fn fileSeekBy(userdata: ?*anyopaque, file: File, offset: i64) File.SeekError!void
fn fileSeekBy(userdata: ?*anyopaque, file: File, offset: i64) File.SeekError!void { const ev: *Evented = @ptrCast(@alignCast(userdata)); var sync: CancelRegion.Sync = try .init(ev); defer sync.deinit(ev); try ev.lseek(&sync, file.handle, @bitCast(offset), linux.SEEK.CUR); }