Make C struct match the binary API more closely

Also make the internal conversion function return errors properly

build.zig

@@ -1,4 +1,5 @@
 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
@@ -33,18 +34,33 @@ 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 lib = b.addLibrary(.{
+    const static_lib = b.addLibrary(.{
         .linkage = .static,
         .name = "zaprus",
         .root_module = lib_mod,
     });
+    static_lib.addIncludePath(.{ .cwd_relative = "include" });
+    static_lib.linkLibC();
 
-    b.installArtifact(lib);
+    b.installArtifact(static_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

@@ -44,10 +44,6 @@
             .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

@@ -0,0 +1,51 @@
+// 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);
+
+struct SaprusMessage* zaprus_connect(const char* payload, size_t len);
+
+// message
+#define SAPRUS_RELAY_MESSAGE_TYPE 0x003C
+#define SAPRUS_FILE_TRANSFER_MESSAGE_TYPE 0x8888
+#define SAPRUS_CONNECTION_MESSAGE_TYPE 0x00E9
+
+struct SaprusMessage {
+  uint16_t packet_type;
+  uint16_t payload_len;
+  union {
+    struct {
+      struct {
+	char dest[4];
+      };
+    } relay;
+    struct {
+      struct {
+	uint16_t src_port;
+	uint16_t dest_port;
+	uint32_t seq_num;
+	uint32_t msg_id;
+	char _reserved;
+	char options;
+      };
+      
+    } connection;
+  } headers;
+  char *payload;
+};
+
+// ptr should be freed by the caller.
+int zaprus_message_to_bytes(struct SaprusMessage msg, char** ptr, size_t* len);
+
+// Return value should be destroyed with zaprus_message_deinit.
+struct SaprusMessage* zaprus_message_from_bytes(const char* bytes, size_t len);
+
+void zaprus_message_deinit(struct SaprusMessage* msg);

src/Client.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, '=');
-
 var rand: ?Random = null;
 
 pub fn init() !void {
@@ -17,14 +14,9 @@ pub fn deinit() void {
     network.deinit();
 }
 
-fn broadcastSaprusMessage(msg: *SaprusMessage, udp_port: u16) !void {
-    if (false) {
-        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;
+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();
@@ -48,22 +40,14 @@ fn broadcastSaprusMessage(msg: *SaprusMessage, udp_port: u16) !void {
 }
 
 pub fn sendRelay(payload: []const u8, dest: [4]u8, allocator: Allocator) !void {
-    const msg_bytes = try allocator.alignedAlloc(
-        u8,
-        @alignOf(SaprusMessage),
-        try SaprusMessage.lengthForPayloadLength(
-            .relay,
-            base64Enc.calcSize(payload.len),
-        ),
-    );
-    defer allocator.free(msg_bytes);
-    const msg: *SaprusMessage = .init(.relay, msg_bytes);
+    const msg = SaprusMessage{
+        .relay = .{
+            .header = .{ .dest = dest },
+            .payload = payload,
+        },
+    };
 
-    const relay = (try msg.getSaprusTypePayload()).relay;
-    relay.dest = dest;
-    _ = base64Enc.encode(relay.getPayload(), payload);
-
-    try broadcastSaprusMessage(msg, 8888);
+    try broadcastSaprusMessage(msg, 8888, allocator);
 }
 
 fn randomPort() u16 {
@@ -75,36 +59,31 @@ 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_bytes = try allocator.alignedAlloc(
-        u8,
-        @alignOf(SaprusMessage),
-        try SaprusMessage.lengthForPayloadLength(
-            .connection,
-            base64Enc.calcSize(payload.len),
-        ),
-    );
+    const msg = SaprusMessage{
+        .connection = .{
+            .header = .{
+                .src_port = initial_port,
+                .dest_port = dest_port,
+            },
+            .payload = payload,
+        },
+    };
 
-    const msg: *SaprusMessage = .init(.connection, msg_bytes);
-
-    const connection = (try msg.getSaprusTypePayload()).connection;
-    connection.src_port = initial_port;
-    connection.dest_port = dest_port;
-    _ = base64Enc.encode(connection.getPayload(), payload);
-
-    try broadcastSaprusMessage(msg, 8888);
+    try broadcastSaprusMessage(msg, 8888, allocator);
 
     return msg;
 }
 
-pub fn connect(payload: []const u8, allocator: Allocator) !?SaprusConnection {
+pub fn connect(payload: []const u8, allocator: Allocator) !?SaprusMessage {
     var initial_port: u16 = 0;
     if (rand) |r| {
         initial_port = r.intRangeAtMost(u16, 1024, 65000);
     } else unreachable;
 
