Initial commit

build.zig

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+const std = @import("std");
+
+// Although this function looks imperative, it does not perform the build
+// directly and instead it mutates the build graph (`b`) that will be then
+// executed by an external runner. The functions in `std.Build` implement a DSL
+// for defining build steps and express dependencies between them, allowing the
+// build runner to parallelize the build automatically (and the cache system to
+// know when a step doesn't need to be re-run).
+pub fn build(b: *std.Build) void {
+    // Standard target options allow the person running `zig build` to choose
+    // what target to build for. Here we do not override the defaults, which
+    // means any target is allowed, and the default is native. Other options
+    // for restricting supported target set are available.
+    const target = b.standardTargetOptions(.{});
+    // Standard optimization options allow the person running `zig build` to select
+    // between Debug, ReleaseSafe, ReleaseFast, and ReleaseSmall. Here we do not
+    // set a preferred release mode, allowing the user to decide how to optimize.
+    const optimize = b.standardOptimizeOption(.{});
+    // It's also possible to define more custom flags to toggle optional features
+    // of this build script using `b.option()`. All defined flags (including
+    // target and optimize options) will be listed when running `zig build --help`
+    // in this directory.
+
+    // Here we define an executable. An executable needs to have a root module
+    // which needs to expose a `main` function. While we could add a main function
+    // to the module defined above, it's sometimes preferable to split business
+    // logic and the CLI into two separate modules.
+    //
+    // If your goal is to create a Zig library for others to use, consider if
+    // it might benefit from also exposing a CLI tool. A parser library for a
+    // data serialization format could also bundle a CLI syntax checker, for example.
+    //
+    // If instead your goal is to create an executable, consider if users might
+    // be interested in also being able to embed the core functionality of your
+    // program in their own executable in order to avoid the overhead involved in
+    // subprocessing your CLI tool.
+    //
+    // If neither case applies to you, feel free to delete the declaration you
+    // don't need and to put everything under a single module.
+    const exe = b.addExecutable(.{
+        .name = "chip8",
+        .root_module = b.createModule(.{
+            // b.createModule defines a new module just like b.addModule but,
+            // unlike b.addModule, it does not expose the module to consumers of
+            // this package, which is why in this case we don't have to give it a name.
+            .root_source_file = b.path("src/main.zig"),
+            // Target and optimization levels must be explicitly wired in when
+            // defining an executable or library (in the root module), and you
+            // can also hardcode a specific target for an executable or library
+            // definition if desireable (e.g. firmware for embedded devices).
+            .target = target,
+            .optimize = optimize,
+            // List of modules available for import in source files part of the
+            // root module.
+            .imports = &.{
+                // Here "chip8" is the name you will use in your source code to
+                // import this module (e.g. `@import("chip8")`). The name is
+                // repeated because you are allowed to rename your imports, which
+                // can be extremely useful in case of collisions (which can happen
+                // importing modules from different packages).
+            },
+        }),
+    });
+
+    const sdl3 = b.dependency("sdl3", .{
+        .target = target,
+        .optimize = optimize,
+    });
+
+    exe.root_module.addImport("sdl3", sdl3.module("sdl3"));
+
+    // This declares intent for the executable to be installed into the
+    // install prefix when running `zig build` (i.e. when executing the default
+    // step). By default the install prefix is `zig-out/` but can be overridden
+    // by passing `--prefix` or `-p`.
+    b.installArtifact(exe);
+
+    // This creates a top level step. Top level steps have a name and can be
+    // invoked by name when running `zig build` (e.g. `zig build run`).
+    // This will evaluate the `run` step rather than the default step.
+    // For a top level step to actually do something, it must depend on other
+    // steps (e.g. a Run step, as we will see in a moment).
+    const run_step = b.step("run", "Run the app");
+
+    // This creates a RunArtifact step in the build graph. A RunArtifact step
+    // invokes an executable compiled by Zig. Steps will only be executed by the
+    // runner if invoked directly by the user (in the case of top level steps)
+    // or if another step depends on it, so it's up to you to define when and
+    // how this Run step will be executed. In our case we want to run it when
+    // the user runs `zig build run`, so we create a dependency link.
+    const run_cmd = b.addRunArtifact(exe);
+    run_step.dependOn(&run_cmd.step);
+
+    // By making the run step depend on the default step, it will be run from the
+    // installation directory rather than directly from within the cache directory.
+    run_cmd.step.dependOn(b.getInstallStep());
+
+    // This allows the user to pass arguments to the application in the build
+    // command itself, like this: `zig build run -- arg1 arg2 etc`
+    if (b.args) |args| {
+        run_cmd.addArgs(args);
+    }
+
+    // Creates an executable that will run `test` blocks from the executable's
+    // root module. Note that test executables only test one module at a time,
+    // hence why we have to create two separate ones.
+    const exe_tests = b.addTest(.{
+        .root_module = exe.root_module,
+    });
+
+    // A run step that will run the second test executable.
+    const run_exe_tests = b.addRunArtifact(exe_tests);
+
+    // A top level step for running all tests. dependOn can be called multiple
+    // times and since the two run steps do not depend on one another, this will
+    // make the two of them run in parallel.
+    const test_step = b.step("test", "Run tests");
+    test_step.dependOn(&run_exe_tests.step);
+
+    // Just like flags, top level steps are also listed in the `--help` menu.
+    //
+    // The Zig build system is entirely implemented in userland, which means
+    // that it cannot hook into private compiler APIs. All compilation work
+    // orchestrated by the build system will result in other Zig compiler
+    // subcommands being invoked with the right flags defined. You can observe
+    // these invocations when one fails (or you pass a flag to increase
+    // verbosity) to validate assumptions and diagnose problems.
+    //
+    // Lastly, the Zig build system is relatively simple and self-contained,
+    // and reading its source code will allow you to master it.
+}

