diff --git a/ARCHITECTURE.md b/ARCHITECTURE.md new file mode 100644 index 0000000000..0e3cae3484 --- /dev/null +++ b/ARCHITECTURE.md @@ -0,0 +1,27 @@ +# Architecture +This file provides information on how FernFlower is structured, with descriptions of how each part of the codebase works. + +## Terms +FernFlower uses a large amount of terms and shorthand names within its code, for which explanations are provided here. +The first name is the full name and the names in parentheses are the shorthand names that are used throughout the code. +* Exprent (expr, exp) Refers to an expression that FernFlower uses to create the java code, such as a constant or method invocation. +* Statement (stat) Refers to a statement within the code used to structure the code, such as an if statement or a loop. + +## The decompilation process +When a method gets decompiled, it passes through multiple stages through which it is converted from bytecode to java code. +At a high level, this process consists of bytecode reading, instruction sequencing, control flow analysis, code structuring, and java writing. +Each of these steps will be outlined in detail below. + +### Bytecode reading and instruction sequencing +This is the simplest part of the process, as it just reads the bytecode bytes out of the code struct and initializing them. This takes place in `StructMethod#parseBytecode`. + +### Control Flow Analysis +Control flow analysis is where the bytecode is analyzed into basic blocks, SSA is run, and the dominator tree is generated to help with analysis and code inference. +Most of this processing happens in `MethodProcessorRunnable.codeToJava`. + +### Code structuring +Right after the control flow analysis, the basic blocks are turned into structured code within the same `MethodProcessorRunnable.codeToJava` method. This creates an intermediate +representation of the method that can be then turned into java code. + +### Java writing +`ClassWriter#methodToJava` takes the intermediate representation (comprised of statements and exprents) and structures that into java code which is then written. \ No newline at end of file diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md new file mode 100644 index 0000000000..03d97b1a66 --- /dev/null +++ b/CONTRIBUTING.md @@ -0,0 +1,39 @@ +# Contributing +Welcome! Thank you for taking an interest in contributing to Quiltflower. + +## Before making a pull request +* Please read the [Quilt Code Of Conduct](https://quiltmc.org/community/code-of-conduct.html) first! +* The ARCHITECTURE.md file in the repository contains technical information on how Quiltflower is structured. Reading that will greatly help with familiarizing yourself with the codebase and with PR development. +* It's highly recommended to talk about the changes you are making [on the Quilt toolchain discord](https://discord.quiltmc.org/toolchain) before submitting them. +* Check out the issue tracker and roadmap! You can find good things to contribute there. + +## Good things to contribute +* Improvements to the readability of the decompiled code. +* New feature support for the decompiler. +* Optimization, to make it run faster and use fewer resources. +* Tests! Tests are always appreciated. + +## Code Style and guidelines +While the code inherited from FernFlower varies with its style and syntax, it's expected that pull requests stick to our established code style. +* We use UpperCamelCase for class names, camelCase for method, variable, local variable, and field names, and UPPER_SNAKE_CASE for static final fields. Please always qualify instance fields with a `this.` qualifier. +* Please try to keep pull requests small and self-contained! It makes reviewing and maintaining the patch much easier. +* FernFlower's code is barely documented, but patches should add documentation in a high level manner so that other devs can understand what is going on within the patch, and any idiosyncrasies within. +* When submitting patches, it is also recommended to cite the relevant portion of the Java Language Specification for future reference and for getting a better understanding of the code that has to be generated by the patch. + +## Tests +* Quiltflower uses a large and expansive test suite to ensure that patches don't cause any regressions. Please make sure that your patches don't break any of the tests! +* In the case that you're adding a new feature to the decompiler, it's acceptable to modify failing tests to make them succeed. Please make a note of this in the pull request. +* When contributing, you should add new tests that cover the area of code that you are targeting. Having more tests makes the decompiler more robust, so it's always appreciated. +* Please also test your code changes against the Minecraft codebase to ensure that your change is properly applied on there too, and does not break any existing code. + +## Resources +FernFlower is a very complex and involved bit of software, and there's a lot going on in a rather questionable structure. Naturally, understanding it all is a challenge so various resources are provided here to aid with the process. +* Knowing how java bytecode works is essential. You can find the detailed description of all the opcodes [here](https://docs.oracle.com/javase/specs/jvms/se16/html/jvms-6.html#jvms-6.5) or a simple list of them [here.](https://en.wikipedia.org/wiki/Java_bytecode_instruction_listings) +* Graph theory comes up frequently in the statement analysis portion of FernFlower. It's useful knowing about [Basic Blocks](https://en.wikipedia.org/wiki/Basic_block), [Control Flow Graphs](https://en.wikipedia.org/wiki/Control-flow_graph), and [Dominators.](https://en.wikipedia.org/wiki/Dominator_(graph_theory)) +* [Static Single Assignment Form](https://en.wikipedia.org/wiki/Static_single_assignment_form) is also used widely to track variables and their versions within the decompilation stages. +* The [Java Language Specification](https://docs.oracle.com/javase/specs/jls/se16/html/), while dense, is a good source of information regarding language features. +* The ARCHITECTURE.md file in the repository contains important information about how FernFlower is structured. +* The [Discord server](https://discord.quiltmc.org/toolchain) contains many people who have worked with the code before, so any remaining questions are best asked there. + +## License +* Quiltflower is licensed under Apache Version 2.0. 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