dirAccess

fn dirAccess(
    userdata: ?*anyopaque,
    dir: Dir,
    sub_path: []const u8,
    options: Dir.AccessOptions,
) Dir.AccessError!void {
    const ev: *Evented = @ptrCast(@alignCast(userdata));

    var path_buffer: [PATH_MAX]u8 = undefined;
    const sub_path_posix = try pathToPosix(sub_path, &path_buffer);

    const mode: u32 =
        @as(u32, if (options.read) linux.R_OK else 0) |
        @as(u32, if (options.write) linux.W_OK else 0) |
        @as(u32, if (options.execute) linux.X_OK else 0);
    const flags: u32 = if (options.follow_symlinks) 0 else linux.AT.SYMLINK_NOFOLLOW;

    var sync: CancelRegion.Sync = try .init(ev);
    defer sync.deinit(ev);
    while (true) {
        try sync.cancel_region.await(.nothing);
        switch (linux.errno(linux.faccessat(dir.handle, sub_path_posix, mode, flags))) {
            .SUCCESS => return,
            .INTR => {},
            .ACCES => return error.AccessDenied,
            .PERM => return error.PermissionDenied,
            .ROFS => return error.ReadOnlyFileSystem,
            .LOOP => return error.SymLinkLoop,
            .TXTBSY => return error.FileBusy,
            .NOTDIR => return error.FileNotFound,
            .NOENT => return error.FileNotFound,
            .NAMETOOLONG => return error.NameTooLong,
            .INVAL => |err| return errnoBug(err),
            .FAULT => |err| return errnoBug(err),
            .IO => return error.InputOutput,
            .NOMEM => return error.SystemResources,
            .ILSEQ => return error.BadPathName,
            else => |err| return unexpectedErrno(err),
        }
    }
}