going off the deep end with with generic message type

Callers can instead use std.mem.bytesAsValue directly.

build.zig

@@ -1,5 +1,4 @@
 const std = @import("std");
-const Step = std.Build.Step;
 
 // Although this function looks imperative, note that its job is to
 // declaratively construct a build graph that will be executed by an external
@@ -34,33 +33,18 @@ pub fn build(b: *std.Build) void {
     });
 
     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 static_lib = b.addLibrary(.{
+    const lib = b.addLibrary(.{
         .linkage = .static,
         .name = "zaprus",
         .root_module = lib_mod,
     });
-    static_lib.addIncludePath(.{ .cwd_relative = "include" });
-    static_lib.linkLibC();
 
-    b.installArtifact(static_lib);
+    b.installArtifact(lib);
-
-    const dynamic_lib = b.addLibrary(.{
-        .linkage = .dynamic,
-        .name = "zaprus",
-        .root_module = lib_mod,
-    });
-    dynamic_lib.addIncludePath(.{ .cwd_relative = "include" });
-    dynamic_lib.linkLibC();
-
-    b.installArtifact(dynamic_lib);
-
-    // C Headers
-    const c_header = b.addInstallHeaderFile(b.path("include/zaprus.h"), "zaprus.h");
-    b.getInstallStep().dependOn(&c_header.step);
 
     // This creates another `std.Build.Step.Compile`, but this one builds an executable
     // rather than a static library.

build.zig.zon

@@ -44,6 +44,10 @@
             .url = "git+https://github.com/Hejsil/zig-clap?ref=0.10.0#e47028deaefc2fb396d3d9e9f7bd776ae0b2a43a",
             .hash = "clap-0.10.0-oBajB434AQBDh-Ei3YtoKIRxZacVPF1iSwp3IX_ZB8f0",
         },
+        .gatorcat = .{
+            .url = "git+https://github.com/kj4tmp/gatorcat#bb1847f6c95852e7a0ec8c07870a948c171d5f98",
+            .hash = "gatorcat-0.3.2-WcrpTf1mBwDrmPaIhKCfLJO064v8Sjjn7DBq4CKZSgHH",
+        },
     },
     .paths = .{
         "build.zig",

include/zaprus.h

@@ -1,15 +0,0 @@
-// client
-
-#include<stdint.h>
-#include<stdlib.h>
-
-int zaprus_init(void);
-
-int zaprus_deinit(void);
-
-int zaprus_send_relay(const char* payload, size_t len, char dest[4]);
-
-int zaprus_send_initial_connection(const char* payload, size_t len, uint16_t initial_port);
-
-void* zaprus_connect(const char* payload, size_t len);
-

src/Client.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, '=');
+
 var rand: ?Random = null;
 
 pub fn init() !void {
@@ -14,9 +17,14 @@ pub fn deinit() void {
     network.deinit();
 }
 
-fn broadcastSaprusMessage(msg: SaprusMessage, udp_port: u16, allocator: Allocator) !void {
+fn broadcastSaprusMessage(msg: *SaprusMessage, udp_port: u16) !void {
-    const msg_bytes = try msg.toBytes(allocator);
+    if (false) {
-    defer allocator.free(msg_bytes);
+        var foo: gcat.nic.RawSocket = try .init("enp7s0"); // /proc/net/dev
+        defer foo.deinit();
+    }
+    const msg_bytes = msg.asBytes();
+    try msg.networkFromNativeEndian();
+    defer msg.nativeFromNetworkEndian() catch unreachable;
 
     var sock = try network.Socket.create(.ipv4, .udp);
     defer sock.close();
@@ -40,14 +48,15 @@ fn broadcastSaprusMessage(msg: SaprusMessage, udp_port: u16, allocator: Allocato
 }
 
 pub fn sendRelay(payload: []const u8, dest: [4]u8, allocator: Allocator) !void {
-    const msg = SaprusMessage{
+    const msg: *SaprusMessageNew(.relay) = try .init(
-        .relay = .{
+        allocator,
-            .header = .{ .dest = dest },
+        @intCast(base64Enc.calcSize(payload.len)),
-            .payload = payload,
+    );
-        },
+    defer msg.deinit(allocator);
-    };
+    msg.dest = dest;
+    _ = base64Enc.encode(msg.getPayload(), payload);
 
