Use writer instead of RawSocket in Client

Use this from the relay message

build.zig

@@ -1,72 +1,121 @@
 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.
+// 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 allows the person running `zig build` to choose
+    // 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.
 
-    const lib_mod = b.createModule(.{
+    // This creates a module, which represents a collection of source files alongside
+    // some compilation options, such as optimization mode and linked system libraries.
+    // Zig modules are the preferred way of making Zig code available to consumers.
+    // addModule defines a module that we intend to make available for importing
+    // to our consumers. We must give it a name because a Zig package can expose
+    // multiple modules and consumers will need to be able to specify which
+    // module they want to access.
+    const mod = b.addModule("zaprus", .{
+        // The root source file is the "entry point" of this module. Users of
+        // this module will only be able to access public declarations contained
+        // in this file, which means that if you have declarations that you
+        // intend to expose to consumers that were defined in other files part
+        // of this module, you will have to make sure to re-export them from
+        // the root file.
         .root_source_file = b.path("src/root.zig"),
+        // Later on we'll use this module as the root module of a test executable
+        // which requires us to specify a target.
         .target = target,
-        .optimize = optimize,
     });
 
-    // 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,
-    });
+    mod.addImport("network", b.dependency("network", .{}).module("network"));
+    mod.addImport("gatorcat", b.dependency("gatorcat", .{}).module("gatorcat"));
 
-    lib_mod.addImport("network", b.dependency("network", .{}).module("network"));
-    lib_mod.addImport("gatorcat", b.dependency("gatorcat", .{}).module("gatorcat"));
-
-    exe_mod.addImport("zaprus", lib_mod);
-    exe_mod.addImport("clap", b.dependency("clap", .{}).module("clap"));
-
-    const lib = b.addLibrary(.{
-        .linkage = .static,
-        .name = "zaprus",
-        .root_module = lib_mod,
-    });
-
-    b.installArtifact(lib);
-
-    // This creates another `std.Build.Step.Compile`, but this one builds an executable
-    // rather than a static library.
+    // 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
+    // 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 = "zaprus",
-        .root_module = exe_mod,
+        .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 "zaprus" is the name you will use in your source code to
+                // import this module (e.g. `@import("zaprus")`). 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).
+                .{ .name = "zaprus", .module = mod },
+                .{ .name = "clap", .module = b.dependency("clap", .{}).module("clap") },
+            },
+        }),
     });
 
     // 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`).
+    // 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);
+    b.installArtifact(b.addLibrary(.{
+        .linkage = .static,
+        .name = "zaprus",
+        .root_module = mod,
+    }));
 
-    // 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.
+    // 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 install step, it will be run from the
+    // 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.
-    // 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
@@ -75,21 +124,42 @@ pub fn build(b: *std.Build) void {
         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,
+    // Creates an executable that will run `test` blocks from the provided module.
+    // Here `mod` needs to define a target, which is why earlier we made sure to
+    // set the releative field.
+    const mod_tests = b.addTest(.{
+        .root_module = mod,
     });
 
-    const run_exe_unit_tests = b.addRunArtifact(exe_unit_tests);
+    // A run step that will run the test executable.
+    const run_mod_tests = b.addRunArtifact(mod_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);
+    // 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_mod_tests.step);
+    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

@@ -37,16 +37,16 @@
     // internet connectivity.
     .dependencies = .{
         .network = .{
-            .url = "https://github.com/ikskuh/zig-network/archive/c76240d2240711a3dcbf1c0fb461d5d1f18be79a.zip",
-            .hash = "network-0.1.0-AAAAAOwlAQAQ6zKPUrsibdpGisxld9ftUKGdMvcCSpaj",
+            .url = "git+https://github.com/ikskuh/zig-network#7947237eec317d9458897f82089f343a05450c2b",
+            .hash = "network-0.1.0-Pm-Agl8xAQBmkwohveGOfTk4zQnuqDs0Ptfbms4KP5Ce",
         },
         .clap = .{
-            .url = "git+https://github.com/Hejsil/zig-clap?ref=0.10.0#e47028deaefc2fb396d3d9e9f7bd776ae0b2a43a",
-            .hash = "clap-0.10.0-oBajB434AQBDh-Ei3YtoKIRxZacVPF1iSwp3IX_ZB8f0",
+            .url = "git+https://github.com/Hejsil/zig-clap#9cfa61596cd44ef7be35f8d2e108d2025e09868e",
+            .hash = "clap-0.10.0-oBajB_TnAQB0l5UdW9WYhhJDEswbedvwFOzzZwGknYeR",
         },
         .gatorcat = .{
-            .url = "git+https://github.com/kj4tmp/gatorcat#bb1847f6c95852e7a0ec8c07870a948c171d5f98",
-            .hash = "gatorcat-0.3.2-WcrpTf1mBwDrmPaIhKCfLJO064v8Sjjn7DBq4CKZSgHH",
+            .url = "git+https://github.com/jeffective/gatorcat#db73d0f7780331d82e785e85773d1afaf154c2e6",
+            .hash = "gatorcat-0.3.11-WcrpTQn0BwArrCFVHy9FPBIPDJQqPrFdJlhiyH7Ng5x4",
         },
     },
     .paths = .{

