236 lines
6.4 KiB
JavaScript
236 lines
6.4 KiB
JavaScript
// Yet Another Hack to fight node.js callback hell: generator-based coroutines
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// Distinctive features:
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// - simple to use:
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// - does not require promisification of existing callback-based code
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// - does not require async/await
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// - safely checks control flow and reports exceptions
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// - also supports promises (like await)
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module.exports.run = runThread;
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module.exports.runParallel = runParallel;
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var current;
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module.exports.unsafe = function()
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{
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return current;
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};
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module.exports.p = function(p)
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{
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p._stack = new Error().stack;
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return p;
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};
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module.exports.callback = module.exports.cb = function()
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{
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return threadCallback.call(current);
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};
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module.exports.errorfirst = module.exports.ef = function()
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{
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return errorFirst.call(current);
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};
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module.exports.throttle = function(count)
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{
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return throttleThread.call(current, count);
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};
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function runThread(generator, onsuccess, onerror)
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{
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var thread = function()
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{
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thread._current = null;
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// pass parameters as yield result
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callGen(thread, 'next', Array.prototype.slice.call(arguments, 0));
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};
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thread._gen = generator.next ? generator : generator();
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thread._finishThrottleQueue = finishThrottleQueue.bind(thread);
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thread._onsuccess = onsuccess;
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thread._onerror = onerror;
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thread._running = false;
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callGen(thread, 'next', []);
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return thread;
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}
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function getStack(fn)
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{
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return fn._stack.replace(/Error[\s\S]*at.*(exports\.(cb|ef|errorfirst|p\s)|Function\.(errorFirst|threadCallback)).*/, '');
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}
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function callGen(thread, method, arg)
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{
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if (thread._running)
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{
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// callback called while generator is already running
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thread._result = [ method, arg ];
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return;
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}
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var v;
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var prev = current;
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thread._running = true;
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current = thread;
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try
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{
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while (1)
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{
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v = thread._gen[method](arg);
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if (!v.done && thread._result)
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{
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method = thread._result[0];
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arg = thread._result[1];
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thread._result = null;
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}
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else
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break;
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}
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}
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catch (e)
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{
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v = { error: e };
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}
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thread._running = false;
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current = prev;
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if (v.done || v.error)
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{
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// generator finished
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thread._done = true;
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process.nextTick(thread._finishThrottleQueue);
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}
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if (v.error)
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{
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if (thread._onerror)
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thread._onerror(v.error);
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else
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throw v.error;
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}
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else if (v.done && thread._onsuccess)
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thread._onsuccess(v.value);
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else if (typeof v.value == 'object' && v.value.then && !thread._current)
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{
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// check if v.value is a Promise
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// (but not if an explicit .then(gen.cb()) callback is already set by caller)
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v.value.then(function(value)
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{
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// use process.nextTick so Promise does not intercept our exceptions
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process.nextTick(function() { callGen(thread, 'next', value); });
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}, function(e)
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{
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if (v.value._stack)
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{
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// report stack trace captured with `yield gen.p(promise)`
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var m = /^([\s\S]*?)((\n\s*at.*)*)$/.exec(e.stack);
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if (m)
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e.stack = m[1]+getStack(v.value)+'\n-- async error thrown at:'+m[2];
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}
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process.nextTick(function() { callGen(thread, 'throw', e); });
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});
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}
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}
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function threadCallback()
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{
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var thread = this;
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var fn = function()
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{
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if (thread._current != fn)
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{
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throw new Error('Broken control flow! Callback'+
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getStack(thread._current)+
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'\nmust be called to resume thread, but this one is called instead:'+
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getStack(fn)+'\n--'
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);
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}
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thread._current = null;
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return callGen(thread, 'next', Array.prototype.slice.call(arguments, 0));
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};
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fn._stack = new Error().stack;
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thread._current = fn;
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return fn;
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}
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function errorFirst()
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{
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var thread = this;
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var fn = function()
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{
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if (thread._current != fn)
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{
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throw new Error('Broken control flow! Callback'+
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getStack(thread._current)+
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'\nmust be called to resume thread, but this one is called instead:'+
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getStack(fn)+'\n--'
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);
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}
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thread._current = null;
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if (arguments[0])
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{
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var e = arguments[0];
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var m = /^([\s\S]*?)((\n\s*at.*)*)$/.exec(e.stack);
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if (m)
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e.stack = m[1]+getStack(fn)+'\n-- async error thrown at:'+m[2];
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return callGen(thread, 'throw', e);
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}
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return callGen(thread, 'next', Array.prototype.slice.call(arguments, 1));
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};
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fn._stack = new Error().stack;
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thread._current = fn;
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return fn;
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}
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function throttleThread(count)
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{
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if (!this.throttleData)
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this.throttleData = this._gen.__proto__._genThreadThrottle = this._gen.__proto__._genThreadThrottle || { queue: [], pending: [] };
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this._finishThrottleQueue();
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if (this.throttleData.queue.length < count)
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{
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this.throttleData.queue.push(this);
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process.nextTick(threadCallback.call(this));
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}
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else
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this.throttleData.pending.push([ this, threadCallback.call(this), count ]);
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}
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function finishThrottleQueue()
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{
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if (!this.throttleData)
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return;
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for (var i = 0; i < this.throttleData.queue.length; i++)
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{
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if (this.throttleData.queue[i]._done)
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{
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this.throttleData.queue.splice(i, 1);
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i--;
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}
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}
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while (this.throttleData.pending.length > 0 && this.throttleData.queue.length < this.throttleData.pending[0][2])
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{
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var t = this.throttleData.pending.shift();
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this.throttleData.queue.push(t[0]);
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process.nextTick(t[1]);
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}
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}
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function runParallel(threads, done)
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{
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var results = [];
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var errors = [];
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var resultCount = 0;
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var allDone = function(i, result, error)
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{
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if (!results[i] && !errors[i])
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{
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if (error)
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errors[i] = error;
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else
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results[i] = result;
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resultCount++;
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if (resultCount == threads.length)
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done(results, errors);
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}
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};
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threads.map((t, i) => runThread(t, function(result) { allDone(i, result); }, function(error) { allDone(i, null, error); }));
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}
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