أمثلة على الربط (Example Bindings)

CXX requires that the whole C++/Rust boundary is declared in cxx::bridge modules inside .rs source code.

#[cxx::bridge] mod ffi { extern "Rust" { type MultiBuf; fn next_chunk(buf: &mut MultiBuf) -> &[u8]; } unsafe extern "C++" { include!("example/include/blobstore.h"); type BlobstoreClient; fn new_blobstore_client() -> UniquePtr<BlobstoreClient>; fn put(self: &BlobstoreClient, buf: &mut MultiBuf) -> Result<u64>; } } // Definitions of Rust types and functions go here

Speaker Notes

Point out:

  • Although this looks like a regular Rust mod, the #[cxx::bridge] procedural macro does complex things to it. The generated code is quite a bit more sophisticated - though this does still result in a mod called ffi in your code.
  • Native support for C++’s std::unique_ptr in Rust
  • Native support for Rust slices in C++
  • Calls from C++ to Rust, and Rust types (in the top part)
  • Calls from Rust to C++, and C++ types (in the bottom part)

Common misconception: It looks like a C++ header is being parsed by Rust, but this is misleading. This header is never interpreted by Rust, but simply #included in the generated C++ code for the benefit of C++ compilers.