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Martin Vrhovšek
2025-11-18 07:43:19 +01:00
commit e3fee7e082
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131
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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.
}

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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",
},
}

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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));
}
}
}
};

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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 => {},
}
}
}
}

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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
}
};
}

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