83 lines
2.3 KiB
TypeScript
83 lines
2.3 KiB
TypeScript
type Key = string | number | symbol;
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/**
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* SetArray acts like a `Set` (allowing only one occurrence of a string `key`), but provides the
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* index of the `key` in the backing array.
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*
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* This is designed to allow synchronizing a second array with the contents of the backing array,
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* like how in a sourcemap `sourcesContent[i]` is the source content associated with `source[i]`,
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* and there are never duplicates.
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*/
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export class SetArray<T extends Key = Key> {
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declare private _indexes: Record<T, number | undefined>;
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declare array: readonly T[];
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constructor() {
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this._indexes = { __proto__: null } as any;
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this.array = [];
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}
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}
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interface PublicSet<T extends Key> {
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array: T[];
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_indexes: SetArray<T>['_indexes'];
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}
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/**
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* Typescript doesn't allow friend access to private fields, so this just casts the set into a type
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* with public access modifiers.
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*/
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function cast<T extends Key>(set: SetArray<T>): PublicSet<T> {
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return set as any;
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}
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/**
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* Gets the index associated with `key` in the backing array, if it is already present.
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*/
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export function get<T extends Key>(setarr: SetArray<T>, key: T): number | undefined {
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return cast(setarr)._indexes[key];
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}
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/**
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* Puts `key` into the backing array, if it is not already present. Returns
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* the index of the `key` in the backing array.
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*/
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export function put<T extends Key>(setarr: SetArray<T>, key: T): number {
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// The key may or may not be present. If it is present, it's a number.
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const index = get(setarr, key);
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if (index !== undefined) return index;
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const { array, _indexes: indexes } = cast(setarr);
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const length = array.push(key);
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return (indexes[key] = length - 1);
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}
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/**
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* Pops the last added item out of the SetArray.
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*/
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export function pop<T extends Key>(setarr: SetArray<T>): void {
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const { array, _indexes: indexes } = cast(setarr);
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if (array.length === 0) return;
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const last = array.pop()!;
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indexes[last] = undefined;
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}
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/**
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* Removes the key, if it exists in the set.
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*/
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export function remove<T extends Key>(setarr: SetArray<T>, key: T): void {
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const index = get(setarr, key);
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if (index === undefined) return;
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const { array, _indexes: indexes } = cast(setarr);
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for (let i = index + 1; i < array.length; i++) {
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const k = array[i];
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array[i - 1] = k;
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indexes[k]!--;
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}
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indexes[key] = undefined;
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array.pop();
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}
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