topic Re: library function to generate unique number for any string in Operating System - HP-UX

library function to generate unique number for any string

Amit Kureel — Tue, 25 Sep 2001 08:42:09 GMT

Is there a library function to generate a unique number for any string that I get as input. Also, it should generate the same number if I pass the same string to it again and again !

Can anybody help ?

Thanks and regards

Amit Kureel

Re: library function to generate unique number for any string

Andreas Voss — Tue, 25 Sep 2001 08:57:35 GMT

Hi,

i know no library function but how about this:

int uniq(str)
char *str;
{
int i,l,n;

for(n=0,i=0,l=strlen(str);i n+=(int)str[i];
return(n);
}

Regards

Re: library function to generate unique number for any string

Volker Borowski — Tue, 25 Sep 2001 09:27:11 GMT

Amit,

I think this is not possible at all.
Any checksum-algorithm might produce the same number for same strings again, but it will never be unique, because due to truncation at a given point, two diffrent strings might return the same number!

Try "man cksum" for a sample.

You could write an algorithm if you limit the amount of characters user in the given string and the maximum length. But this would go closer to some kind of compression.

I do not know, what you want to achieve, but I think the compression algorithms might be close to what you want. The problem is, that you will get a compressed string of a shorter length as a result, and not a simple number.

Hope this helps
Volker

Re: library function to generate unique number for any string

Mike Stroyan — Tue, 25 Sep 2001 19:53:30 GMT

You want XrmStringToQuark from libX11. (The manual does not mention it, but you should use
#include
to get the function declaration.)

The function uses a hash table to implement the mapping. It keeps a copy of each string to verify uniqueness. You can get a string back with XrmQuarkToString.

Re: library function to generate unique number for any string

Wodisch — Fri, 05 Oct 2001 01:08:35 GMT

Hello Amit,

you could use UUID (DCE Universal Unique IDs) in one
way, an array to store them and the appropriate string
for the way back. UUIDs are 128bits in size, and the
creation of them is guaranteed to be unique...

HTH,
Wodisch