-    var initial_conn_res: ?*SaprusMessage = null;
+    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();
@@ -120,26 +99,20 @@ pub fn connect(payload: []const u8, allocator: Allocator) !?SaprusConnection {
     try sock.bind(bind_addr);
 
     const msg = try sendInitialConnection(payload, initial_port, allocator);
-    defer allocator.free(msg.asBytes());
 
-    var response_buf: [4096]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);
 
-    std.debug.print("response bytes: {x}\n", .{response_buf[0..len]});
-    initial_conn_res = SaprusMessage.init(.connection, response_buf[0..len]);
+    initial_conn_res = try SaprusMessage.fromBytes(response_buf[0..len], allocator);
 
     // Complete handshake after awaiting response
-    try broadcastSaprusMessage(msg, randomPort());
+    try broadcastSaprusMessage(msg, randomPort(), allocator);
 
-    if (false) {
-        return initial_conn_res.?;
-    }
-    return null;
+    return initial_conn_res;
 }
 
 const SaprusMessage = @import("message.zig").Message;
-const SaprusConnection = @import("Connection.zig");
 
 const std = @import("std");
 const Random = std.Random;
@@ -147,6 +120,5 @@ const posix = std.posix;
 const mem = std.mem;
 
 const network = @import("network");
-const gcat = @import("gatorcat");
 
 const Allocator = mem.Allocator;

src/c_api.zig

@@ -0,0 +1,115 @@
+const c = @cImport({
+    @cInclude("zaprus.h");
+});
+
+fn zigToCMessage(msg: ?*zaprus.Message) !?*c.SaprusMessage {
+    if (msg) |m| {
+        var res = c.SaprusMessage{
+            .packet_type = @intFromEnum(m.*),
+        };
+        switch (m.*) {
+            .relay => |r| {
+                res.headers.relay = .{
+                    .unnamed_0 = .{
+                        .dest = r.header.dest,
+                    },
+                };
+                res.payload_len = @intCast(r.payload.len);
+                res.payload = (try allocator.alloc(u8, r.payload.len)).ptr;
+            },
+            .connection => |con| {
+                res.headers.connection = .{
+                    .unnamed_0 = .{
+                        .src_port = con.header.src_port,
+                        .dest_port = con.header.dest_port,
+                        .seq_num = con.header.seq_num,
+                        .msg_id = con.header.msg_id,
+                        ._reserved = con.header.reserved,
+                        .options = @bitCast(con.header.options),
+                    },
+                };
+
+                res.payload_len = @intCast(con.payload.len);
+                res.payload = (try allocator.alloc(u8, con.payload.len)).ptr;
+            },
+            .file_transfer => return zaprus.Error.NotImplementedSaprusType,
+            else => return zaprus.Error.UnknownSaprusType,
+        }
+        return &res;
+    } else return null;
+}
+
+fn cToZigMessage(msg: ?*c.SaprusMessage) ?*zaprus.Message {
+    _ = msg;
+    return @constCast(&zaprus.Message{
+        .relay = .{
+            .header = .{ .dest = @splat(0) },
+            .payload = &.{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_send_initial_connection(payload: [*]const u8, len: usize, initial_port: u16) c_int {
+    _ = SaprusClient.sendInitialConnection(payload[0..len], initial_port, allocator) catch return 1;
+    return 0;
+}
+
+export fn zaprus_connect(payload: [*]const u8, len: usize) ?*c.SaprusMessage {
+    if (SaprusClient.connect(payload[0..len], allocator)) |msg| {
+        return zigToCMessage(@constCast(&(msg.?))) catch null;
+    } else |_| {
+        return null;
+    }
+}
+
+// message
+
+/// ptr should be freed by the caller.
+export fn zaprus_message_to_bytes(msg: c.SaprusMessage, ptr: *[*]u8, len: *usize) c_int {
+    if (cToZigMessage(@constCast(&msg))) |m| {
+        const bytes = m.toBytes(allocator) catch return 1;
+        ptr.* = bytes.ptr;
+        len.* = bytes.len;
+        return 0;
+    } else return 1;
+}
+
+/// Return value should be destroyed with zaprus_message_deinit.
+export fn zaprus_message_from_bytes(bytes: [*]const u8, len: usize) ?*c.SaprusMessage {
+    if (zaprus.Message.fromBytes(bytes[0..len], allocator)) |msg| {
+        return zigToCMessage(@constCast(&msg)) catch null;
+    } else |_| return null;
+}
+
+export fn zaprus_message_deinit(msg: *c.SaprusMessage) void {
+    // noop
+    _ = msg;
+    // msg.*.deinit(allocator);
+}
+
+const std = @import("std");
+
+const zaprus = @import("./root.zig");
+const SaprusClient = zaprus.Client;
+
+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);
+        const dest = parseDest(res.args.dest) catch .{ 70, 70, 70, 70 };
         try SaprusClient.sendRelay(
             if (r.len > 0) r else "Hello darkness my old friend",
             dest,
@@ -59,17 +59,23 @@ pub fn main() !void {
         // 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) {
+        const conn_res: ?SaprusMessage = 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;
     }
 
