Complete grayscale filter project

grayscale_filter/build.zig

@@ -0,0 +1,66 @@
+const std = @import("std");
+
+// Although this function looks imperative, note that its job is to
+// declaratively construct a build graph that will be executed by an external
+// runner.
+pub fn build(b: *std.Build) void {
+    // Standard target options allows 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(.{});
+
+    // We will also create a module for our other entry point, 'main.zig'.
+    const exe_mod = b.createModule(.{
+        // `root_source_file` is the Zig "entry point" of the module. If a module
+        // only contains e.g. external object files, you can make this `null`.
+        // In this case the main source file is merely a path, however, in more
+        // complicated build scripts, this could be a generated file.
+        .root_source_file = b.path("src/main.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
+
+    // This creates another `std.Build.Step.Compile`, but this one builds an executable
+    // rather than a static library.
+    const exe = b.addExecutable(.{
+        .name = "grayscale_filter",
+        .root_module = exe_mod,
+    });
+
+    exe.linkLibC();
+    exe.linkSystemLibrary("spng");
+
+    // This declares intent for the executable to be installed into the
+    // standard location when the user invokes the "install" step (the default
+    // step when running `zig build`).
+    b.installArtifact(exe);
+
+    // This *creates* a Run step in the build graph, to be executed when another
+    // step is evaluated that depends on it. The next line below will establish
+    // such a dependency.
+    const run_cmd = b.addRunArtifact(exe);
+
+    // By making the run step depend on the install step, it will be run from the
+    // installation directory rather than directly from within the cache directory.
+    // This is not necessary, however, if the application depends on other installed
+    // files, this ensures they will be present and in the expected location.
+    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);
+    }
+
+    // This creates a build step. It will be visible in the `zig build --help` menu,
+    // and can be selected like this: `zig build run`
+    // This will evaluate the `run` step rather than the default, which is "install".
+    const run_step = b.step("run", "Run the app");
+    run_step.dependOn(&run_cmd.step);
+}

grayscale_filter/build.zig.zon

@@ -0,0 +1,86 @@
+.{
+    // 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 = .grayscale_filter,
+
+    // 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 = 0x376a3a558a44c1a7, // 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 = "0.14.1",
+
+    // 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 = .{
+        // See `zig fetch --save <url>` for a command-line interface for adding dependencies.
+        //.example = .{
+        //    // When updating this field to a new URL, be sure to delete the corresponding
+        //    // `hash`, otherwise you are communicating that you expect to find the old hash at
+        //    // the new URL. If the contents of a URL change this will result in a hash mismatch
+        //    // which will prevent zig from using it.
+        //    .url = "https://example.com/foo.tar.gz",
+        //
+        //    // This is computed from the file contents of the directory of files that is
+        //    // obtained after fetching `url` and applying the inclusion rules given by
+        //    // `paths`.
+        //    //
+        //    // This field is the source of truth; packages do not come from a `url`; they
+        //    // come from a `hash`. `url` is just one of many possible mirrors for how to
+        //    // obtain a package matching this `hash`.
+        //    //
+        //    // Uses the [multihash](https://multiformats.io/multihash/) format.
+        //    .hash = "...",
+        //
+        //    // When this is provided, the package is found in a directory relative to the
+        //    // build root. In this case the package's hash is irrelevant and therefore not
+        //    // computed. This field and `url` are mutually exclusive.
+        //    .path = "foo",
+        //
+        //    // When this is set to `true`, a package is declared to be lazily
+        //    // fetched. This makes the dependency only get fetched if it is
+        //    // actually used.
+        //    .lazy = false,
+        //},
+    },
+
+    // Specifies the set of files and directories that are included in this package.
+    // Only files and directories listed here are included in the `hash` that
+    // is computed for this package. Only files listed here will remain on disk
+    // when using the zig package manager. As a rule of thumb, one should list
+    // files required for compilation plus any license(s).
+    // Paths are relative to the build root. Use the empty string (`""`) to refer to
+    // the build root itself.
+    // A directory listed here means that all files within, recursively, are included.
+    .paths = .{
+        "build.zig",
+        "build.zig.zon",
+        "src",
+        // For example...
+        //"LICENSE",
+        //"README.md",
+    },
+}

