Any suggestions? (C++ reading from file)

**Supernova** · 08-25-2012 11:46 PM

Partly for the learning experience and partly just for the awesomeness of the finished product, I'm starting work on a multi-system game emulator. I'm planning on including MAME, C64, NES, SNES, N64 (depending on hardware), and any other consoles I think to add. Eventually I'm going to be buying some low-spec hardware to run it on and coming up with some sort of case (may use a NES case if I go with a small-enough motherboard, that does induce limitations though).

Anyway, the point of this thread. Step 1 for me right now is writing a GUI program that will allow the user to select an emulator, and from there select a ROM from a list generated from a file containing a list of all available ROMs. It then writes a single command to a batch file which launches the selected emulator with the selected ROM (I already have that part pretty much figured out).

The next step is to figure out how to read the ROM names from the file (I'll worry about generating the file later) and use that to list the available options for the user. I'm thinking maybe a plain .txt file would be easiest - one ROM name per line, then the program reads each line and inserts them as strings into an array so that any one can be referenced by number later (and inserted into the batch file).

Partly due to my inexperience, I've started out working on this program by getting the most basic element working and adding things from there. Here's what I've done today:

Code:

#include <iostream>
#include <fstream>
#include <stdlib.h>

using namespace std;

void launcher();

string emuname;
string gamename;

int main()
{
    int gameno = 0;

    cout << "Hello.\n" "Enter a number to select a game.\n";
    while (true)
    {
    cout << "\n 1. Donkey Kong Country" "\n 2. Super Mario World" "\n 3. The Legend of Zelda: A Link To The Past" "\n enter 0 to quit\n";
    cin >> gameno;
    if (gameno == 1)
    {
        emuname = "zsnesw.exe";
        gamename = "\"Donkey Kong Country.zip\"";
        launcher();
    }
    else if (gameno == 2)
    {
        emuname = "zsnesw.exe";
        gamename = "\"Super Mario World.zip\"";
        launcher();
    }
    else if (gameno == 3)
    {
        emuname = "zsnesw.exe";
        gamename = "\"Zelda - A Link to the Past.zip\"";
        launcher();
    }
    else if (gameno ==0)
    break;

    else
    cout << "Invalid selection.  Choices are:";
    }
    return 0;
    }

void launcher ()
{
        ofstream myfile;
        myfile.open ("temp.bat", ios::in | ios::trunc);
        myfile << emuname << " " << gamename;
        myfile.close();
        system("temp.bat");
}

Would an approach like what I've described above work, or is there a better approach? More importantly, would that approach be useful when I'm ready to start building a GUI? I've never really done much with reading/writing to/from files before, so any tips are appreciated.

**reci** · 08-26-2012 01:24 AM

To clear up, on what machine will this 'emulator' be running? (i.e. computer, game console)

What will be the controller(s)? (i.e. keyboard + mouse, game console controller, etc)

Will you be writing the emulator for these games/consoles, or will your program solely consist of a GUI to select one of many games (and call an external program to start the emulation)?
(if the former, I think you're in over your head)

Will respond more thoroughly after the above is clear.

**Supernova** · 08-26-2012 01:44 AM

Originally Posted by reci

To clear up, on what machine will this 'emulator' be running? (i.e. computer, game console)

What will be the controller(s)? (i.e. keyboard + mouse, game console controller, etc)

Will you be writing the emulator for these games/consoles, or will your program solely consist of a GUI to select one of many games (and call an external program to start the emulation)?
(if the former, I think you're in over your head)

Will respond more thoroughly after the above is clear.

The emulators will be running on a PC, hopefully under Windows XP. Ultimately I would like the GUI to be navigable using only a game controller (N64 controller is one candidate, with USB adapters). The program is only going to be a frontend which will launch one of several emulators with the proper command line arguments (specifically, the name of the ROM file to load into the emulator).

