Monday, 5 July 2021

Learning Rust - because Kata

As per previous posts here, I've been working with Kata Containers this past few months, and, as such, have been tinkering with Rust because a core part of the Kata project, namely the kata-agent is written in that particular new ( to me ) language.

Right now, I'm looking at a mechanism to parse container image names, separating out the registry, namespace, repository and tag.

Therefore, I needed to find a way to parse a string e.g. docker.io/davidhay1969/hello-world-nginx:latest into a series of individual strings: -

docker.io

davidhay1969

hello-world-nginx

latest

I started with dot net perls which introduced me to the split() function, and then proceeded from there ...

I then found the Rust By Example site, which allowed me to test out my learnings interactively ...

I started with, of course, Hello World! 

// This is a comment, and is ignored by the compiler
// You can test this code by clicking the "Run" button over there ->
// or if you prefer to use your keyboard, you can use the "Ctrl + Enter" shortcut
// This code is editable, feel free to hack it!
// You can always return to the original code by clicking the "Reset" button ->
// This is the main function
fn main() {
    // Statements here are executed when the compiled binary is called
    // Print text to the console
    let full_name="Dave;Hay";
    let names = full_name.split(';');
    print!("Hello ");
    for n in names {
        print!("{} ",n);
    }
}

One nice thing is that I can make AND test changes within the web page, rather than having to code/test/code/test in, say, Visual Studio Code.

When I click 'Run', here we go ...

Hello Dave Hay 

and then amended it to meet my specific requirement wrt container images: -

// This is a comment, and is ignored by the compiler
// You can test this code by clicking the "Run" button over there ->
// or if you prefer to use your keyboard, you can use the "Ctrl + Enter" shortcut

// This code is editable, feel free to hack it!
// You can always return to the original code by clicking the "Reset" button ->

// This is the main function
fn main() {
    // Statements here are executed when the compiled binary is called

    // Print text to the console
    let full_container_image="docker.io/davidhay1969/hello-world-nginx:latest";
    let names = full_container_image.split('/');
    println!("The image is :-");
    for n in names {
        println!("{} ",n);
    }
}

One nice thing is that I can make AND test changes within the web page, rather than having to code/test/code/test in, say, Visual Studio Code.

When I click 'Run', here we go ...

The image is :-
docker.io 
davidhay1969 
hello-world-nginx:latest 

Obviously, I need to add some logic to handle the semi-colon ( ; ) between the repository and tag, but that's easy enough to do ....

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