603 lines
17 KiB
JavaScript
603 lines
17 KiB
JavaScript
/**
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* Lightweight thenable implementation that is entirely self-contained within a single
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* function with no external dependencies so it can be easily shipped across to a WorkerModule.
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*
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* This implementation conforms fully to the Promises/A+ spec so it can safely interoperate
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* with other thenable implementations. https://github.com/promises-aplus/promises-spec
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*
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* *However*, it is _not_ a full implementation of ES2015 Promises, e.g. it does not
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* have the same constructor signature and does not expose a `catch` method or the static
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* `resolve`/`reject`/`all`/`race` initializer methods. If you need to hand a Thenable
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* instance off to consuming code that may expect a true Promise, you'll want to wrap it
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* in a native-or-polyfilled Promise first.
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*
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* (Why yet another Promises/A+ implementation? Great question. We needed a polyfill-like
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* thing that was (a) wrapped in a single function for easy serialization across to a Worker,
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* and (b) was as small as possible -- at ~900B minified (~500B gzipped) this is the smallest
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* implementation I've found. And also, exercises like this are challenging and fun.)
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*/
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function BespokeThenable() {
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var state = 0; // 0=pending, 1=fulfilled, -1=rejected
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var queue = [];
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var value;
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var scheduled = 0;
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var completeCalled = 0;
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function then(onResolve, onReject) {
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var nextThenable = BespokeThenable();
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function handleNext() {
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var cb = state > 0 ? onResolve : onReject;
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if (isFn(cb)) {
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try {
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var result = cb(value);
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if (result === nextThenable) {
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recursiveError();
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}
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var resultThen = getThenableThen(result);
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if (resultThen) {
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resultThen.call(result, nextThenable.resolve, nextThenable.reject);
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} else {
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nextThenable.resolve(result);
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}
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} catch (err) {
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nextThenable.reject(err);
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}
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} else {
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nextThenable[state > 0 ? 'resolve' : 'reject'](value);
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}
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}
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queue.push(handleNext);
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if (state) {
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scheduleQueueFlush();
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}
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return nextThenable
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}
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var resolve = oneTime(function (val) {
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if (!completeCalled) {
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complete(1, val);
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}
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});
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var reject = oneTime(function (reason) {
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if (!completeCalled) {
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complete(-1, reason);
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}
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});
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function complete(st, val) {
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completeCalled++;
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var ignoreThrow = 0;
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try {
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if (val === thenableObj) {
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recursiveError();
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}
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var valThen = st > 0 && getThenableThen(val);
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if (valThen) {
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valThen.call(val, oneTime(function (v) {
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ignoreThrow++;
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complete(1, v);
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}), oneTime(function (v) {
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ignoreThrow++;
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complete(-1, v);
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}));
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} else {
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state = st;
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value = val;
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scheduleQueueFlush();
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}
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} catch(e) {
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if (!state && !ignoreThrow) {
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complete(-1, e);
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}
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}
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}
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function scheduleQueueFlush() {
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if (!scheduled) {
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setTimeout(flushQueue, 0); //TODO setImmediate or postMessage approach if available?
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scheduled = 1;
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}
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}
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function flushQueue() {
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var q = queue;
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scheduled = 0;
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queue = [];
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q.forEach(callIt);
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}
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function callIt(fn) {
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fn();
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}
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function getThenableThen(val) {
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var valThen = val && (isFn(val) || typeof val === 'object') && val.then;
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return isFn(valThen) && valThen
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}
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function oneTime(fn) {
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var called = 0;
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return function() {
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var args = [], len = arguments.length;
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while ( len-- ) args[ len ] = arguments[ len ];
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if (!called++) {
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fn.apply(this, args);
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}
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}
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}
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function recursiveError() {
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throw new TypeError('Chaining cycle detected')
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}
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var isFn = function (v) { return typeof v === 'function'; };
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var thenableObj = {
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then: then,
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resolve: resolve,
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reject: reject
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};
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return thenableObj
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}
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/**
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* Thenable implementation that uses a native Promise under the covers. This implementation
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* is preferred if Promise is available, for better performance and dev tools integration.
