Parity-as-a-library

[rphmeier]

• APIs for running full and light nodes
• C interface

[rphmeier]

...and then the ability to cross-compile this library to IOS and Android.
@debris in your experience what will be the hardest part of that?

[debris]

... what will be the hardest part of that?

Probably cross-compiling libraries containing C code... Besides that, writing C interfaces itself, cause it's super time consuming

[arkpar]

The C interface can be simple enough. It's mostly configuration, creating, starting and stopping Parity service and polling for status to detect critical errors. In the simplest implementation configuration can be done by passing text in toml format. So basically just 3 functions.

parity_service_handle parity_create(const char* config);
void parity_destroy(parity_service_handle handle);
void parity_poll_status(parity_service_handle handle, parity_status* status);

All other communication goes over RPC/IPC.

If we want to expose our rich API to C, these bindings need to be auto-generated from RPC traits.

[rphmeier]

That definitely seems like a good approach.
I wonder about the viability of running an RPC server for a hosted node within an app. We might want to just have a native code RPC endpoint

char* parity_rpc(parity_service_handle handle, const char* request);
which just wraps a thread pool + event loop + future.wait() internally.
I'm not sure if null-terminated strings is the best approach here as it's probably for FFI, and most languages these days would deal in a [ptr, len] pair, but the basic idea stays the same.

[adrianbrink]

@debris But wouldn't that be the worry of an implementor to compile libraries that contain C code. From our side we would only need to worry about writing the C interfaces (which will take a lot of time).

[adrianbrink]

To expose the C api something like rusty-binder or rusty-cheddar would be good to use.

Also, let's see if the rust team will support this in the future.

[rphmeier]

@adrianbrink I think @debris was referring to C/C++ libraries we have as dependencies, which may be hard to cross-compile.
To expose a C API we can just use #[no_mangle] pub extern fn in Rust code.

[adrianbrink]

Oh right. Didn't know parity had C/C++ deps.
Yeah, rusty-cheddar/binder could be used then to auto-generate the C header files.

[tomaka]

Reopening as I'm going to work on this soon-ish.