-    try broadcastSaprusMessage(msg, 8888, allocator);
+    try broadcastSaprusMessage(try SaprusMessage.bytesAsValue(msg.asBytes()), 8888);
 }
 
 fn randomPort() u16 {
@@ -59,31 +68,28 @@ fn randomPort() u16 {
     return p;
 }
 
-pub fn sendInitialConnection(payload: []const u8, initial_port: u16, allocator: Allocator) !SaprusMessage {
+pub fn sendInitialConnection(payload: []const u8, initial_port: u16, allocator: Allocator) !*SaprusMessage {
     const dest_port = randomPort();
-    const msg = SaprusMessage{
+    const msg: *SaprusMessage = try .init(allocator, .connection, @intCast(payload.len));
-        .connection = .{
+    defer msg.deinit(allocator);
-            .header = .{
+    const connection = (try msg.getSaprusTypePayload()).connection;
-                .src_port = initial_port,
+    connection.src_port = initial_port;
-                .dest_port = dest_port,
+    connection.dest_port = dest_port;
-            },
+    @memcpy(connection.getPayload(), payload);
-            .payload = payload,
-        },
-    };
 
-    try broadcastSaprusMessage(msg, 8888, allocator);
+    try broadcastSaprusMessage(msg, 8888);
 
     return msg;
 }
 
-pub fn connect(payload: []const u8, allocator: Allocator) !SaprusMessage {
+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;
 
     var initial_conn_res: ?SaprusMessage = null;
-    errdefer if (initial_conn_res) |c| c.deinit(allocator);
+    errdefer if (initial_conn_res) |*c| c.deinit(allocator);
 
     var sock = try network.Socket.create(.ipv4, .udp);
     defer sock.close();
@@ -100,19 +106,25 @@ pub fn connect(payload: []const u8, allocator: Allocator) !SaprusMessage {
 
     const msg = try sendInitialConnection(payload, initial_port, allocator);
 
-    var response_buf: [4096]u8 = undefined;
+    var response_buf: [4096]u8 align(4) = @splat(0);
     _ = try sock.receive(&response_buf); // Ignore message that I sent.
     const len = try sock.receive(&response_buf);
 
-    initial_conn_res = try SaprusMessage.fromBytes(response_buf[0..len], allocator);
+    std.debug.print("response bytes: {x}\n", .{response_buf});
+    initial_conn_res = (try SaprusMessage.bytesAsValue(response_buf[0..len])).*;
 
     // Complete handshake after awaiting response
-    try broadcastSaprusMessage(msg, randomPort(), allocator);
+    try broadcastSaprusMessage(msg, randomPort());
 
+    if (false) {
         return initial_conn_res.?;
+    }
+    return null;
 }
 
 const SaprusMessage = @import("message.zig").Message;
+const SaprusMessageNew = @import("message.zig").MessageNew;
+const SaprusConnection = @import("Connection.zig");
 
 const std = @import("std");
 const Random = std.Random;
@@ -120,5 +132,6 @@ const posix = std.posix;
 const mem = std.mem;
 
 const network = @import("network");
+const gcat = @import("gatorcat");
 
 const Allocator = mem.Allocator;

