repo_description: The Go programming language
repo_topics: go golang language programming-language
code: // 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.
  
  "use strict";
  
  (() => {
  	const enosys = () => {
  		const err = new Error("not implemented");
  		err.code = "ENOSYS";
  		return err;
  	};
  
  	if (!globalThis.fs) {
  		let outputBuf = "";
  		globalThis.fs = {
  			constants: { O_WRONLY: -1, O_RDWR: -1, O_CREAT: -1, O_TRUNC: -1, O_APPEND: -1, O_EXCL: -1, O_DIRECTORY: -1 }, // unused
  			writeSync(fd, buf) {
  				outputBuf += decoder.decode(buf);
  				const nl = outputBuf.lastIndexOf("\n");
  				if (nl != -1) {
  					console.log(outputBuf.substring(0, nl));
  					outputBuf = outputBuf.substring(nl + 1);
  				}
  				return buf.length;
  			},
  			write(fd, buf, offset, length, position, callback) {
  				if (offset !== 0 || length !== buf.length || position !== null) {
  					callback(enosys());
  					return;
  				}
  				const n = this.writeSync(fd, buf);
  				callback(null, n);
  			},
  			chmod(path, mode, callback) { callback(enosys()); },
  			chown(path, uid, gid, callback) { callback(enosys()); },
  			close(fd, callback) { callback(enosys()); },
  			fchmod(fd, mode, callback) { callback(enosys()); },
  			fchown(fd, uid, gid, callback) { callback(enosys()); },
  			fstat(fd, callback) { callback(enosys()); },
  			fsync(fd, callback) { callback(null); },
  			ftruncate(fd, length, callback) { callback(enosys()); },
  			lchown(path, uid, gid, callback) { callback(enosys()); },
  			link(path, link, callback) { callback(enosys()); },
  			lstat(path, callback) { callback(enosys()); },
  			mkdir(path, perm, callback) { callback(enosys()); },
  			open(path, flags, mode, callback) { callback(enosys()); },
  			read(fd, buffer, offset, length, position, callback) { callback(enosys()); },
  			readdir(path, callback) { callback(enosys()); },
  			readlink(path, callback) { callback(enosys()); },
  			rename(from, to, callback) { callback(enosys()); },
  			rmdir(path, callback) { callback(enosys()); },
  			stat(path, callback) { callback(enosys()); },
  			symlink(path, link, callback) { callback(enosys()); },
  			truncate(path, length, callback) { callback(enosys()); },
  			unlink(path, callback) { callback(enosys()); },
  			utimes(path, atime, mtime, callback) { callback(enosys()); },
  		};
  	}
  
  	if (!globalThis.process) {
  		globalThis.process = {
  			getuid() { return -1; },
  			getgid() { return -1; },
  			geteuid() { return -1; },
  			getegid() { return -1; },
  			getgroups() { throw enosys(); },
  			pid: -1,
  			ppid: -1,
  			umask() { throw enosys(); },
  			cwd() { throw enosys(); },
  			chdir() { throw enosys(); },
  		}
  	}
  
  	if (!globalThis.path) {
  		globalThis.path = {
  			resolve(...pathSegments) {
  				return pathSegments.join("/");
  			}
  		}
  	}
  
  	if (!globalThis.crypto) {
  		throw new Error("globalThis.crypto is not available, polyfill required (crypto.getRandomValues only)");
  	}
  
  	if (!globalThis.performance) {
  		throw new Error("globalThis.performance is not available, polyfill required (performance.now only)");
  	}
  
  	if (!globalThis.TextEncoder) {
  		throw new Error("globalThis.TextEncoder is not available, polyfill required");
  	}
  
  	if (!globalThis.TextDecoder) {
  		throw new Error("globalThis.TextDecoder is not available, polyfill required");
  	}
  
  	const encoder = new TextEncoder("utf-8");
  	const decoder = new TextDecoder("utf-8");
  
  	globalThis.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 setInt64 = (addr, v) => {
  				this.mem.setUint32(addr + 0, v, true);
  				this.mem.setUint32(addr + 4, Math.floor(v / 4294967296), true);
  			}
  
