comprehensive-rust/third_party/cxx/book/snippets.rs

//! This file contains various code snippets taken from the CXX book and
//! tutorial. Some have been modified to fit the course better.

// ANCHOR: rust_bridge
#[cxx::bridge]
mod ffi {
    extern "Rust" {
        type MyType; // Opaque type
        fn foo(&self); // Method on `MyType`
        fn bar() -> Box<MyType>; // Free function
    }
}

struct MyType(i32);

impl MyType {
    fn foo(&self) {
        println!("{}", self.0);
    }
}

fn bar() -> Box<MyType> {
    Box::new(MyType(123))
}
// ANCHOR_END: rust_bridge

// ANCHOR: cpp_bridge
#[cxx::bridge]
mod ffi {
    extern "C++" {
        include!("demo/include/blobstore.h");
        type BlobstoreClient;
        fn new_blobstore_client() -> UniquePtr<BlobstoreClient>;
        fn put(&self, parts: &mut MultiBuf) -> u64;
    }

    unsafe extern "C++" {
        fn f();  // safe to call
    }
}
// ANCHOR_END: cpp_bridge

// ANCHOR: shared_types
#[cxx::bridge]
mod ffi {
    #[derive(Clone, Debug, Hash)]
    struct PlayingCard {
        suit: Suit,
        value: u8,  // A=1, J=11, Q=12, K=13
    }

    enum Suit {
        Clubs,
        Diamonds,
        Hearts,
        Spades,
    }
}
// ANCHOR_END: shared_types

// ANCHOR: shared_enums_bridge
#[cxx::bridge]
mod ffi {
    enum Suit {
        Clubs,
        Diamonds,
        Hearts,
        Spades,
    }
}
// ANCHOR_END: shared_enums_bridge

// ANCHOR: shared_enums_rust
#[derive(Copy, Clone, PartialEq, Eq)]
#[repr(transparent)]
pub struct Suit {
    pub repr: u8,
}

#[allow(non_upper_case_globals)]
impl Suit {
    pub const Clubs: Self = Suit { repr: 0 };
    pub const Diamonds: Self = Suit { repr: 1 };
    pub const Hearts: Self = Suit { repr: 2 };
    pub const Spades: Self = Suit { repr: 3 };
}
// ANCHOR_END: shared_enums_rust

// ANCHOR: rust_result
#[cxx::bridge]
mod ffi {
    extern "Rust" {
        fn fallible(depth: usize) -> Result<String>;
    }
}

fn fallible(depth: usize) -> anyhow::Result<String> {
    if depth == 0 {
        return Err(anyhow::Error::msg("fallible1 requires depth > 0"));
    }

    Ok("Success!".into())
}
// ANCHOR_END: rust_result

// ANCHOR: cpp_exception
#[cxx::bridge]
mod ffi {
    unsafe extern "C++" {
        include!("example/include/example.h");
        fn fallible(depth: usize) -> Result<String>;
    }
}

fn main() {
    if let Err(err) = ffi::fallible(99) {
        eprintln!("Error: {}", err);
        process::exit(1);
    }
}
// ANCHOR_END: cpp_exception

// ANCHOR: cxx_overview
#[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
// ANCHOR_END: cxx_overview