src/c_api.zig

@@ -1,32 +0,0 @@
-// client
-export fn zaprus_init() c_int {
-    SaprusClient.init() catch return 1;
-    return 0;
-}
-
-export fn zaprus_deinit() c_int {
-    SaprusClient.deinit();
-    return 0;
-}
-
-export fn zaprus_send_relay(payload: [*]const u8, len: usize, dest: [*]u8) c_int {
-    SaprusClient.sendRelay(payload[0..len], dest[0..4].*, allocator) catch return 1;
-    return 0;
-}
-
-export fn zaprus_connect(payload: [*]const u8, len: usize, output: *SaprusConnection) c_int {
-    output.* = (SaprusClient.connect(payload[0..len], allocator) catch return 1).?;
-    return 0;
-}
-
-const std = @import("std");
-
-const zaprus = @import("./root.zig");
-const SaprusClient = zaprus.Client;
-const SaprusConnection = zaprus.Connection;
-
-const allocator = std.heap.c_allocator;
-
-test {
-    std.testing.refAllDeclsRecursively(@This());
-}

src/main.zig

@@ -50,7 +50,7 @@ pub fn main() !void {
     }
 
     if (res.args.relay) |r| {
-        const dest = parseDest(res.args.dest) catch .{ 70, 70, 70, 70 };
+        const dest = parseDest(res.args.dest);
         try SaprusClient.sendRelay(
             if (r.len > 0) r else "Hello darkness my old friend",
             dest,
@@ -59,16 +59,10 @@ pub fn main() !void {
         // std.debug.print("Sent: {s}\n", .{r});
         return;
     } else if (res.args.connect) |c| {
-        const conn_res: ?SaprusMessage = SaprusClient.connect(if (c.len > 0) c else "Hello darkness my old friend", gpa) 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,
         };
-        defer if (conn_res) |r| r.deinit(gpa);
-        if (conn_res) |r| {
-            std.debug.print("{s}\n", .{r.connection.payload});
-        } else {
-            std.debug.print("No response from connection request\n", .{});
-        }
         return;
     }
 
@@ -86,7 +80,7 @@ fn parseDest(in: ?[]const u8) [4]u8 {
         const addr = std.net.Ip4Address.parse(dest, 0) catch return "FAIL".*;
         return @bitCast(addr.sa.addr);
     }
-    return "zap".*;
+    return "zap\x00".*;
 }
 
 const builtin = @import("builtin");

src/message.zig

@@ -1,6 +1,3 @@
-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) {
@@ -26,186 +23,317 @@ pub const ConnectionOptions = packed struct(u8) {
 pub const Error = error{
     NotImplementedSaprusType,
     UnknownSaprusType,
+    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
-pub const Message = union(PacketType) {
+pub const Message = packed struct {
-    pub const Relay = struct {
+    const Relay = packed struct {
-        pub const Header = 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.* - @sizeOf(Relay)];
+        }
     };
-        header: Header,
+    const Connection = packed struct {
-        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 = .{},
-        };
+        payload: void,
-        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 getPayload(self: *align(1) Connection) []u8 {
-    pub fn deinit(self: Message, allocator: Allocator) void {
+            const len: *u16 = @ptrFromInt(@intFromPtr(self) - @sizeOf(u16));
-        switch (self) {
+            return @as([*]u8, @ptrCast(&self.payload))[0 .. len.* - @sizeOf(Connection)];
-            .relay => |r| allocator.free(r.payload),
+        }
-            .connection => |c| allocator.free(c.payload),
+
+        fn nativeFromNetworkEndian(self: *align(1) Connection) 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 {
+            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);
+        }
+    };
+
+    const Self = @This();
+    const SelfBytes = []align(@alignOf(Self)) u8;
+
+    type: PacketType,
+    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);
+        const res: *Self = @ptrCast(bytes.ptr);
+        res.type = @"type";
+        res.length = payload_len + header_size;
+        return res;
+    }
+
+    pub fn deinit(self: *Self, allocator: Allocator) void {
+        allocator.free(self.asBytes());
+    }
+
+    fn getRelay(self: *Self) *align(1) Relay {
+        return std.mem.bytesAsValue(Relay, &self.bytes);
+    }
+    fn getConnection(self: *Self) *align(1) Connection {
+        return std.mem.bytesAsValue(Connection, &self.bytes);
+    }
+
+    pub fn getSaprusTypePayload(self: *Self) Error!(union(PacketType) {
+        relay: *align(1) Relay,
+        file_transfer: void,
+        connection: *align(1) Connection,
+    }) {
+        return switch (self.type) {
+            .relay => .{ .relay = self.getRelay() },
+            .connection => .{ .connection = self.getConnection() },
+            .file_transfer => Error.NotImplementedSaprusType,
+            else => Error.UnknownSaprusType,
+        };
+    }
+
+    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(),
+            // We know other values are unreachable,
+            // because they would have returned an error from the switch condition.
             else => unreachable,
         }
     }
 