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* @constructor
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*/
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function NativePromiseThenable() {
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var resolve, reject;
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var promise = new Promise(function (res, rej) {
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resolve = res;
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reject = rej;
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});
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return {
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then: promise.then.bind(promise),
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resolve: resolve,
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reject: reject
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}
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}
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/**
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* Promise.all() impl:
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*/
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BespokeThenable.all = NativePromiseThenable.all = function(items) {
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var resultCount = 0;
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var results = [];
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var out = DefaultThenable();
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if (items.length === 0) {
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out.resolve([]);
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} else {
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items.forEach(function (item, i) {
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var itemThenable = DefaultThenable();
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itemThenable.resolve(item);
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itemThenable.then(function (res) {
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resultCount++;
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results[i] = res;
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if (resultCount === items.length) {
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out.resolve(results);
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}
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}, out.reject);
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});
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}
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return out
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};
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/**
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* Choose the best Thenable implementation and export it as the default.
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*/
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var DefaultThenable = typeof Promise === 'function' ? NativePromiseThenable : BespokeThenable;
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/**
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* Main content for the worker that handles the loading and execution of
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* modules within it.
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*/
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function workerBootstrap() {
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var modules = Object.create(null);
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// Handle messages for registering a module
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function registerModule(ref, callback) {
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var id = ref.id;
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var name = ref.name;
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var dependencies = ref.dependencies; if ( dependencies === void 0 ) dependencies = [];
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var init = ref.init; if ( init === void 0 ) init = function(){};
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var getTransferables = ref.getTransferables; if ( getTransferables === void 0 ) getTransferables = null;
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// Only register once
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if (modules[id]) { return }
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try {
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// If any dependencies are modules, ensure they're registered and grab their value
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dependencies = dependencies.map(function (dep) {
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if (dep && dep.isWorkerModule) {
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registerModule(dep, function (depResult) {
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if (depResult instanceof Error) { throw depResult }
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});
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dep = modules[dep.id].value;
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}
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return dep
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});
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// Rehydrate functions
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init = rehydrate(("<" + name + ">.init"), init);
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if (getTransferables) {
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getTransferables = rehydrate(("<" + name + ">.getTransferables"), getTransferables);
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}
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// Initialize the module and store its value
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var value = null;
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if (typeof init === 'function') {
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value = init.apply(void 0, dependencies);
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} else {
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console.error('worker module init function failed to rehydrate');
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}
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modules[id] = {
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id: id,
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value: value,
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getTransferables: getTransferables
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};
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callback(value);
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} catch(err) {
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if (!(err && err.noLog)) {
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console.error(err);
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}
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callback(err);
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}
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}
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// Handle messages for calling a registered module's result function
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function callModule(ref, callback) {
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var ref$1;
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var id = ref.id;
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var args = ref.args;
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if (!modules[id] || typeof modules[id].value !== 'function') {
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callback(new Error(("Worker module " + id + ": not found or its 'init' did not return a function")));
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}
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try {
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var result = (ref$1 = modules[id]).value.apply(ref$1, args);
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if (result && typeof result.then === 'function') {
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result.then(handleResult, function (rej) { return callback(rej instanceof Error ? rej : new Error('' + rej)); });
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} else {
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handleResult(result);
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}
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} catch(err) {
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callback(err);
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}
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function handleResult(result) {
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try {
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var tx = modules[id].getTransferables && modules[id].getTransferables(result);
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if (!tx || !Array.isArray(tx) || !tx.length) {
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tx = undefined; //postMessage is very picky about not passing null or empty transferables
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}
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callback(result, tx);
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} catch(err) {
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console.error(err);
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callback(err);
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}
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}
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}
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function rehydrate(name, str) {
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var result = void 0;
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self.troikaDefine = function (r) { return result = r; };
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var url = URL.createObjectURL(
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new Blob(
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[("/** " + (name.replace(/\*/g, '')) + " **/\n\ntroikaDefine(\n" + str + "\n)")],
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{type: 'application/javascript'}
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)
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);
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try {
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importScripts(url);
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} catch(err) {
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console.error(err);
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}
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URL.revokeObjectURL(url);
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delete self.troikaDefine;
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return result
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}
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// Handler for all messages within the worker
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self.addEventListener('message', function (e) {
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var ref = e.data;
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var messageId = ref.messageId;
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var action = ref.action;
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var data = ref.data;
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try {
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// Module registration
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if (action === 'registerModule') {
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registerModule(data, function (result) {
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if (result instanceof Error) {
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postMessage({
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messageId: messageId,
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success: false,
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error: result.message
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});
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} else {
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postMessage({
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messageId: messageId,
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success: true,
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result: {isCallable: typeof result === 'function'}
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});
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}
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});
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}
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// Invocation
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if (action === 'callModule') {
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callModule(data, function (result, transferables) {
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if (result instanceof Error) {
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postMessage({
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messageId: messageId,
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success: false,
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error: result.message
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});
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} else {
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postMessage({
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messageId: messageId,
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success: true,
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result: result
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}, transferables || undefined);
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}
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});
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}
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} catch(err) {
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postMessage({
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messageId: messageId,
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success: false,
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error: err.stack
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});
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}
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});
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}
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/**
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* Fallback for `defineWorkerModule` that behaves identically but runs in the main
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* thread, for when the execution environment doesn't support web workers or they
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* are disallowed due to e.g. CSP security restrictions.
