Just another imformative explanation from you Tim, really impressive.
I hearing this "high-level ASM" for the first time as I always thought that C is already classified as a "high level abstract" and to some degree machine independent language. I guess I'm way to used to Java as it's basically the only language I'm using for the past 15 years.
I also already tried to search up about creating dynamic libraries that can be loaded at runtime, but from what I found how to actually design them differs vastly between writing something for the windows platform or some linux distribution and that even to maintain source-code level compatibility one has to stuff a lot of pre-processor stuff in a source file so at the time the compilers pre-processor runs over it the result somewhat automagically (yes, spelling intended) comes out as something that only consist of platform specific source which then gets compiled - very confusing.
Luckly what I want to implement doesn't seem all that complicated (although I still wonder if it may be possible to cross-compile a windows binary on a linux system as I don'T really want to clutter up my system of several gigabytes of dev stuff just to compile a few lines into a small lib) but still maybe up for some topic on its own:
As Java offers the JNI which also allows full-duplex bi-directional communication I'd like to (if possible) implement a small lib which just takes the string given by the main application - calls some java code to process it - and sends back the result. But, from as far as I already read up: just connecting two applications by a single lib doesn't seem to be that easy straight forward possible as I hope to as the pointer only stored in the memory spaces of the respective processes. One of the techniques to get around this seem to be things like unix domain sockets, regular ip sockets and even memory mapped files and using some sort of os level event bus system to signal the other program that there new data in the memory to process - isn't there a simpler way?
I also once watched a video on youtube showing the very basics of whats actually inside the java bootstrap binary - and I guess this can also be done within the lib loaded by the main application (so it basically runs a VM inside its process sapce). That would be cool by me as I then still can develop my logic in java and just have it run by the vm created by the main application instead of its own instance.
One may see from as how my text turns into getting harder and harder to read I'm getting more and more confused as on how to get started.
Maybe, for anyone still with me and may willing to give me a help in the right direction, I shall give you some more specific information about what I want to implement:
As I currently working on design a modification for the game Arma3 I face the challenge to implement some way to connect to a database. The current way is to use a lib known as "extDB3". It's basically a wrapper for the mysql-connector/c connecting it with the game using its "extension" api: https://community.bistudio.com/wiki/Extensions
They way this is currently achieved seem to be this:
The developer of the extDB3 lib provides two modes of operation: raw SQL and prepared statements defined via an INI loaded at first time the lib gets initialized. As the extension api of arma3 has a limit on about how much data can be send back from the extension to the game engine (currently about 10kB) there can be results bigger than this which has to be transfered in several consecutive calls to the extension. To make this possible the extDB3 extension buffers the result it gets from the database in what looks like a map along with an id which gets returned upon the initial a-synchronous request and it's up to the arma3 code to keep polling for the data until an empty string is returned to mark the end (I guess that's one example of unknown length at runtime which justify an explicit length/size information).
The main issue I currently face is that most of the code I have to deal with is already several years old (the extDB3 lib was last modified back in 2017 and the base for my own new mission is from about 2014-2017) - and in the mean time the arma3 game engine has evolved so my goal is a complete rewrite to take a) advantage of all the new features and b) make it as performant as possible as the current version really shows how slow it all is when you have more than just a few players interacting with each other and the world which, although extDB3 is pooled and multi-threaded, can add up to some lagg as the main game engine itself (and its multiplayer server) is just one big single threaded mess.
To release the main server instance of it's heavy load the arma3 game provides what they call "headless clients". It's basically just another game client but without the graphical overhead - just the logic itself. The benefit one can get from this is to offload lot'S of work from the main server instance to these headless client instances. This way I managed to get down the overall system usage of one single server instance of about 85% to just about 30% with a second client insatnce with about 20%. Not just I got down the usage but also can now take advantage of the two physical cpus the server has to split of the load between them. My goal with all the rewrite of the game mission and the extension and the database stuff is to maybe split the workload even further to take more advantage of the available system resources (2 quad core cpus) and to hopefully increase the performance even if the server fills up with players (currently I set a max of about 175 players - which the engine in fact do can handle (seen it other servers with 150+ players at the same time - as the staff also had a lot of work done on their own it was quite performant)).
Why do I post this hear instead of the game forum? Well, the way I see it this is a programming "problem" which is best solved in a programmers forum. The game forum for arma3 doesn'T go that deep into programming but only into using the provided tools with the game - which ends about the point where a call is made from the game to the extension. So I doubt I can expect much help over there.
To summarize: What I'm looking for is a way to either connect another process with my own JVM via a dynamic library - or, if that'S not possible, how to start up and run a JVM within the space of another programm by implement its startup code in said dynamic library - to, in the end, be able to develop my extension in java and only use the C lib as communication binding as the arma3 game engine only provides this one option to talk to external code.
Any help and advise are appreciated. Thanks in advance.