大家好，我是彬哥，本节给大家讲下go语言WebAssembly 相关，抛砖引玉了，主要是针对Go语言WebAssembly使用，计划做个网站出来，希望成功。
运行结果图：
结果
步骤 一
linux下编译wasm文件：
Go语言文件 如下
package main
import (
"fmt"
)
func main() {
fmt.Println("Hello, WebAssembly!")
}
编译命令：
GOARCH=wasm GOOS=js go build -o LollipopGo.wasm tmain.go
步骤二
用官方提供的wasm_exec.html
文件位置：
位置
文件位置
文件内容：
<!doctype html>
<!--
Copyright 2018 The Go Authors. All rights reserved.
Use of this source code is governed by a BSD-style
license that can be found in the LICENSE file.
-->
<html>
<head>
<meta charset="utf-8">
<title>Go wasm</title>
</head>
<body>
<!--
Add the following polyfill for Microsoft Edge 17/18 support:
<script src="https://cdn.jsdelivr.net/npm/text-encoding@0.7.0/lib/encoding.min.js"></script>
(see https://caniuse.com/#feat=textencoder)
-->
<script src="wasm_exec.js"></script>
<script>
if (!WebAssembly.instantiateStreaming) { // polyfill
WebAssembly.instantiateStreaming = async (resp, importObject) => {
const source = await (await resp).arrayBuffer();
return await WebAssembly.instantiate(source, importObject);
};
}
const go = new Go();
let mod, inst;
WebAssembly.instantiateStreaming(fetch("LollipopGo.wasm"), go.importObject).then((result) => {
mod = result.module;
inst = result.instance;
document.getElementById("runButton").disabled = false;
});
async function run() {
console.clear();
await go.run(inst);
inst = await WebAssembly.instantiate(mod, go.importObject); // reset instance
}
</script>
<button onClick="run();" id="runButton" disabled>Run</button>
</body>
</html>
wasm_exec.js文件：
// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
(() => {
// Map web browser API and Node.js API to a single common API (preferring web standards over Node.js API).
const isNodeJS = typeof process !== "undefined";
if (isNodeJS) {
global.require = require;
global.fs = require("fs");
const nodeCrypto = require("crypto");
global.crypto = {
getRandomValues(b) {
nodeCrypto.randomFillSync(b);
},
};
global.performance = {
now() {
const [sec, nsec] = process.hrtime();
return sec * 1000 + nsec / 1000000;
},
};
const util = require("util");
global.TextEncoder = util.TextEncoder;
global.TextDecoder = util.TextDecoder;
} else {
if (typeof window !== "undefined") {
window.global = window;
} else if (typeof self !== "undefined") {
self.global = self;
} else {
throw new Error("cannot export Go (neither window nor self is defined)");
}
let outputBuf = "";
global.fs = {
constants: { O_WRONLY: -1, O_RDWR: -1, O_CREAT: -1, O_TRUNC: -1, O_APPEND: -1, O_EXCL: -1 }, // unused
writeSync(fd, buf) {
outputBuf += decoder.decode(buf);
const nl = outputBuf.lastIndexOf("\n");
if (nl != -1) {
console.log(outputBuf.substr(0, nl));
outputBuf = outputBuf.substr(nl + 1);
}
return buf.length;
},
openSync(path, flags, mode) {
const err = new Error("not implemented");
err.code = "ENOSYS";
throw err;
},
};
}
const encoder = new TextEncoder("utf-8");
const decoder = new TextDecoder("utf-8");
global.Go = class {
constructor() {
this.argv = ["js"];
this.env = {};
this.exit = (code) => {
if (code !== 0) {
console.warn("exit code:", code);
}
};
this._callbackTimeouts = new Map();
this._nextCallbackTimeoutID = 1;
const mem = () => {
// The buffer may change when requesting more memory.