src/Client.zig

@@ -1,28 +1,82 @@
 const base64Enc = std.base64.Base64Encoder.init(std.base64.standard_alphabet_chars, '=');
 const base64Dec = std.base64.Base64Decoder.init(std.base64.standard_alphabet_chars, '=');
 
-var rand: ?Random = null;
+rand: Random,
+writer: *std.Io.Writer,
 
-pub fn init() !void {
+const Self = @This();
+
+const max_message_size = 2048;
+
+pub fn init(writer: *std.Io.Writer) !Self {
     var prng = Random.DefaultPrng.init(blk: {
         var seed: u64 = undefined;
         try posix.getrandom(mem.asBytes(&seed));
         break :blk seed;
     });
-    rand = prng.random();
-    try network.init();
+    const rand = prng.random();
+
+    return .{
+        .rand = rand,
+        .writer = writer,
+    };
 }
 
-pub fn deinit() void {
-    network.deinit();
+pub fn deinit(self: *Self) void {
+    self.writer.flush() catch {};
 }
 
-fn broadcastSaprusMessage(msg: *SaprusMessage, udp_port: u16) !void {
-    if (false) {
-        var foo: gcat.nic.RawSocket = try .init("enp7s0"); // /proc/net/dev
-        defer foo.deinit();
+/// Used for relay messages and connection handshake.
+/// Assumes Client .init has been called.
+fn broadcastInitialInterestMessage(self: *Self, msg_bytes: []align(@alignOf(SaprusMessage)) u8) !void {
+    var packet_bytes: [max_message_size]u8 = comptime blk: {
+        var b: [max_message_size]u8 = @splat(0);
+
+        // Destination MAC addr to FF:FF:FF:FF:FF:FF
+        for (0..6) |i| {
+            b[i] = 0xff;
         }
-    const msg_bytes = msg.asBytes();
+
+        // Set Ethernet type to IPv4
+        b[0x0c] = 0x08;
+        b[0x0d] = 0x00;
+
+        // Set IPv4 version to 4
+        b[0x0e] = 0x45;
+
+        // Destination broadcast
+        for (0x1e..0x22) |i| {
+            b[i] = 0xff;
+        }
+
+        // Set TTL
+        b[0x16] = 0x40;
+
+        // Set IPv4 protocol to UDP
+        b[0x17] = 0x11;
+
+        // Set interest filter value to 8888.
+        b[0x24] = 0x22;
+        b[0x25] = 0xb8;
+        break :blk b;
+    };
+    var msg: *SaprusMessage = try .bytesAsValue(msg_bytes);
+    try msg.networkFromNativeEndian();
+    defer msg.nativeFromNetworkEndian() catch unreachable;
+
+    // The byte position within the packet that the saprus message starts at.
+    const saprus_start_byte = 42;
+    @memcpy(packet_bytes[saprus_start_byte .. saprus_start_byte + msg_bytes.len], msg_bytes);
+
+    const writer = self.writer;
+    _ = try writer.write(packet_bytes[0 .. saprus_start_byte + msg_bytes.len]);
+    try writer.flush();
+}
+
+// fn broadcastSaprusMessage(msg_bytes: []align(@alignOf(SaprusMessage)) u8) !void {}
+
+fn broadcastSaprusMessage(msg_bytes: []align(@alignOf(SaprusMessage)) u8, udp_port: u16) !void {
+    const msg: *SaprusMessage = try .bytesAsValue(msg_bytes);
     try msg.networkFromNativeEndian();
     defer msg.nativeFromNetworkEndian() catch unreachable;
 
@@ -44,52 +98,57 @@ fn broadcastSaprusMessage(msg: *SaprusMessage, udp_port: u16) !void {
 
     try sock.bind(bind_addr);
 
