How to make string of numbers shorter?

My sites navigation is like this:

http://www.newsbackup.com/index.php...000000040900000

, depending on the variable "n" (which is always a number), it will take me
anywhere on the site... this number is always changing as I have hundreds of
thousand of pages of text on my site.

Problem:
- in my opinion this just not only look weird, but the variable "n" (number)
is too long.

I need a way to somehow express this number in shorter form. Some encoding
and decoding way to express this number as something shorter.
For example: 000000000040900000 could become something like : AhD7
so the link: http://www.newsbackup.com/index.php...000000040900000
would look like: http://www.newsbackup.com/index.php?n=AhD7

You know what I mean.

So, I tried to think about it, and I played with the idea to use of gzencode
or gzcompress. Tried it, but these will generate the short code full of
characters out of normal ascii, spaces and so.... I can't use that, then my
site won't be search engine friendly.

Please, do you have any suggestions?
Or some short encoding decoding script? Your script can be forever part of
my site.

Joe

.oO(Krakatioison)

>I need a way to somehow express this number in shorter form. Some encoding
>and decoding way to express this number as something shorter.
>For example: 000000000040900000 could become something like : AhD7
>so the link: http://www.newsbackup.com/index.php...000000040900000
>would look like: http://www.newsbackup.com/index.php?n=AhD7

If n is a real number (so that leading zeros don't matter), then you
could try base_convert:

print base_convert('000000000040900000', 10, 36); // ouput: ocmn4
print base_convert('ocmn4', 36, 10); // output: 40900000

http://www.php.net/base_convert

HTH
Micha

base64? (without the leading zeroes of course)

"Michael Fesser" <netizen@gmx.net> wrote in message
 news:gn20o0pal33shhguloncsaj0dgm0i9gtpe@
4ax.com...
> .oO(Krakatioison)
> 
>
> If n is a real number (so that leading zeros don't matter), then you
> could try base_convert:
>
> print base_convert('000000000040900000', 10, 36); // ouput: ocmn4
> print base_convert('ocmn4', 36, 10); // output: 40900000
>
> http://www.php.net/base_convert
>
> HTH
> Micha

Problem is that I need those leading zeros. It will just not work without
them.
Hm... But great Idea. Thanks a lot.
Any better idea? Which would never cut my leading zeros?

Joe




"Joep" <Staat@DeStoep.nl> wrote in message
news:41800ddd$0$78749$e4fe514c@news.xs4all.nl...
> base64? (without the leading zeroes of course)
>
> "Michael Fesser" <netizen@gmx.net> wrote in message
>  news:gn20o0pal33shhguloncsaj0dgm0i9gtpe@
4ax.com... 
>
>

So I played with your idea a bit and wrote this script:

<?

$str= '1000000000040900000';

echo "Original string:".$str."<br>";

$encoded = base_convert($str, 10, 36); //

echo "Encoded string:".$encoded."<br>";

$decoded = base_convert($encoded, 36, 10);

echo "Decoded string:".$decoded."<br>";

?>



Result from the screen looks like this:

Original string: 1000000000040900000
Encoded string: 7lieey0lh7k0
Decoded string: 1000000000040900008

My idea was to add number 1 to the from which I would just cut off. But it's
not working... Decoded string has number 8 at the end. Not 0, as original
had.

Geez... what is happening, am I going blind?

Joe

Krakatioison <klokan@sssbbbccc.com> wrote:
> My idea was to add number 1 to the from which I would just cut off.
> But it's not working... Decoded string has number 8 at the end. Not
> 0, as original had.
> Geez... what is happening, am I going blind?

The docs for that function (base_convert) mention a loss of precision when
using large numbers, and those are definitely large numbers. That's probably
why the 8 is appearing.

--
eth'nT

.oO(Krakatioison)

>Result from the screen looks like this:
>
>Original string: 1000000000040900000
>Encoded string: 7lieey0lh7k0
>Decoded string: 1000000000040900008
>
>My idea was to add number 1 to the from which I would just cut off. But it'
s
>not working... Decoded string has number 8 at the end. Not 0, as original
>had.
>
>Geez... what is happening, am I going blind?

Nope, it's probably because of the way base_convert() works.
My fault, I should have read the warning on the manual page:

"base_convert() may lose precision on large numbers due to properties
related to the internal "double" or "float" type used."

A while ago I wrote a function for calulating permutations, it is also
usable for converting from the decimal system to any other base. I have
to check if it can be adjusted to work with such large numbers ...

Maybe there's another and better way.

Micha

Micha, Ethan,

I thought there must be something like it. But I wasn't sure.
So now I am really puzzled. What would be a best way to deal with this
problem?
I was wondering about using dechex and hexdec.... but that is using
alphabeth only till it gets to F, so as a solution it wouldn't be the best
possible.