grayscale_filter/src/main.zig

@@ -0,0 +1,112 @@
+const std = @import("std");
+const c = @cImport({
+    @cDefine("_NO_CRT_STDIO_INLINE", "1");
+    @cInclude("stdio.h");
+    @cInclude("spng.h");
+});
+
+const PngError = error {
+    CouldNotOpenImage,
+    CouldNotCloseImage,
+    CouldNotGetImageHeader,
+    CouldNotCalcOutputSize,
+    CouldNotDecodeImage,
+    CouldNotEncodeImage,
+};
+
+pub fn main() !void {
+    var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
+    const allocator = arena.allocator();
+    defer arena.deinit();
+
+    const path = "pedro_pascal.png";
+    const fd = try open_image(path, "rb");
+    defer close_image(fd) catch @panic("Failed to close file");
+
+    const ctx = c.spng_ctx_new(0) orelse unreachable;
+    defer c.spng_ctx_free(ctx);
+
+    _ = c.spng_set_png_file(ctx, fd);
+    var header = try get_png_header(ctx);
+    const size = try calc_output_size(ctx);
+    var buffer = try allocator.alloc(u8, size);
+    @memset(buffer[0..], 0);
+
+    try read_data_to_buffer(ctx, buffer[0..]);
+    try apply_grayscale_filter(buffer[0..]);
+    try save_image(&header, buffer[0..]);
+}
+
+fn open_image(path: [*c]const u8, mode: [*c]const u8) !?*c.FILE {
+    const fd = c.fopen(path, mode);
+    if (fd == null) {
+        return error.CouldNotOpenImage;
+    }
+
+    return fd;
+}
+
+fn close_image(fd: ?*c.FILE) !void {
+    if (c.fclose(fd) != 0) {
+        return error.CouldNotCloseImage;
+    }
+}
+
+fn get_png_header(ctx: *c.spng_ctx) !c.spng_ihdr {
+    var header: c.spng_ihdr = undefined;
+    if (c.spng_get_ihdr(ctx, &header) != 0) {
+        return error.CouldNotGetImageHeader;
+    }
+
+    return header;
+}
+
+fn calc_output_size(ctx: *c.spng_ctx) !u64 {
+    var output_size: u64 = 0;
+    if (c.spng_decoded_image_size(ctx, c.SPNG_FMT_RGBA8, &output_size) != 0) {
+        return error.CouldNotCalcOutputSize;
+    }
+
+    return output_size;
+}
+
+fn read_data_to_buffer(ctx: *c.spng_ctx, buffer: []u8) !void {
+    if (c.spng_decode_image(ctx, buffer.ptr, buffer.len, c.SPNG_FMT_RGBA8, 0) != 0) {
+        return error.CouldNotDecodeImage;
+    }
+}
+
+fn apply_grayscale_filter(buffer: []u8) !void {
+    const rfactor: f16 = 0.2126;
+    const gfactor: f16 = 0.7152;
+    const bfactor: f16 = 0.0722;
+    var index: u64 = 0;
+
+    while (index < buffer.len) : (index += 4) {
+        const r: f16 = @floatFromInt(buffer[index]);
+        const g: f16 = @floatFromInt(buffer[index + 1]);
+        const b: f16 = @floatFromInt(buffer[index + 2]);
+
+        const y: f16 = r * rfactor + g * gfactor + b * bfactor;
+
+        buffer[index] = @intFromFloat(y);
+        buffer[index + 1] = @intFromFloat(y);
+        buffer[index + 2] = @intFromFloat(y);
+    }
+}
+
+fn save_image(header: *c.spng_ihdr, buffer: []u8) !void {
+    const path = "pedro_pascal_grayscale.png";
+    const fd = try open_image(path, "wb");
+    defer close_image(fd) catch @panic("Failed to close file");
+
+    const ctx = c.spng_ctx_new(c.SPNG_CTX_ENCODER) orelse unreachable;
+    defer c.spng_ctx_free(ctx);
+
+    _ = c.spng_set_png_file(ctx, fd);
+    _ = c.spng_set_ihdr(ctx, header);
+
+    if (c.spng_encode_image(ctx, buffer.ptr, buffer.len, c.SPNG_FMT_PNG, c.SPNG_ENCODE_FINALIZE) != 0) {
+        return error.CouldNotEncodeImage;
+    }
+}

