Contributing to Ares

This is relatively unpolished. As the wrapper library and the project mature, simpler ways to create custom code will be created. Don't panic.

Contributing to Ares is relatively simple, if you know at least the basics of C++:

What you'll need

A knowledge of C++

Yes, you'll need this.

Microsoft's C++ compiler

Right now, only Microsoft Visual Studio is supported. Due to binary layout issues, gcc-based compilers/IDEs like Dev-C++/WxDev-C++ can not be used to create useful DLLs. If you want a free solution, try Microsoft Visual C++ 2008 Express Edition (highly recommended).

The Microsoft Visual C++ 2008 Redistributables

You can't run Syringe without these. These also come with Microsoft Visual C++ 2008 Express Edition.

The Microsoft Windows SDK

The Microsoft Windows SDK is required to contribute to and compile Ares. Microsoft Visual Studio (Express Edition) comes with it, but if you don't have it, you can freely download it from Microsoft's site, provided you have a legit copy of Windows. The latest version is 6.1, issued in Feb 2008.

A Subversion (SVN) client

TortoiseSVN is recommended.

Getting the code

The code consists of two parts:

yrpp

the wrapper library enabling the use of most ingame functionality through plain C++

Ares itself

the code for Ares itself, the functionality that is actually utilised

Each of them has its own SVN repository:

• Create a folder on your hard drive where you'll be keeping the code, for example, C:\My Documents\Visual Studio Projects\Ares or F:\source\Ares, whatever suits you.
• Create two subfolders in it, one for yrpp and one for Ares.

yrpp

• Right click yrpp's folder, and (as of this point we are assuming that you have successfully installed TortoiseSVN) select SVN Checkout... from the context menu.
  • Enter svn://www.renegadeprojects.com/yrpp/trunk as the Repository address.
  • Leave the other options as they are, and press OK.

Ares

• Right click Ares' folder, and select SVN Checkout... from the context menu.
  • Enter svn://www.renegadeprojects.com/ares/trunk as the Repository address.
  • Leave the other options as they are, and press OK.

The source code in the repository is updated often with changes and bugfixes. Make sure to compile all your code against the latest version of the SVN code.
The SVN Update context menu option will update your local copy.

Code Layout

The files in the yrpp folder are parts of the wrapper library. Ares' code is in the Ares folder. There are other repositories for other DLLs using yrpp - ExceptChecker contains the code for the current YR Development Environment (formerly known as ExceptChecker) DLL. The yrpp/Examples folder contains some examples of using the more complex functionality in yrpp.

Your new code should go in the Ares folder, the YRPP folder should not be modified without approval.

Also, take the time to at least skim over the existing code, including the wrapper library - knowing what is possible already and how is always good.

Writing A Function

All functionality in Ares is implemented as callback functions - when the game hits a certain location in the original code, some Ares function is invoked. To make your function invokable at a certain point, you'll need to assign your function as one of the predefined callbacks or use the Syringe Injection Control File to define that.

Any serious modification will normally require more than one callback.

Currently, callback functions are usually declared like this:

DEFINE_HOOK(address, Functionality_FunctionName, length) {
 // actual code
}

What the actual code does is naturally up to you, but usually you'll need to pull a pointer to one of the game classes from one of the CPU registers. This sort of information is very location-/context-specific, and as such you'll need information from the people familiar with the reverse-engineered ASM view of the code (as it is now, pd, jonwil, VK, DCoder and TSHyper). What the actual game classes do is documented in the wrapper library, look at its header files and the existing code snippets.

An Example

Here's a sample callback. It fixes a comparatively simple bug - that units firing Temporal=yes warheads get experience from erasing friendly units (bug report, Actual code as used in Ares (may differ from shown below)).

Bits marked with (ASM knowledge) you are not required to know, the ASM hackers can explain that part.

// bugfix #379: Temporal friendly kills give veterancy
          //(ASM knowledge) - address and length
DEFINE_HOOK(71A92A, _Temporal_AvoidFriendlies, 5)
{
 // (ASM knowledge) the ESI register contains a pointer to an instance of TemporalClass, so let's get it
 GET(TemporalClass *, Temp, ESI); 

 // House that owns the unit firing this weapon
 HouseClass *hv = Temp->get_Target()->get_Owner();
 // House that owns the unit being erased
 HouseClass *ho = Temp->get_Owner()->get_Owner();

 // proceed normally unless the two houses are allied with each other
 RET_UNLESS(ho->IsAlliedWith(hv));

 return 0x71A97D;
}

Compiling that code to a DLL and placing it in the game directory will give you this functionality...

... almost, there's one more step to do.

Registering the DLL/function with Syringe

To tell Syringe when to invoke the "_Temporal_AvoidFriendlies" function, you just need to create one extra file:

Let's say you called the DLL with that function temporal.dll. Now you need to create a plain text file called temporal.dll.inj in the same directory as the DLL is, and place the following line into it:

71A92A = _Temporal_AvoidFriendlies, 5

That's all. Now, running YR via Syringe will invoke that functionality and prevent units from gaining experience this way.

INJgen

If you've paid attention, you will have noticed that we used same address/length that was specified in the DEFINE_HOOK up above. We have a tool named INJgen, coded up by one of our developers, to automatically generate an .inj file from the sources so you don't have to add it manually.

Appendix A: Setting up the Build Environment

The easiest way to set it up is to use Visual Studio's Project/Solution manager. But some of us prefer manual control over smaller details, so we have a makefile for GNU Make which can be used to compile Ares from the command line. This includes the INJgen step, which you need to do differently if you're using Visual Studio, and the version resource file.