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, 53 insertions, 0 deletions

diff --git a/src/wl/shm/anonymous-file.zig b/src/wl/shm/anonymous-file.zig
new file mode 100644
index 0000000..f73fbc9
--- /dev/null
+++ b/src/wl/shm/anonymous-file.zig
@@ -0,0 +1,53 @@
+const std = @import("std");
+
+const Self = @This();
+
+size: usize = 0,
+name: [24]u8 = undefined,
+fd: std.posix.fd_t = undefined,
+
+pub fn init_random() !Self {
+    var buf: [8]u8 = undefined;
+    try std.posix.getrandom(&buf);
+
+    var self: Self = .{};
+
+    const name = std.fmt.bufPrint(&self.name, "/wl.shm.{x}{x}{x}{x}{x}{x}{x}{x}", .{
+        buf[0],
+        buf[1],
+        buf[2],
+        buf[3],
+        buf[4],
+        buf[5],
+        buf[6],
+        buf[7],
+    }) catch unreachable;
+
+    self.fd = try std.posix.memfd_create(name, 0);
+
+    return self;
+}
+
+pub fn truncate(self: *Self, size: usize) !void {
+    try std.posix.ftruncate(self.fd, size);
+    self.size = size;
+}
+
+pub fn mmap(self: *Self) ![]u8 {
+    return std.posix.mmap(
+        null,
+        self.size,
+        std.os.linux.PROT.READ | std.os.linux.PROT.WRITE,
+        .{
+            .TYPE = .SHARED,
+            .ANONYMOUS = true,
+        },
+        self.fd,
+        0,
+    );
+}
+
+pub fn close(self: *Self) void {
+    std.posix.close(self.fd);
+    self.* = undefined;
+}