+    std.debug.print("{x}\n", .{msg_bytes});
+
     _ = try sock.sendTo(dest_addr, msg_bytes);
 }
 
-pub fn sendRelay(payload: []const u8, dest: [4]u8, allocator: Allocator) !void {
-    const msg: *SaprusMessageNew(.relay) = try .init(
-        allocator,
-        @intCast(base64Enc.calcSize(payload.len)),
-    );
-    defer msg.deinit(allocator);
-    msg.dest = dest;
-    _ = base64Enc.encode(msg.getPayload(), payload);
+pub fn sendRelay(self: *Self, payload: []const u8, dest: [4]u8) !void {
+    var buf: [max_message_size]u8 align(@alignOf(SaprusMessage)) = undefined;
+    const msg_bytes = buf[0..try SaprusMessage.calcSize(
+        .relay,
+        base64Enc.calcSize(payload.len),
+    )];
+    const msg: *SaprusMessage = .init(.relay, msg_bytes);
 
-    try broadcastSaprusMessage(try SaprusMessage.bytesAsValue(msg.asBytes()), 8888);
+    const relay = (try msg.getSaprusTypePayload()).relay;
+    relay.dest = dest;
+    _ = base64Enc.encode(relay.getPayload(), payload);
+
+    try self.broadcastInitialInterestMessage(msg_bytes);
 }
 
-fn randomPort() u16 {
-    var p: u16 = 0;
-    if (rand) |r| {
-        p = r.intRangeAtMost(u16, 1024, 65000);
-    } else unreachable;
-
-    return p;
+fn randomPort(self: Self) u16 {
+    return self.rand.intRangeAtMost(u16, 1024, 65000);
 }
 
-pub fn sendInitialConnection(payload: []const u8, initial_port: u16, allocator: Allocator) !*SaprusMessage {
-    const dest_port = randomPort();
-    const msg: *SaprusMessage = try .init(allocator, .connection, @intCast(payload.len));
-    defer msg.deinit(allocator);
+pub fn sendInitialConnection(
+    self: Self,
+    payload: []const u8,
+    output_bytes: []align(@alignOf(SaprusMessage)) u8,
+    initial_port: u16,
+) !*SaprusMessage {
+    const dest_port = self.randomPort();
+    const msg_bytes = output_bytes[0..try SaprusMessage.calcSize(
+        .connection,
+        base64Enc.calcSize(payload.len),
+    )];
+    const msg: *SaprusMessage = .init(.connection, msg_bytes);
+
     const connection = (try msg.getSaprusTypePayload()).connection;
     connection.src_port = initial_port;
     connection.dest_port = dest_port;
-    @memcpy(connection.getPayload(), payload);
+    _ = base64Enc.encode(connection.getPayload(), payload);
 
-    try broadcastSaprusMessage(msg, 8888);
+    try broadcastSaprusMessage(msg_bytes, 8888);
 
     return msg;
 }
 
-pub fn connect(payload: []const u8, allocator: Allocator) !?SaprusConnection {
-    var initial_port: u16 = 0;
-    if (rand) |r| {
-        initial_port = r.intRangeAtMost(u16, 1024, 65000);
-    } else unreachable;
+pub fn connect(self: Self, payload: []const u8) !?SaprusConnection {
+    const initial_port = self.randomPort();
 
-    var initial_conn_res: ?SaprusMessage = null;
-    errdefer if (initial_conn_res) |*c| c.deinit(allocator);
+    var initial_conn_res: ?*SaprusMessage = null;
 
     var sock = try network.Socket.create(.ipv4, .udp);
     defer sock.close();
@@ -104,17 +163,17 @@ pub fn connect(payload: []const u8, allocator: Allocator) !?SaprusConnection {
     try sock.setReadTimeout(1 * std.time.us_per_s);
     try sock.bind(bind_addr);
 
-    const msg = try sendInitialConnection(payload, initial_port, allocator);
+    var sent_msg_bytes: [max_message_size]u8 align(@alignOf(SaprusMessage)) = undefined;
+    const msg = try self.sendInitialConnection(payload, &sent_msg_bytes, initial_port);
 
-    var response_buf: [4096]u8 align(4) = @splat(0);
+    var response_buf: [max_message_size]u8 align(@alignOf(SaprusMessage)) = undefined;
     _ = try sock.receive(&response_buf); // Ignore message that I sent.
     const len = try sock.receive(&response_buf);
 