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*/
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function defineMainThreadModule(options) {
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var moduleFunc = function() {
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var args = [], len = arguments.length;
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while ( len-- ) args[ len ] = arguments[ len ];
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return moduleFunc._getInitResult().then(function (initResult) {
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if (typeof initResult === 'function') {
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return initResult.apply(void 0, args)
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} else {
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throw new Error('Worker module function was called but `init` did not return a callable function')
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}
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})
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};
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moduleFunc._getInitResult = function() {
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// We can ignore getTransferables in main thread. TODO workerId?
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var dependencies = options.dependencies;
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var init = options.init;
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// Resolve dependencies
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dependencies = Array.isArray(dependencies) ? dependencies.map(function (dep) { return dep && dep._getInitResult ? dep._getInitResult() : dep; }
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) : [];
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// Invoke init with the resolved dependencies
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var initThenable = DefaultThenable.all(dependencies).then(function (deps) {
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return init.apply(null, deps)
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});
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// Cache the resolved promise for subsequent calls
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moduleFunc._getInitResult = function () { return initThenable; };
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return initThenable
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};
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return moduleFunc
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}
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var supportsWorkers = function () {
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var supported = false;
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// Only attempt worker initialization in browsers; elsewhere it would just be
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// noise e.g. loading into a Node environment for SSR.
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if (typeof window !== 'undefined' && typeof window.document !== 'undefined') {
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try {
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// TODO additional checks for things like importScripts within the worker?
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// Would need to be an async check.
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var worker = new Worker(
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URL.createObjectURL(new Blob([''], { type: 'application/javascript' }))
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);
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worker.terminate();
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supported = true;
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} catch (err) {
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if (typeof process !== 'undefined' && process.env.NODE_ENV === 'test') ; else {
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console.log(
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("Troika createWorkerModule: web workers not allowed; falling back to main thread execution. Cause: [" + (err.message) + "]")
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);
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}
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}
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}
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// Cached result
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supportsWorkers = function () { return supported; };
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return supported
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};
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var _workerModuleId = 0;
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var _messageId = 0;
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var _allowInitAsString = false;
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var workers = Object.create(null);
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var openRequests = /*#__PURE__*/(function () {
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var obj = Object.create(null);
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obj._count = 0;
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return obj
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})();
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/**
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* Define a module of code that will be executed with a web worker. This provides a simple
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* interface for moving chunks of logic off the main thread, and managing their dependencies
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* among one another.
