There is an automated tool - c2rust[1], automating a huge chunk of the translation from C to Rust. Moreover, it has a refactoring tool[2] that is scriptable in Lua. One of the good examples of such conversion (still not finished though), while still producing the same output is a rewrite[3][4] of XeTeX engine to Rust (as part of Tectonic[5] engine). It is able to parse arXiv articles dump and generate valid PDFs still.
There is some concept[6] of converting Java to Rust, but it is far from being as useful as c2rust tool. Would be nice to integrate with c2rust somehow, if someone wants to help.
[1] https://github.com/immunant/c2rust
[2] https://c2rust.com/manual/c2rust-refactor/index.html
[3] https://github.com/tectonic-typesetting/tectonic/issues/459
[4] https://github.com/crlf0710/tectonic/tree/oxidize