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The Secret Feature of EM-DOSBOX on Internet Archive

146 points by josephscott 11y ago

kevan 11y ago
>Of course you can’t save your games! They’re not some actual thing playing on your operating system. They live inside a window...But we got a lot of complaints about it...So we fixed it. Great example of usability winning out over technical purity here. Just because something is behaving as we expect it to doesn't mean it can't be changed to make the experience better for everyone.
- db48x 11y ago
  Your point isn't wrong, but there was no "technical purity" motivation for not implementing it from the start. It's just difficult to do well, so we only implemented the easy case (DosBox), and only the easiest of the easy cases (only one saved filesystem, no disk swapping, no ui, etc). It's the same as printing. Everyone writes hilarious complaints in the comments on the word processors about how printing didn't work. Of course you can't print! It's an emulator running in JS in your browser!!!1! But we have ideas for how to implement it, so maybe one day it will work after all. Saved games and networking are higher priority and are further along though.
  - kevan 11y ago
    Ah, I was assuming there would be a kludgy hack to bridge between the emulator's filesystem and localStorage on the browser.
    - db48x 11y ago
      Fear not, there are in fact some kludgy hacks in there. The BrowserFS stuff is really clean though, and since DosBox is written in C and uses the normal POSIX file api (DosBox thinks it was compiled for Linux), plugging the two together was pretty easy.
arcatek 11y ago
Something that most emulators have failed to achieve (and that the Start9 project[1] aims to fix) is the user experience. It's great to have a working emulator, but it's even better to have an emulator that doesn't have a learning curve bigger than the everest. It won't work if we ask our users to download things from the internet (often from third-party websites), especially if they're shipped with adwares (as it happens with some official emulators), or require third-party plugins (remember EPSX?), or don't have any easy screen sharing features, or ... Things like what the article is about are a small step in the right direction. [1] http://start9.io http://start9.io
- TazeTSchnitzel 11y ago
  There's a free service called Console Classix where you can download their app, and it gives you a large library of games for retro consoles you can just click and play straightaway: http://www.consoleclassix.com/ http://www.consoleclassix.com/ I've used it before, it's a pretty good experience. You have to pay to be able to play non-NES and Colecovision games, though. They justify the obvious copyright violation by only letting you play games they have physical copies of, and not letting more people play concurrently than they have cartridges. This... doesn't really avoid the copyright issues, but they do it anyway.
  - arcatek 11y ago
    > They justify the obvious copyright violation by only letting you play games they have physical copies of, and not letting more people play concurrently than they have cartridges. This... doesn't really avoid the copyright issues, but they do it anyway. We found this service before creating Start9, and considered using the same thing. We talked to a lawyer before, who advised us not to do it, and fallbacked on letting people upload games that they are able to according to their local regulation (usually, games they dumped themselves), and forbidding them to lend their accounts to their friends. It's 100% legal, but unfortunately it's still hard for some users to understand why this limitation exists. What I would love to do would be to have kind of a deal with game publishers, but as a single man currently working on the project, I don't the time to contact these studios (especially since most of them have closed since the games have been released, or are under Nintendo's copybag, which won't be ever available to third-parties such as ourselves).
TazeTSchnitzel 11y ago
Em-DOSBox is incredible. I'd previously wondered if it might be possible to run DOSBox in the browser with emscripten, but there seemed to be nothing working out there. Then the Internet Archive started hosting DOS games, and I wondered what they were using, thus I found Em-DOSBox. At the same time, I was getting a bit of nostalgia for Windows 95, the first upgrade to Windows I ever used. And it turns out with a bit of fiddling you can run Windows 95 in DOSBox and have it mostly work. Thus http://win95.ajf.me/ http://win95.ajf.me/ was born. Windows 95 running in the browser. It's still rather unbelievable. You can listen to CANYON.MID on an emulated Sound Blaster 16! (Unlike the Internet Archive's games, this doesn't do any saving to local storage, sorry. I'm not sure it practically could, because it's not using a fake filesystem mapped to fopen() calls by intercepting DOS system calls, as DOSBox typically does, but rather DOSBox is giving Windows 95 a real disk image, so you'd have to stuff 131MB into localStorage.)
