Your browser, my storage
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Your browser, my storagea new approach on data storing
Francesco Fullone
ff AT ideato.it
Who am I
Francesco Fullone aka Fullo
- PHP developer since 1999
- President
- and Open Source Evangelist
- CEO @
- Nerd and geek
What we want is a lot of storage space, on the client, that persists beyond a page refresh and isn’t transmitted to the server.
~ M. Pilgrim
Persistent local storage is one of the areas where client
applications traditionally win against web applications.
A jump in the past
Cookies are introduced in HTTP/1.0, limited to only 20 per
domain and 4KB each.
http://www.flickr.com/photos/betsyweber/4962298614/
Cookies are sent to and from client at any connection.
http://www.flickr.com/photos/dionhinchcliffe/4326080515
Microsoft with Internet Explorer 6 introduced dHTML and the
userData API to store up to 64KB of data
Mozilla introduced with Firefox 2 the DOM Storage API, it will then
know as Web Storage.
Adobe, in 2002, created the Flash Cookies aka “Local Shared
Objects” for Flash 6.
Data storage increased to 100KB but it was difficult to be used.
With Flash 8, in 2006, Adobe introduced the
ExternalInterface to allow Js to access
to the stored resources.
Between 2005 and 2007 dojox.storage is written by Brad Neuberg as a Js->Flash bridge to manage bigger chunks of data
(with user prompt over 1MB).
Google created Gears in 2007, that introduced a database
paradigm (based on SQLite) to the storage problem.
All these storage systems had different APIs, a common
platform is needed by all the browser vendors.
The two approaches of storing:
Application Cache
Offline storage
Application Caching involves saving the application's core logic
and user-interface.
http://www.whatwg.org/specs/web-apps/current-work/#applicationcache
It is enabled by a file .manifest that declares which resources
have to be saved locally.
(limited to 5MB).
CACHE MANIFEST
# Explicitly cached entries
CACHE:index.htmlstylesheet.cssimages/logo.pngscripts/main.js
# Resources that require the user to be online.
NETWORK:login.php/myapihttp://api.twitter.com
# static.html will be served if main.php is inaccessible# offline.jpg will be served in place of all images in images/large/
FALLBACK:/main.php /static.htmlimages/large/ images/offline.jpg
Data storage is about capturing specific
data, or resources the user has expressed
interest in.http://www.flickr.com/photos/bfionline/2380398365/
Approaches to
Data Storage
Web Storage is the simpler implementation of the Data
Storage paradigm.
http://dev.w3.org/html5/webstorage/
Web Storage is based on a structure of key-value pairs like
any JavaScript object.
localStorage.setItem("bar", foo);
Web Storage can save up to 5MB but only as strings. So we have
to force a casting if needed.
var bar = parseInt(localStorage["bar"]);
Web Storage should be local based or session based.
var bar = localStorage["bar"];
var foo = sessionStorage["foo"];
sessionStorage mantains a storage area that's available for the duration of the web session.
Opening a new window/tab will create a new session.
localStorage relies only on client, so we have to track
changes and use storage.events to sync server and client if
needed.
Web SQL Database is just an offline SQL implementation,
based on SQLite.
http://dev.w3.org/html5/webdatabase/
this.db = openDatabase('geomood', '1.0', 'Geo', 8192);
this.db.transaction(function(tx) {
tx.executeSql("create table if not exists checkins(id integer primary key asc, time integer, latitude float, longitude float, mood string)",
[],
function() { console.log("siucc"); }
» );
});
Web SQL Database is not (yet) supported by Microsoft and
Mozilla, instead it is on browsers based on webkit.
IndexedDB is a nice compromise between Web Storage and Web
SQL Database.
http://www.w3.org/TR/IndexedDB/
IndexedDB allows to create an index on a certain field stored in a standard key->value mapping.
IndexedDB is promoted by all browsers vendor, but is not yet officially supported by anyone!
Firefox 4 beta has a partial implementation.
FileAPI or File Storage will give us a way to store a lot of data.
http://www.w3.org/TR/FileAPI/
File API includes FileReader and FileWriter APIs.
Actually (FileReader) is partially supported only by Chrome.
First steps on offline storage development.
http://www.flickr.com/photos/45449692@N00/3161567381
HTML 5 Confusion
Detect if the storing feature is supported by the browser (with
modernizr), otherwise degradate to something else.
(ie. dojox.storage)
Protect against lost data,
sync automatically.
http://www.flickr.com/photos/neate_photos/3529558272/
Automatically detect when
users are online.
http://www.flickr.com/photos/doctorow/2686237951/
Do not exceed in storing data, you can store binary data base64
encoded but remember the pitfalls in performance.
Avoid race conditions.
If possible use WebSQL to use its transactions features.
?
phpDay 201112-14 Maggio 2011
www.phpday.it
via Quinto Bucci 20547023 Cesena (FC)info AT ideato.itwww.ideato.it
rate this talk: http://joind.in/2126