java-remapper

Remap names in JVM bytecode (.class files) using Java deobfuscation mappings. Class, field, and method names, along with descriptors, signatures, annotations, inner classes, and local variables, are rewritten in place. Bytecode instructions are left untouched—only the constant pool and class metadata are updated.

Library

Build an Index from a mapping source, then call remap:

use java_remapper::{Buffer, Context, Index, remap};

fn remap_class(index: &Index, src: &[u8]) -> Result<Vec<u8>, java_remapper::Error> {
    // Optional: record superclass/interface relationships so inherited members
    // can be resolved. Pass every class that belongs to the same unit.
    let mut cx = Context::new();
    cx.populate_inherency([src]);

    // A `Buffer` can be reused across calls.
    let mut buf = Buffer::new();
    let mut dst = Vec::new();
    remap(src, &mut dst, index, &mut buf, &cx)?;
    Ok(dst)
}

Index implements mapping_serde::Deserialize, so it can be built from any format supported by the mapping-serde ecosystem (Tiny1/Tiny2, Enigma, Proguard).

CLI

The java-remapper-cli binary reads a class file or JAR from a path or stdin and writes the remapped result to a path or stdout.

Usage: java-remapper-cli [OPTION]...

      --tiny2  FILE use the FILE as mapping file, in Tiny2 format
      --class  FILE input class file from FILE
      --jar    FILE input JAR file from FILE
  -o, --output FILE output into FILE
  -h, --help        give this help

Feature flags

Hash maps used internally are selected by feature flags.

• ahash (default): use ahash.
• fx-hash: use rustc-hash instead. Enable it with default-features = false, features = ["fx-hash"].

If neither is enabled, the standard library hasher is used. If both are enabled, fx-hash takes precedence.