- digi_owl 11y ago
  Things like this just make my mind spin when contemplating the number of layers invoked to get it working. an OS running inside DOSBOX compiled to JS deliver over HTTP/TCP/IP to be interpreted by a browser (at this point perhaps a OS in its own right) running on top of a OS on top of a CPU. It really feels like we are back in the leased terminal era...
  - seanp2k2 11y ago
    Every few months someone finds a way to put another turtle on top, and some of those attempts stick.
    - breatheoften 11y ago
      Wonder if it would work in iOS Safari running on the iOS simulator ...
  - TazeTSchnitzel 11y ago
    Yep! And you can even run DOS apps inside Windows 95, so you can have Virtual 8086 Mode inside your virtual x86 CPU (DOSBox) inside your JavaScript virtual machine, inside a sandbox... Disk access here is fun through the sheer number of layers. Consider a DOS prompt inside 95. When a DOS application tries to perform an I/O operation, it will make a DOS system call. DOS, in turn, will call the BIOS. This BIOS call will be intercepted by Windows 95 which, since it has no 32-bit disk driver (DOSBox doesn't simulate a real disk controller), will pass it on to DOS (the one underlying 95), which in turn will make a BIOS call. Everything before this point has been under DOSBox's x86 emulation. We then go through to the C++ fake BIOS of DOSBox, which handles the BIOS call by calling the C standard library I/O functions. However, those have been replaced by emscripten's shims, which will grab that data from the asm.js heap somewhere (or does it ferry it out to JS? I'm not sure.) And DOSBox itself has been compiled to asm.js (which your browser may compile to machine code through JIT) and is running in your browser's JS VM. Which, if the browser you're using is on Windows, may be a 32-bit version, which is running under Windows's WOW64 (Windows 32-bit on Windows 64-bit)... The layers never end! http://i.imgur.com/lcZZ5YU.png http://i.imgur.com/lcZZ5YU.png
rocky1138 11y ago
The comment in TFA about exporting the saved game data via URL is a great idea. Imagine being able to send someone to a specific point in a videogame by URL or share an old Wordperfect document, including the content, via a huge URL.
- steckerbrett 11y ago
  Depends on the browser but there's usually a 1k character limit which isn't a great deal of state. Perhaps that's counted badly so you can get 1000 char * 4 bytes for unicode, but I wouldn't bet on it being handled the same in different browsers anyway.
- arcatek 11y ago
  It wouldn't work. Most browsers have a limit of about 2000 characters. Assuming a base64 encoding, it means you have about 1K of available data (since most saves have a power-of-2 size), far from being enough for any real game (especially if you want a save state, instead of an actual save - that would require to store the entire emulator state, which are at least a few megabytes tall).
  - mietek 11y ago
    State could be stored to something like Amazon S3 and referenced using a unique ID, which would then become part of the URL given to the user.
    - jvilk 11y ago
      BrowserFS actually supports Dropbox integration already... so you could do the same with a Dropbox shared folder. (Sidenote: I'm the author of BrowserFS, and helped implement this feature.)
  - rocky1138 11y ago
    I suppose that's true. But, remember, a lot of old console games used passcodes instead of saved states. So for some of this, it might actually work!
na85 11y ago
Can the LocalStorage API be used to store supercookies and thus track users?
- TazeTSchnitzel 11y ago
  It's a persistent storage API, so yes. Browsers usually offer the option to clear localStorage alongside cookies, though.
  - db48x 11y ago
    Since you can clear it it's not a supercookie.
erikb 11y ago
Maybe I'm not enough into the details, but from my perspective it seems as it should be very normal to save things in an emulator. It should not just be possible by default it should be much better than in the original, since we control how we set up the emulator. E.g. I would expect a game that had 3 saving slots to have 1 mio now. I would expect that these files would be stored in my host file system in a way that I can back it up and sync it via dropbox and github. Is that really that uncommon? I mean, there are people who hack games that should not be modified and change the userinterface etc. We should have enough control over our virtual machines to let them do anything.

