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The first WebAssembly program

2022-07-30 06:54:00 【yunteng521】

前言

WebAssembly/wasm WebAssembly 或者 wasm 是一个可移植、体积小、加载快并且兼容 Web 的全新格式,There are many advantages,This chapter tells aboutrust 编码一个 wasm ,html调用
为什么用rust ,参考 https://blog.csdn.net/u012067469/article/details/100100813/
建议,Code in the programming language you are most familiar with
浏览器支持情况 https://developer.mozilla.org/zh-CN/docs/WebAssembly

1:准备
centos7
rust1.55

2：环境搭建
1>rust 安装
根据CPU架构下载相应的安装文件
https://forge.rust-lang.org/infra/other-installation-methods.html#rustup
2> wasm-pack 安装
https://rustwasm.github.io/docs/book/game-of-life/setup.html

3：创建工程
1>You can also download the template first git clone https://github.com/rustwasm/wasm-pack-template
2>cargo generate --git ./wasm-pack-template --name test
在这里插入图片描述
2>编写代码

mod utils;

use wasm_bindgen::prelude::*;

// When the `wee_alloc` feature is enabled, use `wee_alloc` as the global
// allocator.
#[cfg(feature = "wee_alloc")]
#[global_allocator]
static ALLOC: wee_alloc::WeeAlloc = wee_alloc::WeeAlloc::INIT;

#[wasm_bindgen]
extern {
    
    fn alert(s: &str);
}

#[wasm_bindgen]
pub fn greet() {
    
    alert("Hello, test!");
}

//testcode Start your own code 也就3个函数///
#[wasm_bindgen]
pub fn fib(i: u32) -> u32 {
    
    match i {
    
        0 => 0,
        1 => 1,
        _ => fib(i-1) + fib(i-2)
    }
}

#[wasm_bindgen]
pub fn double(i: u32) -> u32 {
    
    2*i
}

#[wasm_bindgen]
pub fn add(i: u32,j:u32) -> u32 {
    
    i+j
}

3>编译
wasm-pack build 坐等完成
在这里插入图片描述
After compiling, there are many more files

这里找到当前目录 ./pkg/test_bg.wasm 这个文件

4：测试wasm
1>创建个webdemo
在这里插入图片描述

test.html 文件内容

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>IFE JavaScript Task 01</title>
</head>
<body>
<label>Please enter the name of the function to call：<input id="aqi-input" type="text"></label>
<br />
<label>Please enter parameter values for the function：<input id="aqi-input1" type="text"></label>
<br />
<button id="button">Confirm to fill in</button>
<div>您输入的值是：<span id="aqi-display">No entry yet</span></div>
<script src="js/testwasm.js"></script>
</script>
</body>
</html>

testwasm.js 内容如下

window.onload = prepare;
    function prepare(){
    
        if (!document.getElementById){
    
            return false;
        }//检查浏览器是否支持document.getElementById的DOM方法
        var submit = document.getElementById("button");
        submit.onclick = function(){
    
            clickButton();
        }//添加事件处理函数,把onclick事件绑定到ID为"button"元素上
		
		loadwasm1('test_bg.wasm').then(
		instance => {
    
		 window._wasminstance = instance ;
		 console.log("wasm load finish");
		});
    }
    function clickButton(){
    
		//let num =loadwasm1('wasm_hello_bg.wasm');
	// console.log(num);
	// return ;
        var output = document.getElementById("aqi-display");
        var input = document.getElementById("aqi-input");
		var input1 = document.getElementById("aqi-input1");
      // text = input.value;//获取ID为"aqi-input"的值
	  var text1 = "";
	  if(window._wasminstance){
    
		  if(typeof(input.value) == 'string'  && typeof(window._wasminstance.exports) == 'object'){
    
			  if(!isNaN(input.value)){
     //是数字
				let number1 = Number(input.value);
					switch(number1){
    
						case 1:text1 = window._wasminstance.exports.double(12).toString();break;
						case 2:text1 = window._wasminstance.exports.fib(12).toString();break;
						case 3:text1 = window._wasminstance.exports.add(12,12).toString();break;
					}
			  }else{
    
				  let instr1 = input.value.trim();
				  let instr2 = input1.value.trim();
				  let params = instr2.length >0?instr2.split("#"):'';
				  let func = window._wasminstance.exports[instr1] ;
				  if (func){
    
					 
					  switch(params.length){
    
						  case 0: text1 = func(); break;
						  case 1: text1 = func(Number(params[0])); break;
						  case 2: text1 = func(Number(params[0]),Number(params[1])); break;
						  default:
						   text1 = func();
					  }
					  
				  }	  
			  }
		  }
	  }
        output.innerHTML = text1;//把值写入ID为"aqi-display"之中
    }
	function loadWebAssembly(fileName) {
    
	  return fetch(fileName)
		.then(response => response.arrayBuffer())
		.then(buffer => WebAssembly.compile(buffer))
		.then(module => {
    return new WebAssembly.Instance(module) });
	};
	
	function loadwasm(fileName){
    
		return fetch(fileName).
		then(response => response.arrayBuffer()).
		then(bufferSource => WebAssembly.instantiate(bufferSource)).
		then(result => result.instance.exports.double(2)) ;
	};
	
	function loadwasm1(fileName){
    
			return fetch(fileName).
			then(response =>response.arrayBuffer()).
			then(bytes => WebAssembly.instantiate(bytes)).
			then(results => results.instance
	  );
	};
	
	function loadwasm2(fileName,importObject){
    
			return fetch(fileName).
			then(response =>response.arrayBuffer()).
			then(bytes => WebAssembly.instantiate(bytes,importObject)).
			then(results => results.instance
	  );
	};

2>测试用的是chrome 97 测试的
在这里插入图片描述

4: 另外一种方式生成wasm（不用模板）
Personally I think this is more convenient
1>cargo new --lib wasm-hello
2> lib.rs 修改代码

extern crate wasm_bindgen;

use wasm_bindgen::prelude::*;

#[wasm_bindgen]
pub fn fib(i: u32) -> u32 {
    match i {
        0 => 0,
        1 => 1,
        _ => fib(i-1) + fib(i-2)
    }
}

3>修改 Cargo.toml 增加

[dependencies]
wasm-bindgen="0.2.53"

[lib]
crate-type=["cdylib","rlib"]

4>wasm-pack build
在pkg 查找生成的wasm文件

5：If you need the project code, upload it later
上一张wasm 文件内容（273B 够小吧）
在这里插入图片描述

wasm文件内容在这里插入图片描述

原网站

版权声明
本文为[yunteng521]所创，转载请带上原文链接，感谢
https://yzsam.com/2022/211/202207300539593827.html

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The first WebAssembly program

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