Bad attempt at using @fieldParentPtr

https://kagi.com/assistant/a8f0a9ac-a11a-472e-af38-98d7e877e293

build.zig.zon

@@ -45,8 +45,8 @@
             .hash = "clap-0.10.0-oBajB434AQBDh-Ei3YtoKIRxZacVPF1iSwp3IX_ZB8f0",
         },
         .gatorcat = .{
-            .url = "git+https://github.com/kj4tmp/gatorcat.git#0a97b666677501db4939e3e8245f88a19e015893",
-            .hash = "gatorcat-0.3.4-WcrpTcleBwCta_9TjomuIGb3bdg2Pke_FXI_WkMTEivH",
+            .url = "git+https://github.com/kj4tmp/gatorcat#bb1847f6c95852e7a0ec8c07870a948c171d5f98",
+            .hash = "gatorcat-0.3.2-WcrpTf1mBwDrmPaIhKCfLJO064v8Sjjn7DBq4CKZSgHH",
         },
     },
     .paths = .{

src/Client.zig

@@ -1,88 +1,22 @@
-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,
-socket: gcat.nic.RawSocket,
-
-const Self = @This();
-
-const max_message_size = 2048;
-
-pub fn init(interface_name: [:0]const u8) !Self {
+pub fn init() !void {
     var prng = Random.DefaultPrng.init(blk: {
         var seed: u64 = undefined;
         try posix.getrandom(mem.asBytes(&seed));
         break :blk seed;
     });
-    const rand = prng.random();
-
-    const socket: gcat.nic.RawSocket = try .init(interface_name);
-
-    return .{
-        .rand = rand,
-        .socket = socket,
-    };
+    rand = prng.random();
+    try network.init();
 }
 
-pub fn deinit(self: *Self) void {
-    self.socket.deinit();
+pub fn deinit() void {
+    network.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;
-        }
-
-        // 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);
-
-    try self.socket.linkLayer().send(packet_bytes[0 .. saprus_start_byte + msg_bytes.len]);
-}
-
-// fn broadcastSaprusMessage(msg_bytes: []align(@alignOf(SaprusMessage)) u8) !void {}
-
-fn broadcastSaprusMessage(msg_bytes: []align(@alignOf(SaprusMessage)) u8, udp_port: u16) !void {
-    if (false) {
-        var foo: gcat.nic.RawSocket = try .init("enp7s0"); // /proc/net/dev
-        defer foo.deinit();
-    }
-    const msg: *SaprusMessage = try .bytesAsValue(msg_bytes);
-    try msg.networkFromNativeEndian();
-    defer msg.nativeFromNetworkEndian() catch unreachable;
+fn broadcastSaprusMessage(msg: SaprusMessage, udp_port: u16, allocator: Allocator) !void {
+    const msg_bytes = try msg.toBytes(allocator);
+    defer allocator.free(msg_bytes);
 
     var sock = try network.Socket.create(.ipv4, .udp);
     defer sock.close();
@@ -102,57 +36,57 @@ fn broadcastSaprusMessage(msg_bytes: []align(@alignOf(SaprusMessage)) u8, udp_po
 
     try sock.bind(bind_addr);
 
-    std.debug.print("{x}\n", .{msg_bytes});
-
     _ = try sock.sendTo(dest_addr, msg_bytes);
 }
 
-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);
+pub fn sendRelay(payload: []const u8, dest: [4]u8, allocator: Allocator) !void {
+    const msg = SaprusMessage{
+        .relay = .{
+            .header = .{ .dest = dest },
+            .payload = payload,
+        },
+    };
 
-    const relay = (try msg.getSaprusTypePayload()).relay;
-    relay.dest = dest;
-    _ = base64Enc.encode(relay.getPayload(), payload);
-
-    try self.broadcastInitialInterestMessage(msg_bytes);
+    try broadcastSaprusMessage(msg, 8888, allocator);
 }
 
-fn randomPort(self: Self) u16 {
-    return self.rand.intRangeAtMost(u16, 1024, 65000);
+fn randomPort() u16 {
+    var p: u16 = 0;
+    if (rand) |r| {
+        p = r.intRangeAtMost(u16, 1024, 65000);
+    } else unreachable;
+
+    return p;
 }
 
