what i've learned

csc309 webserver & javascript cookies

Here is the pickling and cookie webserver example using webpy that I presented in tutorial:

#!/usr/bin/env python

import os
import web
from pickle import load, dump

urls = (
    '/', 'Index'
)
app = web.application(urls, globals())

# global session store & session id 
SESSION_COUNT = 0
SESSIONS = {}


# methods to save & load data to files to persist
# session changes across restarts & crashes
data_fn = 'data.pkl'
def save_data():
    fp = open(data_fn, 'w')
    dump( (SESSIONS, SESSION_COUNT) , fp)
    fp.close()
def load_data():    
    if not os.path.isfile(data_fn): return
    global SESSIONS, SESSION_COUNT
    fp = open(data_fn, 'r')
    SESSIONS, SESSION_COUNT = load(fp)
    fp.close()

# restore our session data
load_data()

def parse_cookies():
    cookies_str = web.ctx.env['HTTP_COOKIE']
    return dict([ c.strip().split('=')
                  for c in cookies_str.split(';')])

class Index(object):
    def GET(self):
        web.header('Content-Type','text/html')

        session = {}

        # see if the user has our cookie already
        if 'HTTP_COOKIE' in web.ctx.env:
            cookies = parse_cookies()
            for name, val in cookies.items():
                web.debug('got cookie: %s = %s' % (name, val))

            # grab the session based on the user's cookie
            if 'session_id' in cookies:
                web.debug('got session id')
                session = SESSIONS[cookies['session_id']]

        # check if we got a session, if not create a new one
        if not session:
            web.debug('missing session, creating new session')
            global SESSION_COUNT
            expires_date = 'Fri, 11-Dec-2010 11:59:59 GMT'
            web.header('Set-Cookie', 'session_id=%s;'
                        ' expires=%s;'
                        % (expires_date, SESSION_COUNT))
            SESSIONS[str(SESSION_COUNT)] = session
            SESSION_COUNT += 1

        # update the session
        session['visits'] = session.setdefault('visits', 0)+1
        save_data()

        return (str(web.ctx.env) + 
                " You've visited %s times!"
                % session['visits'])


    def POST(self):
        self.GET()


if __name__ == "__main__":
    # run the webserver    
    app.run()

And here is the example of using cookies in Javascript:

// Cookies in Javascript

// The manual (tedious) way to set a cookie
document.cookie = ‘ppkcookie1=testcookie;' +
    ' expires=Thu, 2 Aug 2010 20:47:11 UTC; path=/’;

// The easy way
// from http://www.quirksmode.org/js/cookies.html

// if days == 0, the cookie expires when
// the user closes their browser
function createCookie(name,value,days) {
    if (days) {
	var date = new Date();
	date.setTime(date.getTime()+(days*24*60*60*1000));
	var expires = “; expires=”+date.toGMTString();
    } else var expires = “”;
    document.cookie = name+”=”+value+expires+”; path=/”;
}

function readCookie(name) {
    var nameEQ = name + “=”;
    var ca = document.cookie.split(‘;’);
    for(var i=0;i < ca.length;i++) {
	var c = ca[i];
	while (c.charAt(0)==’ ‘) c = c.substring(1,c.length);
	if (c.indexOf(nameEQ) == 0) {
            return c.substring(nameEQ.length,c.length);
        }
    }
    return null;
}

function eraseCookie(name) {
    createCookie(name,”“,-1);
}