-    std.debug.print("response bytes: {x}\n", .{response_buf});
-    initial_conn_res = (try SaprusMessage.bytesAsValue(response_buf[0..len])).*;
+    initial_conn_res = try .networkBytesAsValue(response_buf[0..len]);
 
     // Complete handshake after awaiting response
-    try broadcastSaprusMessage(msg, randomPort());
+    try broadcastSaprusMessage(msg.asBytes(), self.randomPort());
 
     if (false) {
         return initial_conn_res.?;
@@ -123,7 +182,6 @@ pub fn connect(payload: []const u8, allocator: Allocator) !?SaprusConnection {
 }
 
 const SaprusMessage = @import("message.zig").Message;
-const SaprusMessageNew = @import("message.zig").MessageNew;
 const SaprusConnection = @import("Connection.zig");
 
 const std = @import("std");
@@ -132,6 +190,3 @@ const posix = std.posix;
 const mem = std.mem;
 
 const network = @import("network");
-const gcat = @import("gatorcat");
-
-const Allocator = mem.Allocator;

src/RawSocketWriter.zig

@@ -0,0 +1,45 @@
+const std = @import("std");
+const gcat = @import("gatorcat");
+const Writer = @This();
+const assert = std.debug.assert;
+
+interface: std.Io.Writer,
+socket: gcat.nic.RawSocket,
+alloc: std.mem.Allocator,
+
+fn drain(io_w: *std.Io.Writer, data: []const []const u8, splat: usize) std.Io.Writer.Error!usize {
+    const w: *Writer = @alignCast(@fieldParentPtr("interface", io_w));
+    const buffered = io_w.buffered();
+    var res: usize = 0;
+    if (buffered.len > 0) {
+        w.socket.linkLayer().send(buffered) catch return error.WriteFailed;
+        _ = io_w.consumeAll();
+    }
+
+    for (data[0 .. data.len - 1]) |d| {
+        w.socket.linkLayer().send(d) catch return error.WriteFailed;
+        res += d.len;
+    }
+
+    if (splat > 0 and data[data.len - 1].len > 0) {
+        var splatBuffer: std.ArrayList(u8) = .empty;
+        defer splatBuffer.deinit(w.alloc);
+        for (0..splat) |_| {
+            splatBuffer.appendSlice(w.alloc, data[data.len - 1]) catch return error.WriteFailed;
+        }
+        w.socket.linkLayer().send(splatBuffer.items) catch return error.WriteFailed;
+    }
+
+    return res;
+}
+
+pub fn init(interface_name: [:0]const u8, buffer: []u8, alloc: std.mem.Allocator) !Writer {
+    return .{
+        .interface = .{
+            .vtable = &.{ .drain = drain },
+            .buffer = buffer,
+        },
+        .socket = try .init(interface_name),
+        .alloc = alloc,
+    };
+}

src/main.zig

@@ -37,36 +37,37 @@ pub fn main() !void {
         .allocator = gpa,
     }) catch |err| {
         // Report useful error and exit.
-        diag.report(std.io.getStdErr().writer(), err) catch {};
+        try diag.reportToFile(.stderr(), err);
         return err;
     };
     defer res.deinit();
 
-    try SaprusClient.init();
-    defer SaprusClient.deinit();
-
     if (res.args.help != 0) {
-        return clap.help(std.io.getStdErr().writer(), clap.Help, &params, .{});
+        return clap.helpToFile(.stderr(), clap.Help, &params, .{});
     }
 
+    var sock_buffer: [2048]u8 = undefined;
+    var rawSocketWriter: RawSocketWriter = try .init("enp7s0", &sock_buffer, gpa); // /proc/net/dev
+    var client = try SaprusClient.init(&rawSocketWriter.interface);
+    defer client.deinit();
+
     if (res.args.relay) |r| {
         const dest = parseDest(res.args.dest);
-        try SaprusClient.sendRelay(
+        try client.sendRelay(
             if (r.len > 0) r else "Hello darkness my old friend",
             dest,
-            gpa,
         );
         // std.debug.print("Sent: {s}\n", .{r});
         return;
     } else if (res.args.connect) |c| {
-        _ = SaprusClient.connect(if (c.len > 0) c else "Hello darkness my old friend", gpa) catch |err| switch (err) {
+        _ = client.connect(if (c.len > 0) c else "Hello darkness my old friend") catch |err| switch (err) {
             error.WouldBlock => null,
             else => return err,
         };
         return;
     }
 
