@libp2p/gossipsub/src/utils/set.ts

A typescript implementation of gossipsub

/**
 * Exclude up to `ineed` items from a set if item meets condition `cond`
 */
export function removeItemsFromSet<T> (
  superSet: Set<T>,
  ineed: number,
  cond: (peer: T) => boolean = () => true
): Set<T> {
  const subset = new Set<T>()
  if (ineed <= 0) { return subset }

  for (const id of superSet) {
    if (subset.size >= ineed) { break }
    if (cond(id)) {
      subset.add(id)
      superSet.delete(id)
    }
  }

  return subset
}

/**
 * Exclude up to `ineed` items from a set
 */
export function removeFirstNItemsFromSet<T> (superSet: Set<T>, ineed: number): Set<T> {
  return removeItemsFromSet(superSet, ineed, () => true)
}

export class MapDef<K, V> extends Map<K, V> {
  constructor (private readonly getDefault: () => V) {
    super()
  }

  getOrDefault (key: K): V {
    let value = super.get(key)
    if (value === undefined) {
      value = this.getDefault()
      this.set(key, value)
    }
    return value
  }
}