JBcRs ![Latest Version]
JBcRs is a Library to support reading and writing of java class files.
This library is not close from being finished, but certain features have already been implemented:
- Basic parsing:
A class file is parsed rather primitive:
- You have access to the constant pool.
Names, Descriptors and more are represented as
u16
, Indexing into the pool must be done manually. No validation of indices when parsing will be done. - Access Flags are decoded using the bitflags crate to provide a better experience.
- Attributes are always parsed. This might be changed since it allows attackers to craft invalid Debug Attributes, which don't play a serious role in executing the code, Parsing the entire class file then might not work, since an error will be returned.
- You have access to the constant pool.
Names, Descriptors and more are represented as
- More will be coming soon™.
Getting Started:
First, add this library as a dependency to your Cargo.toml
[]
= "0.1.0"
Now, you should choose if you want to use basic
or advanced
,
but since advanced
is not yet implemented, basic
must be used.
Basic
We want to parse a class from a byte array and print its version, access flags and name. Of course you could use std::fs::File or a zip library, but showing this is not the purpose of this tutorial.
use basic;
// You got the bytes from any possible source.
let bytes: & = ;
// After parsing the class file,
// you will get the constant pool
// and the class itself.
// You don't have to annotate the types here.
let : = parse
.expect;
// Print its major and minor version:
println!;
// Access Flags can be printed human readable
println!;
// Printing the name requires us to use the constant pool.
println!;