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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 Base class that implements functionality common
* across both session and local web storage mechanisms.
*
*/
goog.provide('goog.storage.mechanism.HTML5WebStorage');
goog.require('goog.asserts');
goog.require('goog.iter.Iterator');
goog.require('goog.iter.StopIteration');
goog.require('goog.storage.mechanism.ErrorCode');
goog.require('goog.storage.mechanism.IterableMechanism');
/**
* Provides a storage mechanism that uses HTML5 Web storage.
*
* @param {Storage} storage The Web storage object.
* @constructor
* @struct
* @extends {goog.storage.mechanism.IterableMechanism}
*/
goog.storage.mechanism.HTML5WebStorage = function(storage) {
goog.storage.mechanism.HTML5WebStorage.base(this, 'constructor');
/**
* The web storage object (window.localStorage or window.sessionStorage).
* @private {Storage}
*/
this.storage_ = storage;
};
goog.inherits(
goog.storage.mechanism.HTML5WebStorage,
goog.storage.mechanism.IterableMechanism);
/**
* The key used to check if the storage instance is available.
* @private {string}
* @const
*/
goog.storage.mechanism.HTML5WebStorage.STORAGE_AVAILABLE_KEY_ = '__sak';
/**
* Determines whether or not the mechanism is available.
* It works only if the provided web storage object exists and is enabled.
*
* @return {boolean} True if the mechanism is available.
*/
goog.storage.mechanism.HTML5WebStorage.prototype.isAvailable = function() {
if (!this.storage_) {
return false;
}
try {
// setItem will throw an exception if we cannot access WebStorage (e.g.,
// Safari in private mode).
this.storage_.setItem(
goog.storage.mechanism.HTML5WebStorage.STORAGE_AVAILABLE_KEY_, '1');
this.storage_.removeItem(
goog.storage.mechanism.HTML5WebStorage.STORAGE_AVAILABLE_KEY_);
return true;
} catch (e) {
return false;
}
};
/** @override */
goog.storage.mechanism.HTML5WebStorage.prototype.set = function(key, value) {
try {
// May throw an exception if storage quota is exceeded.
this.storage_.setItem(key, value);
} catch (e) {
// In Safari Private mode, conforming to the W3C spec, invoking
// Storage.prototype.setItem will allways throw a QUOTA_EXCEEDED_ERR
// exception. Since it's impossible to verify if we're in private browsing
// mode, we throw a different exception if the storage is empty.
if (this.storage_.length == 0) {
throw goog.storage.mechanism.ErrorCode.STORAGE_DISABLED;
} else {
throw goog.storage.mechanism.ErrorCode.QUOTA_EXCEEDED;
}
}
};
/** @override */
goog.storage.mechanism.HTML5WebStorage.prototype.get = function(key) {
// According to W3C specs, values can be of any type. Since we only save
// strings, any other type is a storage error. If we returned nulls for
// such keys, i.e., treated them as non-existent, this would lead to a
// paradox where a key exists, but it does not when it is retrieved.
// http://www.w3.org/TR/2009/WD-webstorage-20091029/#the-storage-interface
var value = this.storage_.getItem(key);
if (!goog.isString(value) && !goog.isNull(value)) {
throw goog.storage.mechanism.ErrorCode.INVALID_VALUE;
}
return value;
};
/** @override */
goog.storage.mechanism.HTML5WebStorage.prototype.remove = function(key) {
this.storage_.removeItem(key);
};
/** @override */
goog.storage.mechanism.HTML5WebStorage.prototype.getCount = function() {
return this.storage_.length;
};
/** @override */
goog.storage.mechanism.HTML5WebStorage.prototype.__iterator__ = function(
opt_keys) {
var i = 0;
var storage = this.storage_;
var newIter = new goog.iter.Iterator();
newIter.next = function() {
if (i >= storage.length) {
throw goog.iter.StopIteration;
}
var key = goog.asserts.assertString(storage.key(i++));
if (opt_keys) {
return key;
}
var value = storage.getItem(key);
// The value must exist and be a string, otherwise it is a storage error.
if (!goog.isString(value)) {
throw goog.storage.mechanism.ErrorCode.INVALID_VALUE;
}
return value;
};
return newIter;
};
/** @override */
goog.storage.mechanism.HTML5WebStorage.prototype.clear = function() {
this.storage_.clear();
};
/**
* Gets the key for a given key index. If an index outside of
* [0..this.getCount()) is specified, this function returns null.
* @param {number} index A key index.
* @return {?string} A storage key, or null if the specified index is out of
* range.
*/
goog.storage.mechanism.HTML5WebStorage.prototype.key = function(index) {
return this.storage_.key(index);
};
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