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/*
* Copyright (C) 2011 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
* THE POSSIBILITY OF SUCH DAMAGE.
*/
var PersistentCache = {
contains: function(key) {
return key in localStorage;
},
get: function(key) {
var string = localStorage[key];
if (!string)
return string;
// FIXME: We could update the date stored with the value here to make this more of an MRU
// cache (instead of most-recently-stored), but that would result in extra disk access that
// might not be so great.
return JSON.parse(this._parseDateAndJSONFromString(string).json);
},
set: function(key, value) {
try {
localStorage[key] = this._addDateToJSONString(JSON.stringify(value));
} catch (e) {
if (e.code !== 22) // QUOTA_EXCEEDED_ERR
throw e;
// We've run out of space in localStorage. Let's just throw away everything and try
// again.
this._emptyCache();
this.set(key, value);
}
},
prune: function() {
var now = Date.now();
for (var key in localStorage) {
var date = this._parseDateAndJSONFromString(localStorage[key]).date;
if (now - date <= this._dataAgeLimitMS)
continue;
delete localStorage[key];
}
this.set(this._lastPruneDateKey, now);
},
_addDateToJSONString: function(jsonString) {
return Date.now() + this._dateAndJSONSeparator + jsonString;
},
_dataAgeLimitMS: 1000 * 60 * 60 * 24 * 1.1, // Just over one day
_dateAndJSONSeparator: ': ',
_emptyCache: function() {
for (var key in localStorage)
delete localStorage[key];
},
_parseDateAndJSONFromString: function(string) {
var separatorIndex = string.indexOf(this._dateAndJSONSeparator);
return {
date: new Date(parseInt(string.substring(0, separatorIndex), 10)),
json: string.substring(separatorIndex + this._dateAndJSONSeparator.length),
};
},
};
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