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When invoking a WebAssembly routine from Rust code, arguments are stored into an array of u128, and read from a piece of generated trampoline code before calling the compiled target function using the platform ABI calling convention. The WasmTy/WasmRet routines handle the conversion between Rust data types and those u128 buffers. This currently works by in effect converting the Rust object to a u128 and then storing this u128 into the buffer. The generated trampoline code will then read an object of appropriate type from the beginning of that buffer. This does not work on big-endian platforms, since the above approach causes the value to be stored into the rightmost bytes of the u128 buffer, while the trampoline code reads the leftmost bytes. This patch fixes the problem by changing WasmTy/WasmRet to use the leftmost bytes as well, by casting the u128 pointer to a pointer of the correct type before storing to it (or reading from it). (Note that it is not necessary to actually byte-swap the values since the trampoline code will not treat them like WebAssembly little-endian memory, but simply access them in native byte order.)
wasmtime
A standalone runtime for WebAssembly
A Bytecode Alliance project
Guide | Contributing | Website | Chat
Installation
The Wasmtime CLI can be installed on Linux and macOS with a small install script:
$ curl https://wasmtime.dev/install.sh -sSf | bash
Windows or otherwise interested users can download installers and binaries directly from the GitHub Releases page.
Example
If you've got the Rust compiler installed then you can take some Rust source code:
fn main() {
println!("Hello, world!");
}
and compile/run it with:
$ rustup target add wasm32-wasi
$ rustc hello.rs --target wasm32-wasi
$ wasmtime hello.wasm
Hello, world!
Features
-
Lightweight. Wasmtime is a standalone runtime for WebAssembly that scales with your needs. It fits on tiny chips as well as makes use of huge servers. Wasmtime can be embedded into almost any application too.
-
Fast. Wasmtime is built on the optimizing Cranelift code generator to quickly generate high-quality machine code at runtime.
-
Configurable. Whether you need to precompile your wasm ahead of time, generate code blazingly fast with Lightbeam, or interpret it at runtime, Wasmtime has you covered for all your wasm-executing needs.
-
WASI. Wasmtime supports a rich set of APIs for interacting with the host environment through the WASI standard.
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Standards Compliant. Wasmtime passes the official WebAssembly test suite, implements the official C API of wasm, and implements future proposals to WebAssembly as well. Wasmtime developers are intimately engaged with the WebAssembly standards process all along the way too.
Language Support
You can use Wasmtime from a variety of different languages through embeddings of the implementation:
- Rust - the
wasmtimecrate - C - the
wasm.h,wasi.h, andwasmtime.hheaders - Python - the
wasmtimePyPI package - .NET - the
WasmtimeNuGet package - Go - the
wasmtime-gorepository
Documentation
📚 Read the Wasmtime guide here! 📚
The wasmtime guide is the best starting point to learn about what Wasmtime can do for you or help answer your questions about Wasmtime. If you're curious in contributing to Wasmtime, it can also help you do that!.
It's Wasmtime.