+    }
+
+    // despite Linux not needing to use allocators to extract arguments we're using them to ensure
+    // our emulator will work on windows and WASI (Web Assembly System Interface)
+    // which should come in handy should we ever want to port it online (I'm not writing this shit in JavaScript)
+    fn getFileName(allocator: std.mem.Allocator) ![]u8 {
+        const args = try std.process.argsAlloc(allocator);
+
+        return if (args.len <= 1) error.NoArgs else args[1];
+    }
+
+    fn readFile(allocator: std.mem.Allocator, filename: []const u8) ![]u8 {
+        const file = try std.fs.cwd().openFile(filename, .{ .mode = .read_only });
+        defer file.close();
+
+        const len = try file.getEndPos();
+        const buffer = try allocator.alloc(u8, len);
+        // we will free it in the caller function
+
+        _ = try file.read(buffer);
+
+        return buffer;
+    }
+
+    pub fn printMemory(self: *Self) void {
+        var space = false;
+
+        for (self.memory, 1..) |value, i| {
+            const suffix: u8 = if (space) ' ' else 0x0;
+            const newline: u8 = if (i % 16 == 0) '\n' else 0x0;
+
+            std.debug.print("{X:0>2}{c}{c}", .{ value, suffix, newline });
+
+            space = !space;
+        }
+    }
+
+    pub fn returnDisplayData(_: *Self) str.DisplayData {
+        return .{
+            .screen_width = w_pixels,
+            .screen_height = h_pixels,
+            .scale = scale,
+        };
+    }
+
+    // TODO implement some sort of tracking system when display actually changes so we don't call SDL for nothing
+    // one idea is to make a sort of array that tracks modified/changed "pixels"
+    pub fn draw(self: *Self, surface: *sdl3.surface.Surface) !void {
+        for (self.display, 0..) |_, i| {
+            for (self.display[0], 0..) |value, j| {
+                const x = i * w_pixels;
+                const y = j * h_pixels;
+                const width = w_pixels;
+                const height = h_pixels;
+
+                const area: sdl3.rect.IRect = .{
+                    .h = height * scale,
+                    .w = width * scale,
+                    .x = @intCast(x * scale),
+                    .y = @intCast(y * scale),
+                };
+
+                const color: u8 = if (value == 1) str.WHITE else str.BLACK;
+                try surface.fillRect(area, surface.mapRgb(color, color, color));
+            }
+        }
+    }
+};

src/main.zig

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+const std = @import("std");
+const sdl3 = @import("sdl3");
+const chip8 = @import("chip8.zig");
+const str = @import("structs.zig");
+
+pub fn main() !void {
+    const fps = 60;
+
+    var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
+    defer arena.deinit();
+
+    const allocator = arena.allocator();
+
+    // chip8 init
+    var emulator = try chip8.Emulator.init(allocator);
+    defer emulator.destroy();
+
+    emulator.printMemory();
+
+    defer sdl3.shutdown();
+
+    // initialise SDL with subsystems you need here
+    const init_flags = sdl3.InitFlags{ .video = true };
+    try sdl3.init(init_flags);
+    defer sdl3.quit(init_flags);
+
+    // initial window setup
+    const res = emulator.returnDisplayData();
+    const window = try sdl3.video.Window.init("CHIP-8 Emulator", res.screen_width * res.scale, res.screen_height * res.scale, .{});
+    defer window.deinit();
+
+    // useful for limiting the fps and getting the delta time
+    var fps_capper = sdl3.extras.FramerateCapper(f32){ .mode = .{ .limited = fps } };
+
+    var quit = false;
+    while (!quit) {
+        // delay to limit the fps, returned delta time not needed
+        _ = fps_capper.delay();
+
+        // update logic
+        var surface = try window.getSurface();
+        // set background (black)
+        try surface.fillRect(null, surface.mapRgb(str.BLACK, str.BLACK, str.BLACK));
+        try emulator.draw(&surface);
+        try window.updateSurface();
+
+        // event logic
+        while (sdl3.events.poll()) |event| {
+            switch (event) {
+                .quit => quit = true,
+                .terminating => quit = true,
+                else => {},
+            }
+        }
+    }
+}

src/stack.zig

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+const std = @import("std");
+
+pub fn Stack(comptime T: type, comptime size: usize) type {
+    return struct {
+        array: [size]T,
+        i: ?usize,
+
+        const Self = @This();
+
+        pub fn init() Self {
+            return .{
+                .array = std.mem.zeroes([size]T),
+                .i = null,
+            };
+        }
+
+        // this function might as well not exist but might as well set it
+        // nothing else is necessary, because stack will only read what is set at i
+        // and if i gets increased it will only get so when we insert new number
+        pub fn destroy(self: *Self) void {
+            self.i = null;
+        }
+
+        pub fn push(self: *Self, value: T) !void {
+            if (self.i) |index| {
+                if (index >= self.array.len - 1) return error.StackFull;
+                // index points at the last currently stored element
+                self.i = index + 1;
+            } else {
+                // if stack is empty set it to point at first element
+                self.i = 0;
+            }
+
+            self.array[self.i.?] = value;
+        }
+
+        pub fn pop(self: *Self) ?T {
+            if (self.i) |index| {
+                // set the i pointer to the previous element (null if we're popping the only element so far)
+                self.i = if (self.i == 0) null else self.i - 1;
+                return self.array[index];
+            }
+
+            return null; // stack is empty we have nothing to return
+        }
+    };
+}

src/structs.zig

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+pub const DisplayData = struct {
+    screen_width: usize,
+    screen_height: usize,
+    scale: usize,
+};
+
+pub const BLACK = 0x0;
+pub const WHITE = 0xFF;