Need to flush io in release mode

we know the size (assuming the len is correct) so we can preallocate the whole array

src/main.zig

@@ -48,6 +48,8 @@ pub fn main() !void {
         return clap.help(std.io.getStdErr().writer(), clap.Help, &params, .{});
     }
 
+    std.debug.print("main\n", .{});
+
     if (res.args.relay) |r| {
         try Saprus.sendRelay(if (r.len > 0) r else "Hello darkness my old friend", gpa);
         std.debug.print("Sent: {s}\n", .{r});

src/saprus.zig

@@ -85,9 +85,11 @@ pub fn connect(payload: []const u8, allocator: Allocator) !?SaprusMessage {
     var initial_conn_res: ?SaprusMessage = null;
     errdefer if (initial_conn_res) |c| c.deinit(allocator);
 
+    std.debug.print("creating socket\n", .{});
     var sock = try network.Socket.create(.ipv4, .udp);
     defer sock.close();
 
+    std.debug.print("creating endpoint\n", .{});
     // Bind to 255.255.255.255:8888
     const bind_addr = network.EndPoint{
         .address = network.Address{ .ipv4 = network.Address.IPv4.broadcast },
@@ -96,8 +98,10 @@ pub fn connect(payload: []const u8, allocator: Allocator) !?SaprusMessage {
 
     // timeout 1s
     try sock.setReadTimeout(1 * std.time.us_per_s);
+    std.debug.print("binding to socket\n", .{});
     try sock.bind(bind_addr);
 
+    std.debug.print("sending initial connection payload\n", .{});
     const msg = try sendInitialConnection(payload, initial_port, allocator);
 
     var response_buf: [4096]u8 = undefined;

src/saprus_message.zig

@@ -117,12 +117,12 @@ pub const SaprusMessage = union(SaprusPacketType) {
 
     fn fromBytesAux(
         comptime packet: SaprusPacketType,
+        len: u16,
         r: std.io.FixedBufferStream([]const u8).Reader,
         allocator: Allocator,
     ) !SaprusMessage {
         const Header = @field(@FieldType(SaprusMessage, @tagName(packet)), "Header");
-        // Read the length of the header + base64 encoded payload.
-        const len = try r.readInt(u16, .big);
+
         // Read the header for the current message type.
         var header_bytes: [@sizeOf(Header)]u8 = undefined;
         _ = try r.read(header_bytes[0 .. @bitSizeOf(Header) / 8]);
@@ -130,13 +130,13 @@ pub const SaprusMessage = union(SaprusPacketType) {
         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.
-        var payload_buf = std.ArrayList(u8).init(allocator);
-        defer payload_buf.deinit();
-        try r.readAllArrayList(&payload_buf, len);
+        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.items));
-        try base64Dec.decode(payload, payload_buf.items);
+        const payload = try allocator.alloc(u8, try base64Dec.calcSizeForSlice(payload_buf));
+        try base64Dec.decode(payload, payload_buf);
 
         // Return the type of SaprusMessage specified by the `packet` argument.
         return @unionInit(SaprusMessage, @tagName(packet), .{
@@ -153,9 +153,12 @@ pub const SaprusMessage = union(SaprusPacketType) {
         // Read packet type
         const packet_type = @as(SaprusPacketType, @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, r, allocator),
-            .connection => return fromBytesAux(.connection, r, allocator),
+            .relay => return fromBytesAux(.relay, len, r, allocator),
+            .connection => return fromBytesAux(.connection, len, r, allocator),
             .file_transfer => return SaprusError.NotImplementedSaprusType,
             else => return SaprusError.UnknownSaprusType,
         }