ox/src/core/internal/lru.ts

Ethereum Standard Library

/**
 * Map with a LRU (Least recently used) policy.
 *
 * @see https://en.wikipedia.org/wiki/Cache_replacement_policies#LRU
 * @internal
 */
export class LruMap<value = unknown> extends Map<string, value> {
  maxSize: number

  constructor(size: number) {
    super()
    this.maxSize = size
  }

  override get(key: string) {
    const value = super.get(key)

    if (super.has(key) && value !== undefined) {
      this.delete(key)
      super.set(key, value)
    }

    return value
  }

  override set(key: string, value: value) {
    super.set(key, value)
    if (this.maxSize && this.size > this.maxSize) {
      const firstKey = this.keys().next().value
      if (firstKey) this.delete(firstKey)
    }
    return this
  }
}

/**
 * Map with a bounded FIFO eviction policy. Cheaper than {@link LruMap} on hot
 * `get` paths because reads do not reorder entries; only writes touch the
 * eviction queue.
 *
 * @internal
 */
export class BoundedMap<value = unknown> extends Map<string, value> {
  maxSize: number

  constructor(size: number) {
    super()
    this.maxSize = size
  }

  override set(key: string, value: value) {
    if (!super.has(key) && this.maxSize && this.size >= this.maxSize) {
      const firstKey = this.keys().next().value
      if (firstKey !== undefined) this.delete(firstKey)
    }
    return super.set(key, value)
  }
}