-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);
+pub fn sendInitialConnection(payload: []const u8, initial_port: u16, allocator: Allocator) !SaprusMessage {
+    const dest_port = randomPort();
+    const msg = SaprusMessage{
+        .connection = .{
+            .header = .{
+                .src_port = initial_port,
+                .dest_port = dest_port,
+            },
+            .payload = payload,
+        },
+    };
 
-    const connection = (try msg.getSaprusTypePayload()).connection;
-    connection.src_port = initial_port;
-    connection.dest_port = dest_port;
-    _ = base64Enc.encode(connection.getPayload(), payload);
-
-    try broadcastSaprusMessage(msg_bytes, 8888);
+    try broadcastSaprusMessage(msg, 8888, allocator);
 
     return msg;
 }
 
-pub fn connect(self: Self, payload: []const u8) !?SaprusConnection {
-    const initial_port = self.randomPort();
+pub fn connect(payload: []const u8, allocator: Allocator) !?SaprusConnection {
+    var foo: gcat.nic.RawSocket = try .init("enp7s0"); // /proc/net/dev
+    defer foo.deinit();
 
-    var initial_conn_res: ?*SaprusMessage = null;
+    var initial_port: u16 = 0;
+    if (rand) |r| {
+        initial_port = r.intRangeAtMost(u16, 1024, 65000);
+    } else unreachable;
+
+    var initial_conn_res: ?SaprusMessage = null;
+    errdefer if (initial_conn_res) |c| c.deinit(allocator);
 
     var sock = try network.Socket.create(.ipv4, .udp);
     defer sock.close();
@@ -167,17 +101,16 @@ pub fn connect(self: Self, payload: []const u8) !?SaprusConnection {
     try sock.setReadTimeout(1 * std.time.us_per_s);
     try sock.bind(bind_addr);
 
-    var sent_msg_bytes: [max_message_size]u8 align(@alignOf(SaprusMessage)) = undefined;
-    const msg = try self.sendInitialConnection(payload, &sent_msg_bytes, initial_port);
+    const msg = try sendInitialConnection(payload, initial_port, allocator);
 
-    var response_buf: [max_message_size]u8 align(@alignOf(SaprusMessage)) = undefined;
+    var response_buf: [4096]u8 = undefined;
     _ = try sock.receive(&response_buf); // Ignore message that I sent.
     const len = try sock.receive(&response_buf);
 
-    initial_conn_res = try .networkBytesAsValue(response_buf[0..len]);
+    initial_conn_res = try SaprusMessage.fromBytes(response_buf[0..len], allocator);
 
     // Complete handshake after awaiting response
-    try broadcastSaprusMessage(msg.asBytes(), self.randomPort());
+    try broadcastSaprusMessage(msg, randomPort(), allocator);
 
     if (false) {
         return initial_conn_res.?;
@@ -195,3 +128,5 @@ const mem = std.mem;
 
 const network = @import("network");
 const gcat = @import("gatorcat");
+
+const Allocator = mem.Allocator;

src/main.zig

@@ -42,27 +42,27 @@ pub fn main() !void {
     };
     defer res.deinit();
 
+    try SaprusClient.init();
+    defer SaprusClient.deinit();
+
     if (res.args.help != 0) {
         return clap.help(std.io.getStdErr().writer(), clap.Help, &params, .{});
     }
 
-    var client = try SaprusClient.init("enp7s0");
-    defer client.deinit();
-
     if (res.args.relay) |r| {
         const dest = parseDest(res.args.dest);
-        try client.sendRelay(
+        try SaprusClient.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| {
-        _ = client.connect(if (c.len > 0) c else "Hello darkness my old friend") catch |err| switch (err) {
+        _ = SaprusClient.connect(if (c.len > 0) c else "Hello darkness my old friend", gpa) catch |err| switch (err) {
             error.WouldBlock => null,
             else => return err,
         };
-        return;
     }
 
     return clap.help(std.io.getStdErr().writer(), clap.Help, &params, .{});

src/message.zig

@@ -1,3 +1,6 @@
+const base64Enc = std.base64.Base64Encoder.init(std.base64.standard_alphabet_chars, '=');
+const base64Dec = std.base64.Base64Decoder.init(std.base64.standard_alphabet_chars, '=');
+
 /// Type tag for Message union.
 /// This is the first value in the actual packet sent over the network.
 pub const PacketType = enum(u16) {
@@ -20,25 +23,43 @@ pub const ConnectionOptions = packed struct(u8) {
     opt8: bool = false,
 };
 
