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node_modules/eslint-plugin-node/lib/util/cache.js 1.68 KB
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  /**
   * @author Toru Nagashima
   * @copyright 2016 Toru Nagashima. All rights reserved.
   * See LICENSE file in root directory for full license.
   */
  "use strict"
  
  //------------------------------------------------------------------------------
  // Helpers
  //------------------------------------------------------------------------------
  
  const SKIP_TIME = 5000
  
  //------------------------------------------------------------------------------
  // Public Interface
  //------------------------------------------------------------------------------
  
  /**
   * The class of cache.
   * The cache will dispose of each value if the value has not been accessed
   * during 5 seconds.
   */
  module.exports = class Cache {
      /**
       * Initialize this cache instance.
       */
      constructor() {
          this.map = new Map()
      }
  
      /**
       * Get the cached value of the given key.
       * @param {any} key The key to get.
       * @returns {any} The cached value or null.
       */
      get(key) {
          const entry = this.map.get(key)
          const now = Date.now()
  
          if (entry) {
              if (entry.expire > now) {
                  entry.expire = now + SKIP_TIME
                  return entry.value
              }
              this.map.delete(key)
          }
          return null
      }
  
      /**
       * Set the value of the given key.
       * @param {any} key The key to set.
       * @param {any} value The value to set.
       * @returns {void}
       */
      set(key, value) {
          const entry = this.map.get(key)
          const expire = Date.now() + SKIP_TIME
  
          if (entry) {
              entry.value = value
              entry.expire = expire
          }
          else {
              this.map.set(key, { value, expire })
          }
      }
  }