Code-Server x Dart with ffi x Go x Clang

This is an article of Dart Advent Calendar 2019.

An article about Dart's Native Interface. Learn how to use Go and C features with Dart. We've also prepared a Docker Image so you can try out the Native Interface right away.

Native Interface: A feature that allows you to use C language libraries

https://dart.dev/guides/libraries/c-interop

This is a function that allows you to use a C language library. However, C language is not closed to the library in C language.

System languages such as Go and Rust can create Shared Libraries.

You can also use features such as Go and Rust with Dart via this Shared Library.

Very convenient: Full use of OS functions

Dart is still running out of libraries. Therefore, it is necessary to use the library developed in C language or the library developed in Go. The Native Interface makes Dart more convenient.

Development environment: We have prepared a Docker environment.

We have included an editor called Code-Server that runs VS Code online. Therefore, if you start Docker, you can start development immediately.

https://github.com/kyorohiro/my-code-server/tree/master/w/dart_and_go_and_c/

https://github.com/kyorohiro/advent-2019-code-server/tree/master/extra/dart_ffi_and_go_and_c

FROM ubuntu:20.04

WORKDIR /works
# install dart
RUN apt-get update
RUN apt-get install -y wget gnupg1
RUN apt-get install apt-transport-https
RUN sh -c 'wget -qO- https://dl-ssl.google.com/linux/linux_signing_key.pub | apt-key add -'
RUN sh -c 'wget -qO- https://storage.googleapis.com/download.dartlang.org/linux/debian/dart_stable.list > /etc/apt/sources.list.d/dart_stable.list'
RUN apt-get update
RUN apt-get -y install dart

# install go
RUN apt-get install software-properties-common -y
#RUN add-apt-repository ppa:longsleep/golang-backports
RUN apt-get update
RUN apt-get install golang-go -y
RUN apt-get install git -y
RUN go get github.com/ramya-rao-a/go-outline
RUN go get github.com/mdempsky/gocode
RUN go get github.com/uudashr/gopkgs/cmd/gopkgs
RUN go get github.com/sqs/goreturns
RUN go get github.com/rogpeppe/godef

# install c
RUN apt-get install musl-dev -y

# code-server
RUN wget https://github.com/cdr/code-server/releases/download/2.1692-vsc1.39.2/code-server2.1692-vsc1.39.2-linux-x86_64.tar.gz
RUN tar -xzf code-server2.1692-vsc1.39.2-linux-x86_64.tar.gz -C ./ --strip-components 1


RUN /works/code-server --install-extension Dart-Code.dart-code
RUN /works/code-server --install-extension ms-vscode.go
RUN /works/code-server --install-extension ms-vscode.cpptools

WORKDIR /app
ENV PATH=${PATH}:/lib/dart/bin
ENV PATH="${PATH}:/root/.pub-cache/bin"
RUN pub global activate webdev
RUN pub global activate stagehand

CMD ["/works/code-server", "--auth","none", "--host","0.0.0.0","--port","8443", "/app"]

docker-compose.yml

version: '3'
services: 
  app:
    build: ./app
    ports:
     - "8080:8080"
     - "8443:8443"
    volumes: 
      - ./app:/app
    # - /var/run/docker.sock:/var/run/docker.sock
    command: /works/code-server --auth none --host 0.0.0.0 --port 8443 /app 

Specifically, see github.

Start the development environment.

$ git clone https://github.com/kyorohiro/advent-2019-code-server.git
$ cd advent-2019-code-server/extra/dart_fmi_and_go_and_c
$ docker-compose build
$ docker-compose up -d

Open http://127.0.0.1:8443/ in your browser

Create a Shared Library in Go.

Go to VSCode-> File (Menu)-> / app / wgo.

hello.go

package main

import "C"
import "fmt"

//export PrintHello
func PrintHello() {
	fmt.Print("Hello,World")
}

func main() {}

Go's PrintHello function will be called by Dart.

$ go build -o libhello.so  -buildmode=c-shared  hello.go

Will create the files libhello.h and libhello.so. Let's load it from C before loading it with Dart.

main_hello.c

#include <stdio.h>
#include "libhello.h"


int main(int argc, char const *argv[])
{
  PrintHello();
  return 0;
}

Terminal

$ gcc -Wall -o main_hello.exe main_hello.c -L. -lhello
$ LD_LIBRARY_PATH=. ./main_hello.exe -L. -lhello
Hello,World

Oops !! It worked fine.

Try loading from Dart.

Go to VSCode-> File (Menu)-> / app / wdart.

bin/main.dart

import 'dart:ffi' as ffi;

typedef PrintHello_func = ffi.Void Function();
typedef PrintHello = void Function();

void main(List<String> arguments) {
  var path = "/app/wgo/libhello.so";
  ffi.DynamicLibrary dylib = ffi.DynamicLibrary.open(path);
  final PrintHello hello = dylib
      .lookup<ffi.NativeFunction<PrintHello_func>>('PrintHello')
      .asFunction();
  hello();
}

Terminal

$ dart ./bin/main.dart
Hello,World

PS

We also prepared a C language environment. You can see it from the github repository earlier.

Get full access to features developed in Go with Dart. So, from Dart, I can do almost anything. With the support of FMI, I think it's easier to write Native Interfaces.

If it is for the server side, I think that Docker Image etc. is convenient for development.

About the Code-Server used this time, in the following Advent The explanation is divided into more than 20 times, so if you are interested, please refer to it.

https://qiita.com/advent-calendar/2019/code-server

• If you solidify it as a Docker Image and place it on the Hub, it will always work, but it is not solidified as an Image. For personal use, it is recommended to keep it in an Image.

Code

https://github.com/kyorohiro/my-code-server/tree/master/w/dart_and_go_and_c/

https://github.com/kyorohiro/advent-2019-code-server/tree/master/extra/dart_fmi_and_go_and_c