feat: recieve file descriptors

Feels super hacky, but I'm not sure there is a better way to handle
it. The crux of the problem is that wayland does not seem to make any
guarantees about the location of file descriptors.

examples/01_client_connect.zig

@@ -128,7 +128,7 @@ pub fn main() !void {
                     std.debug.print("<- wl_seat.name = {s}\n", .{name.name});
                 },
             }
-        } else if (header.object_id == 1) {
+        } else if (header.object_id == DISPLAY_ID) {
             const event = try wayland.deserialize(wayland.core.Display.Event, header, body);
             switch (event) {
                 .@"error" => |err| std.debug.print("<- error({}): {} {s}\n", .{ err.object_id, err.code, err.message }),
@@ -304,12 +304,19 @@ pub fn main() !void {
         } else if (header.object_id == wl_keyboard_id) {
             const event = try wayland.deserialize(wayland.core.Keyboard.Event, header, body);
             switch (event) {
-                // .keymap => |keymap| {},
+                .keymap => |keymap| {
+                    const fd = conn.fd_queue.orderedRemove(0);
+                    std.debug.print("keymap format={}, size={}, fd={}\n", .{
+                        keymap.format,
+                        keymap.size,
+                        fd,
+                    });
+                },
                 else => {
                     std.debug.print("<- wl_keyboard@{}\n", .{event});
                 },
             }
-        } else if (header.object_id == 1) {
+        } else if (header.object_id == DISPLAY_ID) {
             const event = try wayland.deserialize(wayland.core.Display.Event, header, body);
             switch (event) {
                 .@"error" => |err| std.debug.print("<- error({}): {} {s}\n", .{ err.object_id, err.code, err.message }),

src/main.zig

@@ -113,7 +113,7 @@ pub fn deserializeArguments(comptime Signature: type, buffer: []const u32) !Sign
     var result: Signature = undefined;
     var pos: usize = 0;
     inline for (std.meta.fields(Signature)) |field| {
-        if (field.type == types.Fd) continue; // Must be handled
+        if (field.type == types.Fd) continue;
         switch (@typeInfo(field.type)) {
             .Int => |int_info| switch (int_info.signedness) {
                 .signed => @field(result, field.name) = try readInt(buffer, &pos),
@@ -458,6 +458,7 @@ pub const Conn = struct {
     allocator: std.mem.Allocator,
     send_buffer: []u32,
     recv_buffer: []u32,
+    fd_queue: std.ArrayListUnmanaged(std.os.fd_t),
     socket: std.net.Stream,
 
     pub fn init(alloc: std.mem.Allocator, display_path: []const u8) !Conn {
@@ -467,6 +468,7 @@ pub const Conn = struct {
             .allocator = alloc,
             .send_buffer = send_buffer,
             .recv_buffer = recv_buffer,
+            .fd_queue = .{},
             .socket = try std.net.connectUnixSocket(display_path),
         };
     }
@@ -474,6 +476,7 @@ pub const Conn = struct {
     pub fn deinit(conn: *Conn) void {
         conn.allocator.free(conn.send_buffer);
         conn.allocator.free(conn.recv_buffer);
+        conn.fd_queue.deinit(conn.allocator);
         conn.socket.close();
     }
 
@@ -526,21 +529,58 @@ pub const Conn = struct {
 
     pub const Message = struct { Header, []const u32 };
     pub fn recv(conn: *Conn) !Message {
-        // TODO: recvmesg and read fds
+        // TODO: make this less messy
+        // Read header
+        @memset(conn.recv_buffer, 0);
+        var iov: [1]std.os.iovec = .{.{
+            .iov_base = std.mem.sliceAsBytes(conn.recv_buffer).ptr,
+            .iov_len = @sizeOf(Header),
+        }};
+        var control_msg: cmsg(std.os.fd_t) = undefined;
+        const control_bytes = std.mem.asBytes(&control_msg);
+        var socket_msg = std.os.msghdr{
+            .name = null,
+            .namelen = 0,
+            .iov = &iov,
+            .iovlen = iov.len,
+            .control = control_bytes.ptr,
+            .controllen = @intCast(control_bytes.len),
+            .flags = 0,
+        };
+
+        const size = std.os.linux.recvmsg(conn.socket.handle, &socket_msg, 0);
+
+        if (size < @sizeOf(Header)) return error.SocketClosed;
+
         var header: Header = undefined;
-        const header_bytes_read = try conn.socket.readAll(std.mem.asBytes(&header));
-        if (header_bytes_read < @sizeOf(Header)) {
-            return error.SocketClosed;
+        @memcpy(std.mem.asBytes(&header), iov[0].iov_base[0..@sizeOf(Header)]);
+
+        if (socket_msg.controllen != 0) {
+            try conn.fd_queue.append(conn.allocator, control_msg.data);
         }
 
-        const msg_size = (header.size_and_opcode.size - @sizeOf(Header)) / @sizeOf(u32);
-        if (msg_size > conn.recv_buffer.len) {
-            var new_size = conn.recv_buffer.len * 2;
-            while (new_size < msg_size) new_size *= 2;
-            conn.recv_buffer = try conn.allocator.realloc(conn.recv_buffer, new_size);
+        // Read body
+        const body_size = (header.size_and_opcode.size - @sizeOf(Header)) / @sizeOf(u32);
+
+        iov[0] = .{
+            .iov_base = std.mem.sliceAsBytes(conn.recv_buffer).ptr,
+            .iov_len = body_size * @sizeOf(u32),
+        };
+        socket_msg = std.os.msghdr{
+            .name = null,
+            .namelen = 0,
+            .iov = &iov,
+            .iovlen = iov.len,
+            .control = control_bytes.ptr,
+            .controllen = @intCast(control_bytes.len),
+            .flags = 0,
+        };
+        const size2 = std.os.linux.recvmsg(conn.socket.handle, &socket_msg, 0);
+        const message = conn.recv_buffer[0 .. size2 / @sizeOf(u32)];
+
+        if (socket_msg.controllen != 0) {
+            try conn.fd_queue.append(conn.allocator, control_msg.data);
         }
-        const bytes_read = try conn.socket.readAll(std.mem.sliceAsBytes(conn.recv_buffer[0..msg_size]));
-        const message = conn.recv_buffer[0 .. bytes_read / @sizeOf(u32)];
 
         return .{ header, message };
     }