OK: How about this:

$ cat testMD5.pl
use strict;

foreach my $url(qw@ /index.html /about/time.html @){
        hashit($url);
}

sub hashit {
   my $url=shift;
   my @ltrs=split(//,$url);
   my $hash = 0;

   foreach my $ltr(@ltrs){
        $hash = ( $hash + ord($ltr)) %10000;
   }
   printf "%s: %0.4d\n",$url,$hash
   
}
[download]

which yields:

$ perl testMD5.pl 
/index.html: 1066
/about/time.html: 1547
[download]

Keep in mind this is hardly bullet proof. You need to also keep in mind a method to detect hash collisions and and a rehash algorithm.

This brings to mind "the old days" circa 1974 writing assemblers for 8080 microprocessors. Symbol "folding" and hashing.

UPDATE: Limiting yourself to four digits may not be very useful if you have a lot of pages that you are trying to index into your database. The wider your hash is the less likely there will be hash collisions.

---

Peter L. Berghold -- Unix Professional
Peter -at- Berghold -dot- Net; AOL IM redcowdawg Yahoo IM: blue_cowdawg

The perl code will produce the same hash for "abc.html" as for "bca.html"

In any case, the likelihood of a hash collision for any non-trivial website is substantial. If you hash 100 files you have about a 40% chance of a collision.

If you hash 220 files, the likelihood is about 90%

Now that iam thinking of it more and more, i don't have to turn the 'path' back to a 'number'

So, what i want is a function foo() that does this:

foo( "some long string" ) --> 1234

=====================
1. User requests a specific html page( .htaccess gives my script the absolute path for that .html page)
2. turn the 'path' to 4-digit number and store it to tha database as 'pin' (how?)
3. i store that number to the database. I DONT EVEN HAVE TO STORE THE HTML PAGE'S PATH TO THE DATABASE ANYMORE!!! this is just great!

At some later time i want to check the weblog of that .html page

1. request the page as: http://mydomain.gr/index.html?show=log
2. .htaccess gives my script the absolute path of the requested .html file
3. turn the 'path' to 4-digit number (this is what i'am asking)
4. use 'pin' variable to select all log records for that specific .html page (based on the 'pin' column)


Since i have the requested 'path' which has been converted to a database stored 4-digit number, i'am aware for which page i'am requesting detailed data from, so i look upon the 'pin' column in the database and thus i know which records i want to select. NO NEED to store absolute apths anymore, just a 4-digit number for each .html page

No need, to turn the number back to a path anymore, just the path to a number, to identify the specific .html page

Does your solution which SEEMS GREAT APPLY to my specifications?

The OP seems a bit unwilling to listen, but if you truncate the hash, you meet his spec.

use Digest::MD5 qw/ md5_hex /;

my $digest=md5_hex("http://www.berghold.net");
printf "%d\n", hex(substr($digest, -4)) % 10_000;
[download]

So the one-liner he's looking for would be hex(substr(md5_hex($someurl), -4)) % 10_000. I'm betting that is somewhat collision resistant. The OP still should consider enlarging his int2 column to int4 or int8 or even char(4)