Why Port 10k LOC to Rust

Lessons learned

Who?

Kai, hacker from Bochum.

Interested in cryptography and reverse engineering.

flanfly / @_cibo_

What?

First commit is from September 2011

Everything was done in C++11 and Qt 4 later 5

Heavy use of template meta programming

ensure(lambda.count(source(*p.first,graph)));
unsigned int rank = std::accumulate(p.first,p.second,
	 lambda.at(source(*p.first,graph)) + get_edge(*p.first,graph).second,
#ifdef _MSC_VER
	 [&](int acc,po::digraph<N,std::pair<int,int>>::edge_descriptor e)
#else
	 [&](int acc,typename po::digraph<N,std::pair<int,int>>::edge_descriptor e)
#endif
	 {
		 return std::max(acc,reinterpret_cast<int>(lambda.at(source(e,graph)) +
						get_edge(e,graph).second));
	 });

ensure(lambda.insert(std::make_pair(*i,rank)).second);

Rust has Sum Types

Rust

match instr {
	Instr::Phi(ref vec) => ...
	Instr::Add(ref a, ref b) => ...
	...
}

C++

struct vis : public boost::static_visitor<std::string>
{
	std::string operator()(const int_add<rvalue>&) const { ... }
	std::string operator()(const univ_phi<rvalue>&) const { ... }
	...
};
vis v;

boost::apply_visitor(v,i);

Rust has the Borrow Checker

template<typename T,typename D>
struct basic_loc
{
	const T* operator->(void) const { return read(); }
	const T& operator*(void) const { return *read(); }
	//T* operator->(void) { return write(); }
	//T& operator*(void) { return *write(); }

	const T* read(void) const
	{
		std::shared_ptr<loc_control<T>> cb = static_cast<const D*>(this)->control();

		if(!cb->has_object())
			cb->inner = unmarshal<T>(_uuid,cb->storage());
		if(!cb->object())
			throw std::runtime_error("reading deleted loc");
		return cb->object();
	}

	T& write(void) { .. }
}