It's trivial to call c from rust normally, is there a way to do so from a substrate project? I can't find anything online saying it's possible or it's not possible.
I have a c library I'd like to use as part of a substrate project and I was wondering if it would be possible to use it without rewriting it.
Many FFI libraries are no_std compliant, this is the only hard requirement for being used in substrate runtimes. Checkout the list here and look for that tag for options to move forward:
https://lib.rs/development-tools/ffi
If you are using this library outside the runtime, you should be able to use any rust library.
Related
I'm writing a smart contract and want to know which external crates will work and which won't. I don't want to go through the trouble of importing them into my contracts and checking if everything compiles properly every time I want to use a crate.
As an example, say I wanted to use the rand crate but then found out it wasn't compatible. How could I check this beforehand?
As a general rule of thumb, anything that supports wasm32-unknown-unknown will be compatible with your smart contract. An easy way to check this is by going to crates.io and checking there. In your example, when going to the rand page and doing a quick find all for wasm32, you can see at the bottom that wasm32-unknown-unknown is not "automatically supported":
This is a good rule to follow, but there are edge cases where a crate might compile to wasm32 but fail at runtime for incompatible functionality.
VPP provides the I/S for developing custom plugins that can be hooked into a graph of nodes. I've only seen examples for such plugins written in the C language, and was wondering whether other language, Go for instance, can also be used to write such plugins.
I have no idea what "VPP" is but nonetheless the answer is: "maybe"; here's why:
Go code is able to interface with C libraries via its facility known as cgo.
cgo is a multiple-faceted thing: it allows you to "export" certain Go functions in a certain way so that they can be called from the C side, and it allows you to call functions from the C side. It also allows you to write bits of inline C code to provide glue for the C side, when necessary.
Since some time Go building toolset (at least its "reference" implementation) provides for compiling Go code into a static or dynamic library with C-compatible API.
See this.
With these things in mind, in theory, it should be possible to do what you're after.
Note some possible obstacles:
Most of the time, if a "platform" allows you to write a "plugin" in C, it presupposes your plugin will make extensive use of the platform's own API.
This usually means your plugin is supposed to include certain header files provided by the platform.
The platform might also require your plugin to link against some platform-provided library (usually shared), or libraries.
cgo can do all of the above, but you will need to scrutinize the API provided by the platform and maybe write Go helpers to make its usage more natural for the Go code.
Building/linking issues (usually the locations of the header files and the libs) may also be a thing to solve.
When creating a new app in Xamarin Forms I see these two options:
Configure your Forms App
Shared Code:
Use .NET Standard
Use Shared Library
Can someone explain the difference? I looked at the help and I am still confused. I'd appreciate if someone can give me any advice on this. Not sure if it helps but this app is self contained and no code in the app will need to be shared with any other application.
In terms of what you can achieve with both, it is the same. So, in the end, it's mostly a matter of taste.
The biggest difference is that a shared project is compiled into the app itself. It is nothing more than it says on the tin: it's a shared folder that you can use in all platform projects. Using platform-specific code is done through compiler directives.
With a .NET Standard project, you will get a physical binary. It is a project of its own. You can reuse it in other .NET Standard projects, although you already mentioned you won't be using it for that. Executing platform-specific code requires a bit different approach, using the DependencyService.
Seeing that they made a choice to replace the PCL with .NET Standard but keep the shared project points out that the shared project is here to stay for a while. I tend to like the .NET Standard library more. It feels cleaner and forces you to write cleaner code. Also, .NET Standard isn't going anywhere soon and if you decide that code should be reused down the road, you have the ability to.
A good overview, together with pros and cons can be found in the Microsoft Docs: https://learn.microsoft.com/en-us/xamarin/cross-platform/app-fundamentals/code-sharing
I'm tasked with creating an SDK that can be consumed from both Android & Java applications using ReactiveX programming. I already have an android project using RxAndroid created, but now I need to extend it with RxJava2.
The question I'm facing is whether I should create 'regular' java class library and use it for both scenarios or create 2 separate packages (which would mean a lot of duplicate code + maintenance).
Is this even possible? And if so, is it a good practice?
whether I should create 'regular' java class library and use it for both scenarios
Yes. What I would do to start is simply change your Android library project to be a standard Java library and replace RxAndroid dependency by RxJava. Most code should still compile. Code which doesn't will mostly use schedulers provided by RxAndroid and can be changed to take Scheduler parameters.
Then create an Android Library project which depends on the Java Library and put the RxAndroid-specific code there.
As an addition to #AlexeyRomanov's answer, feel free to check out this library which could be used for both Android and Java projects: https://github.com/JakeWharton/RxRelay.
Its basically an extension to RxJava, but it might give you a solid idea where to go. Good luck!
I've found a ton of information about how to use cgo to call C libraries from Go, but I'm interested in the opposite: writing a library in Go, and linking/using it in various C programs.
Is this possible? Any good resources for this? Thanks.
This can not be done currently. Go has to be the entry point and without the use of gccgo, you can't compile Go into a shared library.
There is a proposal to change this, so it may or may not be an option at some point. Refer to this document for details.