  			const setInt32 = (addr, v) => {
  				this.mem.setUint32(addr + 0, v, true);
  			}
  
  			const getInt64 = (addr) => {
  				const low = this.mem.getUint32(addr + 0, true);
  				const high = this.mem.getInt32(addr + 4, true);
  				return low + high * 4294967296;
  			}
  
  			const loadValue = (addr) => {
  				const f = this.mem.getFloat64(addr, true);
  				if (f === 0) {
  					return undefined;
  				}
  				if (!isNaN(f)) {
  					return f;
  				}
  
  				const id = this.mem.getUint32(addr, true);
  				return this._values[id];
  			}
  
  			const storeValue = (addr, v) => {
  				const nanHead = 0x7FF80000;
  
  				if (typeof v === "number" && v !== 0) {
  					if (isNaN(v)) {
  						this.mem.setUint32(addr + 4, nanHead, true);
  						this.mem.setUint32(addr, 0, true);
  						return;
  					}
  					this.mem.setFloat64(addr, v, true);
  					return;
  				}
  
  				if (v === undefined) {
  					this.mem.setFloat64(addr, 0, true);
  					return;
  				}
  
  				let id = this._ids.get(v);
  				if (id === undefined) {
  					id = this._idPool.pop();
  					if (id === undefined) {
  						id = this._values.length;
  					}
  					this._values[id] = v;
  					this._goRefCounts[id] = 0;
  					this._ids.set(v, id);
  				}
  				this._goRefCounts[id]++;
  				let typeFlag = 0;
  				switch (typeof v) {
  					case "object":
  						if (v !== null) {
  							typeFlag = 1;
  						}
  						break;
  					case "string":
  						typeFlag = 2;
  						break;
  					case "symbol":
  						typeFlag = 3;
  						break;
  					case "function":
  						typeFlag = 4;
  						break;
  				}
  				this.mem.setUint32(addr + 4, nanHead | typeFlag, true);
  				this.mem.setUint32(addr, id, 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 testCallExport = (a, b) => {
  				this._inst.exports.testExport0();
  				return this._inst.exports.testExport(a, b);
  			}
  
  			const timeOrigin = Date.now() - performance.now();
  			this.importObject = {
  				_gotest: {
  					add: (a, b) => a + b,
  					callExport: testCallExport,
  				},
  				gojs: {
  					// 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) => {
  						sp >>>= 0;
  						const code = this.mem.getInt32(sp + 8, true);
  						this.exited = true;
  						delete this._inst;
  						delete this._values;
  						delete this._goRefCounts;
  						delete this._ids;
  						delete this._idPool;
  						this.exit(code);
  					},
  
  					// func wasmWrite(fd uintptr, p unsafe.Pointer, n int32)
  					"runtime.wasmWrite": (sp) => {
  						sp >>>= 0;
  						const fd = getInt64(sp + 8);
  						const p = getInt64(sp + 16);
  						const n = this.mem.getInt32(sp + 24, true);
  						fs.writeSync(fd, new Uint8Array(this._inst.exports.mem.buffer, p, n));
  					},
  
  					// func resetMemoryDataView()
  					"runtime.resetMemoryDataView": (sp) => {
  						sp >>>= 0;
  						this.mem = new DataView(this._inst.exports.mem.buffer);
  					},
  
  					// func nanotime1() int64
  					"runtime.nanotime1": (sp) => {
  						sp >>>= 0;
  						setInt64(sp + 8, (timeOrigin + performance.now()) * 1000000);
  					},
  
  					// func walltime() (sec int64, nsec int32)
  					"runtime.walltime": (sp) => {
  						sp >>>= 0;
  						const msec = (new Date).getTime();
  						setInt64(sp + 8, msec / 1000);
  						this.mem.setInt32(sp + 16, (msec % 1000) * 1000000, true);
  					},
  
  					// func scheduleTimeoutEvent(delay int64) int32
  					"runtime.scheduleTimeoutEvent": (sp) => {
  						sp >>>= 0;
  						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),
  						));
  						this.mem.setInt32(sp + 16, id, true);
  					},
  