146 points by josephscott 11y ago

kevan 11y ago

>Of course you can’t save your games! They’re not some actual thing playing on your operating system. They live inside a window...But we got a lot of complaints about it...So we fixed it. Great example of usability winning out over technical purity here. Just because something is behaving as we expect it to doesn't mean it can't be changed to make the experience better for everyone.

db48x 11y ago
Your point isn't wrong, but there was no "technical purity" motivation for not implementing it from the start. It's just difficult to do well, so we only implemented the easy case (DosBox), and only the easiest of the easy cases (only one saved filesystem, no disk swapping, no ui, etc). It's the same as printing. Everyone writes hilarious complaints in the comments on the word processors about how printing didn't work. Of course you can't print! It's an emulator running in JS in your browser!!!1! But we have ideas for how to implement it, so maybe one day it will work after all. Saved games and networking are higher priority and are further along though.
- kevan 11y ago
  Ah, I was assuming there would be a kludgy hack to bridge between the emulator's filesystem and localStorage on the browser.
  - db48x 11y ago
    Fear not, there are in fact some kludgy hacks in there. The BrowserFS stuff is really clean though, and since DosBox is written in C and uses the normal POSIX file api (DosBox thinks it was compiled for Linux), plugging the two together was pretty easy.

arcatek 11y ago

Something that most emulators have failed to achieve (and that the Start9 project[1] aims to fix) is the user experience. It's great to have a working emulator, but it's even better to have an emulator that doesn't have a learning curve bigger than the everest. It won't work if we ask our users to download things from the internet (often from third-party websites), especially if they're shipped with adwares (as it happens with some official emulators), or require third-party plugins (remember EPSX?), or don't have any easy screen sharing features, or ... Things like what the article is about are a small step in the right direction. [1] http://start9.io http://start9.io

TazeTSchnitzel 11y ago
There's a free service called Console Classix where you can download their app, and it gives you a large library of games for retro consoles you can just click and play straightaway: http://www.consoleclassix.com/ http://www.consoleclassix.com/ I've used it before, it's a pretty good experience. You have to pay to be able to play non-NES and Colecovision games, though. They justify the obvious copyright violation by only letting you play games they have physical copies of, and not letting more people play concurrently than they have cartridges. This... doesn't really avoid the copyright issues, but they do it anyway.
- arcatek 11y ago
  > They justify the obvious copyright violation by only letting you play games they have physical copies of, and not letting more people play concurrently than they have cartridges. This... doesn't really avoid the copyright issues, but they do it anyway. We found this service before creating Start9, and considered using the same thing. We talked to a lawyer before, who advised us not to do it, and fallbacked on letting people upload games that they are able to according to their local regulation (usually, games they dumped themselves), and forbidding them to lend their accounts to their friends. It's 100% legal, but unfortunately it's still hard for some users to understand why this limitation exists. What I would love to do would be to have kind of a deal with game publishers, but as a single man currently working on the project, I don't the time to contact these studios (especially since most of them have closed since the games have been released, or are under Nintendo's copybag, which won't be ever available to third-parties such as ourselves).

TazeTSchnitzel 11y ago

Em-DOSBox is incredible. I'd previously wondered if it might be possible to run DOSBox in the browser with emscripten, but there seemed to be nothing working out there. Then the Internet Archive started hosting DOS games, and I wondered what they were using, thus I found Em-DOSBox. At the same time, I was getting a bit of nostalgia for Windows 95, the first upgrade to Windows I ever used. And it turns out with a bit of fiddling you can run Windows 95 in DOSBox and have it mostly work. Thus http://win95.ajf.me/ http://win95.ajf.me/ was born. Windows 95 running in the browser. It's still rather unbelievable. You can listen to CANYON.MID on an emulated Sound Blaster 16! (Unlike the Internet Archive's games, this doesn't do any saving to local storage, sorry. I'm not sure it practically could, because it's not using a fake filesystem mapped to fopen() calls by intercepting DOS system calls, as DOSBox typically does, but rather DOSBox is giving Windows 95 a real disk image, so you'd have to stuff 131MB into localStorage.)