http_server/build.zig

@@ -0,0 +1,75 @@
+const std = @import("std");
+
+// Although this function looks imperative, note that its job is to
+// declaratively construct a build graph that will be executed by an external
+// runner.
+pub fn build(b: *std.Build) void {
+    // Standard target options allows 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(.{});
+
+    // We will also create a module for our other entry point, 'main.zig'.
+    const exe_mod = b.createModule(.{
+        // `root_source_file` is the Zig "entry point" of the module. If a module
+        // only contains e.g. external object files, you can make this `null`.
+        // In this case the main source file is merely a path, however, in more
+        // complicated build scripts, this could be a generated file.
+        .root_source_file = b.path("src/main.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
+
+    // This creates another `std.Build.Step.Compile`, but this one builds an executable
+    // rather than a static library.
+    const exe = b.addExecutable(.{
+        .name = "http_server",
+        .root_module = exe_mod,
+    });
+
+    // This declares intent for the executable to be installed into the
+    // standard location when the user invokes the "install" step (the default
+    // step when running `zig build`).
+    b.installArtifact(exe);
+
+    // This *creates* a Run step in the build graph, to be executed when another
+    // step is evaluated that depends on it. The next line below will establish
+    // such a dependency.
+    const run_cmd = b.addRunArtifact(exe);
+
+    // By making the run step depend on the install step, it will be run from the
+    // installation directory rather than directly from within the cache directory.
+    // This is not necessary, however, if the application depends on other installed
+    // files, this ensures they will be present and in the expected location.
+    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);
+    }
+
+    // This creates a build step. It will be visible in the `zig build --help` menu,
+    // and can be selected like this: `zig build run`
+    // This will evaluate the `run` step rather than the default, which is "install".
+    const run_step = b.step("run", "Run the app");
+    run_step.dependOn(&run_cmd.step);
+
+    const exe_unit_tests = b.addTest(.{
+        .root_module = exe_mod,
+    });
+
+    const run_exe_unit_tests = b.addRunArtifact(exe_unit_tests);
+
+    // Similar to creating the run step earlier, this exposes a `test` step to
+    // the `zig build --help` menu, providing a way for the user to request
+    // running the unit tests.
+    const test_step = b.step("test", "Run unit tests");
+    test_step.dependOn(&run_exe_unit_tests.step);
+}

http_server/build.zig.zon

@@ -0,0 +1,86 @@
+.{
+    // 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 = .http_server,
+
+    // 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 = 0x411f0d318fc38a3a, // 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 = "0.14.1",
+
+    // 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 = .{
+        // See `zig fetch --save <url>` for a command-line interface for adding dependencies.
+        //.example = .{
+        //    // When updating this field to a new URL, be sure to delete the corresponding
+        //    // `hash`, otherwise you are communicating that you expect to find the old hash at
+        //    // the new URL. If the contents of a URL change this will result in a hash mismatch
+        //    // which will prevent zig from using it.
+        //    .url = "https://example.com/foo.tar.gz",
+        //
+        //    // This is computed from the file contents of the directory of files that is
+        //    // obtained after fetching `url` and applying the inclusion rules given by
+        //    // `paths`.
+        //    //
+        //    // This field is the source of truth; packages do not come from a `url`; they
+        //    // come from a `hash`. `url` is just one of many possible mirrors for how to
+        //    // obtain a package matching this `hash`.
+        //    //
+        //    // Uses the [multihash](https://multiformats.io/multihash/) format.
+        //    .hash = "...",
+        //
+        //    // When this is provided, the package is found in a directory relative to the
+        //    // build root. In this case the package's hash is irrelevant and therefore not
+        //    // computed. This field and `url` are mutually exclusive.
+        //    .path = "foo",
+        //
+        //    // When this is set to `true`, a package is declared to be lazily
+        //    // fetched. This makes the dependency only get fetched if it is
+        //    // actually used.
+        //    .lazy = false,
+        //},
+    },
+
+    // Specifies the set of files and directories that are included in this package.
+    // Only files and directories listed here are included in the `hash` that
+    // is computed for this package. Only files listed here will remain on disk
+    // when using the zig package manager. As a rule of thumb, one should list
+    // files required for compilation plus any license(s).
+    // Paths are relative to the build root. Use the empty string (`""`) to refer to
+    // the build root itself.
+    // A directory listed here means that all files within, recursively, are included.
+    .paths = .{
+        "build.zig",
+        "build.zig.zon",
+        "src",
+        // For example...
+        //"LICENSE",
+        //"README.md",
+    },
+}

