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Rust

How to install and use the Extism Rust PDK​

Create a Rust project​

cargo new --lib my-plugin

In the generated Cargo.toml, be sure to include:

[lib]
crate_type = ["cdylib"]

Installation​

cargo add extism-pdk

Compiling to WebAssembly​

cargo build --release --target wasm32-unknown-unknown

NOTE: --target wasm32-wasi is also fully supported

Latest Docs​

https://docs.rs/extism-pdk

Example Usage​

Using Config, I/O, & Persisted Variables​

lib.rs
use extism_pdk::*;
use serde::Serialize;

const VOWELS: &[char] = &['a', 'A', 'e', 'E', 'i', 'I', 'o', 'O', 'u', 'U'];

#[derive(Serialize)]
struct TestOutput {
    pub count: i32,
    pub config: String,
    pub a: String,
}

#[plugin_fn]
pub fn count_vowels(input: String) -> FnResult<Json<TestOutput>> {
    let mut count = 0;
    for ch in input.chars() {
        if VOWELS.contains(&ch) {
            count += 1;
        }
    }

    set_var!("a", "this is var a")?;

    let a = var::get("a")?.expect("variable 'a' set");
    let a = String::from_utf8(a).expect("string from varible value");
    let config = config::get("thing").expect("'thing' key set in config");

    let output = TestOutput { count, config, a };
    Ok(Json(output))
}

Using Extism built-in HTTP​

lib.rs
use extism_pdk::*;

#[plugin_fn]
// see https://docs.rs/extism-pdk/latest/extism_pdk/struct.HttpRequest.html for docs on this type
pub fn http_get(Json(req): Json<HttpRequest>) -> FnResult<HttpResponse> {
    info!("Request to: {}", req.url);
    let res = http::request::<()>(&req, None)?;
    Ok(res)
}