How to make string of numbers shorter?

[Krakatioison]

My sites navigation is like this:

http://www.newsbackup.com/index.php?...00000040900000

, 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: 000000000040900 000 could become something like : AhD7
so the link: http://www.newsbackup.com/index.php?...00000040900000
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

[Michael Fesser]

.oO(Krakatioiso n)

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: 000000000040900 000 could become something like : AhD7
so the link: http://www.newsbackup.com/index.php?...00000040900000
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('0 000000000409000 00', 10, 36); // ouput: ocmn4
print base_convert('o cmn4', 36, 10); // output: 40900000

http://www.php.net/base_convert

HTH
Micha

[Joep]

base64? (without the leading zeroes of course)

"Michael Fesser" <ne*****@gmx.ne t> wrote in message
news:gn******** *************** *********@4ax.c om...

.oO(Krakatioiso n)

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: 000000000040900 000 could become something like : AhD7
so the link: http://www.newsbackup.com/index.php?...00000040900000
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('0 000000000409000 00', 10, 36); // ouput: ocmn4
print base_convert('o cmn4', 36, 10); // output: 40900000

http://www.php.net/base_convert

HTH
Micha

[Krakatioison]

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" <St***@DeStoep. nl> wrote in message
news:41******** *************** @news.xs4all.nl ...

base64? (without the leading zeroes of course)

"Michael Fesser" <ne*****@gmx.ne t> wrote in message
news:gn******** *************** *********@4ax.c om...

.oO(Krakatioiso n)

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: 000000000040900 000 could become something like : AhD7
so the link: http://www.newsbackup.com/index.php?...00000040900000
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('0 000000000409000 00', 10, 36); // ouput: ocmn4
print base_convert('o cmn4', 36, 10); // output: 40900000

http://www.php.net/base_convert

HTH
Micha

[Krakatioison]

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

<?

$str= '10000000000409 00000';

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

$encoded = base_convert($s tr, 10, 36); //

echo "Encoded string:".$encod ed."<br>";

$decoded = base_convert($e ncoded, 36, 10);

echo "Decoded string:".$decod ed."<br>";

?>

Result from the screen looks like this:

Original string: 100000000004090 0000
Encoded string: 7lieey0lh7k0
Decoded string: 100000000004090 0008

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

[Ethan T]

Krakatioison <kl****@sssbbbc cc.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

[Michael Fesser]

.oO(Krakatioiso n)

Result from the screen looks like this:

Original string: 100000000004090 0000
Encoded string: 7lieey0lh7k0
Decoded string: 100000000004090 0008

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_conve rt() 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

[Krakatioison]

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

[Michael Fesser]

.oO(Krakatioiso n)

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) {
$base = strlen($alphabe t);
$result = '';
while (bccomp($number , 0) == 1) {
$result = $alphabet{bcmod ($number, $base)}.$result ;
$number = bcdiv($number, $base, 0);
}
return $result;
}

function decode($number, $alphabet) {
$base = strlen($alphabe t);
$alphabet = array_flip(str_ split($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($stri ng) {
return preg_split('##' , $string, -1, PREG_SPLIT_NO_E MPTY);
}
Test results:

Alphabet: 01
Original string: 100000000004090 0000
Encoded string: 110111100000101 101101011001110 101001110101000 001010110100000
Decoded string: 100000000004090 0000

Alphabet: 0123456789ABCDE F
Original string: 100000000004090 0000
Encoded string: DE0B6B3A9D415A0
Decoded string: 100000000004090 0000

Alphabet: 0123456789ABCDE FGHIJKLMNOPQRST UVWXYZ
Original string: 100000000004090 0000
Encoded string: 7LIEEY0LH7KW
Decoded string: 100000000004090 0000

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

HTH
Micha

[Pedro Graca]

["Followup-To:" header set to comp.lang.php.]
Krakatioison wrote:

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

<?

$str= '10000000000409 00000';

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

$encoded = base_convert($s tr, 10, 36); //

echo "Encoded string:".$encod ed."<br>";

$decoded = base_convert($e ncoded, 36, 10);

echo "Decoded string:".$decod ed."<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, ' ==> ';

$encoded = base_convert($s tr1, 10, 36);
$encoded .= '-' . base_convert($s tr2, 10, 36);
echo 'Encoded string: ', $encoded, "\n";

$enc = explode('-', $encoded);
$decoded = substr('0000000 0' . base_convert($e nc[0], 36, 10), -9);
$decoded .= substr('0000000 0' . base_convert($e nc[1], 36, 10), -9);
echo ' Decoded string: ', $decoded, "\n\n";
}

/* test data */
$str= '00000000004090 0000'; test($str);
$str= '00000000004090 0001'; test($str);
$str= '90000000004090 0000'; test($str);
$str= '90000000004090 0001'; test($str);
$str= '12345678901234 5678'; test($str);
$str= '98765432109876 5432'; test($str);
$str= '11111111111111 1111'; test($str);
$str= '55555555555555 5555'; test($str);
$str= '99999999999999 9999'; test($str);
$str= '00000000000000 0000'; test($str);
?>

php$ php longn.php
Original string: 000000000040900 000 ==> Encoded string: 0-ocmn4
Decoded string: 000000000040900 000

Original string: 000000000040900 001 ==> Encoded string: 0-ocmn5
Decoded string: 000000000040900 001

Original string: 900000000040900 000 ==> Encoded string: evu4g0-ocmn4
Decoded string: 900000000040900 000

Original string: 900000000040900 001 ==> Encoded string: evu4g0-ocmn5
Decoded string: 900000000040900 001

Original string: 123456789012345 678 ==> Encoded string: 21i3v9-7clzi
Decoded string: 123456789012345 678

Original string: 987654321098765 432 ==> Encoded string: gc0uy9-1msvw8
Decoded string: 987654321098765 432

Original string: 111111111111111 111 ==> Encoded string: 1u5hvr-1u5hvr
Decoded string: 111111111111111 111

Original string: 555555555555555 555 ==> Encoded string: 96rher-96rher
Decoded string: 555555555555555 555

Original string: 999999999999999 999 ==> Encoded string: gjdgxr-gjdgxr
Decoded string: 999999999999999 999

Original string: 000000000000000 000 ==> Encoded string: 0-0
Decoded string: 000000000000000 000
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