  					// func clearTimeoutEvent(id int32)
  					"runtime.clearTimeoutEvent": (sp) => {
  						sp >>>= 0;
  						const id = this.mem.getInt32(sp + 8, true);
  						clearTimeout(this._scheduledTimeouts.get(id));
  						this._scheduledTimeouts.delete(id);
  					},
  
  					// func getRandomData(r []byte)
  					"runtime.getRandomData": (sp) => {
  						sp >>>= 0;
  						crypto.getRandomValues(loadSlice(sp + 8));
  					},
  
  					// func finalizeRef(v ref)
  					"syscall/js.finalizeRef": (sp) => {
  						sp >>>= 0;
  						const id = this.mem.getUint32(sp + 8, true);
  						this._goRefCounts[id]--;
  						if (this._goRefCounts[id] === 0) {
  							const v = this._values[id];
  							this._values[id] = null;
  							this._ids.delete(v);
  							this._idPool.push(id);
  						}
  					},
  
  					// func stringVal(value string) ref
  					"syscall/js.stringVal": (sp) => {
  						sp >>>= 0;
  						storeValue(sp + 24, loadString(sp + 8));
  					},
  
  					// func valueGet(v ref, p string) ref
  					"syscall/js.valueGet": (sp) => {
  						sp >>>= 0;
  						const result = Reflect.get(loadValue(sp + 8), loadString(sp + 16));
  						sp = this._inst.exports.getsp() >>> 0; // see comment above
  						storeValue(sp + 32, result);
  					},
  
  					// func valueSet(v ref, p string, x ref)
  					"syscall/js.valueSet": (sp) => {
  						sp >>>= 0;
  						Reflect.set(loadValue(sp + 8), loadString(sp + 16), loadValue(sp + 32));
  					},
  
  					// func valueDelete(v ref, p string)
  					"syscall/js.valueDelete": (sp) => {
  						sp >>>= 0;
  						Reflect.deleteProperty(loadValue(sp + 8), loadString(sp + 16));
  					},
  
  					// func valueIndex(v ref, i int) ref
  					"syscall/js.valueIndex": (sp) => {
  						sp >>>= 0;
  						storeValue(sp + 24, Reflect.get(loadValue(sp + 8), getInt64(sp + 16)));
  					},
  
  					// valueSetIndex(v ref, i int, x ref)
  					"syscall/js.valueSetIndex": (sp) => {
  						sp >>>= 0;
  						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) => {
  						sp >>>= 0;
  						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() >>> 0; // see comment above
  							storeValue(sp + 56, result);
  							this.mem.setUint8(sp + 64, 1);
  						} catch (err) {
  							sp = this._inst.exports.getsp() >>> 0; // see comment above
  							storeValue(sp + 56, err);
  							this.mem.setUint8(sp + 64, 0);
  						}
  					},
  
  					// func valueInvoke(v ref, args []ref) (ref, bool)
  					"syscall/js.valueInvoke": (sp) => {
  						sp >>>= 0;
  						try {
  							const v = loadValue(sp + 8);
  							const args = loadSliceOfValues(sp + 16);
  							const result = Reflect.apply(v, undefined, args);
  							sp = this._inst.exports.getsp() >>> 0; // see comment above
  							storeValue(sp + 40, result);
  							this.mem.setUint8(sp + 48, 1);
  						} catch (err) {
  							sp = this._inst.exports.getsp() >>> 0; // see comment above
  							storeValue(sp + 40, err);
  							this.mem.setUint8(sp + 48, 0);
  						}
  					},
  
  					// func valueNew(v ref, args []ref) (ref, bool)
  					"syscall/js.valueNew": (sp) => {
  						sp >>>= 0;
  						try {
  							const v = loadValue(sp + 8);
  							const args = loadSliceOfValues(sp + 16);
  							const result = Reflect.construct(v, args);
  							sp = this._inst.exports.getsp() >>> 0; // see comment above
  							storeValue(sp + 40, result);
  							this.mem.setUint8(sp + 48, 1);
  						} catch (err) {
  							sp = this._inst.exports.getsp() >>> 0; // see comment above
  							storeValue(sp + 40, err);
  							this.mem.setUint8(sp + 48, 0);
  						}
  					},
  
  					// func valueLength(v ref) int
  					"syscall/js.valueLength": (sp) => {
  						sp >>>= 0;
  						setInt64(sp + 16, parseInt(loadValue(sp + 8).length));
  					},
  
  					// valuePrepareString(v ref) (ref, int)
  					"syscall/js.valuePrepareString": (sp) => {
  						sp >>>= 0;
  						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) => {
  						sp >>>= 0;
  						const str = loadValue(sp + 8);
  						loadSlice(sp + 16).set(str);
  					},
  
  					// func valueInstanceOf(v ref, t ref) bool
  					"syscall/js.valueInstanceOf": (sp) => {
  						sp >>>= 0;
  						this.mem.setUint8(sp + 24, (loadValue(sp + 8) instanceof loadValue(sp + 16)) ? 1 : 0);
  					},
  
  					// func copyBytesToGo(dst []byte, src ref) (int, bool)
  					"syscall/js.copyBytesToGo": (sp) => {
  						sp >>>= 0;
  						const dst = loadSlice(sp + 8);
  						const src = loadValue(sp + 32);
  						if (!(src instanceof Uint8Array || src instanceof Uint8ClampedArray)) {
  							this.mem.setUint8(sp + 48, 0);
  							return;
  						}
  						const toCopy = src.subarray(0, dst.length);
  						dst.set(toCopy);
  						setInt64(sp + 40, toCopy.length);
  						this.mem.setUint8(sp + 48, 1);
  					},
  
  					// func copyBytesToJS(dst ref, src []byte) (int, bool)
  					"syscall/js.copyBytesToJS": (sp) => {
  						sp >>>= 0;
  						const dst = loadValue(sp + 8);
  						const src = loadSlice(sp + 16);
  						if (!(dst instanceof Uint8Array || dst instanceof Uint8ClampedArray)) {
  							this.mem.setUint8(sp + 48, 0);
  							return;
  						}
  						const toCopy = src.subarray(0, dst.length);
  						dst.set(toCopy);
  						setInt64(sp + 40, toCopy.length);
  						this.mem.setUint8(sp + 48, 1);
  					},
  
  					"debug": (value) => {
  						console.log(value);
  					},
  				}
  			};
  		}
  
  		async run(instance) {
  			if (!(instance instanceof WebAssembly.Instance)) {
  				throw new Error("Go.run: WebAssembly.Instance expected");
  			}
  			this._inst = instance;
  			this.mem = new DataView(this._inst.exports.mem.buffer);
  			this._values = [ // JS values that Go currently has references to, indexed by reference id
  				NaN,
  				0,
  				null,
  				true,
  				false,
  				globalThis,
  				this,
  			];
  			this._goRefCounts = new Array(this._values.length).fill(Infinity); // number of references that Go has to a JS value, indexed by reference id
  			this._ids = new Map([ // mapping from JS values to reference ids
  				[0, 1],
  				[null, 2],
  				[true, 3],
  				[false, 4],
  				[globalThis, 5],
  				[this, 6],
  			]);
  			this._idPool = [];   // unused ids that have been garbage collected
  			this.exited = false; // whether the Go program has exited
  
  			// 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(this.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));
  			});
  			argvPtrs.push(0);
  
  			const keys = Object.keys(this.env).sort();
  			keys.forEach((key) => {
  				argvPtrs.push(strPtr(`${key}=${this.env[key]}`));
  			});
  			argvPtrs.push(0);
  
  			const argv = offset;
  			argvPtrs.forEach((ptr) => {
  				this.mem.setUint32(offset, ptr, true);
  				this.mem.setUint32(offset + 4, 0, true);
  				offset += 8;
  			});
  
  			// The linker guarantees global data starts from at least wasmMinDataAddr.
  			// Keep in sync with cmd/link/internal/ld/data.go:wasmMinDataAddr.
  			const wasmMinDataAddr = 4096 + 8192;
  			if (offset >= wasmMinDataAddr) {
  				throw new Error("total length of command line and environment variables exceeds limit");
  			}
  
  			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;
  			};
  		}
  	}
  })();
  