-pub const MessageTypeError = error{
+pub const Error = error{
     NotImplementedSaprusType,
     UnknownSaprusType,
-};
-pub const MessageParseError = MessageTypeError || error{
     InvalidMessage,
 };
 
 // ZERO COPY STUFF
 // &payload could be a void value that is treated as a pointer to a [*]u8
-/// All Saprus messages
-pub const Message = packed struct {
+pub const ZeroCopyMessage = packed struct {
     const Relay = packed struct {
         dest: @Vector(4, u8),
         payload: void,
 
-        pub fn getPayload(self: *align(1) Relay) []u8 {
-            const len: *u16 = @ptrFromInt(@intFromPtr(self) - @sizeOf(u16));
-            return @as([*]u8, @ptrCast(&self.payload))[0 .. len.* - @bitSizeOf(Relay) / 8];
+        pub fn getPayload(self: *align(@alignOf(ZeroCopyMessage)) Relay) []u8 {
+            // Cast the 'self' pointer (which points to the Relay header,
+            // located at the same memory as the parent's 'bytes' field)
+            // to a pointer to void, as required by @fieldParentPtr for a void field.
+            // Preserve the known alignment.
+            const self_as_void_ptr: *align(@alignOf(ZeroCopyMessage)) void = @ptrCast(self);
+
+            // Cast the resulting *void pointer to the parent type *ZeroCopyMessage.
+            // This cast performs the necessary alignment check.
+            const parent: *ZeroCopyMessage = @alignCast(@fieldParentPtr("bytes", self_as_void_ptr));
+
+            // The 'length' field in the parent ZeroCopyMessage contains
+            // the size of the header (Relay) + payload length.
+            const total_len = parent.length;
+
+            // Payload length = total_len - size of the Relay header
+            const payload_len = total_len - @sizeOf(Relay);
+
+            // The payload starts immediately after the fixed fields of the Relay struct.
+            // The address of the 'payload' field represents this starting point.
+            const payload_start_ptr: [*]u8 = @ptrCast(&self.payload);
+
+            // Return a slice from the payload start address with the calculated length.
+            return payload_start_ptr[0..payload_len];
         }
     };
     const Connection = packed struct {
@@ -52,17 +73,17 @@ 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.* - @bitSizeOf(Connection) / 8];
+            return @as([*]u8, @ptrCast(&self.payload))[0 .. len.* - @sizeOf(Connection)];
         }
 
-        fn nativeFromNetworkEndian(self: *align(1) Connection) void {
+        fn nativeFromNetworkEndian(self: *align(1) Connection) Error!void {
             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);
         }
 
-        fn networkFromNativeEndian(self: *align(1) Connection) void {
+        fn networkFromNativeEndian(self: *align(1) Connection) Error!void {
             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);
@@ -71,87 +92,70 @@ pub const Message = packed struct {
     };
 
     const Self = @This();
-    const SelfBytes = []align(@alignOf(Self)) u8;
 
     type: PacketType,
     length: u16,
     bytes: void = {},
 
-    /// 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));
+    pub fn init(allocator: Allocator, comptime @"type": PacketType, payload_len: u16) !*Self {
+        const header_size = @sizeOf(switch (@"type") {
+            .relay => Relay,
+            .connection => Connection,
+            else => return error.Bad,
+        });
+        const size = payload_len + @sizeOf(Self) + header_size;
+        const bytes = try allocator.alignedAlloc(u8, @alignOf(Self), size);
         const res: *Self = @ptrCast(bytes.ptr);
         res.type = @"type";
-        res.length = @intCast(bytes.len - @sizeOf(Self));
+        res.length = payload_len + header_size;
         return res;
     }
 
-    /// 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);
+    pub fn deinit(self: *Self, allocator: Allocator) void {
+        allocator.free(self.asBytes());
     }
 
-    fn getRelay(self: *Self) *align(1) Relay {
+    fn getRelay(self: *Self) *align(@alignOf(Self)) Relay {
         return std.mem.bytesAsValue(Relay, &self.bytes);
     }
-    fn getConnection(self: *Self) *align(1) Connection {
+    fn getConnection(self: *Self) *align(@alignOf(Self)) Connection {
         return std.mem.bytesAsValue(Connection, &self.bytes);
     }
 
