Faster set for mongodb/bson object ids (2x speedup)

ObjectIdSet.ts

import { ObjectId } from 'bson';

export class ObjectIdSet {
  map = new Map<number, Set<number>>();
  constructor(values: Iterable<ObjectId>) {
    for (const value of values) {
      this.add(value);
    }
  }
  add(value: ObjectId): this {
    const buf = Buffer.isBuffer(value.id) ? value.id : Buffer.from(value.id);
    const i1 = buf.readUIntBE(0, 6);
    const i2 = buf.readUIntBE(6, 6);
    this.map.set(i2, this.map.get(i2)?.add(i1) ?? new Set([i1]));
    return this;
  }
  has(value: ObjectId) {
    const buf = Buffer.isBuffer(value.id) ? value.id : Buffer.from(value.id);
    return !!this.map.get(buf.readUIntBE(6, 6))?.has(buf.readUIntBE(0, 6));
  }
}

ObjectIdSetBigint.ts

import { ObjectId } from 'bson';

function toBigInt(value: ObjectId) {
  const buf = Buffer.isBuffer(value.id) ? value.id : Buffer.from(value.id);
  return (BigInt(buf.readUint32BE(0)) << 64n) | buf.readBigUint64BE(4);
}

function* mapIterable<T, R>(iterable: Iterable<T>, iteratee: (value: T) => R) {
  for (const value of iterable) {
    yield (iteratee(value));
  }
}

export class ObjectIdSet {
  set: Set<bigint>;
  constructor(values: Iterable<ObjectId>) {
    const bigInts = Array.isArray(values)
      ? values.map(toBigInt)
      : mapIterable(values, toBigInt);
    this.set = new Set(bigInts);
  }
  add(value: ObjectId): this {
    this.set.add(toBigInt(value));
    return this;
  }
  has(value: ObjectId): boolean {
    return this.set.has(toBigInt(value));
  }
  clear(): void {
    this.set.clear();
  }
  delete(value: ObjectId): boolean {
    return this.set.delete(toBigInt(value));
  }
  get size() {
    return this.set.size;
  }
}