-    return clap.help(std.io.getStdErr().writer(), clap.Help, &params, .{});
+    return clap.helpToFile(.stderr(), clap.Help, &params, .{});
 }
 
 fn parseDest(in: ?[]const u8) [4]u8 {
@@ -91,5 +92,6 @@ const ArrayList = std.ArrayList;
 const zaprus = @import("zaprus");
 const SaprusClient = zaprus.Client;
 const SaprusMessage = zaprus.Message;
+const RawSocketWriter = zaprus.RawSocketWriter;
 
 const clap = @import("clap");

src/message.zig

@@ -20,130 +20,14 @@ pub const ConnectionOptions = packed struct(u8) {
     opt8: bool = false,
 };
 
-pub const Error = error{
+pub const MessageTypeError = error{
     NotImplementedSaprusType,
     UnknownSaprusType,
+};
+pub const MessageParseError = MessageTypeError || error{
     InvalidMessage,
 };
 
-pub fn MessageNew(comptime packet_type: PacketType) type {
-    comptime {
-        if (packet_type == .file_transfer)
-            @compileError("File transfer not implemented");
-        if (packet_type != .relay and packet_type != .connection)
-            @compileError("Unkown message type");
-    }
-
-    return packed struct {
-        const Self = @This();
-        const SelfBytes = []align(@alignOf(Self)) u8;
-
-        const Relay = struct {
-            pub fn getPayload(self: *Self) []u8 {
-                return @as([*]align(@alignOf(Self)) u8, @ptrCast(&self.payload))[0 .. self.length - 4];
-            }
-        };
-        const Connection = packed struct {
-            pub fn getPayload(self: Self) []u8 {
-                return @as([*]u8, &self.payload)[0 .. self.length - 4];
-            }
-        };
-
-        type: PacketType = packet_type,
-        length: u16,
-
-        // Relay
-        dest: if (packet_type == .relay) @Vector(4, u8) else void,
-
-        // Connection
-        src_port: if (packet_type == .connection) u16 else void, // random number > 1024
-        dest_port: if (packet_type == .connection) u16 else void, // random number > 1024
-        seq_num: if (packet_type == .connection) u32 else void,
-        msg_id: if (packet_type == .connection) u32 else void,
-        reserved: if (packet_type == .connection) u8 else void,
-        options: if (packet_type == .connection) ConnectionOptions else void = if (packet_type == .connection) .{} else {},
-
-        // Relay or Connection
-        payload: switch (packet_type) {
-            .relay, .connection => void,
-            else => noreturn,
-        },
-
-        pub usingnamespace switch (packet_type) {
-            .relay => Relay,
-            .connection => Connection,
-            .file_transfer => @compileError("File Transfer message type not implemented"),
-            else => @compileError("Unknown message type"),
-        };
-
-        pub fn init(allocator: Allocator, payload_len: u16) !*Self {
-            const size = payload_len + @sizeOf(Self);
-            const bytes = try allocator.alignedAlloc(u8, @alignOf(Self), size);
-            const res: *Self = @ptrCast(bytes.ptr);
-            res.type = packet_type;
-            res.length = payload_len;
-            return res;
-        }
-
-        pub fn deinit(self: *Self, allocator: Allocator) void {
-            allocator.free(self.asBytes());
-        }
-
-        pub fn nativeFromNetworkEndian(self: *Self) void {
-            self.type = @enumFromInt(bigToNative(
-                @typeInfo(@TypeOf(self.type)).@"enum".tag_type,
-                @intFromEnum(self.type),
-            ));
-            self.length = bigToNative(@TypeOf(self.length), self.length);
-
-            if (packet_type == .connection) {
-                self.src_port = bigToNative(@TypeOf(self.src_port), self.src_port);
-                self.dest_port = bigToNative(@TypeOf(self.dest_port), self.dest_port);
-                self.seq_num = bigToNative(@TypeOf(self.seq_num), self.seq_num);
-                self.msg_id = bigToNative(@TypeOf(self.msg_id), self.msg_id);
-            }
-        }
-
-        pub fn networkFromNativeEndian(self: *Self) void {
-            self.type = @enumFromInt(bigToNative(
-                @typeInfo(@TypeOf(self.type)).@"enum".tag_type,
-                @intFromEnum(self.type),
-            ));
-            self.length = bigToNative(@TypeOf(self.length), self.length);
-
-            if (packet_type == .connection) {
-                self.src_port = nativeToBig(@TypeOf(self.src_port), self.src_port);
-                self.dest_port = nativeToBig(@TypeOf(self.dest_port), self.dest_port);
-                self.seq_num = nativeToBig(@TypeOf(self.seq_num), self.seq_num);
-                self.msg_id = nativeToBig(@TypeOf(self.msg_id), self.msg_id);
-            }
-        }
-
-        pub fn asBytes(self: *Self) SelfBytes {
-            const size = @sizeOf(Self) + self.length;
-            return @as([*]align(@alignOf(Self)) u8, @ptrCast(self))[0..size];
-        }
-    };
-}
-
-test MessageNew {
-    comptime for (@typeInfo(MessageNew(.connection)).@"struct".decls) |field| {
-        @compileLog(field);
-    };
-}
-
-// pub fn bytesAsMessage(bytes: []const u8) !*Self {
-//     const res = std.mem.bytesAsValue(Self, bytes);
-//     return switch (res.type) {
-//         .relay, .connection => if (bytes.len == res.length + @sizeOf(Self))
-//             res
-//         else
-//             Error.InvalidMessage,
-//         .file_transfer => Error.NotImplementedSaprusType,
-//         else => Error.UnknownSaprusType,
-//     };
-// }
-
 // ZERO COPY STUFF
 // &payload could be a void value that is treated as a pointer to a [*]u8
 /// All Saprus messages
@@ -154,7 +38,7 @@ pub const Message = packed struct {
 
