How to reference flutter assets in Rust code

[beetee17]

Hi, pardon my ignorance as I am new to ffigen and Rust.

Essentially, I found this library as I was searching for a way to use Huggingface's tokenizers library in my Flutter app.

I have gotten most of it set up, and I do get an output when I call the API's function that downloads the tokenizer first before using it locally.

However, I would like my app to work without a network connection, hence I would like to be able to use another one of the API's functions that accepts file paths to the tokenizer and loads it locally.

I have tried copying the files to $crate/src, as well as to the $app/assets folder, ios/Runner and ios/Runner/$crate.

However, referencing the path (relative or absolute) yields: Err value: Os { code: 2, kind: NotFound, message: "No such file or directory" }.

I did a recursive search on the current working directory in Rust using WalkDir, which has made me realise that the Rust code's cwd is somewhere else (perhaps in the Device filesystem?).

Is it therefore possible to reference a local file through Rust? If not directly then maybe by changing the cwd?

I was also thinking of reading the byte data in Flutter and sending that to my Rust function to write it to a file in its cwd.

Edit:

I just tried updating the Cargo.toml file to include my assets folder as such:

[package]
name = "rust"
version = "0.1.0"
edition = "2021"
include = ["assets"]

After running cargo package --list, I get the following output which was promising:

Cargo.toml
Cargo.lock
assets/albert-base-v2-spiece.model
assets/vocab.txt

However the same error persists when I try loading the file: let tokenizer = Tokenizer::from_file("assets/albert-base-v2-spiece.model").unwrap();

[fzyzcjy]

At least for android, if I remember correctly, the "asset" files are not really a real file in disk but somehow part inside the apk file.

Method 1: https://stackoverflow.com/questions/27140634/how-to-embed-resources-in-rust-executable Then the model is within your .so and you can use it like a u8 array.

Method 2: Let Flutter manage it. Look at flutter doc to see how to manage an "asset". You may need a few lines of flutter code to copy the asset to, say, temporary folder, before rust can see it.

[beetee17]

Hi there, thanks for the reply! I will give the second option a shot before the first as I am more familiar with Flutter. When you say copy the asset over to tmp, do you mean the tmp on Rust's filesystem? As during WalkDir I did see a ./tmp folder.

However, I'm not sure how I would be able to access this folder in my Flutter code.

[beetee17]

I was also wondering why my attempt in the edit did not work, which was to include the assets path in Cargo.toml. I got the idea from a related discussion on this repo: https://github.com/fzyzcjy/flutter_rust_bridge/discussions/275 where the OP was trying to load mp3 sounds into Kira from an assets folder. This would've been a much more straightforward solution if it worked!

[fzyzcjy]

No, I mean https://pub.dev/packages/path_provider getTemporaryDirectory(); (or any other dir you like).

[fzyzcjy]

https://doc.rust-lang.org/cargo/reference/manifest.html#the-exclude-and-include-fields

explicitly specify which files are included when packaging a project to be published,

But you are compiling and only get a .so, not publish package to Crates.io

[beetee17]

No, I mean https://pub.dev/packages/path_provider getTemporaryDirectory(); (or any other dir you like).

Thank you it worked perfectly!