32 breaking releases
new 0.33.0 | Dec 7, 2024 |
---|---|
0.32.0 | Nov 25, 2024 |
0.31.0 | Nov 6, 2024 |
0.25.0 | Jul 16, 2024 |
0.1.0 | Mar 23, 2023 |
#95 in WebAssembly
31,680 downloads per month
Used in 22 crates
(14 directly)
5.5MB
96K
SLoC
wasmer-wasi
This crate provides the necessary imports to use WASI easily from Wasmer. WebAssembly System Interface (WASI for short) is a modular system interface for WebAssembly. WASI is being standardized in the WebAssembly subgroup.
Very succinctly, from the user perspective, WASI is a set of
WebAssembly module imports under a specific namespace (which
varies based on the WASI version). A program compiled for the
wasm32-wasi
target will be able to support standard I/O, file I/O,
filesystem manipulation, memory management, time, string, environment
variables, program startup etc.
Wasmer WASI is created with the aim to be fully sandboxed.
We are able to achieve that thanks to our Virtual Filesystem implementation (wasmer-vfs
)
and by only allowing secure systemcalls back to the host.
Note: If you encounter any sandboxing issue please open an issue in the wasmer repo https://github.com/wasmerio/wasmer.
This crate provides the necessary API to create the imports to use
WASI easily from the Wasmer runtime, through our ImportObject
API.
Supported WASI versions
WASI version | Support |
---|---|
wasi_unstable |
✅ |
wasi_snapshot_preview1 |
✅ |
The special Latest
version points to wasi_snapshot_preview1
.
Learn more about the WASI version process (ephemeral, snapshot, old).
Usage
Let's consider the following hello.rs
Rust program:
fn main() {
println!("Hello, {:?}", std::env::args().nth(1));
}
Then, let's compile it to a WebAssembly module with WASI support:
$ rustc --target wasm32-wasi hello.rs
Finally, let's execute it with the wasmer
CLI:
$ wasmer run hello.wasm Gordon
Hello, Some("Gordon")
… and programatically with the wasmer
and the wasmer-wasi
libraries:
use std::io::Read;
use wasmer::{Module, Store};
use wasmer_wasix::{Pipe, WasiEnv};
let wasm_path = "hello.wasm";
// Let's declare the Wasm module with the text representation.
let wasm_bytes = std::fs::read(wasm_path)?;
// Create a Store.
let mut store = Store::default();
println!("Compiling module...");
// Let's compile the Wasm module.
let module = Module::new(&store, wasm_bytes)?;
let (stdout_tx, mut stdout_rx) = Pipe::channel();
// Run the module.
WasiEnv::builder("hello")
.args(&["Gordon"])
// .env("KEY", "Value")
.stdout(Box::new(stdout_tx))
.run_with_store(module, &mut store)?;
eprintln!("Run complete - reading output");
let mut buf = String::new();
stdout_rx.read_to_string(&mut buf).unwrap();
eprintln!("Output: {buf}");
Check the fully working example using WASI.
More resources
This library is about the WASI implementation inside the Wasmer runtime. It contains documentation about the implementation itself. However, if you wish to learn more about WASI, here is a list of links that may help you:
wasi-libc
, WASI libc implementation for WebAssembly programs built on top of WASI system calls. It provides a wide array of POSIX-compatible C APIs, including support for standard I/O, file I/O, filesystem manipulation, memory management, time, string, environment variables, program startup, and many other APIs,wasi-sdk
, WASI-enabled WebAssembly C/C++ toolchain, based onwasi-libc
,- WASI API documentation,
- WASI C API header file,
- WASI Application Binary Interface
(ABI),
where we learn about
_start
and_initialize
(for reactors) for example.
Dependencies
~30–50MB
~879K SLoC