Browse Source

Add WebAssembly Hello World Example

master
Noah Petherbridge 2 years ago
parent
commit
ad9d14bdab
  1. 1
      .gitignore
  2. 2
      canvas/draw.go
  3. 2
      canvas/engine.go
  4. 2
      canvas/events.go
  5. 2
      canvas/text.go
  6. 2
      canvas/texture.go
  7. BIN
      examples/hello-wasm/DejaVuSans.ttf
  8. 11
      examples/hello-wasm/Makefile
  9. 81
      examples/hello-wasm/README.md
  10. BIN
      examples/hello-wasm/gopher.png
  11. 46
      examples/hello-wasm/index.html
  12. 177
      examples/hello-wasm/main_wasm.go
  13. 127
      examples/hello-wasm/server.go
  14. 533
      examples/hello-wasm/wasm_exec.js

1
.gitignore

@ -0,0 +1 @@
*.wasm

2
canvas/draw.go

@ -4,7 +4,7 @@ import (
"fmt"
"syscall/js"
"git.kirsle.net/apps/doodle/lib/render"
"git.kirsle.net/go/render"
)
// Methods here implement the drawing functions of the render.Engine

2
canvas/engine.go

@ -4,7 +4,7 @@ import (
"syscall/js"
"time"
"git.kirsle.net/apps/doodle/lib/render/event"
"git.kirsle.net/go/render/event"
)
// Engine implements a rendering engine targeting an HTML canvas for

2
canvas/events.go

@ -3,7 +3,7 @@ package canvas
import (
"syscall/js"
"git.kirsle.net/apps/doodle/lib/render/event"
"git.kirsle.net/go/render/event"
)
// EventClass to categorize JavaScript events.

2
canvas/text.go

@ -7,7 +7,7 @@ import (
"path/filepath"
"strings"
"git.kirsle.net/apps/doodle/lib/render"
"git.kirsle.net/go/render"
)
// FontFilenameToName converts a FontFilename to its CSS font name.

2
canvas/texture.go

@ -8,7 +8,7 @@ import (
"image/png"
"syscall/js"
"git.kirsle.net/apps/doodle/lib/render"
"git.kirsle.net/go/render"
)
// Texture can hold on to cached image textures.

BIN
examples/hello-wasm/DejaVuSans.ttf

Binary file not shown.

11
examples/hello-wasm/Makefile

@ -0,0 +1,11 @@
.PHONY: build
build:
GOOS=js GOARCH=wasm go build -v -o hello.wasm main_wasm.go
.PHONY: serve
serve: build
go run server.go
.PHONY: clean
clean:
rm -f hello.wasm

81
examples/hello-wasm/README.md

@ -0,0 +1,81 @@
# Hello WASM
This is a port of the "hello-world" example for a WebAssembly target.
Differences compared to the SDL2 version include:
* Import render/canvas instead of render/sdl
* Load the gopher.png via ajax HTTP request, as the syscall to open a file from
disk is not supported in a WASM environment.
* A call to the `canvas.AddEventListeners()` function to set up DOM event
bindings, which enables key and mouse events to be handled in the
canvas.Engine.
```diff
--- ../hello-world/main.go 2019-12-22 15:17:42.186838967 -0800
+++ main_wasm.go 2019-12-22 16:21:58.449699021 -0800
@@ -1,13 +1,17 @@
+// +build js,wasm
+
+// This is a version of the 'hello-world' example but build for WebAssembly.
+
package main
import (
"image/png"
"log"
- "os"
+ "net/http"
"time"
"git.kirsle.net/go/render"
- "git.kirsle.net/go/render/sdl"
+ "git.kirsle.net/go/render/canvas"
)
var (
@@ -30,7 +34,11 @@
)
func main() {
- mw := sdl.New("Hello World", 800, 600)
+ mw, _ := canvas.New("canvas")
setup(mw)
for {
@@ -61,17 +69,22 @@
}
}
-func setup(e render.Engine) {
+func setup(e *canvas.Engine) {
if err := e.Setup(); err != nil {
panic(err)
}
- // Load gopher sprite.
- fh, err := os.Open("gopher.png")
+ // Bind DOM event handlers.
+ e.AddEventListeners()
+
+ // Load gopher sprite via ajax request.
+ resp, err := http.Get("gopher.png")
if err != nil {
log.Fatalf("read gopher.png: %s", err)
}
+ defer resp.Body.Close()
- img, _ := png.Decode(fh)
+ img, _ := png.Decode(resp.Body)
gopher, _ = e.StoreTexture("gopher.png", img)
texSize = gopher.Size()
```
## Credits
Gopher image was created by Takuya Ueda (https://twitter.com/tenntenn)
from https://github.com/golang-samples/gopher-vector
This example comes with the DejaVu Sans font. License information
at https://dejavu-fonts.github.io/License.html