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*
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* @param {object} options
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* @param {function} options.init
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* @param {array} [options.dependencies]
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* @param {function} [options.getTransferables]
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* @param {string} [options.name]
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* @param {string} [options.workerId]
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* @return {function(...[*]): {then}}
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*/
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function defineWorkerModule(options) {
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if ((!options || typeof options.init !== 'function') && !_allowInitAsString) {
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throw new Error('requires `options.init` function')
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}
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var dependencies = options.dependencies;
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var init = options.init;
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var getTransferables = options.getTransferables;
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var workerId = options.workerId;
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if (!supportsWorkers()) {
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return defineMainThreadModule(options)
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}
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if (workerId == null) {
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workerId = '#default';
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}
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var id = "workerModule" + (++_workerModuleId);
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var name = options.name || id;
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var registrationThenable = null;
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dependencies = dependencies && dependencies.map(function (dep) {
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// Wrap raw functions as worker modules with no dependencies
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if (typeof dep === 'function' && !dep.workerModuleData) {
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_allowInitAsString = true;
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dep = defineWorkerModule({
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workerId: workerId,
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name: ("<" + name + "> function dependency: " + (dep.name)),
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init: ("function(){return (\n" + (stringifyFunction(dep)) + "\n)}")
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});
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_allowInitAsString = false;
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}
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// Grab postable data for worker modules
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if (dep && dep.workerModuleData) {
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dep = dep.workerModuleData;
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}
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return dep
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});
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function moduleFunc() {
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var args = [], len = arguments.length;
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while ( len-- ) args[ len ] = arguments[ len ];
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// Register this module if needed
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if (!registrationThenable) {
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registrationThenable = callWorker(workerId,'registerModule', moduleFunc.workerModuleData);
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}
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// Invoke the module, returning a thenable
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return registrationThenable.then(function (ref) {
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var isCallable = ref.isCallable;
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if (isCallable) {
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return callWorker(workerId,'callModule', {id: id, args: args})
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} else {
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throw new Error('Worker module function was called but `init` did not return a callable function')
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}
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})
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}
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moduleFunc.workerModuleData = {
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isWorkerModule: true,
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id: id,
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name: name,
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dependencies: dependencies,
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init: stringifyFunction(init),
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getTransferables: getTransferables && stringifyFunction(getTransferables)
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};
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return moduleFunc
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}
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/**
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* Stringifies a function into a form that can be deserialized in the worker
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* @param fn
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*/
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function stringifyFunction(fn) {
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var str = fn.toString();
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// If it was defined in object method/property format, it needs to be modified
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if (!/^function/.test(str) && /^\w+\s*\(/.test(str)) {
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str = 'function ' + str;
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}
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return str
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}
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function getWorker(workerId) {
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var worker = workers[workerId];
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if (!worker) {
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// Bootstrap the worker's content
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var bootstrap = stringifyFunction(workerBootstrap);
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// Create the worker from the bootstrap function content
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worker = workers[workerId] = new Worker(
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URL.createObjectURL(
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new Blob(
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[("/** Worker Module Bootstrap: " + (workerId.replace(/\*/g, '')) + " **/\n\n;(" + bootstrap + ")()")],
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{type: 'application/javascript'}
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)
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)
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);
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// Single handler for response messages from the worker
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worker.onmessage = function (e) {
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var response = e.data;
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var msgId = response.messageId;
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var callback = openRequests[msgId];
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if (!callback) {
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throw new Error('WorkerModule response with empty or unknown messageId')
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}
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delete openRequests[msgId];
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openRequests._count--;
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callback(response);
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};
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}
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return worker
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}
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// Issue a call to the worker with a callback to handle the response
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function callWorker(workerId, action, data) {
|
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var thenable = DefaultThenable();
|
|
var messageId = ++_messageId;
|
|
openRequests[messageId] = function (response) {
|
|
if (response.success) {
|
|
thenable.resolve(response.result);
|
|
} else {
|
|
thenable.reject(new Error(("Error in worker " + action + " call: " + (response.error))));
|
|
}
|
|
};
|
|
openRequests._count++;
|
|
if (openRequests._count > 1000) { //detect leaks
|
|
console.warn('Large number of open WorkerModule requests, some may not be returning');
|
|
}
|
|
getWorker(workerId).postMessage({
|
|
messageId: messageId,
|
|
action: action,
|
|
data: data
|
|
});
|
|
return thenable
|
|
}
|
|
|
|
/**
|
|
* Just the {@link Thenable} function wrapped as a worker module. If another worker
|
|
* module needs Thenable as a dependency, it's better to pass this module rather than
|
|
* the raw function in its `dependencies` array so it only gets registered once.
|
|
*/
|
|
var ThenableWorkerModule = /*#__PURE__*/defineWorkerModule({
|
|
name: 'Thenable',
|
|
dependencies: [DefaultThenable],
|
|
init: function(Thenable) {
|
|
return Thenable
|
|
}
|
|
});
|
|
|
|
export { DefaultThenable as Thenable, ThenableWorkerModule, defineWorkerModule, stringifyFunction };
|