         pub fn getPayload(self: *align(1) Relay) []u8 {
             const len: *u16 = @ptrFromInt(@intFromPtr(self) - @sizeOf(u16));
-            return @as([*]u8, @ptrCast(&self.payload))[0 .. len.* - @sizeOf(Relay)];
+            return @as([*]u8, @ptrCast(&self.payload))[0 .. len.* - @bitSizeOf(Relay) / 8];
         }
     };
     const Connection = packed struct {
@@ -168,7 +52,7 @@ pub const Message = packed struct {
 
         pub fn getPayload(self: *align(1) Connection) []u8 {
             const len: *u16 = @ptrFromInt(@intFromPtr(self) - @sizeOf(u16));
-            return @as([*]u8, @ptrCast(&self.payload))[0 .. len.* - @sizeOf(Connection)];
+            return @as([*]u8, @ptrCast(&self.payload))[0 .. len.* - @bitSizeOf(Connection) / 8];
         }
 
         fn nativeFromNetworkEndian(self: *align(1) Connection) void {
@@ -193,23 +77,27 @@ pub const Message = packed struct {
     length: u16,
     bytes: void = {},
 
-    pub fn init(allocator: Allocator, comptime @"type": PacketType, payload_len: u16) !*Self {
-        const header_size = @sizeOf(switch (@"type") {
-            .relay => Relay,
-            .connection => Connection,
-            .file_transfer => return Error.NotImplementedSaprusType,
-            else => return Error.UnknownSaprusType,
-        });
-        const size = payload_len + @sizeOf(Self) + header_size;
-        const bytes = try allocator.alignedAlloc(u8, @alignOf(Self), size);
+    /// Takes a byte slice, and returns a Message struct backed by the slice.
+    /// This properly initializes the top level headers within the slice.
+    /// This is used for creating new messages. For reading messages from the network,
+    /// see: networkBytesAsValue.
+    pub fn init(@"type": PacketType, bytes: []align(@alignOf(Self)) u8) *Self {
+        std.debug.assert(bytes.len >= @sizeOf(Self));
         const res: *Self = @ptrCast(bytes.ptr);
         res.type = @"type";
-        res.length = payload_len + header_size;
+        res.length = @intCast(bytes.len - @sizeOf(Self));
         return res;
     }
 
-    pub fn deinit(self: *Self, allocator: Allocator) void {
-        allocator.free(self.asBytes());
+    /// Compute the number of bytes required to store a given payload size for a given message type.
+    pub fn calcSize(comptime @"type": PacketType, payload_len: usize) MessageTypeError!u16 {
+        const header_size = @bitSizeOf(switch (@"type") {
+            .relay => Relay,
+            .connection => Connection,
+            .file_transfer => return MessageTypeError.NotImplementedSaprusType,
+            else => return MessageTypeError.UnknownSaprusType,
+        }) / 8;
+        return @intCast(payload_len + @sizeOf(Self) + header_size);
     }
 
     fn getRelay(self: *Self) *align(1) Relay {
@@ -219,7 +107,8 @@ pub const Message = packed struct {
         return std.mem.bytesAsValue(Connection, &self.bytes);
     }
 