Any other ideas?

Joe

.oO(Krakatioison)

>I thought there must be something like it. But I wasn't sure.
>So now I am really puzzled. What would be a best way to deal with this
>problem?
>I was wondering about using dechex and hexdec.... but that is using
>alphabeth only till it gets to F, so as a solution it wouldn't be the best
>possible.

A quick 'n dirty hack, using the BCMath extension (should be compiled-in
by default) for converting any (really big) number from base 10 to any
base you like and back:

function encode($number, $alphabet) {
$base = strlen($alphabet);
$result = '';
while (bccomp($number, 0) == 1) {
$result = $alphabet{bcmod($number, $base)}.$result;
$number = bcdiv($number, $base, 0);
}
return $result;
}

function decode($number, $alphabet) {
$base = strlen($alphabet);
$alphabet = array_flip(str_split($alphabet));
$c = strlen($number)-1;
$result = 0;
for ($i = 0; $i <= $c; $i++) {
$temp = bcmul($alphabet[$number{$i}], bcpow($base, $c-$i));
$result = bcadd($result, $temp);
}
return $result;
}


The str_split() function is PHP5, if you don't have it you can use this
one instead:

function str_split($string) {
return preg_split('##', $string, -1, PREG_SPLIT_NO_EMPTY);
}


Test results:

Alphabet:        01
Original string: 1000000000040900000
Encoded string:   1101111000001011011010110011101010011101
0100000101011010000
0
Decoded string:  1000000000040900000

Alphabet:        0123456789ABCDEF
Original string: 1000000000040900000
Encoded string:  DE0B6B3A9D415A0
Decoded string:  1000000000040900000

Alphabet:        0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ
Original string: 1000000000040900000
Encoded string:  7LIEEY0LH7KW
Decoded string:  1000000000040900000

With the last alphabet the encoding saves 7 chars ... not that much ...

HTH
Micha

["Followup-To:" header set to comp.lang.php.]
Krakatioison wrote:
> So I played with your idea a bit and wrote this script:
>
> <?
>
> $str= '1000000000040900000';
>
> echo "Original string:".$str."<br>";
>
> $encoded = base_convert($str, 10, 36); //
>
> echo "Encoded string:".$encoded."<br>";
>
> $decoded = base_convert($encoded, 36, 10);
>
> echo "Decoded string:".$decoded."<br>";
>
> ?>

Are your numbers 'n' always 18 digits long?

php$ cat longn.php
<?php
function test($str) {
if (strlen($str) != 18) {echo "$str: Oops, wrong length\n\n"; return;}
$str1 = substr($str, 0, 9);
$str2 = substr($str, 9, 9);
echo 'Original string: ', $str, ' ==> ';

$encoded = base_convert($str1, 10, 36);
$encoded .= '-' . base_convert($str2, 10, 36);
echo 'Encoded string: ', $encoded, "\n";

$enc = explode('-', $encoded);
$decoded = substr('00000000' . base_convert($enc[0], 36, 10), -9);
$decoded .= substr('00000000' . base_convert($enc[1], 36, 10), -9);
echo ' Decoded string: ', $decoded, "\n\n";
}

/* test data */
$str= '000000000040900000'; test($str);
$str= '000000000040900001'; test($str);
$str= '900000000040900000'; test($str);
$str= '900000000040900001'; test($str);
$str= '123456789012345678'; test($str);
$str= '987654321098765432'; test($str);
$str= '111111111111111111'; test($str);
$str= '555555555555555555'; test($str);
$str= '999999999999999999'; test($str);
$str= '000000000000000000'; test($str);
?>

php$ php longn.php
Original string: 000000000040900000 ==> Encoded string: 0-ocmn4
Decoded string: 000000000040900000

Original string: 000000000040900001 ==> Encoded string: 0-ocmn5
Decoded string: 000000000040900001

Original string: 900000000040900000 ==> Encoded string: evu4g0-ocmn4
Decoded string: 900000000040900000

Original string: 900000000040900001 ==> Encoded string: evu4g0-ocmn5
Decoded string: 900000000040900001

Original string: 123456789012345678 ==> Encoded string: 21i3v9-7clzi
Decoded string: 123456789012345678

Original string: 987654321098765432 ==> Encoded string: gc0uy9-1msvw8
Decoded string: 987654321098765432

Original string: 111111111111111111 ==> Encoded string: 1u5hvr-1u5hvr
Decoded string: 111111111111111111

Original string: 555555555555555555 ==> Encoded string: 96rher-96rher
Decoded string: 555555555555555555

Original string: 999999999999999999 ==> Encoded string: gjdgxr-gjdgxr
Decoded string: 999999999999999999

Original string: 000000000000000000 ==> Encoded string: 0-0
Decoded string: 000000000000000000


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