BIN
examples/hello-wasm/gopher.png

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After

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46
examples/hello-wasm/index.html

@ -0,0 +1,46 @@
<!DOCTYPE html>
<html>
<head>
<title>go/render: hello wasm!</title>
<style>
#canvas {
position: fixed;
width: 100%;
height: 100%;
top: 0;
right: 0;
left: 0;
bottom: 0;
}
@font-face {
font-family: "DejaVuSans";
src: url("fonts/DejaVuSans.ttf") format("truetype");
}
</style>
</head>
<body>
<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);
};
}
(function() {
const go = new Go();
WebAssembly.instantiateStreaming(fetch("hello.wasm"), go.importObject).then(result => {
console.clear();
go.run(result.instance);
WebAssembly.instantiate(result.module, go.importObject); // reset instance
})
})();
</script>
<canvas id="canvas"></canvas>
</body>
</html>

177
examples/hello-wasm/main_wasm.go

@ -0,0 +1,177 @@
// +build js,wasm
// This is a version of the 'hello-world' example but build for WebAssembly.
package main
import (
"image/png"
"log"
"net/http"
"time"
"git.kirsle.net/go/render"
"git.kirsle.net/go/render/canvas"
)
var (
// Cap animation speed to 60 FPS
targetFPS = 1000 / 60
// Gopher sprite variables
gopher render.Texturer
texSize render.Rect
speed int32 = 4
position = render.NewPoint(0, 0)
velocity = render.NewPoint(speed, speed)
// Decorative border variables
borderColor = render.Red
borderSize int32 = 12
// Background color of the window.
bgColor = render.RGBA(255, 255, 128, 255)
)
func main() {
// Parameter to New() is the HTML Canvas ID.
mw, err := canvas.New("canvas")
if err != nil {
panic(err)
}
setup(mw)
for {
start := time.Now()
ev, err := mw.Poll()
if err != nil {
panic(err)
}
if ev.Escape {
mw.Teardown()
break
}
update(mw)
draw(mw)
mw.Present()
// Delay to maintain constant 60 FPS.
var delay uint32
elapsed := time.Now().Sub(start)
tmp := elapsed / time.Millisecond
if targetFPS-int(tmp) > 0 {
delay = uint32(targetFPS - int(tmp))
}
mw.Delay(delay)
}
}
func setup(e *canvas.Engine) {
if err := e.Setup(); err != nil {
panic(err)
}
// Bind DOM event handlers.
e.AddEventListeners()
// Load gopher sprite via ajax request.
resp, err := http.Get("gopher.png")
if err != nil {
log.Fatalf("GET gopher.png: %s", err)
}
defer resp.Body.Close()
img, _ := png.Decode(resp.Body)
gopher, _ = e.StoreTexture("gopher.png", img)
texSize = gopher.Size()
}
func update(e render.Engine) {
position.X += velocity.X
position.Y += velocity.Y
// Bounce off the walls.
w, h := e.WindowSize()
if velocity.X > 0 && position.X+texSize.W >= int32(w)-borderSize {
velocity.X *= -1
} else if velocity.X < 0 && position.X <= borderSize {
velocity.X *= -1
}
if velocity.Y > 0 && position.Y+texSize.H >= int32(h)-borderSize {
velocity.Y *= -1
} else if velocity.Y < 0 && position.Y <= borderSize {
velocity.Y *= -1
}
}
func draw(e render.Engine) {
w, h := e.WindowSize()
drawBorder(e, w, h)
// Draw some text centered along the top of the canvas.
text := render.Text{
Text: "Hello, world!",
Size: 24,
Color: render.SkyBlue,
Shadow: render.Blue,
FontFilename: "DejaVuSans.ttf",
}
rect, _ := e.ComputeTextRect(text)
e.DrawText(text, render.NewPoint(
(int32(w)/2)-(rect.W/2),
25,
))
