61 lines
1.8 KiB
JavaScript
61 lines
1.8 KiB
JavaScript
Tracker.memoize = function(func, hasher){
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var memoize = function(key) {
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var cache = memoize.cache;
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var address = "" + (hasher ? hasher.apply(this, arguments) : key);
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if (!_.has(cache, address)) {
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cache[address] = new CacheObject(func, address, arguments, cache, this);
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}
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return cache[address].get();
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};
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memoize.cache = {};
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return memoize;
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};
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function CacheObject(func, address, args, cache, context){
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var self = this;
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self.currentValue = null;
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self.dep = new Tracker.Dependency();
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self.numRun = 0;
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//spawn a new autorun that keeps the value up-to-date
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Tracker.nonreactive(function() {
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Tracker.autorun(function(computation) {
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//if this isn't the first run and nobody is listening,
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//delete itself from cache and stop the computation
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if (!computation.firstRun && !self.dep.hasDependents()){
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computation.stop();
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delete cache[address];
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return;
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}
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//if we haven't run this before this flush, reset the counter after the flush
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if(self.numRun === 0){
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Tracker.afterFlush(function(){
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self.numRun = 0;
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});
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}
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self.numRun++;
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//call the expensive function
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//even if we don't use its value, we need to track its dependencies
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var newValue = func.apply(context, args);
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//prevent dependency loops, the memoized function shouldn't re-run
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//more than once per flush
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if (self.numRun > 1){
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newValue = NaN;
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if(_.isNaN(self.currentValue)) return;
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}
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//if the value changed, store the new value
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if (self.currentValue !== newValue){
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self.currentValue = newValue;
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//tell the dependents that we've changed
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self.dep.changed();
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}
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});
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});
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}
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CacheObject.prototype.get = function() {
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//if there is an active computation, track dependents
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if (Tracker.active) this.dep.depend();
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return this.currentValue;
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};
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