Rust Ffi

Covers the full FFI workflow from manual extern declarations through bindgen automation, cbindgen for exporting Rust to C, and the sys crate pattern for wrapping native libraries. Shows practical build.rs configurations for linking, allowlisting specific symbols in bindgen to avoid pulling in system headers, and writing safe Drop-based wrappers around unsafe handles. The examples are comprehensive, walking through CString conversions, null checks, and proper error handling at FFI boundaries. Honest take: this is exactly the reference you want when integrating C libraries, with enough real patterns that you won't just cargo cult Stack Overflow snippets. The split between raw bindings and safe wrappers follows established Rust conventions well.