I have some NFC tags (NTAG216) every tag has a unique serial number, I want to use this tags as a user login token so it most be unique in some way. The tags have a single record with a link like so "https://www.example.com?t=DAFDSAG" I want to add a parameter to that GET with the tag serial number, something like "https://www.example.com?t=DAFDSAG&s={serial number}".
If the serial number of the tag is stored at addr 00 and 01, is it possible to have a record with "https://www.example.com?t=DAFDSAG&s={addr 00 and addr 01}" ? meaning that all tags will have a unique url created based on the serial number.
Thanks !!!
Yes possible see Section 8.7.1 of https://www.nxp.com/docs/en/data-sheet/NTAG213_215_216.pdf
Just write the default Ndef URL to the Tag e.g. https://www.example.com?t=DAFDSAG&s=00000000000000
You just configure the mirror option to replace the blocks containing the zero with the UID
Note the UID should never be used for an security or login process as it is very unsecure, as it is so easy to copy and fake the UID, especially using the UID mirror option.
A NFC UID is only designed to prevent card clash when 2 cards are in range.
Related
I understood the process to shorten the URL with base 62 at How do I create a URL shortener?.
Steps given are
Think of an alphabet we want to use. In your case, that's [a-zA-Z0-9]. It contains 62 letters.
Take an auto-generated, unique numerical key (the auto-incremented id of a MySQL table for example).
For this example, I will use 12510 (125 with a base of 10).
Now you have to convert 12510 to X62 (base 62)
My question is why not just create unique numerical key and return it ? What is the advantage of concerting numerical key > Base 62 > then Finally some alphanumeric number ?
Is it because final alphanumeric number will be much smaller than unique numerical key ?
Yes. The idea is to make it short and usable in a URL. A number in base 62 will use fewer characters than the same number in base 10. Notice also that URL shorteners use short hosts, such as g.co.
I can see you understand that, yes, a number written in base 62 takes less characters than a number in base 10 just like a number in base 10 takes less characters than a number in base 2 (e.g. 0101 is 3 characters longer than just '5').
So, I'll answer specifically "Why".
Sometimes a link is shortened to be more visually pleasing. A company worried about their public perception likely doesn't want their links to look like an error code due to how long they are so they resort to shortening. That's why some url shortening services allow you to add your own "vanity url" which customizes the domain name, so that a link can be shortened and branded.
Other times a link is shortened to minimize character count when working with constraints, like Twitter. For example, at my company we shortened the links in our automated Twilio messages because SMS messages that contain more than 160 characters are technically 2 concatenated messages so it is more expensive to send.
And finally if the link is being shared through a medium that cannot be directly clicked on (e.g. verbally, on paper), making it shorter makes it much easier to type into an address bar manually. (Imagine trying to type the url to this SO question when someone is reading it to you.) I assume this is also at least partially why the base used for these links usually stop at around 62. If you start including other arbitrary characters to higher the base and consequentially make the link marginally shorter, it'll become harder to communicate, read and type. ("domain.name/5omeC0d3" vs "domian.name/🈲}♠"
I have an API in rails that will handle a lot of requests. Lets say millions a day. I want to be able to assign a unique id to each of these requests. The way i am doing it is starting with a uid of 3 letters/numbers and continue up till 9 letters/numbers when the previous bracket is all taken.
One one i am doing it is generate the uid in real time when the request comes, so the app will try to find the first available uid and assign it. But after a while i have the impression that this will impact the performance of the app.
The second way I am thinking is to auto-generate all the possible uids in advance and have a flag assigned to them [free/taken] so that when a request comes in i assign the first free uid to it, which should be very fast if that filed is indexed.
Any suggestions are much appreciated. Thank you
I would just generate a random string and assign it while it doesn't exist. Before I get into that let me just mention that SecureRandom.uuid is the best way to go. It generates random uuids whose chance of collision are mathematically improbable.