-    pub fn getSaprusTypePayload(self: *Self) Error!(union(PacketType) {
+    /// Access the message Saprus payload.
+    pub fn getSaprusTypePayload(self: *Self) MessageTypeError!(union(PacketType) {
         relay: *align(1) Relay,
         file_transfer: void,
         connection: *align(1) Connection,
@@ -227,12 +116,13 @@ pub const Message = packed struct {
         return switch (self.type) {
             .relay => .{ .relay = self.getRelay() },
             .connection => .{ .connection = self.getConnection() },
-            .file_transfer => Error.NotImplementedSaprusType,
-            else => Error.UnknownSaprusType,
+            .file_transfer => MessageTypeError.NotImplementedSaprusType,
+            else => MessageTypeError.UnknownSaprusType,
         };
     }
 
-    pub fn nativeFromNetworkEndian(self: *Self) Error!void {
+    /// Convert the message to native endianness from network endianness in-place.
+    pub fn nativeFromNetworkEndian(self: *Self) MessageTypeError!void {
         self.type = @enumFromInt(bigToNative(
             @typeInfo(@TypeOf(self.type)).@"enum".tag_type,
             @intFromEnum(self.type),
@@ -255,12 +145,13 @@ pub const Message = packed struct {
         }
     }
 
-    pub fn networkFromNativeEndian(self: *Self) Error!void {
+    /// Convert the message to network endianness from native endianness in-place.
+    pub fn networkFromNativeEndian(self: *Self) MessageTypeError!void {
         try switch (try self.getSaprusTypePayload()) {
             .relay => {},
             .connection => |*con| con.*.networkFromNativeEndian(),
-            .file_transfer => Error.NotImplementedSaprusType,
-            else => Error.UnknownSaprusType,
+            .file_transfer => MessageTypeError.NotImplementedSaprusType,
+            else => MessageTypeError.UnknownSaprusType,
         };
         self.type = @enumFromInt(nativeToBig(
             @typeInfo(@TypeOf(self.type)).@"enum".tag_type,
@@ -269,18 +160,29 @@ pub const Message = packed struct {
         self.length = nativeToBig(@TypeOf(self.length), self.length);
     }
 
-    pub fn bytesAsValue(bytes: SelfBytes) !*Self {
+    /// Convert network endian bytes to a native endian value in-place.
+    pub fn networkBytesAsValue(bytes: SelfBytes) MessageParseError!*Self {
+        const res = std.mem.bytesAsValue(Self, bytes);
+        try res.nativeFromNetworkEndian();
+        return .bytesAsValue(bytes);
+    }
+
+    /// Create a structured view of the bytes without initializing the length or type,
+    /// and without converting the endianness.
+    pub fn bytesAsValue(bytes: SelfBytes) MessageParseError!*Self {
         const res = std.mem.bytesAsValue(Self, bytes);
         return switch (res.type) {
             .relay, .connection => if (bytes.len == res.length + @sizeOf(Self))
                 res
             else
-                Error.InvalidMessage,
-            .file_transfer => Error.NotImplementedSaprusType,
-            else => Error.UnknownSaprusType,
+                MessageParseError.InvalidMessage,
+            .file_transfer => MessageParseError.NotImplementedSaprusType,
+            else => MessageParseError.UnknownSaprusType,
         };
     }
 
+    /// Deprecated.
+    /// If I need the bytes, I should just pass around the slice that is backing this to begin with.
     pub fn asBytes(self: *Self) SelfBytes {
         const size = @sizeOf(Self) + self.length;
         return @as([*]align(@alignOf(Self)) u8, @ptrCast(self))[0..size];
@@ -288,12 +190,13 @@ pub const Message = packed struct {
 };
 
 test "testing variable length zero copy struct" {
-    const gpa = std.testing.allocator;
+    {
+        // Relay test
         const payload = "Hello darkness my old friend";
+        var msg_bytes: [try Message.calcSize(.relay, payload.len)]u8 align(@alignOf(Message)) = undefined;
 
         // Create a view of the byte slice as a Message
-    const msg: *Message = try .init(gpa, .relay, payload.len);
-    defer msg.deinit(gpa);
+        const msg: *Message = .init(.relay, &msg_bytes);
 
         {
             // Set the message values
@@ -308,15 +211,13 @@ test "testing variable length zero copy struct" {
         }
 
