hex to another base

[Nel]

I am trying to find a php solution to encoding an md5 hex string into
another base.

Using ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwx yz1234567890 as a
characters for a base 62
i.e.
A = 1
a = 27
0 = 62
00 = 3844
000 = 238328

This should make the hex string much shorter.

1. Does anyone understand what I'm trying to do here?
2. Has this wheel already been invented?
3. Any ideas about the most efficient way to encode and decode this kind of
thing?

Thanks,

Nel

[Justin Koivisto]

Nel wrote:

I am trying to find a php solution to encoding an md5 hex string into
another base.

Using ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwx yz1234567890 as a
characters for a base 62
i.e.
A = 1
a = 27
0 = 62
00 = 3844
000 = 238328

This should make the hex string much shorter.

1. Does anyone understand what I'm trying to do here?
2. Has this wheel already been invented?
3. Any ideas about the most efficient way to encode and decode this kind of
thing?

http://www.pgregg.com/projects/php/b...conversion.php

However, the order that is used on that for the characters are:

0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmn opqrstuvwxyz

(which seems more logical than having the digits at the end)

--
Justin Koivisto, ZCE - ju****@koivi.com
http://koivi.com

[Francois Bonzon]

On 2006-02-20 17:44:26 +0100, Justin Koivisto <ju****@koivi.com> said:

Nel wrote:

I am trying to find a php solution to encoding an md5 hex string into
another base.

Using ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwx yz1234567890 as
a characters for a base 62
i.e.
A = 1
a = 27
0 = 62
00 = 3844
000 = 238328

This should make the hex string much shorter.

1. Does anyone understand what I'm trying to do here?
2. Has this wheel already been invented?
3. Any ideas about the most efficient way to encode and decode this
kind of thing?

http://www.pgregg.com/projects/php/b...conversion.php

However, the order that is used on that for the characters are:

0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmn opqrstuvwxyz

(which seems more logical than having the digits at the end)

If you're trying to save memory, IMHO the best way to represent your
MD5 hex string is with binary data. Check out the functions pack() to
encode to binary data, and bin2hex() to decode. Example:

<?

echo $hex_string = md5('abc123'), "\n";
$binary_data = pack('H*', $hex_string);
echo bin2hex($binary_data), "\n";

// Outputs:
// e99a18c428cb38d5f260853678922e03
// e99a18c428cb38d5f260853678922e03

?>

[Nel]

"Francois Bonzon" wrote in message news:43******@epflnews.epfl.ch...

If you're trying to save memory, IMHO the best way to represent your MD5
hex string is with binary data. Check out the functions pack() to encode
to binary data, and bin2hex() to decode. Example:

<?

echo $hex_string = md5('abc123'), "\n";
$binary_data = pack('H*', $hex_string);
echo bin2hex($binary_data), "\n";

// Outputs:
// e99a18c428cb38d5f260853678922e03
// e99a18c428cb38d5f260853678922e03

?>

Hi Francois,

In this cas I am trying to pass a shorter URL and moving from base 16 to 62
knocks off about 10 chars from the URL. Not as many as I'd hoped for, but
it's a definate improvement.

Nel

[Nel]

"Justin Koivisto" <ju****@koivi.com> wrote in message
news:U_******************************@onvoy.com...

Nel wrote:

I am trying to find a php solution to encoding an md5 hex string into
another base.

Using ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwx yz1234567890 as a
characters for a base 62
i.e.
A = 1
a = 27
0 = 62
00 = 3844
000 = 238328

This should make the hex string much shorter.

1. Does anyone understand what I'm trying to do here?
2. Has this wheel already been invented?
3. Any ideas about the most efficient way to encode and decode this kind
of
thing?

http://www.pgregg.com/projects/php/b...conversion.php

However, the order that is used on that for the characters are:

0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmn opqrstuvwxyz

(which seems more logical than having the digits at the end)

--
Justin Koivisto, ZCE - ju****@koivi.com
http://koivi.com

Perfect Justin ;)
Thanks

Nel

[Tim Roberts]

"Nel" <ne***@ne14.co.NOSPAMuk> wrote:

In this cas I am trying to pass a shorter URL and moving from base 16 to 62
knocks off about 10 chars from the URL. Not as many as I'd hoped for, but
it's a definate improvement.

You don't have to "hope", you can compute this. The number of bits per
digit is the logarithm in base 2 of the number base. Base 16 packs 4 bits
per digit. Base 62 packs 5.9 bits per digit. The string will be about 1/3
shorter.
--
- Tim Roberts, ti**@probo.com
Providenza & Boekelheide, Inc.