If I were intending to actually write all these emulators I'd be in way, waaaay over my head

A note if you want to compile that code: I've just been tossing the .exe into a folder with zsnesw.exe and the 3 roms I used, whose filenames are found in the code. However, I've also (due I believe to the use of stdlib.h) had to put libgcc_s_dw2-1.dll and libstdc++-6.dll in the folder to get it to run; something's up with my compiler settings but that's a separate issue and I have an easy workaround for now.

**reci** · 08-26-2012 03:53 AM

Okay, that sounds reasonable

The launcher() function should have emuname and gamename as parameters and not global variables...
And rather than writing a .bat with those, calling system(emuname+" "+gamename);, or the like, would probably be simpler, no?

On the organization of ROM files; you could have them manually typed in a text file, but that would take much time if adding to your collection of games. I suggest having your program scan a folder structure like the following and associate the games based on which console folder they belong:

Console 1
- Game 1
- Game 2
Console 2
- Game 3
Console 3
- Game 4
- Game 5

And when selecting a game, the console folder containing the game determines what emuname to use.

Good luck on this. Having it all self-contained sounds like it would make for a better gaming experience!

**Supernova** · 08-27-2012 06:32 AM

Originally Posted by reci

Okay, that sounds reasonable

The launcher() function should have emuname and gamename as parameters and not global variables...
And rather than writing a .bat with those, calling system(emuname+" "+gamename);, or the like, would probably be simpler, no?

On the organization of ROM files; you could have them manually typed in a text file, but that would take much time if adding to your collection of games. I suggest having your program scan a folder structure like the following and associate the games based on which console folder they belong:

Yeah, I started out with emuname and gamename being passed to launcher() as parameters, and to be honest I don't remember exactly why I tried global variables

Running the one command directly via system(emuname+" "+gamename); would indeed be simpler - apparently I didn't do enough research into the system() function.

I think at one point I was imagining a separate .exe which could be run to generate a list whenever changes were made, but I guess just merging that into the main program would be a better idea. What would be the typical procedure for scanning a folder structure like the one you described?

**reci** · 08-27-2012 04:55 PM

Let me google that for you

And yes, I would imagine having it all in one .exe would be best.

Having the "folder scanner" run its scan every time the "game select" screen is accessed.
And perhaps a refresh button on that screen to re-scan the folders.

Do post a published version, as others may find it useful

**Supernova** · 08-29-2012 12:42 AM

Hmm. Looks like this particular problem is a little more complicated than I anticipated. I did turn up this: Filesystem V3 Reference , but I don't really know anything about the Boost libraries.

It probably helps that of the classes I start tomorrow, one is a CS course taught from the book Problem Solving With C++

Also this could drag on for some time, especially as I'm starting classes, but I definitely intend to publish all this when It's in a working state.

**Sornaensis** · 08-29-2012 05:24 AM

You should come into IRC more often.

**DrunkenArse** · 08-30-2012 12:32 AM

Originally Posted by Supernova

Yeah, I started out with emuname and gamename being passed to launcher() as parameters, and to be honest I don't remember exactly why I tried global variables

If I was caught doing something like that (not that I do things like that), I'd probably blame it on satan

**Supernova** · 08-30-2012 01:05 AM

Originally Posted by PhilosopherStoned

If I was caught doing something like that (not that I do things like that), I'd probably blame it on satan

Segfaults? Satan.

**Supernova** · 09-02-2012 04:12 AM

Hey guys. Just a quick update. Haven't really been moving on this lately while I got settled into my college schedule. I sat down just a bit ago with the intent of removing the write to the .bat (and thus removing launcher() as well). I ran into some trouble with system() however, from what I gather it seems it will only take a single string constant as an argument, and I'm not sure how I'm going to incorporate the string variables into that. Google hasn't turned up much yet (I found some reference material here but nothing that I could work out a solution from. I have to be up for work tomorrow morning, so I'm gonna pick up on this some time tomorrow.