build.zig.zon

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+.{
+    // This is the default name used by packages depending on this one. For
+    // example, when a user runs `zig fetch --save <url>`, this field is used
+    // as the key in the `dependencies` table. Although the user can choose a
+    // different name, most users will stick with this provided value.
+    //
+    // It is redundant to include "zig" in this name because it is already
+    // within the Zig package namespace.
+    .name = .chip8,
+    // This is a [Semantic Version](https://semver.org/).
+    // In a future version of Zig it will be used for package deduplication.
+    .version = "0.0.0",
+    // Together with name, this represents a globally unique package
+    // identifier. This field is generated by the Zig toolchain when the
+    // package is first created, and then *never changes*. This allows
+    // unambiguous detection of one package being an updated version of
+    // another.
+    //
+    // When forking a Zig project, this id should be regenerated (delete the
+    // field and run `zig build`) if the upstream project is still maintained.
+    // Otherwise, the fork is *hostile*, attempting to take control over the
+    // original project's identity. Thus it is recommended to leave the comment
+    // on the following line intact, so that it shows up in code reviews that
+    // modify the field.
+    .fingerprint = 0xa61914ab9792a718, // Changing this has security and trust implications.
+    // Tracks the earliest Zig version that the package considers to be a
+    // supported use case.
+    .minimum_zig_version = "0.15.2",
+    // This field is optional.
+    // Each dependency must either provide a `url` and `hash`, or a `path`.
+    // `zig build --fetch` can be used to fetch all dependencies of a package, recursively.
+    // Once all dependencies are fetched, `zig build` no longer requires
+    // internet connectivity.
+    .dependencies = .{
+        .sdl3 = .{
+            .url = "git+https://github.com/Gota7/zig-sdl3?ref=v0.1.5#014b7bcb2899f3ed9c945c4abfcfe1b25d75bfeb",
+            .hash = "sdl3-0.1.5-NmT1QxARJgAH1Wp0cMBJDAc9vD7weufTkIwVa5rehA2q",
+        },
+    },
+    .paths = .{
+        "build.zig",
+        "build.zig.zon",
+        "src",
+        // For example...
+        //"LICENSE",
+        //"README.md",
+    },
+}

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;