Skip to content

Extend the book's async page to show multiple calls to rust::Fn producing a stream #861

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
wants to merge 2 commits into
base: master
Choose a base branch
from
Open

Extend the book's async page to show multiple calls to rust::Fn producing a stream #861

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
bf24824
Extend the book's async example to show multiple calls to rust::Fn to…
jerel May 3, 2021
f39f1f1
Improved grammar
jerel May 3, 2021
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
22 changes: 22 additions & 0 deletions book/src/async.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -84,3 +84,25 @@ void shim_doThing(
});
}
```

### Streams

The async example above can be extended to support streaming data as well using a channel such as [`futures::channel::mpsc::unbounded`] instead of oneshot and passing `DoThingContext` to the closure as a reference:

[`futures::channel::mpsc::unbounded`]: https://docs.rs/futures/0.3.8/futures/channel/mpsc/fn.unbounded.html

```cpp
// bridge_shim.cc

#include "path/to/bridge.rs.h"
#include "rust/cxx.h"

void shim_doThing(
Arg arg,
rust::Fn<void(const DoThingContext &ctx, Ret ret)> done,
rust::Box<DoThingContext> ctx) noexcept {
done(*ctx, std::move(res));
done(*ctx, std::move(res));
done(*ctx, std::move(res));
Comment on lines +104 to +106
Copy link
Owner

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Are you able to share some code structure that is more illustrative of how these res values would be obtained asynchronously in C++? As is, this example looks like it is just synchronously sending 3 values, which would not make sense to treat as futures::Stream in Rust. And something like co_await arg->next() does not work because this function is not a coroutine.

I am not familiar enough with streaming APIs in C++ to tell from this example how it would translate to usable real-world code.

}
```