return new DataView(this._inst.exports.mem.buffer);
}
const setInt64 = (addr, v) => {
mem().setUint32(addr + 0, v, true);
mem().setUint32(addr + 4, Math.floor(v / 4294967296), true);
}
const getInt64 = (addr) => {
const low = mem().getUint32(addr + 0, true);
const high = mem().getInt32(addr + 4, true);
return low + high * 4294967296;
}
const loadValue = (addr) => {
const f = mem().getFloat64(addr, true);
if (!isNaN(f)) {
return f;
}
const id = mem().getUint32(addr, true);
return this._values[id];
}
const storeValue = (addr, v) => {
const nanHead = 0x7FF80000;
if (typeof v === "number") {
if (isNaN(v)) {
mem().setUint32(addr + 4, nanHead, true);
mem().setUint32(addr, 0, true);
return;
}
mem().setFloat64(addr, v, true);
return;
}
switch (v) {
case undefined:
mem().setUint32(addr + 4, nanHead, true);
mem().setUint32(addr, 1, true);
return;
case null:
mem().setUint32(addr + 4, nanHead, true);
mem().setUint32(addr, 2, true);
return;
case true:
mem().setUint32(addr + 4, nanHead, true);
mem().setUint32(addr, 3, true);
return;
case false:
mem().setUint32(addr + 4, nanHead, true);
mem().setUint32(addr, 4, true);
return;
}
let ref = this._refs.get(v);
if (ref === undefined) {
ref = this._values.length;
this._values.push(v);
this._refs.set(v, ref);
}
let typeFlag = 0;
switch (typeof v) {
case "string":
typeFlag = 1;
break;
case "symbol":
typeFlag = 2;
break;
case "function":
typeFlag = 3;
break;
}
mem().setUint32(addr + 4, nanHead | typeFlag, true);
mem().setUint32(addr, ref, true);
}
const loadSlice = (addr) => {
const array = getInt64(addr + 0);
const len = getInt64(addr + 8);
return new Uint8Array(this._inst.exports.mem.buffer, array, len);
}
const loadSliceOfValues = (addr) => {
const array = getInt64(addr + 0);
const len = getInt64(addr + 8);
const a = new Array(len);
for (let i = 0; i < len; i++) {
a[i] = loadValue(array + i * 8);
}
return a;
}
const loadString = (addr) => {
const saddr = getInt64(addr + 0);
const len = getInt64(addr + 8);
return decoder.decode(new DataView(this._inst.exports.mem.buffer, saddr, len));
}
const timeOrigin = Date.now() - performance.now();
this.importObject = {
go: {
// func wasmExit(code int32)
"runtime.wasmExit": (sp) => {
const code = mem().getInt32(sp + 8, true);
this.exited = true;
delete this._inst;
delete this._values;
delete this._refs;
this.exit(code);
},
// func wasmWrite(fd uintptr, p unsafe.Pointer, n int32)
"runtime.wasmWrite": (sp) => {
const fd = getInt64(sp + 8);
const p = getInt64(sp + 16);
const n = mem().getInt32(sp + 24, true);
fs.writeSync(fd, new Uint8Array(this._inst.exports.mem.buffer, p, n));
},
// func nanotime() int64
"runtime.nanotime": (sp) => {
setInt64(sp + 8, (timeOrigin + performance.now()) * 1000000);
},
// func walltime() (sec int64, nsec int32)
"runtime.walltime": (sp) => {
const msec = (new Date).getTime();
setInt64(sp + 8, msec / 1000);
mem().setInt32(sp + 16, (msec % 1000) * 1000000, true);
},
// func scheduleCallback(delay int64) int32
"runtime.scheduleCallback": (sp) => {
const id = this._nextCallbackTimeoutID;
this._nextCallbackTimeoutID++;
this._callbackTimeouts.set(id, setTimeout(
() => { this._resolveCallbackPromise(); },
getInt64(sp + 8) + 1, // setTimeout has been seen to fire up to 1 millisecond early
));
mem().setInt32(sp + 16, id, true);
},
// func clearScheduledCallback(id int32)
"runtime.clearScheduledCallback": (sp) => {
const id = mem().getInt32(sp + 8, true);
clearTimeout(this._callbackTimeouts.get(id));
this._callbackTimeouts.delete(id);
},
// func getRandomData(r []byte)
"runtime.getRandomData": (sp) => {
crypto.getRandomValues(loadSlice(sp + 8));
},
// func stringVal(value string) ref
"syscall/js.stringVal": (sp) => {
storeValue(sp + 24, loadString(sp + 8));
},
// func valueGet(v ref, p string) ref
"syscall/js.valueGet": (sp) => {
storeValue(sp + 32, Reflect.get(loadValue(sp + 8), loadString(sp + 16)));
},
// func valueSet(v ref, p string, x ref)
"syscall/js.valueSet": (sp) => {
Reflect.set(loadValue(sp + 8), loadString(sp + 16), loadValue(sp + 32));
},
// func valueIndex(v ref, i int) ref
"syscall/js.valueIndex": (sp) => {
storeValue(sp + 24, Reflect.get(loadValue(sp + 8), getInt64(sp + 16)));
},
// valueSetIndex(v ref, i int, x ref)
"syscall/js.valueSetIndex": (sp) => {
Reflect.set(loadValue(sp + 8), getInt64(sp + 16), loadValue(sp + 24));
},
// func valueCall(v ref, m string, args []ref) (ref, bool)
"syscall/js.valueCall": (sp) => {
try {
const v = loadValue(sp + 8);
const m = Reflect.get(v, loadString(sp + 16));
const args = loadSliceOfValues(sp + 32);