-    fn toBytesAux(
+    pub fn networkFromNativeEndian(self: *Self) Error!void {
-        header: anytype,
+        try switch (try self.getSaprusTypePayload()) {
-        payload: []const u8,
+            .relay => {},
-        buf: *std.ArrayList(u8),
+            .connection => |*con| con.*.networkFromNativeEndian(),
-        allocator: Allocator,
+            .file_transfer => Error.NotImplementedSaprusType,
-    ) !void {
+            else => Error.UnknownSaprusType,
-        const Header = @TypeOf(header);
+        };
-        // Create a growable string to store the base64 bytes in.
+        self.type = @enumFromInt(nativeToBig(
-        // Doing this first so I can use the length of the encoded bytes for the length field.
+            @typeInfo(@TypeOf(self.type)).@"enum".tag_type,
-        var payload_list = std.ArrayList(u8).init(allocator);
+            @intFromEnum(self.type),
-        defer payload_list.deinit();
+        ));
-        const buf_w = payload_list.writer();
+        self.length = nativeToBig(@TypeOf(self.length), self.length);
-
-        // 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 bytesAsValue(bytes: SelfBytes) !*Self {
-    pub fn toBytes(self: Message, allocator: Allocator) ![]u8 {
+        const res = std.mem.bytesAsValue(Self, bytes);
-        // Create a growable list of bytes to store the output in.
+        return switch (res.type) {
-        var buf = std.ArrayList(u8).init(allocator);
+            .relay, .connection => if (bytes.len == res.length + @sizeOf(Self))
-        errdefer buf.deinit();
+                res
-
+            else
-        // Start with writing the message type, which is the first 16 bits of every Saprus message.
+                Error.InvalidMessage,
-        try buf.appendSlice(asBytes(&nativeToBig(u16, @intFromEnum(self))));
+            .file_transfer => Error.NotImplementedSaprusType,
-
+            else => Error.UnknownSaprusType,
-        // 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.
+    pub fn asBytes(self: *Self) SelfBytes {
-        return buf.toOwnedSlice();
+        const size = @sizeOf(Self) + self.length;
-    }
+        return @as([*]align(@alignOf(Self)) u8, @ptrCast(self))[0..size];
-
-    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,
-        }
     }
 };
 
+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 Message
+    const msg: *Message = try .init(gpa, .relay, payload.len);
+    defer msg.deinit(gpa);
+
+    {
+        // 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);
+    }
+
+    {
+        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});
+    }
+
+    if (false) {
+        // Illegal behavior
+        std.debug.print("{any}\n", .{(try msg.getSaprusTypePayload()).connection});
+    }
+
+    try std.testing.expectEqualDeep(msg, try Message.bytesAsValue(msg.asBytes()));
+}
+
 const std = @import("std");
 const Allocator = std.mem.Allocator;
 
 const asBytes = std.mem.asBytes;
 const nativeToBig = std.mem.nativeToBig;
+const bigToNative = std.mem.bigToNative;
 
-test "Round trip Relay toBytes and fromBytes" {
+test {
-    const gpa = std.testing.allocator;
+    std.testing.refAllDeclsRecursive(@This());
-    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);
-}
-
-test "Round trip Connection toBytes and fromBytes" {
-    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);
 }

src/root.zig

@@ -1,4 +1,4 @@
 pub const Client = @import("Client.zig");
-pub usingnamespace @import("message.zig");
+pub const Connection = @import("Connection.zig");
 
-pub usingnamespace @import("c_api.zig");
+pub usingnamespace @import("message.zig");