1## wazero imports
2
3Packages in this directory implement the *host* imports needed for specific
4languages or shared compiler toolchains.
5
6* [AssemblyScript](assemblyscript) e.g. `asc X.ts --debug -b none -o X.wasm`
7* [Emscripten](emscripten) e.g. `em++ ... -s STANDALONE_WASM -o X.wasm X.cc`
8* [WASI](wasi_snapshot_preview1) e.g. `tinygo build -o X.wasm -target=wasi X.go`
9
10Note: You may not see a language listed here because it either works without
11host imports, or it uses WASI. Refer to https://wazero.io/languages/ for more.
12
13Please [open an issue](https://github.com/tetratelabs/wazero/issues/new) if you
14would like to see support for another compiled language or toolchain.
15
16## Overview
17
18WebAssembly has a virtual machine architecture where the *host* is the process
19embedding wazero and the *guest* is a program compiled into the WebAssembly
20Binary Format, also known as Wasm (`%.wasm`).
21
22The only features that work by default are computational in nature, and the
23only way to communicate is via functions, memory or global variables.
24
25When a compiler targets Wasm, it often needs to import functions from the host
26to satisfy system calls needed for functionality like printing to the console,
27getting the time, or generating random values. The technical term for this
28bridge is Application Binary Interface (ABI), but we'll call them simply host
29imports.
30
31Packages in this directory are sometimes well re-used, such as the case in
32[WASI](https://wazero.io/specs/#wasi). For example, Rust, TinyGo, and Zig can
33all target WebAssembly in a way that imports the same "wasi_snapshot_preview1"
34module in the compiled `%.wasm` file. To support any of these, wazero users can
35invoke `wasi_snapshot_preview1.Instantiate` on their `wazero.Runtime`.
36
37Other times, host imports are either completely compiler-specific, such as the
38case with `GOOS=js GOARCH=wasm`, or coexist alongside WASI, such as the case
39with Emscripten.
View as plain text