salesforce-recaseify

Recover IDs that may have had their case changed (all upper or all lower).

The last three letters of a Salesforce ID are a compacted way of remembering the original case of the previous 15 characters. Each letter represents a "mask" that covers 5 of the 15 characters. The mask is simple: if there's a 1 in that spot, then uppercase, otherwise lowercase.

This old page has a really nice diagram, but keep in mind, it's showing you how to go from 15 to 18, which is the opposite of what I'm doing here. But, the chart with A=00000 etc is very useful.

Here's a working example

1. For each of the last 3 characters of the 18 digit ID:
2. Calculate the distance from the letter A. For numbers, you can do 26 + theNumber. A=0, B=1, C=2, etc.
3. Get a binary representation of that same number. Hopefully you already know this one. A=00000, B=00001, C=00010, etc.
4. Reverse that binary. I have no idea why this is done, I would love to know.
5. Put those three masks together in the order you saw them.
6. Smash your big mask together with the first 15 characters of your ID using the following:
7. If 1, uppercase, if 0, lowercase.

Example

My input ID is A1NG0000006HIZRMAI.

M = 12 = 01100 =(reverse) 00110
A = 0 = 00000
I = 8 = 00100

mask = 00110 00000 00100
  id = A1NG0 00000 6HIZR MA5
       a1NG0 00000 6hIzr MA5 =>

  15:   a1NG0000006hIzr
  18:   a1NG0000006hIzrMA5