RE: Incrementing Character Fields

[david.kahn@xxxxxxxxxx]

"Brendan Bispham" <midrangel@black-and-blue.com> wrote:

>I think base 32 is the best I have come up with, as 26
>alphabetic characters and 10 digits mean that you can
>cover 32 different characters? In theory - fine, but in
>practise - I'm lost.

Brendan,

You can convert any 10 digit base 10 number to a valid object name using a
maximum of 7 significant characters. An object name has to begin with A-Z,
$, # or @. This gives you 29 possibilities for character 1. Subsequent
characters can be any of these plus 0-9, _ and . giving you 41
possibilities for each character in positions 2 - 10. So let A through Z
represent 0 through 26, $ represent 27, # represent 28, @ represent 29, 0
through 9 represent 30 through 39, _ represent 40 and . represent 41.

As an object name is (a maximum of) 10 characters we can represent any
number that will convert to base 41 as long as the leading digit does not
go above 29. This gives us a highest number of (30(41**9))-1. So a decimal
value of 9,999,999,999 would give 2-4-12-35-26-40-0 in base 41. This
translates to "BDL5Z_0". Putting in the leading "zeroes" we get an object
name of AAABDL5Z_0.

Incidentally, Leif's solution of using a 4 byte binary representation not
only fails to produce valid object names but can't represent numbers higher
than 4,294,967,295. Decimal 9,999,999,999 requires 9 digits in hexadecimal.

Dave Kahn, ABB Steward Ltd.
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