Working with nice union

This let's us easily use a single type for all Saprus messages, and unwrap the specific type with a switch.

src/main.zig

@@ -9,33 +9,30 @@ const SaprusPacketType = enum(u16) {
     file_transfer = 0x8888,
 };
 
-const SaprusHeaderFrame = struct {
-    msg_type: SaprusPacketType,
-    payload: []u8,
+const SaprusMessage = union(SaprusPacketType) {
+    relay: struct {
+        dest: [4]u8,
+        payload: []u8,
+    },
+    file_transfer: void, // unimplemented
 
     const Self = @This();
 
     fn toBytes(s: Self, allocator: Allocator) ![]u8 {
-        const buf = try allocator.alloc(u8, 4 + s.payload.len);
-        std.mem.writeInt(u16, buf[0..2], @intFromEnum(s.msg_type), .big);
-        std.mem.writeInt(u16, buf[2..4], @intCast(s.payload.len), .big);
-        std.mem.copyForwards(u8, buf[4..], s.payload);
-        return buf;
-    }
-};
+        var buf = std.ArrayList(u8).init(allocator);
+        const w = buf.writer();
+        try w.writeInt(u16, @intFromEnum(@as(SaprusPacketType, s)), .big);
 
-const SaprusRelayMessage = struct {
-    dest: [4]u8,
-    payload: []u8,
+        switch (s) {
+            .relay => |relay| {
+                try w.writeAll(&relay.dest);
+                try w.writeInt(u16, @intCast(relay.payload.len), .big);
+                try w.writeAll(relay.payload);
+            },
+            .file_transfer => unreachable,
+        }
 
-    const Self = @This();
-
-    fn toBytes(s: Self, allocator: Allocator) ![]u8 {
-        const buf = try allocator.alloc(u8, 4 + s.payload.len);
-        std.mem.copyForwards(u8, buf[0..4], &s.dest);
-        std.mem.copyForwards(u8, buf[4..], s.payload);
-        std.debug.print("in tobytes {x}\n", .{buf});
-        return buf;
+        return buf.toOwnedSlice();
     }
 };
 
@@ -48,22 +45,13 @@ pub fn main() !void {
 
     var allocator = if (dba) |*d| d.allocator() else std.heap.smp_allocator;
 
-    const str_msg = "Hello darkness my old friend";
-    var payload_bytes: [str_msg.len + 1]u8 = @splat(0);
-    // const payload_bytes = try allocator.alloc(u8, str_msg.len);
-    // defer allocator.free(payload_bytes);
-    // std.mem.copyForwards(u8, payload_bytes[0..], str_msg);
-    std.mem.copyBackwards(u8, payload_bytes[0..], str_msg);
-    const relay: SaprusRelayMessage = .{
-        .dest = [_]u8{ 255, 255, 255, 255 },
-        .payload = payload_bytes[0..str_msg.len],
-    };
-    const relay_bytes = try relay.toBytes(allocator);
-    defer allocator.free(relay_bytes);
-    const msg: SaprusHeaderFrame = .{
-        .msg_type = .relay,
-        .payload = relay_bytes,
+    const msg = SaprusMessage{
+        .relay = .{
+            .dest = .{ 255, 255, 255, 255 },
+            .payload = @ptrCast(@constCast("Hello darkness my old friend")),
+        },
     };
+
     const msg_bytes = try msg.toBytes(allocator);
     defer allocator.free(msg_bytes);
 
@@ -88,25 +76,7 @@ pub fn main() !void {
 
     try sock.bind(bind_addr);
 
-    // std.debug.print("relay: {x}\n", .{relay_bytes});
-    std.debug.print("message bytes: {x}\n", .{msg_bytes});
-
-    // @breakpoint();
     _ = try sock.sendTo(dest_addr, msg_bytes);
-
-    // // Prints to stderr (it's a shortcut based on `std.io.getStdErr()`)
-    // std.debug.print("All your {any} are belong to us.\n", .{msg});
-
-    // // stdout is for the actual output of your application, for example if you
-    // // are implementing gzip, then only the compressed bytes should be sent to
-    // // stdout, not any debugging messages.
-    // const stdout_file = std.io.getStdOut().writer();
-    // var bw = std.io.bufferedWriter(stdout_file);
-    // const stdout = bw.writer();
-
-    // try stdout.print("Run `zig build test` to run the tests.\n", .{});
-
-    // try bw.flush(); // Don't forget to flush!
 }
 
 test "simple test" {