mirror of https://github.com/zulip/zulip.git
103 lines
2.3 KiB
TypeScript
103 lines
2.3 KiB
TypeScript
import * as blueslip from "./blueslip";
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export class LazySet {
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private data:
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| {
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arr: number[];
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set: undefined;
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}
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| {
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arr: undefined;
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set: Set<number>;
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};
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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: number[]) {
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this.data = {
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arr: vals,
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set: undefined,
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};
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}
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get size(): number {
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const {data} = this;
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if (data.set !== undefined) {
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return data.set.size;
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}
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return data.arr.length;
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}
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keys(): IterableIterator<number> {
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const {data} = this;
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if (data.set !== undefined) {
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return data.set.keys();
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}
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return data.arr.values();
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}
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_make_set(): Set<number> {
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if (this.data.set !== undefined) {
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return this.data.set;
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}
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this.data = {
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arr: undefined,
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set: new Set(this.data.arr),
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};
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return this.data.set;
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}
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map<T>(f: (v: number, k: number) => T): T[] {
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return [...this.keys()].map((v, k) => f(v, k));
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}
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has(v: number): boolean {
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const set = this._make_set();
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const val = this._clean(v);
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return set.has(val);
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}
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add(v: number): void {
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const set = this._make_set();
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const val = this._clean(v);
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set.add(val);
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}
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delete(v: number): boolean {
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const set = this._make_set();
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const val = this._clean(v);
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return set.delete(val);
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}
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_clean(v: number | string): number {
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if (typeof v !== "number") {
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blueslip.error("not a number", {v});
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return Number.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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