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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 a convenient API for data persistence with expiration.
*
*/
goog.provide('goog.storage.ExpiringStorage');
goog.require('goog.storage.RichStorage');
goog.require('goog.storage.RichStorage.Wrapper');
goog.require('goog.storage.mechanism.Mechanism');
/**
* Provides a storage with expirning keys.
*
* @param {!goog.storage.mechanism.Mechanism} mechanism The underlying
* storage mechanism.
* @constructor
* @extends {goog.storage.RichStorage}
*/
goog.storage.ExpiringStorage = function(mechanism) {
goog.base(this, mechanism);
};
goog.inherits(goog.storage.ExpiringStorage, goog.storage.RichStorage);
/**
* Metadata key under which the expiration time is stored.
*
* @type {string}
* @protected
*/
goog.storage.ExpiringStorage.EXPIRATION_TIME_KEY = 'expiration';
/**
* Metadata key under which the creation time is stored.
*
* @type {string}
* @protected
*/
goog.storage.ExpiringStorage.CREATION_TIME_KEY = 'creation';
/**
* Returns the wrapper creation time.
*
* @param {!Object} wrapper The wrapper.
* @return {number|undefined} Wrapper creation time.
*/
goog.storage.ExpiringStorage.getCreationTime = function(wrapper) {
return wrapper[goog.storage.ExpiringStorage.CREATION_TIME_KEY];
};
/**
* Returns the wrapper expiration time.
*
* @param {!Object} wrapper The wrapper.
* @return {number|undefined} Wrapper expiration time.
*/
goog.storage.ExpiringStorage.getExpirationTime = function(wrapper) {
return wrapper[goog.storage.ExpiringStorage.EXPIRATION_TIME_KEY];
};
/**
* Checks if the data item has expired.
*
* @param {!Object} wrapper The wrapper.
* @return {boolean} True if the item has expired.
*/
goog.storage.ExpiringStorage.isExpired = function(wrapper) {
var creation = goog.storage.ExpiringStorage.getCreationTime(wrapper);
var expiration = goog.storage.ExpiringStorage.getExpirationTime(wrapper);
return !!expiration && expiration < goog.now() ||
!!creation && creation > goog.now();
};
/**
* Set an item in the storage.
*
* @param {string} key The key to set.
* @param {*} value The value to serialize to a string and save.
* @param {number=} opt_expiration The number of miliseconds since epoch
* (as in goog.now()) when the value is to expire. If the expiration
* time is not provided, the value will persist as long as possible.
* @override
*/
goog.storage.ExpiringStorage.prototype.set = function(
key, value, opt_expiration) {
var wrapper = goog.storage.RichStorage.Wrapper.wrapIfNecessary(value);
if (wrapper) {
if (opt_expiration) {
if (opt_expiration < goog.now()) {
goog.storage.ExpiringStorage.prototype.remove.call(this, key);
return;
}
wrapper[goog.storage.ExpiringStorage.EXPIRATION_TIME_KEY] =
opt_expiration;
}
wrapper[goog.storage.ExpiringStorage.CREATION_TIME_KEY] = goog.now();
}
goog.base(this, 'set', key, wrapper);
};
/**
* Get an item wrapper (the item and its metadata) from the storage.
*
* @param {string} key The key to get.
* @param {boolean=} opt_expired If true, return expired wrappers as well.
* @return {(!Object|undefined)} The wrapper, or undefined if not found.
* @override
*/
goog.storage.ExpiringStorage.prototype.getWrapper = function(key, opt_expired) {
var wrapper = goog.base(this, 'getWrapper', key);
if (!wrapper) {
return undefined;
}
if (!opt_expired && goog.storage.ExpiringStorage.isExpired(wrapper)) {
goog.storage.ExpiringStorage.prototype.remove.call(this, key);
return undefined;
}
return wrapper;
};
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