go/wasm_exec.js at master · golang/go · GitHub

Nov 10, 2018

neelance all: add support for synchronous callbacks to js/wasm

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	// 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.

	(() => {
	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)");
	}

	// Map web browser API and Node.js API to a single common API (preferring web standards over Node.js API).
	const isNodeJS = global.process && global.process.title === "node";
	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 {
	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);
	},
	fsync(fd, callback) {
	callback(null);
	},
	};
	}

	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._pendingCallback = null;
	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 (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 trigger a synchronous callback to Go. 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 scheduleCallback(delay int64) int32
	"runtime.scheduleCallback": (sp) => {
	const id = this._nextCallbackTimeoutID;
	this._nextCallbackTimeoutID++;
	this._callbackTimeouts.set(id, setTimeout(
	() => { this._resume(); },
	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) => {
	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));
	},

	"debug": (value) => {
	console.log(value);
	},
	}
	};
	}

	async run(instance) {
	this._inst = instance;
	this._values = [ // TODO: garbage collection
	NaN,
	0,
	null,
	true,
	false,
	global,
	this._inst.exports.mem,
	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) => {
	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;
	});

	this._inst.exports.run(argc, argv);
	if (this.exited) {
	this._resolveExitPromise();
	}
	await this._exitPromise;
	}

	_resume() {
	if (this.exited) {
	throw new Error("bad callback: Go program has already exited");
	}
	this._inst.exports.resume();
	if (this.exited) {
	this._resolveExitPromise();
	}
	}

	_makeCallbackHelper(id) {
	const go = this;
	return function () {
	const cb = { id: id, this: this, args: arguments };
	go._pendingCallback = cb;
	go._resume();
	return cb.result;
	};
	}
	}

	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._pendingCallback = { id: 0 };
	go._resume();
	}
	});
	return go.run(result.instance);
	}).catch((err) => {
	throw err;
	});
	}
	})();

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