src/message.zig

@@ -28,6 +28,59 @@ pub const Error = error{
     UnknownSaprusType,
 };
 
+// ZERO COPY STUFF
+// &payload could be a void value that is treated as a pointer to a [*]u8
+pub const ZeroCopyMessage = packed struct {
+    pub const Relay = packed struct {
+        dest: @Vector(4, u8),
+        /// @as([*]u8, @ptrCast(&payload))
+        payload: void,
+    };
+    pub 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,
+    };
+
+    const Self = @This();
+
+    type: PacketType,
+    length: u16,
+    bytes: void = {},
+
+    fn getRelay(self: *align(1) Self) *align(1) const Relay {
+        return std.mem.bytesAsValue(Relay, &self.bytes);
+    }
+    fn getConnection(self: *align(1) Self) *align(1) const Connection {
+        return std.mem.bytesAsValue(Connection, &self.bytes);
+    }
+};
+
+test "testing variable length zero copy struct" {
+    const gpa = std.testing.allocator;
+    const bytes = try gpa.alloc(u8, @sizeOf(ZeroCopyMessage) + 64);
+    defer gpa.free(bytes);
+    // const zcm = std.mem.bytesAsValue(ZeroCopyMessage, bytes).*;
+    const zcm: *align(1) ZeroCopyMessage = @ptrCast(bytes.ptr);
+    // @compileLog(@typeInfo(@TypeOf(ZeroCopyMessage{ .type = .relay, .length = 0 })));
+    // @compileLog(@typeInfo(@TypeOf(zcm)));
+    // _ = zcm;
+    zcm.type = .relay;
+    zcm.length = 3;
+    std.debug.print("{any}\n", .{zcm});
+    std.debug.print("{any}\n", .{zcm.getRelay()});
+    std.debug.print("{any}\n", .{zcm.getConnection()});
+    std.debug.print("{x}\n", .{std.mem.asBytes(zcm.getConnection())});
+    std.debug.print("{x}\n", .{std.mem.asBytes(zcm.getRelay())});
+    std.debug.print("{x}\n", .{bytes});
+
+    try std.testing.expect(true);
+}
+
 /// All Saprus messages
 pub const Message = union(PacketType) {
     pub const Relay = struct {
@@ -209,3 +262,7 @@ test "Round trip Connection toBytes and fromBytes" {
 
     try std.testing.expectEqualDeep(msg, from_bytes);
 }
+
+test {
+    std.testing.refAllDeclsRecursive(@This());
+}