e.Copy(gopher, texSize, render.Rect{
X: position.X,
Y: position.Y,
W: texSize.W,
H: texSize.H,
})
}
func drawBorder(e render.Engine, w, h int) {
// Draw the decorative border. We're going for a "ridged" border
// style here. First draw the light and dark edges of the top/left
// sides of the border.
e.DrawBox(borderColor.Lighten(40), render.Rect{
X: 0,
Y: 0,
W: int32(w),
H: int32(h),
})
e.DrawBox(borderColor.Darken(40), render.Rect{
X: borderSize / 2,
Y: borderSize / 2,
W: int32(w) - (borderSize / 2),
H: int32(h) - (borderSize / 2),
})
// Now inset a bit and draw the light/dark edges of the bottom/right.
e.DrawBox(borderColor.Darken(40), render.Rect{
X: borderSize,
Y: borderSize,
W: int32(w),
H: int32(h),
})
e.DrawBox(borderColor.Lighten(40), render.Rect{
X: borderSize,
Y: borderSize,
W: int32(w) - borderSize - (borderSize / 2),
H: int32(h) - borderSize - (borderSize / 2),
})
e.DrawBox(bgColor, render.Rect{
X: borderSize,
Y: borderSize,
W: int32(w) - (borderSize * 2),
H: int32(h) - (borderSize * 2),
})
}

127
examples/hello-wasm/server.go

@ -0,0 +1,127 @@
// +build disabled
package main
import (
"fmt"
"io/ioutil"
"log"
"net/http"
"os/exec"
"path/filepath"
"github.com/fsnotify/fsnotify"
)
func main() {
const wasm = "/doodle.wasm"
// Watch the dev directory for changes.
go watchChanges()
http.Handle("/", http.FileServer(http.Dir(".")))
http.HandleFunc(wasm, func(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "application/wasm")
http.ServeFile(w, r, "."+wasm)
})
fmt.Println("Listening at http://localhost:8080/")
log.Fatal(http.ListenAndServe(":8080", nil))
}
// onChange handler to rebuild the wasm file automatically.
func onChange() {
out, err := exec.Command("make").Output()
if err != nil {
log.Printf("error: %s", err)
}
log.Printf("%s", out)
log.Printf("Doodle WASM file rebuilt")
}
// Watch the Doodle source tree for changes to Go files and rebuild
// the wasm binary automatically.
func watchChanges() {
watcher, err := fsnotify.NewWatcher()
if err != nil {
log.Printf("error: %s", err)
return
}
defer watcher.Close()
done := make(chan bool)
go func() {
log.Println("Starting watch files loop")
for {
select {
case event, ok := <-watcher.Events:
if !ok {
return
}
log.Printf("event: %s", event)
if event.Op&fsnotify.Write == fsnotify.Write {
log.Printf("modified file: %s", event.Name)
onChange()
}
case err, ok := <-watcher.Errors:
if !ok {
return
}
log.Printf("error: %s", err)
}
}
}()
log.Println("Adding source directory to watcher")
dirs := crawlDirectory("../")
// Watch all these folders.
for _, dir := range dirs {
err = watcher.Add(dir)
if err != nil {
log.Printf("error: %s", err)
}
}
<-done
}
// Crawl the filesystem and return paths with Go files.
func crawlDirectory(root string) []string {
var (
ext = ".go"
result []string
has bool
)
files, err := ioutil.ReadDir(root)
if err != nil {
log.Fatalln(err)
}
for _, file := range files {
if file.Name() == ".git" {
continue
}
// Recursively scan subdirectories.
if file.IsDir() {
result = append(result,
crawlDirectory(filepath.Join(root, file.Name()))...,
)
continue
}
// This root has a file we want?
if filepath.Ext(file.Name()) == ext {
has = true
}
}
if has {
result = append(result, root)
}
return result
}

