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