WebXtism is a Rust library designed to provide a flexible and efficient runtime environment for WebAssembly (Wasm) plugins, particularly in a web context. It leverages the Wasmer runtime for executing Wasm modules and offers an extensible plugin system. The plugins are compatible with extism and this project is designed to use their PDK in any language they support.
This crate is highly experimental and not ready for any kind of production use!
Extism already provides a Rust implementation, so why another one?
The official implementation uses Wasmtime, while this one uses Wasmer. Switching the runtime results in a different feature set:
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Cross-Platform Support: Wasmer is designed to be a universal runtime that can run WebAssembly on various platforms, including desktop, server, embedded environments, and the Web.
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Singlepass Compiler: Wasmer includes a Singlepass compiler that is optimized for use cases where fast compilation times are more critical than runtime performance, such as embedded systems. This is in addition to its Cranelift and LLVM compilers, offering flexibility in performance and compilation speed.
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Middleware System: Wasmer supports a middleware system that allows developers to extend and customize the runtime. This feature is particularly useful for applications that require specific functionality or optimizations.
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WASI/WASIX Support: While both Wasmer and Wasmtime support the WebAssembly System Interface (WASI), Wasmer extends the interface, which they call WASIX. It adds features like multithreading, sockets, and support for asynchronous runtimes (like tokio).
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Compilation: Wasmer supports compiling WebAssembly modules to native code, which can then be serialized to disk and loaded directly. This is especially interesting for embedded, because it allows shipping without a compiler.
- Wasm Execution: Run Wasm modules efficiently using Wasmer.
- Plugin System: Easily load and manage extism plugins from various sources such as files, data, or URLs.
- Logging: Integrated logging support for debugging and information tracking using the tracing crate.
Native (Windows/macOS/Linux/iOS/Android) and Web support using the same codebase is a major goal of this implementation. However, there is a caveat:
Web has some restrictions when it comes to threading. Rust nightly for wasm32-unknown-unknown has had support for native threads for a long time (when certain compile flags are enabled and cross origin isolation is activated), but JsValues cannot be shared (they don't implement Send or Sync). Transfer is possible using the Web API, but that has to be done manually and explicitly.
So, wasmer's Instance does not implement Send or Sync on the wasm32 target. This results in this project only supporting plugin function calls on the thread the plugin was created on. It was implemented in the way that calls on the wrong thread simply fail with an error, rather than being caught by the compiler (Plugin still implements Send and Sync). This limitation is caused by wasmer requiring all wasm function imports to implement Send and Sync even on Web, thus making it impossible to check this at compile time.
Add the following to your Cargo.toml:
[dependencies]
webxtism = "0.1.0"Note that the extism kernel is loaded from github in build.rs, meaning that it needs Internet access during the build!
use webxtism::{Context, Plugin, PluginIdentifier, WasmInput};
// Create a new context
let context = Context::<String>::default();
// Load and instantiate a plugin
let plugin = Plugin::new(&context, "my_plugin", WasmInput::file("path/to/wasm_file.wasm"), &[]).await.unwrap();
// Interact with the plugin
// ...Contributions are welcome! Please submit a pull request or open an issue for any bugs or feature requests.
This project is licensed under the BSD 3-Clause "Revised" license. See the LICENSE file for details.