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67 lines
3.8 KiB
Markdown
67 lines
3.8 KiB
Markdown
# Lillero
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Lillero is a lightweight and simple Java ASM patching framework built on top of [ObjectWeb's ASM library](https://asm.ow2.io/).
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## How
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This library provides the core interface, `IInjector`, as well as a small set of utils to make your life easier. All patches should implement `IInjector` and be declared as [services](https://docs.oracle.com/javase/8/docs/api/java/util/ServiceLoader.html).
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Some methods *must* be implemented, specifying which class and method will be patched:
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* `targetClass()`: returns the *fully qualified name* of the class to patch (example: `net.minecraft.client.Minecraft`).
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* `methodName()`: returns the name of the method to patch.
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* `methodDesc()`: returns descriptor (arguments and return type) of method to patch.
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* `inject(ClassNode, MethodNode)`: will be invoked providing you the ClassNode and MethodNode you requested. This is where the actual patching will happen.
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There's some more optional methods you *don't have to* implement, but really should because they will make your life considerably easier when it's time to debug:
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* `name()` : returns patch name
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* `reason()` : returns patch description
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Finally, you should mark your classes as service providers, by creating a text file called `ftbsc.lll.IInjector` in `src/main/resources/META-INF/services` on your project. Inside, put the fully qualified names of your patches (example: `ftbsc.bscv.asm.patches.TestPatch$TickPatch`).
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If you use Gradle (you do) don't forget to add this library as a dependency in your `build.gradle`:
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```groovy
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repositories {
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maven { url = 'https://maven.fantabos.co' }
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}
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dependencies {
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implementation 'ftbsc:lll:<whatever the latest version is>'
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}
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```
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You are going to need an appropriate loader to use Lillero patches: **this is just a library and does nothing by itself**. You need to make it work by loading services implementing the `IInjector` interface, and by calling their `inject(ClassNode, MethodNode)` methods with the appropriate parameters.
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Finally, know that you can spare yourself some trouble, by using this [annotation processor](https://git.fantabos.co/lillero-processor/) to reduce boilerplate to a minimum.
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#### Tips specific to Minecraft patching
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* You want to be using Notch (fully obfuscated) names whenever you are told to reference a class or method by name, since those are the ones that exist at runtime.
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- Use MCP (AKA unobfuscated) names if you are running from ForgeGradle's runClient task.
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- If you are using our loader (see below), use Searge (obfuscated but unique) names in every place you are told to use a name - ModLauncher will do the rest.
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* Use our [loader](https://git.fantabos.co/lillero-loader/) that hooks into Forge's ModLauncher if you're writing a Forge mod.
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* Make sure to dunk on all the naysayers who tried to force you to use Mixin!
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#### Example Minecraft patch
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The following is an example patch, located at `src/main/java/example/patches/SamplePatch.java`:
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```java
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package example.patches;
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import ftbsc.lll.IInjector;
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public class SamplePatch implements IInjector {
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public String name() { return "SamplePatch"; }
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public String targetClass() { return "net.minecraft.client.Minecraft"; }
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public String methodName() { return "func_71407_l"; } //Searge name for tick()
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public String methodDesc() { return "()V"; } //void, no args
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public void inject(ClassNode clazz, MethodNode main) {
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InsnList insnList = new InsnList();
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insnList.add(new InsnNode(POP));
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main.instructions.insert(insnList);
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}
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}
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```
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When loaded into Minecraft, this patch will crash the game with a NegativeArraySizeException as soon as it's done loading - so you know it's working.
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The following is the service registration file, located at `src/main/resources/META-INF/services/ftbsc.lll.IInjector`:
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```
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example.patches.SamplePatch
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```
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Happy patching!
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