-    /// Access the message Saprus payload.
-    pub fn getSaprusTypePayload(self: *Self) MessageTypeError!(union(PacketType) {
-        relay: *align(1) Relay,
+    pub fn getSaprusTypePayload(self: *Self) Error!(union(PacketType) {
+        relay: *align(@alignOf(Self)) Relay,
         file_transfer: void,
-        connection: *align(1) Connection,
+        connection: *align(@alignOf(Self)) Connection,
     }) {
         return switch (self.type) {
             .relay => .{ .relay = self.getRelay() },
             .connection => .{ .connection = self.getConnection() },
-            .file_transfer => MessageTypeError.NotImplementedSaprusType,
-            else => MessageTypeError.UnknownSaprusType,
+            .file_transfer => Error.NotImplementedSaprusType,
+            else => Error.UnknownSaprusType,
         };
     }
 
-    /// Convert the message to native endianness from network endianness in-place.
-    pub fn nativeFromNetworkEndian(self: *Self) MessageTypeError!void {
+    pub fn nativeFromNetworkEndian(self: *Self) Error!void {
         self.type = @enumFromInt(bigToNative(
             @typeInfo(@TypeOf(self.type)).@"enum".tag_type,
             @intFromEnum(self.type),
         ));
         self.length = bigToNative(@TypeOf(self.length), self.length);
-        errdefer {
-            // If the payload specific headers fail, revert the top level header values
-            self.type = @enumFromInt(nativeToBig(
-                @typeInfo(@TypeOf(self.type)).@"enum".tag_type,
-                @intFromEnum(self.type),
-            ));
-            self.length = nativeToBig(@TypeOf(self.length), self.length);
-        }
         switch (try self.getSaprusTypePayload()) {
             .relay => {},
-            .connection => |*con| con.*.nativeFromNetworkEndian(),
+            .connection => |*con| try con.*.nativeFromNetworkEndian(),
             // We know other values are unreachable,
             // because they would have returned an error from the switch condition.
             else => unreachable,
         }
     }
 
-    /// Convert the message to network endianness from native endianness in-place.
-    pub fn networkFromNativeEndian(self: *Self) MessageTypeError!void {
+    pub fn networkFromNativeEndian(self: *Self) Error!void {
         try switch (try self.getSaprusTypePayload()) {
             .relay => {},
             .connection => |*con| con.*.networkFromNativeEndian(),
-            .file_transfer => MessageTypeError.NotImplementedSaprusType,
-            else => MessageTypeError.UnknownSaprusType,
+            .file_transfer => Error.NotImplementedSaprusType,
+            else => Error.UnknownSaprusType,
         };
         self.type = @enumFromInt(nativeToBig(
             @typeInfo(@TypeOf(self.type)).@"enum".tag_type,
@@ -160,106 +164,206 @@ pub const Message = packed struct {
         self.length = nativeToBig(@TypeOf(self.length), self.length);
     }
 
-    /// 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);
+    pub fn bytesAsValueUnchecked(bytes: []align(@alignOf(Self)) u8) *Self {
+        return std.mem.bytesAsValue(Self, 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);
+    pub fn bytesAsValue(bytes: []align(@alignOf(Self)) u8) !*Self {
+        const res = bytesAsValueUnchecked(bytes);
         return switch (res.type) {
             .relay, .connection => if (bytes.len == res.length + @sizeOf(Self))
                 res
             else
-                MessageParseError.InvalidMessage,
-            .file_transfer => MessageParseError.NotImplementedSaprusType,
-            else => MessageParseError.UnknownSaprusType,
+                Error.InvalidMessage,
+            .file_transfer => Error.NotImplementedSaprusType,
+            else => Error.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 {
+    pub fn asBytes(self: *Self) []align(@alignOf(Self)) u8 {
         const size = @sizeOf(Self) + self.length;
         return @as([*]align(@alignOf(Self)) u8, @ptrCast(self))[0..size];
     }
 };
 
