Reversing GTA:SA Code

Reversing GTA:SA code is the process of turning the x86 assembler instructions back into readable C++ code. It is made to fully understand logic inside of the GTA:SA engine. Results of code reversal can be put down as assembler hooks and/or localized C++ implementations.

Assembler Hooking

This is the method MTA:BLUE developers use to provide features to the MTA runtime. When logic patterns have been analysed inside of the GTA:SA engine by careful study of the assembler instructions, manipulations to the assembler instructions can be made. This way the logical flow of engine code is tampered with. Changes are local to the game executable.

Pros and Cons

Pro	Contra	Neutral
Exploits of the engine stay hidden Rockstar code is not shown to public	Research is not shared with other developers Hackish agenda on an open source project Progress on GTA:SA research is slowed down Only experts of their research can modify their hacks (elitist thinking) Logic may not be compatible across multiple GTA:SA versions	Cooperation of multiple GTA:SA mods

(The arguments are interpretations by The_GTA.)

Localized C++ Implementations

This is the way MTA:Eir developers use to provide features to the MTA runtime. First, the logic inside of the engine is analyzed. The researcher attempts to give meaning to said logic, by giving names to functions and variables that make sense. Once he thinks he fully understands the researched section of code, he rewrites the x86 assembler instructions into C++. Every researched function has to be given a comment header with a function description. The more a function is split into subroutines or the more patterns found have been put into shared functions, the better is the result of the research. Since the whole engine logic ties together, code research has to be revisited from time to time to make sure it is up to date in the context of the whole engine.

Changes to the original GTA:SA logic have to be marked with a comment that describes what has changed and where exactly. Additions which benefit the MTA runtime are often marked as "MTA extension". Bugfixes to the engine have to be explained in a comment.

Since the rewritten version of code has to perfectly match the original GTA:SA logic, it is a very tiring and time-consuming process. But once the code has been completely reversed and localized, it is open for every developer to try his hands on it.

What is Localization?

Localization is the process of extracting GTA:SA logic from its engine so that MTA can execute it stand-alone. It is required so that changes to the structures of GTA:SA can be made without breaking things. When code has been first rewritten the researcher is free to use the original GTA:SA binary offsets to reference structures and classes that he has found. This changes with Localization.

A binary offset is complex. It can be tied to many locations inside of the binary. Worst case scenario is if there are obfuscated references to the binary offset that cannot be spotted at development time but cause crashes during testing.

(WIP...)