The Injector has several layers (or steps) in it’s patching process. These layers can be put into two seperate categories: pre-processing and post-processing. The injector patches the EaglercraftX build with the pre-processor ahead of time, and then the post-processor is appended to the EaglercraftX build.
The preprocessor’s job is to find and hook into as many internal TeaVM / Minecraft methods as possible.
The first thing it does is it adds a piece of pre-initialisation code at the start of the TeaVM module, to define global varaibles such as ModAPI and ModAPI.hooks.
Then it:
Hooks into the $rt_metadata function, intercepting its arguments and storing them in the array ModAPI.hooks._rippedData.
Hooks into the the teavm threading shim and adds controls to freeze the callstack.
Looks for the #game_frame element, and then adds the post-processing codes after it (modapi_postinit, modapi_modloader and modapi_guikit). It also stores a copy of the modapi_postinit script into a fourth post init script, for the post-processing scripts to inject into the dedicated server.
Searches for constructors and appends them to the ModAPI.hooks._rippedConstructors dictionary.
Extracts and hooks into all class methods, storing their type (instance or static) into ModAPI.hooks._rippedMethodTypeMap, and storing the method itself in ModAPI.hooks.methods
Finds static class variables, and build a proxy object for them, to allow for readwrite access even though there is no way to expose their context. The keys for the static properties of a specific class are stored under ModAPI.hooks._rippedStaticIndexer and the proxy objects are stored in ModAPI.hooks._rippedStaticProperties.
Finally, it adds references (not hooks, as they would tank performance) to all TeaVM internal methods, most importantly $rt_str and $rt_ustr, used for interaction with jcl strings.
The post processor is much simpler than the preprocessor, but it effectively uses the data in ModAPI.hooks to create a (mostly) backwards compatible ModAPI global.