1#[cxx::bridge(namespace = "org::blobstore")] 2mod ffi { 3 // Shared structs with fields visible to both languages. 4 struct BlobMetadata { 5 size: usize, 6 tags: Vec<String>, 7 } 8 9 // Rust types and signatures exposed to C++. 10 extern "Rust" { 11 type MultiBuf; 12 13 fn next_chunk(buf: &mut MultiBuf) -> &[u8]; 14 } 15 16 // C++ types and signatures exposed to Rust. 17 unsafe extern "C++" { 18 include!("demo/include/blobstore.h"); 19 20 type BlobstoreClient; 21 22 fn new_blobstore_client() -> UniquePtr<BlobstoreClient>; 23 fn put(&self, parts: &mut MultiBuf) -> u64; 24 fn tag(&self, blobid: u64, tag: &str); 25 fn metadata(&self, blobid: u64) -> BlobMetadata; 26 } 27} 28 29// An iterator over contiguous chunks of a discontiguous file object. 30// 31// Toy implementation uses a Vec<Vec<u8>> but in reality this might be iterating 32// over some more complex Rust data structure like a rope, or maybe loading 33// chunks lazily from somewhere. 34pub struct MultiBuf { 35 chunks: Vec<Vec<u8>>, 36 pos: usize, 37} 38pub fn next_chunk(buf: &mut MultiBuf) -> &[u8] { 39 let next = buf.chunks.get(buf.pos); 40 buf.pos += 1; 41 next.map_or(&[], Vec::as_slice) 42} 43 44fn main() { 45 let client = ffi::new_blobstore_client(); 46 47 // Upload a blob. 48 let chunks = vec![b"fearless".to_vec(), b"concurrency".to_vec()]; 49 let mut buf = MultiBuf { chunks, pos: 0 }; 50 let blobid = client.put(&mut buf); 51 println!("blobid = {}", blobid); 52 53 // Add a tag. 54 client.tag(blobid, "rust"); 55 56 // Read back the tags. 57 let metadata = client.metadata(blobid); 58 println!("tags = {:?}", metadata.tags); 59} 60