http_server/src/config.zig

@@ -0,0 +1,19 @@
+const std = @import("std");
+
+pub const Socket = struct {
+    _address: std.net.Address,
+    _stream: std.net.Stream,
+
+    pub fn init() !Socket {
+        const host = [4]u8{127, 0, 0, 1};
+        const port = 1987;
+        const addr = std.net.Address.initIp4(host, port);
+        const socket = try std.posix.socket(
+            addr.any.family,
+            std.posix.SOCK.STREAM,
+            std.posix.IPPROTO.TCP,
+        );
+        const stream = std.net.Stream{ .handle = socket };
+        return Socket{ ._address = addr, ._stream = stream };
+    }
+};

http_server/src/main.zig

@@ -0,0 +1,26 @@
+const std = @import("std");
+const SocketConf = @import("config.zig");
+const Request = @import("request.zig");
+const Method = Request.Method;
+const Response = @import("response.zig");
+
+pub fn main() !void {
+    const stdout = std.io.getStdOut().writer();
+    const socket = try SocketConf.Socket.init();
+    try stdout.print("Server address: {any}\n", .{socket._address});
+    var server = try socket._address.listen(.{});
+    const connection = try server.accept();
+    var buffer: [1000]u8 = undefined;
+    for (0..buffer.len) |i| {
+        buffer[i] = 0;
+    }
+    _ = try Request.read_request(connection, buffer[0..buffer.len]);
+    const request = Request.parse_request(&buffer);
+    if (request.method == Method.GET) {
+        if (std.mem.eql(u8, request.uri, "/")) {
+            try Response.send_200(connection);
+        } else {
+            try Response.send_404(connection);
+        }
+    }
+}

http_server/src/request.zig

@@ -0,0 +1,51 @@
+const std = @import("std");
+const Connection = std.net.Server.Connection;
+const Map = std.static_string_map.StaticStringMap;
+
+pub const Method = enum {
+    GET,
+
+    pub fn init(method: [] const u8) !Method {
+        return MethodMap.get(method).?;
+    }
+
+    pub fn is_supported(method: [] const u8) bool {
+        const m = MethodMap.get(method);
+
+        if (m) |_| {
+            return true;
+        }
+
+        return false;
+    }
+};
+
+const MethodMap = Map(Method).initComptime(.{
+    .{"GET", Method.GET},
+});
+
+pub const Request = struct {
+    method: Method,
+    version: [] const u8,
+    uri: [] const u8,
+
+    pub fn init(method: Method, version: [] const u8, uri: [] const u8) Request {
+        return Request{.method = method, .version = version, .uri = uri};
+    }
+};
+
+pub fn read_request(connection: Connection, buffer: []u8) !void {
+    const reader = connection.stream.reader();
+    _ = try reader.read(buffer);
+}
+
+pub fn parse_request(text: [] u8) Request {
+    const line_index = std.mem.indexOfScalar(u8, text, '\n') orelse text.len;
+    var iterator     = std.mem.splitScalar(u8, text[0..line_index], ' ');
+    const method     = try Method.init(iterator.next().?);
+    const uri        = iterator.next().?;
+    const version    = iterator.next().?;
+    const request    = Request.init(method, version, uri);
+
+    return request;
+}

