Alphanumeric key incrementing routine

*

* Creates next string key from the passed one using specified set of characters

*

* Parameters

*    1 - Current Key

*    2 - Defines the list of allowed characters

*        BASEnn - See DO CASE in the body of the program

*        CUSTOM - the list of character as parameter 3

*    3 - List of characters

*

* Returns     Next key

*

*   Note 1  Routine ignores (doesn't change) positions with the characters not in the specified list

*   Note 2  When max possible value is reached, the next return value will be the min possible value

*

 

FUNCTION NextKey

LPARAMETERS tcOldVal, tcOpt, tcCharList

LOCAL lcNewVal, i, lcDigits, lcLetters, lnCharListLen, lcOldChar, lcNewChar, lcCharList, lnPos, lcOpt

LOCAL lnNextPos

 

lcOpt = IIF(EMPTY(tcOpt), "BASE10", UPPER(tcOpt))

* Get the list of appropriate characters

lcCharList = NextKeyFillCharList(lcOpt, tcCharList)

lnCharListLen = LEN(lcCharList)

lcNewVal = tcOldVal

 

* Scan string from the right to the left

FOR i = LEN(lcNewVal) TO 1 STEP -1

 

    lcOldChar = SUBSTR(tcOldVal, i, 1)

    * Is the current charater in the list?

    lnPos = AT(lcOldChar, lcCharList)

    IF lnPos = 0

        * Not in the list, keep it

        LOOP

    ENDIF

 

    * Get the next character position

    lnNextPos = (lnPos % lnCharListLen) + 1

    * Get the next character 

    lcNewChar = SUBSTR(lcCharList,lnNextPos,1)

    * Stuff it back in the string

    lcNewVal = STUFF(lcNewVal, i, 1, lcNewChar)

    * Check if we have to carry over to the next position

    IF lnNextPos > 1

        * We are done

        EXIT

    ENDIF

 

ENDFOR

 

RETURN lcNewVal

*------------------------------------------------------------

* Fill the list of characters based on character set requested

FUNCTION NextKeyFillCharList

LPARAMETERS tcCharSet, tcCharList

LOCAL lcCharList, lcDigits, lcLetters

* Fill string 'lcCharList' with appropriate characters

lcDigits = "0123456789"

lcLetters = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"

 

DO CASE

CASE tcCharSet = "CUSTOM"  

    lcCharList = tcCharList

CASE tcCharSet == "BASE10" 

    * Just Digits

    lcCharList = lcDigits

CASE tcCharSet == "BASE16L" 

    * Hexadecimal in lower case

    lcCharList = lcDigits + "abcdef"

CASE tcCharSet == "BASE16" 

    * Hexadecimal in upper case

    lcCharList = lcDigits + "ABCDEF"

CASE tcCharSet == "BASE26L" 

    * Lower case letters

    lcCharList = LOWER(lcLetters)

CASE tcCharSet == "BASE26" 

    * Upper case letters

    lcCharList = lcLetters

CASE tcCharSet == "BASE36L" 

    * Digits + Lower case letters

    lcCharList = lcDigits + LOWER(lcLetters)

CASE tcCharSet == "BASE36" 

    * Digits + Upper case letters

    lcCharList = lcDigits + lcLetters

CASE tcCharSet == "BASE52" 

    * All letters

    lcCharList = lcLetters + LOWER(lcLetters)

CASE tcCharSet == "BASE62" 

    * Digits + All letters

    lcCharList = lcDigits + lcLetters + LOWER(lcLetters)

OTHERWISE

    * The same as BASE10

    lcCharList = lcDigits

ENDCASE

RETURN lcCharList