CND-DET routines 6/8

 BBS: Inland Empire Archive
Date: 03-25-93 (15:36)             Number: 291
From: DIRK THEURER                 Refer#: NONE
  To: ALL                           Recvd: NO  
Subj: CND-DET routines 6/8           Conf: (2) Quik_Bas

'
' CND-DET routines (part 6)
'

            IF NoOfGottenChars < DataLength THEN
              GetCNDNumber% = 7
              FOR i = 1 TO 500: NEXT i
              FOSSILFlush
              EXIT FUNCTION
              '
              ' fatal error - number of characters received did not match
              '               indicated number of characters
              '
            ELSE
              Timeout = 0 ' might not need to set this one
              DO
                i$ = GetChar$
                IF i$ <> "" THEN
                  Timeout = 0
                  EXIT DO
                END IF
                Timeout = Timeout + 1
              LOOP WHILE Timeout < 500

              IF Timeout THEN
                '
                ' fatal error - timed out getting CRC value
                '
                GetCNDNumber% = 8
                FOR i = 1 TO 500: NEXT i
                FOSSILFlush
                EXIT FUNCTION
              END IF

              '
              ' received all CND data for current call
              '
              ' format into CND data type
              '
              CND.CNDCRC = ASC(i$)
'
' - The following 'snippet' is from Quinn Tyler Jackson. It is a POSSIBLE
'   method of calculating the CRC for the CND data packet. (It makes sense
'   to me too, Quinn. :-) )
' - I've modified Quinn's original snippet to use my own variable
'   names ("CNDData" which is DIMmed as variable length string and
'   I DIMmed TempCRCSum as LONG for the temporary sum).
' - This snippet has NOT BEEN TESTED! (I _hope_ it works. %-} )
'
' Verbal description given to me:
'   "The CRC is the twos compliment of the modulo 256 sum of the other
'   words in the data message."
'
' Quinn's interpretation (most likely accurate or VERY close):
'   "Add up the ASCII values of the bytes of the data, MOD 256 the
'   result, and NOT that."
'
' TempCRCSum = 0
' FOR i% = LEN(CNDData)
'   TempCRCSum = TempCRCSum + ASC(MID$(CNDData, i%, 1))
' NEXT i%
' TempCRCSum = NOT(TempCRCSum MOD 256)
'
' TempCRCSum can be converted to an integer and compared directly to
' CND.CNDCRC. If they match, then all the credit goes to Quinn! :-)
'
'
' Continues...
'



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 * Origin: RAVE * Burnaby, BC (1:153/810)