WebAssembly 与 Rust 编程系列05 Rust编写wasm模块

Rust 开发环境安装

官方的下载链接

下载 rustup-init.exe 点击安装

完成之后会在我们的用户Home目录添加两个文件夹

.cargo/bin: cargo 及 rust 相应的命令行工具.rustup: rust的配置目录

其中 cargo 是 rust的包管理工具,类似npm之于node,maven之于java,composer之于PHP

检查安装

C:\Users\admin>rustc --version rustc 1.44.1 (c7087fe00 2020-06-17) C:\Users\admin>rustup --version rustup 1.21.1 (7832b2ebe 2019-12-20)

安装 WEBASSEMBLY 目标

我们需要把rust代码编译成wasm目标模块,必须安装 rust WebAssembly 对应的target

我们可以通过 rustup 的target命令, 了解可用的target 以及是否安装

C:\Users\admin>rustup target --help rustup-target Modify a toolchain's supported targets USAGE: rustup target <SUBCOMMAND> FLAGS: -h, --help Prints help information SUBCOMMANDS: list List installed and available targets add Add a target to a Rust toolchain remove Remove a target from a Rust toolchain help Prints this message or the help of the given subcommand(s)

显示列表: rustup target list

C:\Users\admin>rustup target list aarch64-apple-ios arm-linux-androideabi arm-unknown-linux-gnueabi arm-unknown-linux-gnueabihf arm-unknown-linux-musleabi ... ... thumbv7neon-unknown-linux-gnueabihf thumbv8m.base-none-eabi thumbv8m.main-none-eabi thumbv8m.main-none-eabihf wasm32-unknown-emscripten wasm32-unknown-unknown wasm32-wasi x86_64-apple-darwin x86_64-apple-ios x86_64-fortanix-unknown-sgx x86_64-fuchsia x86_64-linux-android x86_64-pc-windows-gnu x86_64-pc-windows-msvc (installed) x86_64-rumprun-netbsd

我们需要安装的是 wasm32-unknown-unknown

rustup target add wasm32-unknown-unknown

rust WebAssembly Hello Project

创建新的空工程

cargo new --lib hello-wasm

在 Cargo.toml 中包含了工程的基本信息

[package] name = "hello-wasm" version = "0.1.0" authors = ["austindev <austinxishou@yahoo.com>"] edition = "2018" # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html [dependencies]

在 src/lib.rs 只有最基本的测试示例:

#[cfg(test)] mod tests { #[test] fn it_works() { assert_eq!(2 + 2, 4); } }

当然可以直接运行 cargo test 执行测试,当然这里我们并不需要它,可以直接删除

定义一个简单函数并导出:

# [no_mangle] pub extern "C" fn add_one(x: i32)-> i32 { x + 1 }

编译成wasm

> cargo build --release --target wasm32-unknown-unknown Finished release [optimized] target(s) in 0.02s

js 引用demo

fetch('hello_wasm.wasm') .then(res => res.arrayBuffer() ).then(bytes => WebAssembly.instantiate(bytes, {}) ).then(results => { console.log(`wasm `, results.instance.exports) console.log('wasm call result:' + results.instance.exports.add_one(3)); });

控制台输出: