wasm_exec.js

// 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.
//
// This file has been modified for use by the TinyGo compiler.

(() => {
    // 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");
    }

    const enosys = () => {
        const err = new Error("not implemented");
        err.code = "ENOSYS";
        return err;
    };

    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) {
                    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 (!global.process) {
        global.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 (!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");
    let reinterpretBuf = new DataView(new ArrayBuffer(8));
    var logLine = [];

    global.Go = class {
        constructor() {
            this._callbackTimeouts = new Map();
            this._nextCallbackTimeoutID = 1;

            const mem = () => {
                // The buffer may change when requesting more memory.
                return new DataView(this._inst.exports.memory.buffer);
            }

            const unboxValue = (v_ref) => {
                reinterpretBuf.setBigInt64(0, v_ref, true);
                const f = reinterpretBuf.getFloat64(0, true);
                if (f === 0) {
                    return undefined;
                }
                if (!isNaN(f)) {
                    return f;
                }

                const id = v_ref & 0xffffffffn;
                return this._values[id];
            }


            const loadValue = (addr) => {
                let v_ref = mem().getBigUint64(addr, true);
                return unboxValue(v_ref);
            }

            const boxValue = (v) => {
                const nanHead = 0x7FF80000n;

                if (typeof v === "number") {
                    if (isNaN(v)) {
                        return nanHead << 32n;
                    }
                    if (v === 0) {
                        return (nanHead << 32n) | 1n;
                    }
                    reinterpretBuf.setFloat64(0, v, true);
                    return reinterpretBuf.getBigInt64(0, true);
                }

                switch (v) {
                    case undefined:
                        return 0n;
                    case null:
                        return (nanHead << 32n) | 2n;
                    case true:
                        return (nanHead << 32n) | 3n;
                    case false:
                        return (nanHead << 32n) | 4n;
                }

                let id = this._ids.get(v);
                if (id === undefined) {
                    id = this._idPool.pop();
                    if (id === undefined) {
                        id = BigInt(this._values.length);
                    }
                    this._values[id] = v;
                    this._goRefCounts[id] = 0;
                    this._ids.set(v, id);
                }
                this._goRefCounts[id]++;
                let typeFlag = 1n;
                switch (typeof v) {
                    case "string":
                        typeFlag = 2n;
                        break;
                    case "symbol":
                        typeFlag = 3n;
                        break;
                    case "function":
                        typeFlag = 4n;
                        break;
                }
                return id | ((nanHead | typeFlag) << 32n);
            }

            const storeValue = (addr, v) => {
                let v_ref = boxValue(v);
                mem().setBigUint64(addr, v_ref, true);
            }

            const loadSlice = (array, len, cap) => {
                return new Uint8Array(this._inst.exports.memory.buffer, array, len);
            }

            const loadSliceOfValues = (array, len, cap) => {
                const a = new Array(len);
                for (let i = 0; i < len; i++) {
                    a[i] = loadValue(array + i * 8);
                }
                return a;
            }

            const loadString = (ptr, len) => {
                return decoder.decode(new DataView(this._inst.exports.memory.buffer, ptr, len));
            }

            const timeOrigin = Date.now() - performance.now();
            this.importObject = {
                wasi_snapshot_preview1: {
                    // https://github.com/WebAssembly/WASI/blob/main/phases/snapshot/docs.md#fd_write
                    fd_write: function(fd, iovs_ptr, iovs_len, nwritten_ptr) {
                        let nwritten = 0;
                        if (fd == 1) {
                            for (let iovs_i=0; iovs_i<iovs_len;iovs_i++) {
                                let iov_ptr = iovs_ptr+iovs_i*8; // assuming wasm32
                                let ptr = mem().getUint32(iov_ptr + 0, true);
                                let len = mem().getUint32(iov_ptr + 4, true);
                                nwritten += len;
                                for (let i=0; i<len; i++) {
                                    let c = mem().getUint8(ptr+i);
                                    if (c == 13) { // CR
                                        // ignore
                                    } else if (c == 10) { // LF
                                        // write line
                                        let line = decoder.decode(new Uint8Array(logLine));
                                        logLine = [];
                                        console.log(line);
                                    } else {
                                        logLine.push(c);
                                    }
                                }
                            }
                        } else {
                            console.error('invalid file descriptor:', fd);
                        }
                        mem().setUint32(nwritten_ptr, nwritten, true);
                        return 0;
                    },
                    fd_close: () => 0,      // dummy
                    fd_fdstat_get: () => 0, // dummy
                    fd_seek: () => 0,       // dummy
                    "proc_exit": (code) => {
                        if (global.process) {
                            // Node.js
                            process.exit(code);
                        } else {
                            // Can't exit in a browser.
                            throw 'trying to exit with code ' + code;
                        }
                    },
                    random_get: (bufPtr, bufLen) => {
                        crypto.getRandomValues(loadSlice(bufPtr, bufLen));
                        return 0;
                    },
                },
                gojs: {
                    // func ticks() float64
                    "runtime.ticks": () => {
                        return timeOrigin + performance.now();
                    },

                    // func sleepTicks(timeout float64)
                    "runtime.sleepTicks": (timeout) => {
                        // Do not sleep, only reactivate scheduler after the given timeout.
                        setTimeout(this._inst.exports.go_scheduler, timeout);
                    },

                    // func finalizeRef(v ref)
                    "syscall/js.finalizeRef": (v_ref) => {
                        // Note: TinyGo does not support finalizers so this should never be
                        // called.
                        console.error('syscall/js.finalizeRef not implemented');
                    },

                    // func stringVal(value string) ref
                    "syscall/js.stringVal": (value_ptr, value_len) => {
                        const s = loadString(value_ptr, value_len);
                        return boxValue(s);
                    },

                    // func valueGet(v ref, p string) ref
                    "syscall/js.valueGet": (v_ref, p_ptr, p_len) => {
                        let prop = loadString(p_ptr, p_len);
                        let v = unboxValue(v_ref);
                        let result = Reflect.get(v, prop);
                        return boxValue(result);
                    },

                    // func valueSet(v ref, p string, x ref)
                    "syscall/js.valueSet": (v_ref, p_ptr, p_len, x_ref) => {
                        const v = unboxValue(v_ref);
                        const p = loadString(p_ptr, p_len);
                        const x = unboxValue(x_ref);
                        Reflect.set(v, p, x);
                    },

                    // func valueDelete(v ref, p string)
                    "syscall/js.valueDelete": (v_ref, p_ptr, p_len) => {
                        const v = unboxValue(v_ref);
                        const p = loadString(p_ptr, p_len);
                        Reflect.deleteProperty(v, p);
                    },

                    // func valueIndex(v ref, i int) ref
                    "syscall/js.valueIndex": (v_ref, i) => {
                        return boxValue(Reflect.get(unboxValue(v_ref), i));
                    },

                    // valueSetIndex(v ref, i int, x ref)
                    "syscall/js.valueSetIndex": (v_ref, i, x_ref) => {
                        Reflect.set(unboxValue(v_ref), i, unboxValue(x_ref));
                    },

                    // func valueCall(v ref, m string, args []ref) (ref, bool)
                    "syscall/js.valueCall": (ret_addr, v_ref, m_ptr, m_len, args_ptr, args_len, args_cap) => {
                        const v = unboxValue(v_ref);
                        const name = loadString(m_ptr, m_len);
                        const args = loadSliceOfValues(args_ptr, args_len, args_cap);
                        try {
                            const m = Reflect.get(v, name);
                            storeValue(ret_addr, Reflect.apply(m, v, args));
                            mem().setUint8(ret_addr + 8, 1);
                        } catch (err) {
                            storeValue(ret_addr, err);
                            mem().setUint8(ret_addr + 8, 0);
                        }
                    },

                    // func valueInvoke(v ref, args []ref) (ref, bool)
                    "syscall/js.valueInvoke": (ret_addr, v_ref, args_ptr, args_len, args_cap) => {
                        try {
                            const v = unboxValue(v_ref);
                            const args = loadSliceOfValues(args_ptr, args_len, args_cap);
                            storeValue(ret_addr, Reflect.apply(v, undefined, args));
                            mem().setUint8(ret_addr + 8, 1);
                        } catch (err) {
                            storeValue(ret_addr, err);
                            mem().setUint8(ret_addr + 8, 0);
                        }
                    },

                    // func valueNew(v ref, args []ref) (ref, bool)
                    "syscall/js.valueNew": (ret_addr, v_ref, args_ptr, args_len, args_cap) => {
                        const v = unboxValue(v_ref);
                        const args = loadSliceOfValues(args_ptr, args_len, args_cap);
                        try {
                            storeValue(ret_addr, Reflect.construct(v, args));
                            mem().setUint8(ret_addr + 8, 1);
                        } catch (err) {
                            storeValue(ret_addr, err);
                            mem().setUint8(ret_addr+ 8, 0);
                        }
                    },

                    // func valueLength(v ref) int
                    "syscall/js.valueLength": (v_ref) => {
                        return unboxValue(v_ref).length;
                    },

                    // valuePrepareString(v ref) (ref, int)
                    "syscall/js.valuePrepareString": (ret_addr, v_ref) => {
                        const s = String(unboxValue(v_ref));
                        const str = encoder.encode(s);
                        storeValue(ret_addr, str);
                        mem().setInt32(ret_addr + 8, str.length, true);
                    },

                    // valueLoadString(v ref, b []byte)
                    "syscall/js.valueLoadString": (v_ref, slice_ptr, slice_len, slice_cap) => {
                        const str = unboxValue(v_ref);
                        loadSlice(slice_ptr, slice_len, slice_cap).set(str);
                    },

                    // func valueInstanceOf(v ref, t ref) bool
                    "syscall/js.valueInstanceOf": (v_ref, t_ref) => {
                        return unboxValue(v_ref) instanceof unboxValue(t_ref);
                    },

                    // func copyBytesToGo(dst []byte, src ref) (int, bool)
                    "syscall/js.copyBytesToGo": (ret_addr, dest_addr, dest_len, dest_cap, src_ref) => {
                        let num_bytes_copied_addr = ret_addr;
                        let returned_status_addr = ret_addr + 4; // Address of returned boolean status variable

                        const dst = loadSlice(dest_addr, dest_len);
                        const src = unboxValue(src_ref);
                        if (!(src instanceof Uint8Array || src instanceof Uint8ClampedArray)) {
                            mem().setUint8(returned_status_addr, 0); // Return "not ok" status
                            return;
                        }
                        const toCopy = src.subarray(0, dst.length);
                        dst.set(toCopy);
                        mem().setUint32(num_bytes_copied_addr, toCopy.length, true);
                        mem().setUint8(returned_status_addr, 1); // Return "ok" status
                    },

                    // copyBytesToJS(dst ref, src []byte) (int, bool)
                    // Originally copied from upstream Go project, then modified:
                    //   https://github.com/golang/go/blob/3f995c3f3b43033013013e6c7ccc93a9b1411ca9/misc/wasm/wasm_exec.js#L404-L416
                    "syscall/js.copyBytesToJS": (ret_addr, dst_ref, src_addr, src_len, src_cap) => {
                        let num_bytes_copied_addr = ret_addr;
                        let returned_status_addr = ret_addr + 4; // Address of returned boolean status variable

                        const dst = unboxValue(dst_ref);
                        const src = loadSlice(src_addr, src_len);
                        if (!(dst instanceof Uint8Array || dst instanceof Uint8ClampedArray)) {
                            mem().setUint8(returned_status_addr, 0); // Return "not ok" status
                            return;
                        }
                        const toCopy = src.subarray(0, dst.length);
                        dst.set(toCopy);
                        mem().setUint32(num_bytes_copied_addr, toCopy.length, true);
                        mem().setUint8(returned_status_addr, 1); // Return "ok" status
                    },
                }
            };

            // Go 1.20 uses 'env'. Go 1.21 uses 'gojs'.
            // For compatibility, we use both as long as Go 1.20 is supported.
            this.importObject.env = this.importObject.gojs;
        }

        async run(instance) {
            this._inst = instance;
            this._values = [ // JS values that Go currently has references to, indexed by reference id
                NaN,
                0,
                null,
                true,
                false,
                global,
                this,
            ];
            this._goRefCounts = []; // 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
            this._idPool = [];      // unused ids that have been garbage collected
            this.exited = false;    // whether the Go program has exited

            const mem = new DataView(this._inst.exports.memory.buffer)

            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._start();
                if (this.exited) {
                    break;
                }
                await callbackPromise;
            }
        }

        _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();
        WebAssembly.instantiate(fs.readFileSync(process.argv[2]), go.importObject).then((result) => {
            return go.run(result.instance);
        }).catch((err) => {
            console.error(err);
            process.exit(1);
        });
    }
})();