mirror of https://github.com/zulip/zulip.git
82 lines
1.7 KiB
JavaScript
82 lines
1.7 KiB
JavaScript
export class LazySet {
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/*
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This class is optimized for a very
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particular use case.
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We often have lots of subscribers on
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a stream. We get an array from the
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backend, because it's JSON.
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Often the only operation we need
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on subscribers is to get the length,
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which is plenty cheap as an array.
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Making an array from a set is cheap
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for one stream, but it's expensive
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for all N streams at page load.
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Once somebody does an operation
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where sets are useful, such
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as has/add/delete, we convert it over
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to a set for a one-time cost.
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*/
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constructor(vals) {
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this.arr = vals;
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this.set = undefined;
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}
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keys() {
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if (this.set !== undefined) {
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return this.set.keys();
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}
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return this.arr.values();
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}
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_make_set() {
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if (this.set !== undefined) {
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return;
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}
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this.set = new Set(this.arr);
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this.arr = undefined;
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}
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get size() {
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if (this.set !== undefined) {
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return this.set.size;
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}
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return this.arr.length;
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}
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map(f) {
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return Array.from(this.keys(), f);
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}
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has(v) {
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this._make_set();
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const val = this._clean(v);
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return this.set.has(val);
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}
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add(v) {
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this._make_set();
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const val = this._clean(v);
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this.set.add(val);
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}
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delete(v) {
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this._make_set();
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const val = this._clean(v);
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return this.set.delete(val);
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}
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_clean(v) {
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if (typeof v !== "number") {
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blueslip.error("not a number");
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return parseInt(v, 10);
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}
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return v;
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}
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}
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