Unsigned Long in LotusScript? How to turn off overflow detection on long? - lotus-domino

Question

Context: I'm implementing a SHA-256 hashing to Lotusscript.
Hashing works on 32bits. LotusScript has only signed Long. When result are bigger than 2,147,483,647 we get overflow.
QUESTION: how to turn off overflow detection on Long?
If impossible, is there a working around? I was thinking at what Richard Schwartz has wroten in http://femkegoedhart.com/2012/02/05/lotusscript-timedifference-long-data-type-grrr/, how could I use NotesDateTime to help work around my problem?
Should I "forget this" but then how to hash in Lotusscript (ok I can think to use LS2J and use a standard java SHA 256)
Of course if you've got a LS implementation of SHA-256 it's also a good response :-)
Thank for your help, I feel a bit lost...
part of the code:
Dim T1 As Long
Dim h2 As Long
Dim Sigma1 As Long
Dim K_t As Long
h2=1541459225
Sigma1 = 21895337
K_t=1116352408
MsgBox String(32-Len(Bin$(h2)),"0")+Bin$(h2)+" " +"Bin$(h2)"+Chr$(13)+ _
String(32-Len(Bin$(Sigma1)),"0")+Bin$(Sigma1)+" " +"Bin$(Sigma1)"+Chr$(13)+ _
String(32-Len(Bin$(K_t)),"0")+Bin$(K_t)+" " +"Bin$(K_t)",,"DEBUG"
T1 = h2 + Sigma1
MsgBox "T1 = " & T1 & " binary representation:" + String(32-Len(Bin$(T1)),"0")+ Bin$(T1)
T1 = h2 + Sigma1 + K_t ' **this line cause overflow**
MsgBox "T1 = " & T1 & " binary representation:" + String(32-Len(Bin$(T1)),"0")+ Bin$(T1)
NB I based my implementation on the work of Chris Veness: http://www.movable-type.co.uk/scripts/sha256.html

Answer 1

You can't turn off the overflow detection on a LONG in LotusScript. Also your sample above the BIN() function will attempt to convert to a long, so that rules out the use of DOUBLE.
The dateTime, object while it treats the number as LONG unsigned, it is probably a bit of hack to use.
Personally I'd recommend creating a small C DLL which does the work and passes it back as a string.
Alternatively create your code in Java as it doesn't have the same limitations that LS has.

Answer 2

As answered Simon O'Doherty, there is no way to turn off the overflow detection on a LONG in LotusScript.
I abandon the LS way... for now (maybe will I do an other attempt one day. Frantisek Kossuth, your right I need to take from the begining the variable limits... that the tricky part here)
Thanks for your help!
*Simon: I prefere to do LS2J than DLL!
I join the very simple class in java:
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
public class SHA256 {
public String sha256(String message) throws NoSuchAlgorithmException {
MessageDigest md1 = MessageDigest.getInstance("SHA-256");
String resu = A9Utility.bytesToHex(md1.digest(message.getBytes()));
System.out.println("here SHA256: resu ="+resu);
return resu;
}
}
for A9Utility.bytesToHex, I used the https://code.google.com/p/a9cipher/source/browse/src/cosc385final/A9Utility.java
so my call in LS is now:
UseLSX "*javacon"
Use "SHA256"
[...]
Dim mySession As JavaSession
Dim myClass As JavaClass
Dim myObject As JavaObject
Set mySession = New JavaSession()
Set myClass = mySession.GetClass("SHA256")
Set myObject = myClass.CreateObject()
Dim resu As String
resu = myObject.sha256(message)

Answer 3

You can use an COM component in LS and call it. There are a number of well developed and proven SHA-256 (and other hashes) COM components out there.
If you follow this route, you will need to 'handle' the return value as a string or some other binary encoding (base64?) as the result may (or may not) require unsigned longs to hold a raw value. Most of these components provide methods for doing this.
Bit 'old fashioned' for todays apps, but hey, you're using LS, so maybe that is not a concern.