 test "testing variable length zero copy struct" {
+    const gpa = std.testing.allocator;
+    const payload = "Hello darkness my old friend";
+
+    // Create a view of the byte slice as a ZeroCopyMessage
+    const zcm: *ZeroCopyMessage = try .init(gpa, .relay, payload.len);
+    defer zcm.deinit(gpa);
+    std.debug.print("outer: {*}\n", .{zcm});
+
     {
-        // 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 = .init(.relay, &msg_bytes);
-
+        // Set the message values
         {
-            // Set the message values
-            {
-                // These are both set by the init call.
-                // msg.type = .relay;
-                // msg.length = payload_len;
-            }
-            const relay = (try msg.getSaprusTypePayload()).relay;
-            relay.dest = .{ 1, 2, 3, 4 };
-            @memcpy(relay.getPayload(), payload);
+            // These are both set by the init call.
+            // zcm.type = .relay;
+            // zcm.length = payload_len;
         }
-
-        {
-            // 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("relay network bytes: {x}\n", .{msg_bytes});
-            std.debug.print("bytes len: {d}\n", .{msg_bytes.len});
-        }
-
-        if (false) {
-            // Illegal behavior
-            std.debug.print("{any}\n", .{(try msg.getSaprusTypePayload()).connection});
-        }
-
-        try std.testing.expectEqualDeep(msg, try Message.bytesAsValue(msg.asBytes()));
+        const relay = (try zcm.getSaprusTypePayload()).relay;
+        relay.dest = .{ 1, 2, 3, 4 };
+        @memcpy(relay.getPayload(), payload);
     }
 
     {
-        // Connection test
-        const payload = "Hello darkness my old friend";
-        var msg_bytes: [try Message.calcSize(.connection, payload.len)]u8 align(@alignOf(Message)) = undefined;
+        const bytes = zcm.asBytes();
 
-        // 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});
-        }
+        // Print the message as hex using the network byte order
+        try zcm.networkFromNativeEndian();
+        // We know the error from nativeFromNetworkEndian is unreachable because
+        // it would have returned an error from networkFromNativeEndian.
+        defer zcm.nativeFromNetworkEndian() catch unreachable;
+        std.debug.print("network bytes: {x}\n", .{bytes});
+        std.debug.print("bytes len: {d}\n", .{bytes.len});
     }
+
+    if (false) {
+        // Illegal behavior
+        std.debug.print("{any}\n", .{(try zcm.getSaprusTypePayload()).connection});
+    }
+
+    try std.testing.expectEqualDeep(zcm, try ZeroCopyMessage.bytesAsValue(zcm.asBytes()));
 }
 