         {
-        const bytes = msg.asBytes();
-
             // Print the message as hex using the network byte order
             try msg.networkFromNativeEndian();
             // We know the error from nativeFromNetworkEndian is unreachable because
             // it would have returned an error from networkFromNativeEndian.
             defer msg.nativeFromNetworkEndian() catch unreachable;
-        std.debug.print("network bytes: {x}\n", .{bytes});
-        std.debug.print("bytes len: {d}\n", .{bytes.len});
+            std.debug.print("relay network bytes: {x}\n", .{msg_bytes});
+            std.debug.print("bytes len: {d}\n", .{msg_bytes.len});
         }
 
         if (false) {
@@ -327,6 +228,38 @@ test "testing variable length zero copy struct" {
         try std.testing.expectEqualDeep(msg, try Message.bytesAsValue(msg.asBytes()));
     }
 
+    {
+        // Connection test
+        const payload = "Hello darkness my old friend";
+        var msg_bytes: [try Message.calcSize(.connection, payload.len)]u8 align(@alignOf(Message)) = undefined;
+
+        // Create a view of the byte slice as a Message
+        const msg: *Message = .init(.connection, &msg_bytes);
+
+        {
+            // Initializing connection header values
+            const connection = (try msg.getSaprusTypePayload()).connection;
+            connection.src_port = 1;
+            connection.dest_port = 2;
+            connection.seq_num = 3;
+            connection.msg_id = 4;
+            connection.reserved = 5;
+            connection.options = @bitCast(@as(u8, 6));
+            @memcpy(connection.getPayload(), payload);
+        }
+
+        {
+            // Print the message as hex using the network byte order
+            try msg.networkFromNativeEndian();
+            // We know the error from nativeFromNetworkEndian is unreachable because
+            // it would have returned an error from networkFromNativeEndian.
+            defer msg.nativeFromNetworkEndian() catch unreachable;
+            std.debug.print("connection network bytes: {x}\n", .{msg_bytes});
+            std.debug.print("bytes len: {d}\n", .{msg_bytes.len});
+        }
+    }
+}
+
 const std = @import("std");
 const Allocator = std.mem.Allocator;
 
@@ -334,6 +267,51 @@ const asBytes = std.mem.asBytes;
 const nativeToBig = std.mem.nativeToBig;
 const bigToNative = std.mem.bigToNative;
 
+test "Round trip Relay toBytes and fromBytes" {
+    if (false) {
+        const gpa = std.testing.allocator;
+        const msg = Message{
+            .relay = .{
+                .header = .{ .dest = .{ 255, 255, 255, 255 } },
+                .payload = "Hello darkness my old friend",
+            },
+        };
+
+        const to_bytes = try msg.toBytes(gpa);
+        defer gpa.free(to_bytes);
+
+        const from_bytes = try Message.fromBytes(to_bytes, gpa);
+        defer from_bytes.deinit(gpa);
+
+        try std.testing.expectEqualDeep(msg, from_bytes);
+    }
+    return error.SkipZigTest;
+}
+
+test "Round trip Connection toBytes and fromBytes" {
+    if (false) {
+        const gpa = std.testing.allocator;
+        const msg = Message{
+            .connection = .{
+                .header = .{
+                    .src_port = 0,
+                    .dest_port = 0,
+                },
+                .payload = "Hello darkness my old friend",
+            },
+        };
+
+        const to_bytes = try msg.toBytes(gpa);
+        defer gpa.free(to_bytes);
+
+        const from_bytes = try Message.fromBytes(to_bytes, gpa);
+        defer from_bytes.deinit(gpa);
+
+        try std.testing.expectEqualDeep(msg, from_bytes);
+    }
+    return error.SkipZigTest;
+}
+
 test {
     std.testing.refAllDeclsRecursive(@This());
 }

src/root.zig

@@ -1,4 +1,12 @@
 pub const Client = @import("Client.zig");
 pub const Connection = @import("Connection.zig");
+pub const RawSocketWriter = @import("RawSocketWriter.zig");
 
-pub usingnamespace @import("message.zig");
+const msg = @import("message.zig");
+
+pub const PacketType = msg.PacketType;
+pub const foo = msg.foo;
+pub const ConnectionOptions = msg.ConnectionOptions;
+pub const MessageTypeError = msg.MessageTypeError;
+pub const MessageParseError = msg.MessageParseError;
+pub const Message = msg.Message;