storeValue(sp + 56, Reflect.apply(m, v, args));
mem().setUint8(sp + 64, 1);
} catch (err) {
storeValue(sp + 56, err);
mem().setUint8(sp + 64, 0);
}
},
// func valueInvoke(v ref, args []ref) (ref, bool)
"syscall/js.valueInvoke": (sp) => {
try {
const v = loadValue(sp + 8);
const args = loadSliceOfValues(sp + 16);
storeValue(sp + 40, Reflect.apply(v, undefined, args));
mem().setUint8(sp + 48, 1);
} catch (err) {
storeValue(sp + 40, err);
mem().setUint8(sp + 48, 0);
}
},
// func valueNew(v ref, args []ref) (ref, bool)
"syscall/js.valueNew": (sp) => {
try {
const v = loadValue(sp + 8);
const args = loadSliceOfValues(sp + 16);
storeValue(sp + 40, Reflect.construct(v, args));
mem().setUint8(sp + 48, 1);
} catch (err) {
storeValue(sp + 40, err);
mem().setUint8(sp + 48, 0);
}
},
// func valueLength(v ref) int
"syscall/js.valueLength": (sp) => {
setInt64(sp + 16, parseInt(loadValue(sp + 8).length));
},
// valuePrepareString(v ref) (ref, int)
"syscall/js.valuePrepareString": (sp) => {
const str = encoder.encode(String(loadValue(sp + 8)));
storeValue(sp + 16, str);
setInt64(sp + 24, str.length);
},
// valueLoadString(v ref, b []byte)
"syscall/js.valueLoadString": (sp) => {
const str = loadValue(sp + 8);
loadSlice(sp + 16).set(str);
},
// func valueInstanceOf(v ref, t ref) bool
"syscall/js.valueInstanceOf": (sp) => {
mem().setUint8(sp + 24, loadValue(sp + 8) instanceof loadValue(sp + 16));
},
"debug": (value) => {
console.log(value);
},
}
};
}
async run(instance) {
this._inst = instance;
this._values = [ // TODO: garbage collection
NaN,
undefined,
null,
true,
false,
global,
this._inst.exports.mem,
this,
];
this._refs = new Map();
this._callbackShutdown = false;
this.exited = false;
const mem = new DataView(this._inst.exports.mem.buffer)
// Pass command line arguments and environment variables to WebAssembly by writing them to the linear memory.
let offset = 4096;
const strPtr = (str) => {
let ptr = offset;
new Uint8Array(mem.buffer, offset, str.length + 1).set(encoder.encode(str + "\0"));
offset += str.length + (8 - (str.length % 8));
return ptr;
};
const argc = this.argv.length;
const argvPtrs = [];
this.argv.forEach((arg) => {
argvPtrs.push(strPtr(arg));
});
const keys = Object.keys(this.env).sort();
argvPtrs.push(keys.length);
keys.forEach((key) => {
argvPtrs.push(strPtr(`${key}=${this.env[key]}`));
});
const argv = offset;
argvPtrs.forEach((ptr) => {
mem.setUint32(offset, ptr, true);
mem.setUint32(offset + 4, 0, true);
offset += 8;
});
while (true) {
const callbackPromise = new Promise((resolve) => {
this._resolveCallbackPromise = () => {
if (this.exited) {
throw new Error("bad callback: Go program has already exited");
}
setTimeout(resolve, 0); // make sure it is asynchronous
};
});
this._inst.exports.run(argc, argv);
if (this.exited) {
break;
}
await callbackPromise;
}
}
static _makeCallbackHelper(id, pendingCallbacks, go) {
return function() {
pendingCallbacks.push({ id: id, args: arguments });
go._resolveCallbackPromise();
};
}
static _makeEventCallbackHelper(preventDefault, stopPropagation, stopImmediatePropagation, fn) {
return function(event) {
if (preventDefault) {
event.preventDefault();
}
if (stopPropagation) {
event.stopPropagation();
}
if (stopImmediatePropagation) {
event.stopImmediatePropagation();
}
fn(event);
};
}
}
if (isNodeJS) {
if (process.argv.length < 3) {
process.stderr.write("usage: go_js_wasm_exec [wasm binary] [arguments]\n");
process.exit(1);
}
const go = new Go();
go.argv = process.argv.slice(2);
go.env = process.env;
go.exit = process.exit;
WebAssembly.instantiate(fs.readFileSync(process.argv[2]), go.importObject).then((result) => {
process.on("exit", (code) => { // Node.js exits if no callback is pending
if (code === 0 && !go.exited) {
// deadlock, make Go print error and stack traces
go._callbackShutdown = true;
go._inst.exports.run();
}
});
return go.run(result.instance);
}).catch((err) => {
throw err;
});
}
})();
步骤三 自建http服务器
http_get.go
package main
import (
"flag"
"log"
"net/http"
"strings"
)
var (
listen = flag.String("listen", ":8080", "listen address")
dir = flag.String("dir", ".", "directory to serve")
)
func main() {
flag.Parse()
log.Printf("listening on %q...", *listen)
log.Fatal(http.ListenAndServe(*listen, http.HandlerFunc(func(resp http.ResponseWriter, req *http.Request) {
if strings.HasSuffix(req.URL.Path, ".wasm") {
resp.Header().Set("content-type", "application/wasm")
}
http.FileServer(http.Dir(*dir)).ServeHTTP(resp, req)
})))
}
以上演示结束！代码上传到社区的git的codeclass
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