Comments on: Full xStream launch (and new name) in the wings

By: RP

RP — Wed, 19 Apr 2006 01:02:02 +0000

Well, I wanted to check xStream forums to see if anything change, but apparently the forums are dead, sadly it seems this program won’t be going anywhere, unless a miracle (read “DNF”) will happend…

By: Tom Edwards

Tom Edwards — Sat, 25 Mar 2006 06:38:55 +0000

a lot could have changed since then

I think we might have noticed something like that…

By: Andy Simpson

Andy Simpson — Fri, 24 Mar 2006 22:57:01 +0000

Oops. Forgot to include a major point. They both seem to do the same kind of profiling, redundancy, similiar systems. If this stuff all still holds true today, I’d say you’d have to be a madman to use xStream. Steam does everything identically for almost the same effort (if you can’t search and replace fopen with STEAM_fopen you’re in trouble) and is the more mature and proven product.

By: Andy Simpson

Andy Simpson — Fri, 24 Mar 2006 22:52:15 +0000

Wow, Google kicks ass. But old - painfully old, a lot could have changed since then. What’s immediately striking is that internally - Steam looks a heck of a lot like xStream. More than I realised.

Anyways, I can start by saying that I know nothing about filesystem drivers especially, but I do know that if you’re writing an application, it doesn’t so much matter to you where the file is, on a network share or whatever, as the OS abstracts all the details away from you.

xStream seems to work by providing a virtual drive system just like a network share is a virtual drive. It’s not on your PC, but you can access it like it is. Steam does an incredibly similiar thing, but rather than just hooking the filesystem, it actually requires you to use the Steam equivalents. In many ways, it’s a better system because you can do more intelligent things, like have Steam be aware of the context in which you’re loading stuff, or the game can more intelligently give clues to the Steam API, like, if you’re in a multiplayer map cycle, it would be a great idea to get cracking on the next two/three maps in that cycle! Or if you’re in single player, begin to load resources for every map you can reach from the map you’re in.

By: Tom Edwards

Tom Edwards — Fri, 24 Mar 2006 07:56:39 +0000

I’ve seen the tools they use, that’s good enough for me. I don’t think I should be distributing a presentation with “Valve Confidential” written on every slide though. You can find it through Google, that’s all I will say.

xStream does indeed hook in, using a system driver. I can’t imagine how that works, though…

By: Andy Simpson

Andy Simpson — Thu, 23 Mar 2006 20:58:21 +0000

Thing is, you’re pretty much speculating on what Steam is or isn’t capable of. Unless you’ve actually seen the Steam Filesystem API, and if you have, please tell me where I can! Currently, we can only infer what Steam can do from what Source/GoldSource games have done with it.

The feeling I have is that XStream does some clever stuff by hooking the filesystem, which is how it can work without modification of existing code. Problem is, it could be trying to be too clever. The more clever something is, the harder it is to get it working reliably. What if during the profiling stage, a certain model or sound never gets encountered, so it’s never loaded, so XStream doesn’t know when it’s needed. Then on your play-through, the game tries to load it and… bang. You get a freeze or something when it isn’t ready to download. I mean sure, it’s an edge case, but it can happen if you try and be too clever!