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 王天杨
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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<T extends Key = Key> {
declare private _indexes: Record<T, number | undefined>;
declare array: readonly T[];
constructor() {
this._indexes = { __proto__: null } as any;
this.array = [];
}
}
interface PublicSet<T extends Key> {
array: T[];
_indexes: SetArray<T>['_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<T extends Key>(set: SetArray<T>): PublicSet<T> {
return set as any;
}
/**
* Gets the index associated with `key` in the backing array, if it is already present.
*/
export function get<T extends Key>(setarr: SetArray<T>, 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<T extends Key>(setarr: SetArray<T>, 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<T extends Key>(setarr: SetArray<T>): 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<T extends Key>(setarr: SetArray<T>, 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();
}
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