digi_owl 11y ago
Things like this just make my mind spin when contemplating the number of layers invoked to get it working. an OS running inside DOSBOX compiled to JS deliver over HTTP/TCP/IP to be interpreted by a browser (at this point perhaps a OS in its own right) running on top of a OS on top of a CPU. It really feels like we are back in the leased terminal era...
- seanp2k2 11y ago
  Every few months someone finds a way to put another turtle on top, and some of those attempts stick.
  - breatheoften 11y ago
    Wonder if it would work in iOS Safari running on the iOS simulator ...
- TazeTSchnitzel 11y ago
  Yep! And you can even run DOS apps inside Windows 95, so you can have Virtual 8086 Mode inside your virtual x86 CPU (DOSBox) inside your JavaScript virtual machine, inside a sandbox... Disk access here is fun through the sheer number of layers. Consider a DOS prompt inside 95. When a DOS application tries to perform an I/O operation, it will make a DOS system call. DOS, in turn, will call the BIOS. This BIOS call will be intercepted by Windows 95 which, since it has no 32-bit disk driver (DOSBox doesn't simulate a real disk controller), will pass it on to DOS (the one underlying 95), which in turn will make a BIOS call. Everything before this point has been under DOSBox's x86 emulation. We then go through to the C++ fake BIOS of DOSBox, which handles the BIOS call by calling the C standard library I/O functions. However, those have been replaced by emscripten's shims, which will grab that data from the asm.js heap somewhere (or does it ferry it out to JS? I'm not sure.) And DOSBox itself has been compiled to asm.js (which your browser may compile to machine code through JIT) and is running in your browser's JS VM. Which, if the browser you're using is on Windows, may be a 32-bit version, which is running under Windows's WOW64 (Windows 32-bit on Windows 64-bit)... The layers never end! http://i.imgur.com/lcZZ5YU.png http://i.imgur.com/lcZZ5YU.png

rocky1138 11y ago

The comment in TFA about exporting the saved game data via URL is a great idea. Imagine being able to send someone to a specific point in a videogame by URL or share an old Wordperfect document, including the content, via a huge URL.

steckerbrett 11y ago
Depends on the browser but there's usually a 1k character limit which isn't a great deal of state. Perhaps that's counted badly so you can get 1000 char * 4 bytes for unicode, but I wouldn't bet on it being handled the same in different browsers anyway.
arcatek 11y ago
It wouldn't work. Most browsers have a limit of about 2000 characters. Assuming a base64 encoding, it means you have about 1K of available data (since most saves have a power-of-2 size), far from being enough for any real game (especially if you want a save state, instead of an actual save - that would require to store the entire emulator state, which are at least a few megabytes tall).
- mietek 11y ago
  State could be stored to something like Amazon S3 and referenced using a unique ID, which would then become part of the URL given to the user.
  - jvilk 11y ago
    BrowserFS actually supports Dropbox integration already... so you could do the same with a Dropbox shared folder. (Sidenote: I'm the author of BrowserFS, and helped implement this feature.)
- rocky1138 11y ago
  I suppose that's true. But, remember, a lot of old console games used passcodes instead of saved states. So for some of this, it might actually work!

na85 11y ago

Can the LocalStorage API be used to store supercookies and thus track users?

TazeTSchnitzel 11y ago
It's a persistent storage API, so yes. Browsers usually offer the option to clear localStorage alongside cookies, though.
- db48x 11y ago
  Since you can clear it it's not a supercookie.

erikb 11y ago

Maybe I'm not enough into the details, but from my perspective it seems as it should be very normal to save things in an emulator. It should not just be possible by default it should be much better than in the original, since we control how we set up the emulator. E.g. I would expect a game that had 3 saving slots to have 1 mio now. I would expect that these files would be stored in my host file system in a way that I can back it up and sync it via dropbox and github. Is that really that uncommon? I mean, there are people who hack games that should not be modified and change the userinterface etc. We should have enough control over our virtual machines to let them do anything.