533
examples/hello-wasm/wasm_exec.js

@ -0,0 +1,533 @@
// 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 multiple JavaScript environments to a single common API,
// preferring web standards over Node.js API.
//
// Environments considered:
// - Browsers
// - Node.js
// - Electron
// - Parcel
if (typeof global !== "undefined") {
// global already exists
} else if (typeof window !== "undefined") {
window.global = window;
} else if (typeof self !== "undefined") {
self.global = self;
} else {
throw new Error("cannot export Go (neither global, window nor self is defined)");
}
if (!global.require && typeof require !== "undefined") {
global.require = require;
}
if (!global.fs && global.require) {
global.fs = require("fs");
}
if (!global.fs) {
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;
},
write(fd, buf, offset, length, position, callback) {
if (offset !== 0 || length !== buf.length || position !== null) {
throw new Error("not implemented");
}
const n = this.writeSync(fd, buf);
callback(null, n);
},
open(path, flags, mode, callback) {
const err = new Error("not implemented");
err.code = "ENOSYS";
callback(err);
},
read(fd, buffer, offset, length, position, callback) {
const err = new Error("not implemented");
err.code = "ENOSYS";
callback(err);
},
fsync(fd, callback) {
callback(null);
},
};
}
if (!global.crypto) {
const nodeCrypto = require("crypto");
global.crypto = {
getRandomValues(b) {
nodeCrypto.randomFillSync(b);
},
};
}
if (!global.performance) {
global.performance = {
now() {
const [sec, nsec] = process.hrtime();
return sec * 1000 + nsec / 1000000;
},
};
}
if (!global.TextEncoder) {
global.TextEncoder = require("util").TextEncoder;
}
if (!global.TextDecoder) {
global.TextDecoder = require("util").TextDecoder;
}
// End of polyfills for common API.
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._exitPromise = new Promise((resolve) => {
this._resolveExitPromise = resolve;
});
this._pendingEvent = null;
this._scheduledTimeouts = 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 (f === 0) {
return undefined;
}
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;
}
if (v === 0) {
mem().setUint32(addr + 4, nanHead, true);
mem().setUint32(addr, 1, true);
return;
}
mem().setFloat64(addr, v, true);
return;
}
switch (v) {
case undefined:
mem().setFloat64(addr, 0, 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: {
// Go's SP does not change as long as no Go code is running. Some operations (e.g. calls, getters and setters)
// may synchronously trigger a Go event handler. This makes Go code get executed in the middle of the imported
// function. A goroutine can switch to a new stack if the current stack is too small (see morestack function).
// This changes the SP, thus we have to update the SP used by the imported function.
// 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 scheduleTimeoutEvent(delay int64) int32
"runtime.scheduleTimeoutEvent": (sp) => {
const id = this._nextCallbackTimeoutID;
this._nextCallbackTimeoutID++;
this._scheduledTimeouts.set(id, setTimeout(
() => {
this._resume();
while (this._scheduledTimeouts.has(id)) {
// for some reason Go failed to register the timeout event, log and try again
// (temporary workaround for https://github.com/golang/go/issues/28975)
console.warn("scheduleTimeoutEvent: missed timeout event");
this._resume();
}
},
getInt64(sp + 8) + 1, // setTimeout has been seen to fire up to 1 millisecond early
));
mem().setInt32(sp + 16, id, true);
