55 lines
1.1 KiB
JavaScript
55 lines
1.1 KiB
JavaScript
module.exports = Pend;
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function Pend() {
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this.pending = 0;
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this.max = Infinity;
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this.listeners = [];
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this.waiting = [];
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this.error = null;
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}
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Pend.prototype.go = function(fn) {
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if (this.pending < this.max) {
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pendGo(this, fn);
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} else {
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this.waiting.push(fn);
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}
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};
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Pend.prototype.wait = function(cb) {
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if (this.pending === 0) {
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cb(this.error);
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} else {
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this.listeners.push(cb);
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}
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};
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Pend.prototype.hold = function() {
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return pendHold(this);
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};
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function pendHold(self) {
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self.pending += 1;
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var called = false;
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return onCb;
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function onCb(err) {
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if (called) throw new Error("callback called twice");
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called = true;
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self.error = self.error || err;
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self.pending -= 1;
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if (self.waiting.length > 0 && self.pending < self.max) {
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pendGo(self, self.waiting.shift());
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} else if (self.pending === 0) {
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var listeners = self.listeners;
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self.listeners = [];
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listeners.forEach(cbListener);
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}
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}
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function cbListener(listener) {
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listener(self.error);
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}
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}
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function pendGo(self, fn) {
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fn(pendHold(self));
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}
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