     return clap.help(std.io.getStdErr().writer(), clap.Help, &params, .{});
 }
 
-fn parseDest(in: ?[]const u8) [4]u8 {
+fn parseDest(in: ?[]const u8) ![4]u8 {
     if (in) |dest| {
         if (dest.len <= 4) {
             var res: [4]u8 = @splat(0);
@@ -77,10 +83,10 @@ fn parseDest(in: ?[]const u8) [4]u8 {
             return res;
         }
 
-        const addr = std.net.Ip4Address.parse(dest, 0) catch return "FAIL".*;
+        const addr = try std.net.Ip4Address.parse(dest, 0);
         return @bitCast(addr.sa.addr);
     }
-    return "zap\x00".*;
+    return .{ 70, 70, 70, 70 };
 }
 
 const builtin = @import("builtin");

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) {
@@ -20,195 +23,153 @@ 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 {
-    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.* - @sizeOf(Relay)];
-        }
-    };
-    const Connection = 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,
-
-        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)];
-        }
-
-        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 = {},
-
-    /// Takes a byte slice, and returns a Message struct backed by the slice.
-    /// This properly initializes the top level headers within the slice.
-    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 = @intCast(bytes.len - @sizeOf(Self));
-        return res;
-    }
-
-    pub fn lengthForPayloadLength(comptime @"type": PacketType, payload_len: usize) MessageTypeError!u16 {
-        std.debug.assert(payload_len < std.math.maxInt(u16));
-        const header_size = @sizeOf(switch (@"type") {
-            .relay => Relay,
-            .connection => Connection,
-            .file_transfer => return MessageTypeError.NotImplementedSaprusType,
-            else => return MessageTypeError.UnknownSaprusType,
-        });
-        return @intCast(payload_len + @sizeOf(Self) + header_size);
-    }
-
-    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) MessageTypeError!(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 => MessageTypeError.NotImplementedSaprusType,
-            else => MessageTypeError.UnknownSaprusType,
+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,
 
-    pub fn nativeFromNetworkEndian(self: *Self) MessageTypeError!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.
+    /// 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,
         }
     }
 
-    pub fn networkFromNativeEndian(self: *Self) MessageTypeError!void {
-        try switch (try self.getSaprusTypePayload()) {
-            .relay => {},
-            .connection => |*con| con.*.networkFromNativeEndian(),
-            .file_transfer => MessageTypeError.NotImplementedSaprusType,
-            else => MessageTypeError.UnknownSaprusType,
-        };
-        self.type = @enumFromInt(nativeToBig(
-            @typeInfo(@TypeOf(self.type)).@"enum".tag_type,
-            @intFromEnum(self.type),
-        ));
-        self.length = nativeToBig(@TypeOf(self.length), self.length);
+    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);
     }
 
-    /// 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];
+    /// 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,
+        }
     }
 };
 
-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" {
     const gpa = std.testing.allocator;
@@ -248,7 +209,3 @@ test "Round trip Connection toBytes and fromBytes" {
 
     try std.testing.expectEqualDeep(msg, from_bytes);
 }
-
-test {
-    std.testing.refAllDeclsRecursive(@This());
-}

src/root.zig

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