},
// func clearTimeoutEvent(id int32)
"runtime.clearTimeoutEvent": (sp) => {
const id = mem().getInt32(sp + 8, true);
clearTimeout(this._scheduledTimeouts.get(id));
this._scheduledTimeouts.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) => {
const result = Reflect.get(loadValue(sp + 8), loadString(sp + 16));
sp = this._inst.exports.getsp(); // see comment above
storeValue(sp + 32, result);
},
// 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);
const result = Reflect.apply(m, v, args);
sp = this._inst.exports.getsp(); // see comment above
storeValue(sp + 56, result);
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);
const result = Reflect.apply(v, undefined, args);
sp = this._inst.exports.getsp(); // see comment above
storeValue(sp + 40, result);
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);
const result = Reflect.construct(v, args);
sp = this._inst.exports.getsp(); // see comment above
storeValue(sp + 40, result);
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));
},
// func copyBytesToGo(dst []byte, src ref) (int, bool)
"syscall/js.copyBytesToGo": (sp) => {
const dst = loadSlice(sp + 8);
const src = loadValue(sp + 32);
if (!(src instanceof Uint8Array)) {
mem().setUint8(sp + 48, 0);
return;
}
const toCopy = src.subarray(0, dst.length);
dst.set(toCopy);
setInt64(sp + 40, toCopy.length);
mem().setUint8(sp + 48, 1);
},
// func copyBytesToJS(dst ref, src []byte) (int, bool)
"syscall/js.copyBytesToJS": (sp) => {
const dst = loadValue(sp + 8);
const src = loadSlice(sp + 16);
if (!(dst instanceof Uint8Array)) {
mem().setUint8(sp + 48, 0);
return;
}
const toCopy = src.subarray(0, dst.length);
dst.set(toCopy);
setInt64(sp + 40, toCopy.length);
mem().setUint8(sp + 48, 1);
},
"debug": (value) => {
console.log(value);
},
}
};
}
async run(instance) {
this._inst = instance;
this._values = [ // TODO: garbage collection
NaN,
0,
null,
true,
false,
global,
this,
];
this._refs = new Map();
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) => {
const ptr = offset;
const bytes = encoder.encode(str + "\0");
new Uint8Array(mem.buffer, offset, bytes.length).set(bytes);
offset += bytes.length;
if (offset % 8 !== 0) {
offset += 8 - (offset % 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;
});
this._inst.exports.run(argc, argv);
if (this.exited) {
this._resolveExitPromise();
}
await this._exitPromise;
}
_resume() {
if (this.exited) {
throw new Error("Go program has already exited");
}
this._inst.exports.resume();
if (this.exited) {
this._resolveExitPromise();
}
}
_makeFuncWrapper(id) {
const go = this;
return function () {
const event = { id: id, this: this, args: arguments };
go._pendingEvent = event;
go._resume();
return event.result;
};
}
}
if (
global.require &&
global.require.main === module &&
global.process &&
global.process.versions &&
!global.process.versions.electron
) {
if (process.argv.length < 3) {
console.error("usage: go_js_wasm_exec [wasm binary] [arguments]");
process.exit(1);
}
const go = new Go();
go.argv = process.argv.slice(2);
go.env = Object.assign({ TMPDIR: require("os").tmpdir() }, 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 event handler is pending
if (code === 0 && !go.exited) {
// deadlock, make Go print error and stack traces
go._pendingEvent = { id: 0 };
go._resume();
}
});
return go.run(result.instance);
}).catch((err) => {
console.error(err);
process.exit(1);
});
}
})();
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