From 0a4c945e48717b24fdb6416e47bbb2fa2a7372b4 Mon Sep 17 00:00:00 2001
From: Nathan Reiner <nathan@nathanreiner.xyz>
Date: Sat, 23 Aug 2025 08:06:17 +0200
Subject: add Fd type for requests

This is not tested code, since there are no requests
implemented yet using file descriptors.
---
 src/ancillary-data.zig | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++
 src/types.zig          |  4 +++-
 src/wl/display.zig     |  9 +++++++
 3 files changed, 77 insertions(+), 1 deletion(-)
 create mode 100644 src/ancillary-data.zig

(limited to 'src')

diff --git a/src/ancillary-data.zig b/src/ancillary-data.zig
new file mode 100644
index 0000000..0754720
--- /dev/null
+++ b/src/ancillary-data.zig
@@ -0,0 +1,65 @@
+const std = @import("std");
+
+const ControlMessage = extern struct {
+    const Level = enum(u32) {
+        socket = std.posix.SOL.SOCKET,
+    };
+
+    // WARNING: this kind enum might be wrong for non-linux posix systems.
+    const Kind = enum(u32) {
+        rights = 1,
+        credentials = 2,
+    };
+
+    const Header = extern struct {
+        length: usize,
+        level: Level,
+        kind: Kind,
+    };
+
+    header: Header,
+    payload: union {
+        fd: [255]std.posix.fd_t,
+    },
+
+    pub fn alignment(length: usize) usize {
+        return (length + @sizeOf(usize) - 1) & ~(@sizeOf(usize) - 1);
+    }
+
+    pub fn space(self: @This()) usize {
+        return self.alignment(self.length) + self.alignment(@sizeOf(Header));
+    }
+
+    pub fn from_fds(fds: []std.posix.fd_t) @This() {
+        var self: @This() = .{
+        };
+
+        self.level = .socket;
+        self.kind = .rights;
+        self.length = self.alignment(@sizeOf(Header)) + (fds.len * @sizeOf(std.posix.fd_t));
+
+        @memcpy(self.payload, fds);
+    }
+};
+
+pub fn send_fds(socket: std.posix.socket_t, fds: []std.posix.fd_t) !void {
+    var iobuf: [1]u8 = std.mem.zeroes([1]u8);
+
+    const io = std.posix.iovec {
+        .base = &iobuf,
+        .len = iobuf.len,
+    };
+
+    var cmsg: ControlMessage = .from_fds(fds);
+
+    const msghdr = std.posix.msghdr_const {
+        .name = null,
+        .namelen = 0,
+        .iov = &io,
+        .iolen = 1,
+        .control = &cmsg,
+        .controllen = cmsg.control_length(),
+    };
+
+    _ = try std.posix.sendmsg(socket, &msghdr, 0);
+}
diff --git a/src/types.zig b/src/types.zig
index 2849af1..023f319 100644
--- a/src/types.zig
+++ b/src/types.zig
@@ -1,6 +1,8 @@
 const std = @import("std");
 
-pub const Fd = struct { fd: std.posix.fd_t };
+pub const Fd = struct {
+    fd: std.posix.fd_t
+};
 
 pub const Fixed = struct {
     n: u24,
diff --git a/src/wl/display.zig b/src/wl/display.zig
index db5ed3c..ed4a94f 100644
--- a/src/wl/display.zig
+++ b/src/wl/display.zig
@@ -1,6 +1,7 @@
 const std = @import("std");
 const wayland = @import("../root.zig");
 const wl = wayland.wl;
+const ancillary_data = @import("../ancillary-data.zig");
 
 const log = std.log.scoped(.display);
 
@@ -85,6 +86,7 @@ pub fn request(self: *Self, object: anytype, args: @TypeOf(object.*).Request) !v
             const id: u32 = @truncate(object.handle);
 
             var size: u32 = 8;
+            comptime var fds: []std.posix.fd_t = &.{};
 
             inline for (data) |value| {
                 switch (@TypeOf(value)) {
@@ -94,6 +96,7 @@ pub fn request(self: *Self, object: anytype, args: @TypeOf(object.*).Request) !v
                         const padding_size: usize = padding_len(u8, value.len + 1);
                         size += @as(u32, @intCast(@sizeOf(u32) + (value.len + 1) + padding_size));
                     },
+                    wayland.types.Fd => |fd| fds = fds ++ .{ fd },
                     else => |t| switch (@typeInfo(t)) {
                         .pointer => |ptr| if (ptr.size == .slice) {
                             const padding_size: usize = padding_len(ptr.child, value.len);
@@ -119,6 +122,7 @@ pub fn request(self: *Self, object: anytype, args: @TypeOf(object.*).Request) !v
                             _ = try self.stream.writeAll(std.mem.asBytes(&@as(u8, 0)));
                         }
                     },
+                    wayland.types.Fd => {},
                     else => |t| switch (@typeInfo(t)) {
                         .pointer => |ptr| if (ptr.size == .slice) {
                             const padding_size: usize = @mod(@as(usize, @bitCast(-@as(isize, @intCast(value.len * @sizeOf(ptr.child))))), 4);
@@ -132,6 +136,11 @@ pub fn request(self: *Self, object: anytype, args: @TypeOf(object.*).Request) !v
                     },
                 }
             }
+
+            if (fds.len > 0) {
+                try ancillary_data.send_fds(self.stream.handle, fds);
+            }
+
             return;
         }
     }
-- 
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