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// 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 factory methods for selecting the best storage
* mechanism, depending on availability and needs.
*
*/
goog.provide('goog.storage.mechanism.mechanismfactory');
goog.require('goog.storage.mechanism.HTML5LocalStorage');
goog.require('goog.storage.mechanism.HTML5SessionStorage');
goog.require('goog.storage.mechanism.IEUserData');
goog.require('goog.storage.mechanism.IterableMechanism');
goog.require('goog.storage.mechanism.PrefixedMechanism');
/**
* The key to shared userData storage.
* @type {string}
*/
goog.storage.mechanism.mechanismfactory.USER_DATA_SHARED_KEY =
'UserDataSharedStore';
/**
* Returns the best local storage mechanism, or null if unavailable.
* Local storage means that the database is placed on user's computer.
* The key-value database is normally shared between all the code paths
* that request it, so using an optional namespace is recommended. This
* provides separation and makes key collisions unlikely.
*
* @param {string=} opt_namespace Restricts the visibility to given namespace.
* @return {goog.storage.mechanism.IterableMechanism} Created mechanism or null.
*/
goog.storage.mechanism.mechanismfactory.create = function(opt_namespace) {
var factory = goog.storage.mechanism.mechanismfactory;
return factory.createHTML5LocalStorage(opt_namespace) ||
factory.createIEUserData(opt_namespace);
};
/**
* Returns an HTML5 local storage mechanism, or null if unavailable.
* Since the HTML5 local storage does not support namespaces natively,
* and the key-value database is shared between all the code paths
* that request it, it is recommended that an optional namespace is
* used to provide key separation employing a prefix.
*
* @param {string=} opt_namespace Restricts the visibility to given namespace.
* @return {goog.storage.mechanism.IterableMechanism} Created mechanism or null.
*/
goog.storage.mechanism.mechanismfactory.createHTML5LocalStorage = function(
opt_namespace) {
var storage = new goog.storage.mechanism.HTML5LocalStorage();
if (storage.isAvailable()) {
return opt_namespace ? new goog.storage.mechanism.PrefixedMechanism(
storage, opt_namespace) : storage;
}
return null;
};
/**
* Returns an HTML5 session storage mechanism, or null if unavailable.
* Since the HTML5 session storage does not support namespaces natively,
* and the key-value database is shared between all the code paths
* that request it, it is recommended that an optional namespace is
* used to provide key separation employing a prefix.
*
* @param {string=} opt_namespace Restricts the visibility to given namespace.
* @return {goog.storage.mechanism.IterableMechanism} Created mechanism or null.
*/
goog.storage.mechanism.mechanismfactory.createHTML5SessionStorage = function(
opt_namespace) {
var storage = new goog.storage.mechanism.HTML5SessionStorage();
if (storage.isAvailable()) {
return opt_namespace ? new goog.storage.mechanism.PrefixedMechanism(
storage, opt_namespace) : storage;
}
return null;
};
/**
* Returns an IE userData local storage mechanism, or null if unavailable.
* Using an optional namespace is recommended to provide separation and
* avoid key collisions.
*
* @param {string=} opt_namespace Restricts the visibility to given namespace.
* @return {goog.storage.mechanism.IterableMechanism} Created mechanism or null.
*/
goog.storage.mechanism.mechanismfactory.createIEUserData = function(
opt_namespace) {
var storage = new goog.storage.mechanism.IEUserData(opt_namespace ||
goog.storage.mechanism.mechanismfactory.USER_DATA_SHARED_KEY);
if (storage.isAvailable()) {
return storage;
}
return null;
};
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