YABR - Yet Another Bytecode Reader/Writer

YABR is a bidirectional Java (de)compiler, program-analysis, and transformation framework. It spans bytecode, SSA, a structured IR, execution, and source, so a program can be lifted, analyzed, transformed, executed, compiled, and decompiled across one ecosystem.

Projects using YABR

• JStudio - A Java reverse engineering and analysis IDE.
• J2CS - A Java to C# transpiler.
• Dukes-8-Bit-Challenge - A game-jam submission using YABR in buildSrc/ for compile-time transformations.

Building

• Java 11+

./gradlew build
./gradlew :all:shadowJar

Installation

The published artifact is the merged jar from the all module. Via JitPack:

repositories {
    mavenCentral()
    maven { url = uri("https://jitpack.io") }
}

dependencies {
    implementation("com.github.Tonic-Box.YABR:all:<version>")
}

Quick Start

// Load a class
ClassPool pool = ClassPool.getDefault();
ClassFile cf = pool.loadClass(inputStream);

// Create a new class with a default constructor
int access = new AccessBuilder().setPublic().build();
ClassFile newClass = ClassFactory.createClass(pool, "com/example/MyClass", access);

// Add a field with a getter and setter
FieldEntry field = newClass.createNewField(access, "value", "I", new ArrayList<>());
ClassFactory.generateGetter(newClass, field, false);
ClassFactory.generateSetter(newClass, field, false);

// Write the class
newClass.rebuild();
byte[] bytes = newClass.write();

Examples

Runnable examples are in examples/src/main/java/com/tonic/demo/, including class creation, SSA transformation, LLVM lowering, AST mutation, decompilation, call graphs, dependency analysis, type inference, and pattern search.

Documentation

Getting Started

Guide	Description
Quick Start	Load, create, and modify classes in five minutes
Architecture	Module structure and design

Class Files & Bytecode

Guide	Description
Class Files	ClassPool, ClassFile, ConstPool
Bytecode API	Low-level bytecode editing
Generation API	Fluent class/method generation
Visitors	Traversal and transformation patterns
Frame Computation	StackMapTable generation

SSA & IR

Guide	Description
SSA Guide	SSA intermediate representation
SSA Transforms	Optimization and analysis passes
LLVM Lowering	Lower SSA IR to textual LLVM IR
LLVM Lifting	Lift LLVM IR back to SSA

Source & Decompilation

Guide	Description
AST Guide	AST recovery, mutation, and emission
AST Editor	ExprEditor-style AST transformation
Parser API	Java source parser
Decompiler API	Class -> Java source decompilation

Analysis

Guide	Description
Analysis APIs	Overview of the analysis suite
Call Graph API	Call-graph construction
Data Flow API	Data-flow analysis
Dependency API	Dependency analysis
PDG API	Program Dependence Graph with slicing
SDG API	Interprocedural System Dependence Graph
CPG API	Code Property Graph with taint analysis
Pattern Search API	Structural bytecode pattern search
Similarity API	Method similarity and fingerprinting
Type Inference API	Type inference
Xref API	Cross-references

Execution & Runtime

Guide	Description
Execution API	Concrete bytecode execution
Simulation API	Abstract simulation
Abstract Execution API	Operand-stack and local def-use
Instrumentation API	Bytecode instrumentation and hooks
Verifier API	Bytecode verification

Language & Query

Guide	Description
Query API	Bytecode query language
Renamer API	Class, method, and field renaming

Project Layout

YABR is a Gradle multi-project. Production code is split into layered modules (core, bytecode, renamer, ssa, source, analyses, execution, query) whose dependencies are acyclic and build-enforced; the all module merges them into a single jar. See Architecture.

Acknowledgements

Inspired by classpooly.

License

MIT