+/// All Saprus messages
+pub const Message = union(PacketType) {
+    pub const Relay = struct {
+        pub const Header = packed struct {
+            dest: @Vector(4, u8),
+        };
+        header: Header,
+        payload: []const u8,
+    };
+    pub const Connection = struct {
+        pub const Header = packed struct {
+            src_port: u16, // random number > 1024
+            dest_port: u16, // random number > 1024
+            seq_num: u32 = 0,
+            msg_id: u32 = 0,
+            reserved: u8 = 0,
+            options: ConnectionOptions = .{},
+        };
+        header: Header,
+        payload: []const u8,
+    };
+    relay: Relay,
+    file_transfer: void, // unimplemented
+    connection: Connection,
+
+    /// Should be called for any Message that was declared using a function that you pass an allocator to.
+    pub fn deinit(self: Message, allocator: Allocator) void {
+        switch (self) {
+            .relay => |r| allocator.free(r.payload),
+            .connection => |c| allocator.free(c.payload),
+            else => unreachable,
+        }
+    }
+
+    fn toBytesAux(
+        header: anytype,
+        payload: []const u8,
+        buf: *std.ArrayList(u8),
+        allocator: Allocator,
+    ) !void {
+        const Header = @TypeOf(header);
+        // Create a growable string to store the base64 bytes in.
+        // Doing this first so I can use the length of the encoded bytes for the length field.
+        var payload_list = std.ArrayList(u8).init(allocator);
+        defer payload_list.deinit();
+        const buf_w = payload_list.writer();
+
+        // Write the payload bytes as base64 to the growable string.
+        try base64Enc.encodeWriter(buf_w, payload);
+
+        // At this point, payload_list contains the base64 encoded payload.
+
+        // Add the payload length to the output buf.
+        try buf.*.appendSlice(
+            asBytes(&nativeToBig(u16, @intCast(payload_list.items.len + @bitSizeOf(Header) / 8))),
+        );
+
+        // Add the header bytes to the output buf.
+        var header_buf: [@sizeOf(Header)]u8 = undefined;
+        var header_buf_stream = std.io.fixedBufferStream(&header_buf);
+        try header_buf_stream.writer().writeStructEndian(header, .big);
+        // Add the exact number of bits in the header without padding.
+        try buf.*.appendSlice(header_buf[0 .. @bitSizeOf(Header) / 8]);
+
+        try buf.*.appendSlice(payload_list.items);
+    }
+
+    /// Caller is responsible for freeing the returned bytes.
+    pub fn toBytes(self: Message, allocator: Allocator) ![]u8 {
+        // Create a growable list of bytes to store the output in.
+        var buf = std.ArrayList(u8).init(allocator);
+        errdefer buf.deinit();
+
+        // Start with writing the message type, which is the first 16 bits of every Saprus message.
+        try buf.appendSlice(asBytes(&nativeToBig(u16, @intFromEnum(self))));
+
+        // Write the proper header and payload for the given packet type.
+        switch (self) {
+            .relay => |r| try toBytesAux(r.header, r.payload, &buf, allocator),
+            .connection => |c| try toBytesAux(c.header, c.payload, &buf, allocator),
+            .file_transfer => return Error.NotImplementedSaprusType,
+        }
+
+        // Collect the growable list as a slice and return it.
+        return buf.toOwnedSlice();
+    }
+
+    fn fromBytesAux(
+        comptime packet: PacketType,
+        len: u16,
+        r: std.io.FixedBufferStream([]const u8).Reader,
+        allocator: Allocator,
+    ) !Message {
+        const Header = @field(@FieldType(Message, @tagName(packet)), "Header");
+
+        // Read the header for the current message type.
+        var header_bytes: [@sizeOf(Header)]u8 = undefined;
+        _ = try r.read(header_bytes[0 .. @bitSizeOf(Header) / 8]);
+        var header_stream = std.io.fixedBufferStream(&header_bytes);
+        const header = try header_stream.reader().readStructEndian(Header, .big);
+
+        // Read the base64 bytes into a list to be able to call the decoder on it.
+        const payload_buf = try allocator.alloc(u8, len - @bitSizeOf(Header) / 8);
+        defer allocator.free(payload_buf);
+        _ = try r.readAll(payload_buf);
+
+        // Create a buffer to store the payload in, and decode the base64 bytes into the payload field.
+        const payload = try allocator.alloc(u8, try base64Dec.calcSizeForSlice(payload_buf));
+        try base64Dec.decode(payload, payload_buf);
+
+        // Return the type of Message specified by the `packet` argument.
+        return @unionInit(Message, @tagName(packet), .{
+            .header = header,
+            .payload = payload,
+        });
+    }
+
+    /// Caller is responsible for calling .deinit on the returned value.
+    pub fn fromBytes(bytes: []const u8, allocator: Allocator) !Message {
+        var s = std.io.fixedBufferStream(bytes);
+        const r = s.reader();
+
+        // Read packet type
+        const packet_type = @as(PacketType, @enumFromInt(try r.readInt(u16, .big)));
+
+        // Read the length of the header + base64 encoded payload.
+        const len = try r.readInt(u16, .big);
+
+        switch (packet_type) {
+            .relay => return fromBytesAux(.relay, len, r, allocator),
+            .connection => return fromBytesAux(.connection, len, r, allocator),
+            .file_transfer => return Error.NotImplementedSaprusType,
+            else => return Error.UnknownSaprusType,
+        }
+    }
+};
+
 const std = @import("std");
 const Allocator = std.mem.Allocator;
 
@@ -268,48 +372,42 @@ 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 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 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);
+    const from_bytes = try Message.fromBytes(to_bytes, gpa);
+    defer from_bytes.deinit(gpa);
 
-        try std.testing.expectEqualDeep(msg, from_bytes);
-    }
-    return error.SkipZigTest;
+    try std.testing.expectEqualDeep(msg, from_bytes);
 }
 
 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 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 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);
+    const from_bytes = try Message.fromBytes(to_bytes, gpa);
+    defer from_bytes.deinit(gpa);
 
-        try std.testing.expectEqualDeep(msg, from_bytes);
-    }
-    return error.SkipZigTest;
+    try std.testing.expectEqualDeep(msg, from_bytes);
 }
 
 test {