[mapguide-users] Base64 decoding process

[Jim O'Leary]

I was a bit off. Thanks Traian!


Traian Stanev wrote:
> 
> First of all, w = 48 = 110000, not 100000.
> 
> Then "piw" => 101001 100010 110000 => 1010 0110 0010 1100 => A6 2C => 2C
> A6 (little endian byte order) => 11430.
> 
> 
> Traian
> 
> 
> -----Original Message-----
> From: mapguide-users-bounces at lists.osgeo.org
> [mailto:mapguide-users-bounces at lists.osgeo.org] On Behalf Of Jim O'Leary
> Sent: Friday, December 28, 2007 5:56 PM
> To: mapguide-users at lists.osgeo.org
> Subject: [mapguide-users] Base64 decoding process
> 
> 
> I'm trying to figure out the Base64 decoding process that MapGuide uses
> to store the user's selections on the map.
> 
> When I select a given parcel in Sheboygan, the Properties pane tells me
> 
> FeatId = 11430
> 
> When I capture the selection XML for this feature, it gives me the
> the ID tag as
> 
> <ID>piwAAA==</ID>
> 
> I break down this Base64-encoded string as follows, using a Base64
> translation table:
> 
> p = 41 = 101001
> i = 34 = 100010
> w = 48 = 100000
> 
> Putting those three 6 bit binary numbers in one line yields
> 
> 101001 100010 100000
> 
> I am assuming that the A characters represent 0, or no valid bits.
> 
> Recombining these three 6 bit binary numbers into 8 bit numbers yields
> 
> 10100110 00101000 00
> 
> Turning these binary numbers in decimal yields
> 
> 10100111 = 166
> 00101000 = 40
> 
> Here I am lost. How does 166 and 40 equate to 11430, which is the FeatId
> that this Base64-encoded string evaluates to?
> 
> Thanks
> --
> View this message in context:
> http://www.nabble.com/Base64-decoding-process-tp14532589s16610p14532589.html
> Sent from the MapGuide Users mailing list archive at Nabble.com.
> 
> _______________________________________________
> mapguide-users mailing list
> mapguide-users at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/mapguide-users
> _______________________________________________
> mapguide-users mailing list
> mapguide-users at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/mapguide-users
> 
> 

-- 
View this message in context: http://www.nabble.com/Base64-decoding-process-tp14532589s16610p14537520.html
Sent from the MapGuide Users mailing list archive at Nabble.com.