http_server/src/response.zig

@@ -0,0 +1,24 @@
+const std = @import("std");
+const Connection = std.net.Server.Connection;
+
+pub fn send_200(connection: Connection) !void {
+    const message = (
+        "HTTP/1.1 200 OK\nContent-Length: 48"
+        ++ "\nContent-Type: text/html\n"
+        ++ "Connection: Closed\n\n<html><body>"
+        ++ "<h1>Hello, World!</h1></body></html>"
+    );
+
+    _ = try connection.stream.write(message);
+}
+
+pub fn send_404(connection: Connection) !void {
+    const message = (
+        "HTTP/1.1 404 Not Found\nContent-Length: 50"
+        ++ "\nContent-Type: text/html\n"
+        ++ "Connection: Closed\n\n<html><body>"
+        ++ "<h1>File not found!</h1></body></html>"
+    );
+
+    _ = try connection.stream.write(message);
+}

stack_ds/build.zig

@@ -0,0 +1,75 @@
+const std = @import("std");
+
+// Although this function looks imperative, note that its job is to
+// declaratively construct a build graph that will be executed by an external
+// runner.
+pub fn build(b: *std.Build) void {
+    // Standard target options allows 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(.{});
+
+    // We will also create a module for our other entry point, 'main.zig'.
+    const exe_mod = b.createModule(.{
+        // `root_source_file` is the Zig "entry point" of the module. If a module
+        // only contains e.g. external object files, you can make this `null`.
+        // In this case the main source file is merely a path, however, in more
+        // complicated build scripts, this could be a generated file.
+        .root_source_file = b.path("src/main.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
+
+    // This creates another `std.Build.Step.Compile`, but this one builds an executable
+    // rather than a static library.
+    const exe = b.addExecutable(.{
+        .name = "stack_ds",
+        .root_module = exe_mod,
+    });
+
+    // This declares intent for the executable to be installed into the
+    // standard location when the user invokes the "install" step (the default
+    // step when running `zig build`).
+    b.installArtifact(exe);
+
+    // This *creates* a Run step in the build graph, to be executed when another
+    // step is evaluated that depends on it. The next line below will establish
+    // such a dependency.
+    const run_cmd = b.addRunArtifact(exe);
+
+    // By making the run step depend on the install step, it will be run from the
+    // installation directory rather than directly from within the cache directory.
+    // This is not necessary, however, if the application depends on other installed
+    // files, this ensures they will be present and in the expected location.
+    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);
+    }
+
+    // This creates a build step. It will be visible in the `zig build --help` menu,
+    // and can be selected like this: `zig build run`
+    // This will evaluate the `run` step rather than the default, which is "install".
+    const run_step = b.step("run", "Run the app");
+    run_step.dependOn(&run_cmd.step);
+
+    const exe_unit_tests = b.addTest(.{
+        .root_module = exe_mod,
+    });
+
+    const run_exe_unit_tests = b.addRunArtifact(exe_unit_tests);
+
+    // Similar to creating the run step earlier, this exposes a `test` step to
+    // the `zig build --help` menu, providing a way for the user to request
+    // running the unit tests.
+    const test_step = b.step("test", "Run unit tests");
+    test_step.dependOn(&run_exe_unit_tests.step);
+}

