60 lines
1.6 KiB
Rust
60 lines
1.6 KiB
Rust
#[cxx::bridge(namespace = "org::blobstore")]
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mod ffi {
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// Shared structs with fields visible to both languages.
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struct BlobMetadata {
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size: usize,
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tags: Vec<String>,
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}
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// Rust types and signatures exposed to C++.
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extern "Rust" {
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type MultiBuf;
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fn next_chunk(buf: &mut MultiBuf) -> &[u8];
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}
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// C++ types and signatures exposed to Rust.
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unsafe extern "C++" {
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include!("demo/include/blobstore.h");
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type BlobstoreClient;
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fn new_blobstore_client() -> UniquePtr<BlobstoreClient>;
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fn put(&self, parts: &mut MultiBuf) -> u64;
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fn tag(&self, blobid: u64, tag: &str);
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fn metadata(&self, blobid: u64) -> BlobMetadata;
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}
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}
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// An iterator over contiguous chunks of a discontiguous file object.
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//
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// Toy implementation uses a Vec<Vec<u8>> but in reality this might be iterating
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// over some more complex Rust data structure like a rope, or maybe loading
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// chunks lazily from somewhere.
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pub struct MultiBuf {
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chunks: Vec<Vec<u8>>,
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pos: usize,
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}
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pub fn next_chunk(buf: &mut MultiBuf) -> &[u8] {
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let next = buf.chunks.get(buf.pos);
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buf.pos += 1;
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next.map_or(&[], Vec::as_slice)
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}
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fn main() {
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let client = ffi::new_blobstore_client();
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// Upload a blob.
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let chunks = vec![b"fearless".to_vec(), b"concurrency".to_vec()];
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let mut buf = MultiBuf { chunks, pos: 0 };
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let blobid = client.put(&mut buf);
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println!("blobid = {}", blobid);
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// Add a tag.
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client.tag(blobid, "rust");
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// Read back the tags.
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let metadata = client.metadata(blobid);
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println!("tags = {:?}", metadata.tags);
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}
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