Anyway, here is a way to use your own custom random string generator that will only assign if it doesn't already exist:
def generate_random_uid
begin
uid = my_custom_random_string_method
object.uid = uid
end while ObjectModel.exists? uid: uid
object.save
end
The do while block will execute once and set a variable called uid to be a random string you generate in the method my_custom_random_string_method, then in the while part it checks if a record exists whose uid attribute matches the random uid you just generated, if it does it runs the do block again, rinse and repeat until the expression in the while part returns false meaning the uid doesn't exists, then your object is saved and the uid written to the db. This guarantees that you will only ever save the object with a uid that doesn't exist in your db.
My SQL code gives me over 10 000 rows, each containing client id, name, address and so forth. In my PowerBuilder 10.5 window I've set my DataWindow in which I'm retrieving my SQL code using id as retrieve argument. I have a Single line Edit (sle_id) in which the user can write an id and search by it. What I've figured out is that all of my clients have id's length of 8 characters and starting with either "46XXXXXXXX" or "7052XXXX". So to optimize my retrieve time I want to write a code in the clicked event of my "Start" button that is located in PowerBuilder window that would first check if the id starts with one of does two options: "46..." or "7052...". I assume I'd need to use length of the characters? For example, this is what I'd want...
IF sle_id.text STARTS with 46 or 7052 THEN retrieve
ELSE MessageBox ("INFO", "Your id must have begin with either 32 or 7052")
END IF;
Of course, I need something better then "Starts with". Much oblige for all the help!
there are some string functions in powerbuilder. I think you need this:
If( left(sle_id.text, 2) = "46" or left(sle_id.text, 4) = "7052" ) then
Best Regards
Gábor
I think you're trying to solve the wrong problem. Your database should have an index on client id. If the client id is unique use a unique index.
I have a source file that contains two fields: IP_ADDRESS and USER_NAME. I want to check whether the IP address is correct or not before loading it to the datawarehouse using DATASTAGE. How do I do this?
I was browsing Stack Overflow and think I might have a solution to your question. If you create a job to grab all of the IP_ADDRESS's from the file and send them to a BASIC transformer (search for BASIC transformer in DataStage. It is NOT the one that is normally on the palette). From there, set the Stage Variables as 'SetUserStatus() and write out the column name to a peek stage (You don't need the output at all. The SetUserStatus is the important part). This will now allow you to pass up the Command Output (list of IP Addresses) to a Sequence. From the Sequence, start with the job you just created (BASIC transformer job) and link that to a User Variables Activity. In the User Variables Activity stage, Set the name to something like 'IP Address' and Expression as IP_ADDRESS.$UserStatus. You can then use a Loop to take that output that is now a List and send each individual IP Address to an Execute Stage with a Ping command to see if it returns a valid IP Address. If it does return a valid IP then have your job that writes the USER_NAME and IP_ADDRESS to do a 'Select' statement where the IP_ADDRESS = the valid IP_ADDRESS. For the ones that aren't valid, you can send them down a different path and have them write out to '.txt' file somewhere so you know which ones weren't valid. I'm sure you will need a few more steps in there but that should be the gist of it.
Hope my quick stab at your issue helps.
Yes, you can use a transformer or a transformer and a filter to do that, depending on the version of Datastage you're using. If you're using PX, just encode the validation logic in a transformer stage, and then, on the output link set up a filter that doesn't allow the rows to pass forward if they didn't pass the validation logic.
Today I asked myself how can I handle user input if the user have not to enter it...
A firstname and lastname is all he must enter. The adress he needs not to fill out.
Now I have to decide, is the missing data a user mistake or didn`t the user want to enter
data?
How can I deal with such a scenario?
If the address field is perfectly valid when blank (i.e. "") then I would first do a check against the length of the data within the address text field.
If the length of the data is > 0 then the validation routine should take place, else the form should continue to process...
If you wanted to get slightly more intelligent with this (and depending on your requirements) you could perhaps put some code in place to check whether the user has entered the address box with their cursor at any point and then carry out validation accordingly.