stack_ds/build.zig.zon

@@ -0,0 +1,86 @@
+.{
+    // 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 = .stack_ds,
+
+    // 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 = 0x1bafbea10418f5f, // 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 = "0.14.1",
+
+    // 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 = .{
+        // See `zig fetch --save <url>` for a command-line interface for adding dependencies.
+        //.example = .{
+        //    // When updating this field to a new URL, be sure to delete the corresponding
+        //    // `hash`, otherwise you are communicating that you expect to find the old hash at
+        //    // the new URL. If the contents of a URL change this will result in a hash mismatch
+        //    // which will prevent zig from using it.
+        //    .url = "https://example.com/foo.tar.gz",
+        //
+        //    // This is computed from the file contents of the directory of files that is
+        //    // obtained after fetching `url` and applying the inclusion rules given by
+        //    // `paths`.
+        //    //
+        //    // This field is the source of truth; packages do not come from a `url`; they
+        //    // come from a `hash`. `url` is just one of many possible mirrors for how to
+        //    // obtain a package matching this `hash`.
+        //    //
+        //    // Uses the [multihash](https://multiformats.io/multihash/) format.
+        //    .hash = "...",
+        //
+        //    // When this is provided, the package is found in a directory relative to the
+        //    // build root. In this case the package's hash is irrelevant and therefore not
+        //    // computed. This field and `url` are mutually exclusive.
+        //    .path = "foo",
+        //
+        //    // When this is set to `true`, a package is declared to be lazily
+        //    // fetched. This makes the dependency only get fetched if it is
+        //    // actually used.
+        //    .lazy = false,
+        //},
+    },
+
+    // Specifies the set of files and directories that are included in this package.
+    // Only files and directories listed here are included in the `hash` that
+    // is computed for this package. Only files listed here will remain on disk
+    // when using the zig package manager. As a rule of thumb, one should list
+    // files required for compilation plus any license(s).
+    // Paths are relative to the build root. Use the empty string (`""`) to refer to
+    // the build root itself.
+    // A directory listed here means that all files within, recursively, are included.
+    .paths = .{
+        "build.zig",
+        "build.zig.zon",
+        "src",
+        // For example...
+        //"LICENSE",
+        //"README.md",
+    },
+}

stack_ds/src/main.zig

@@ -0,0 +1,27 @@
+const std = @import("std");
+const Stack = @import("stack.zig").Stack;
+
+pub fn main() !void {
+    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
+    const allocator = gpa.allocator();
+    const Stacku8 = Stack(u8);
+
+    var stack: Stacku8 = try Stacku8.init(allocator, 100);
+    defer stack.deinit();
+
+    try stack.push(10);
+    try stack.push(20);
+    try stack.push(30);
+    try stack.push(40);
+    try stack.push(50);
+    try stack.push(60);
+
+    std.debug.print("Stack length: {d}\n", .{stack.length});
+    std.debug.print("Stack capacity: {d}\n", .{stack.capacity});
+
+    var popped = stack.pop();
+    std.debug.print("Stack len: {d}. Popped value: {d}\n", .{stack.length, popped.?});
+    popped = stack.pop();
+    std.debug.print("Stack len: {d}. Popped value: {d}\n", .{stack.length, popped.?});
+    std.debug.print("Stack state: {any}\n", .{stack.items[0..stack.length]});
+}

stack_ds/src/stack.zig

@@ -0,0 +1,56 @@
+const std = @import("std");
+const Allocator = std.mem.Allocator;
+
+pub fn Stack(comptime T: type) type {
+    return struct {
+        items: []T,
+        capacity: usize,
+        length: usize,
+        allocator: Allocator,
+        const Self = @This();
+
+        pub fn init(allocator: Allocator, capacity: usize) !Stack(T) {
+            var buf = try allocator.alloc(T, capacity);
+
+            return .{
+                .items = buf[0..],
+                .capacity = capacity,
+                .length = 0,
+                .allocator = allocator,
+            };
+        }
+
+        pub fn push(self: *Self, item: T) !void {
+            if (self.length == self.capacity) {
+                const new_capacity: usize = self.capacity * 2;
+                var new_buf = try self.allocator.alloc(T, new_capacity);
+                @memcpy(new_buf[0..self.capacity], self.items);
+                self.allocator.free(self.items);
+                self.items = new_buf;
+                self.capacity = new_capacity;
+            }
+
+            self.items[self.length] = item;
+            self.length += 1;
+        }
+
+        pub fn pop(self: *Self) ?T {
+            if (self.length == 0) {
+                return null;
+            }
+
+            const index: usize = self.length - 1;
+            const out = self.items[index];
+            self.items[index] = undefined;
+            self.length -= 1;
+
+            return out;
+        }
+
+        pub fn deinit(self: *Self) void {
+            self.allocator.free(self.items);
+            self.capacity = 0;
+            self.length = 0;
+        }
+    };
+}