Add ancillary data mechanism to send fds to compositor.

Currently we are just attaching the fds to the object id.
In theory this is not a valid implementation, since if we
have more than MAX_FD file descriptors this will not work.
But since this wont be the case in basically all cases of
the wayland protocol, we can just ignore that for now.

1 files changed, 19 insertions, 19 deletions

diff --git a/src/ancillary-data.zig b/src/ancillary-data.zig
index 0754720..667ba1f 100644
--- a/src/ancillary-data.zig
+++ b/src/ancillary-data.zig
@@ -18,47 +18,47 @@ const ControlMessage = extern struct {
     };
 
     header: Header,
-    payload: union {
+    payload: extern union {
         fd: [255]std.posix.fd_t,
     },
 
     pub fn alignment(length: usize) usize {
-        return (length + @sizeOf(usize) - 1) & ~(@sizeOf(usize) - 1);
+        return (length + @sizeOf(usize) - 1) & ~(@as(usize, @sizeOf(usize) - 1));
     }
 
-    pub fn space(self: @This()) usize {
-        return self.alignment(self.length) + self.alignment(@sizeOf(Header));
+    pub fn space(length: usize) usize {
+        return alignment(length) + alignment(@sizeOf(Header));
     }
 
     pub fn from_fds(fds: []std.posix.fd_t) @This() {
-        var self: @This() = .{
-        };
+        var self: @This() = undefined;
 
-        self.level = .socket;
-        self.kind = .rights;
-        self.length = self.alignment(@sizeOf(Header)) + (fds.len * @sizeOf(std.posix.fd_t));
+        self.header.level = .socket;
+        self.header.kind = .rights;
+        self.header.length = alignment(@sizeOf(Header)) + (fds.len * @sizeOf(std.posix.fd_t));
 
-        @memcpy(self.payload, fds);
+        @memcpy(self.payload.fd[0..fds.len], fds);
+
+        return self;
     }
 };
 
-pub fn send_fds(socket: std.posix.socket_t, fds: []std.posix.fd_t) !void {
-    var iobuf: [1]u8 = std.mem.zeroes([1]u8);
+pub fn send_fds(socket: std.posix.socket_t, fds: []std.posix.fd_t, data: []const u8) !void {
+    var cmsg: ControlMessage = .from_fds(fds);
 
     const io = std.posix.iovec {
-        .base = &iobuf,
-        .len = iobuf.len,
+        .base = @constCast(@ptrCast(data)),
+        .len = data.len,
     };
 
-    var cmsg: ControlMessage = .from_fds(fds);
-
     const msghdr = std.posix.msghdr_const {
         .name = null,
         .namelen = 0,
-        .iov = &io,
-        .iolen = 1,
+        .iov = @ptrCast(&io),
+        .iovlen = 1,
         .control = &cmsg,
-        .controllen = cmsg.control_length(),
+        .controllen = @intCast(ControlMessage.space(fds.len)),
+        .flags = 0,
     };
 
     _ = try std.posix.sendmsg(socket, &msghdr, 0);