atomicFileInit

fn atomicFileInit(
    ev: *Evented,
    dest_basename: []const u8,
    permissions: File.Permissions,
    dir: Dir,
    close_dir_on_deinit: bool,
) Dir.CreateFileAtomicError!File.Atomic {
    while (true) {
        var random_integer: u64 = undefined;
        random(ev, @ptrCast(&random_integer));
        const tmp_sub_path = std.fmt.hex(random_integer);
        const file = dirCreateFile(ev, dir, &tmp_sub_path, .{
            .permissions = permissions,
            .exclusive = true,
        }) catch |err| switch (err) {
            error.PathAlreadyExists => continue,
            error.DeviceBusy => continue,
            error.FileBusy => continue,

            error.IsDir => return error.Unexpected, // No path components.
            error.FileTooBig => return error.Unexpected, // Creating, not opening.
            error.FileLocksUnsupported => return error.Unexpected, // Not asking for locks.
            error.PipeBusy => return error.Unexpected, // Not opening a pipe.

            else => |e| return e,
        };
        return .{
            .file = file,
            .file_basename_hex = random_integer,
            .dest_sub_path = dest_basename,
            .file_open = true,
            .file_exists = true,
            .close_dir_on_deinit = close_dir_on_deinit,
            .dir = dir,
        };
    }
}