text: // Copyright 2011 The Closure Library Authors. All Rights Reserved.
  //
  // Licensed under the Apache License, Version 2.0 (the "License");
  // you may not use this file except in compliance with the License.
  // You may obtain a copy of the License at
  //
  //      http://www.apache.org/licenses/LICENSE-2.0
  //
  // Unless required by applicable law or agreed to in writing, software
  // distributed under the License is distributed on an "AS-IS" BASIS,
  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  // See the License for the specific language governing permissions and
  // limitations under the License.
  
  /**
   * @fileoverview Provides a convenient API for data persistence using a selected
   * data storage mechanism.
   *
   */
  
  goog.provide('goog.storage.Storage');
  
  goog.require('goog.json');
  goog.require('goog.storage.ErrorCode');
  
  
  
  /**
   * The base implementation for all storage APIs.
   *
   * @param {!goog.storage.mechanism.Mechanism} mechanism The underlying
   *     storage mechanism.
   * @constructor
   */
  goog.storage.Storage = function(mechanism) {
    /**
     * The mechanism used to persist key-value pairs.
     *
     * @protected {goog.storage.mechanism.Mechanism}
     */
    this.mechanism = mechanism;
  };
  
  
  /**
   * Sets an item in the data storage.
   *
   * @param {string} key The key to set.
   * @param {*} value The value to serialize to a string and save.
   */
  goog.storage.Storage.prototype.set = function(key, value) {
    if (!goog.isDef(value)) {
      this.mechanism.remove(key);
      return;
    }
    this.mechanism.set(key, goog.json.serialize(value));
  };
  
  
  /**
   * Gets an item from the data storage.
   *
   * @param {string} key The key to get.
   * @return {*} Deserialized value or undefined if not found.
   */
  goog.storage.Storage.prototype.get = function(key) {
    var json;
    try {
      json = this.mechanism.get(key);
    } catch (e) {
      // If, for any reason, the value returned by a mechanism's get method is not
      // a string, an exception is thrown.  In this case, we must fail gracefully
      // instead of propagating the exception to clients.  See b/8095488 for
      // details.
      return undefined;
    }
    if (goog.isNull(json)) {
      return undefined;
    }
    /** @preserveTry */
    try {
      return goog.json.parse(json);
    } catch (e) {
      throw goog.storage.ErrorCode.INVALID_VALUE;
    }
  };
  
  
  /**
   * Removes an item from the data storage.
   *
   * @param {string} key The key to remove.
   */
  goog.storage.Storage.prototype.remove = function(key) {
    this.mechanism.remove(key);
  };
  