web/lru-memory-cache-object.ts

// Copyright 2021 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

export class LRUMemoryCacheObject {
  capacity: number;

  cache: Map<string, any>;

  /**
   * Creates a new LRUMemoryCacheObject instance.
   *
   * @param capacity The max capacity of the LRUMemoryCacheObject.
   */
  constructor(capacity: number) {
    this.capacity = capacity;
    this.cache = new Map();
  }

  /**
   * Reads the cached object.
   *
   * @param key The accessor for a value in the LRUMemoryCacheObject.
   */
  read(key: string): any {
    if (!this.cache.has(key)) {
      return undefined;
    }
    const value = this.cache.get(key);
    this.cache.delete(key);
    this.cache.set(key, value);
    return value;
  }

  /**
   * Writes value using key in the cache.
   *
   * @param key The key to use for LRUMemoryCacheObject.
   * @param value The value to be set.
   */
  write(key: string, value: any): void {
    if (this.cache.has(key)) {
      this.cache.delete(key);
    }
    this.cache.set(key, value);
    if (this.cache.size > this.capacity) {
      this.cache.delete(this.cache.keys().next().value!);
    }
  }

  /**
   * Deletes a key from the cache.
   *
   * @param key The key to delete in LRUMemoryCacheObject.
   */
  delete(key: string): void {
    this.cache.delete(key);
  }

  /**
   * Resets the cache.
   */
  clear(): void {
    this.cache.clear();
  }
}