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  • Simple DLL function question--Data type conversion

    Hello,

    Suppose I want to call a DLL function that receives a SINGLE and returns a LONG.
    The only way I can get this to work at this point is to DIM a AS LONG in the DLL,
    and then EXPORT it AS SINGLE to a LONG in the main EXE. I know this is not the way
    to do this. In the DLL, how can I:
    Code:
     FUNCTION TestFloattoInt (x AS SINGLE) EXPORT AS **LONG**
    instead of EXPORT AS SINGLE? EXPORT AS LONG always returns a 0 in PBMAIN's MsgBox.
    What is the simplest way to do this?

    Code:
    #COMPILE EXE
    DEFSNG B-Z
    
    DECLARE FUNCTION TestFloattoInt LIB "DLLTEST2.DLL" ALIAS "TESTFLOATTOINT" (x AS SINGLE)' EXPORT AS LONG
    
    FUNCTION PBMAIN() AS LONG
    DIM a AS LONG
    x=32.155
    a=TestFloattoInt(x)
    MSGBOX STR$(a)
    END FUNCTION
    DLLTEST2.DLL:

    [code]

    #COMPILE DLL

    FUNCTION TestFloattoInt (x AS SINGLE) EXPORT AS SINGLE
    DIM a AS LONG
    MSGBOX "PowerBasic DLL Message: Input value is " + STR$(x)
    a=x
    TestFloattoInt = a
    END FUNCTION



    ------------------
    Todd Wasson
    http://PerformanceSimulations.Com
    PowerBasic Racing Simulator (October 2007 clip - 15.1MB wmv file) http:http://www.performancesimulations.co...m-GenIV-12.wmv

  • #2
    Todd,

    A long variable doesn't have decimal places, therefor
    you are getting a zero value, you are not using INT to
    get the value. Plus TestFloattoInt needs to be LONG Not
    Single.

    Phil

    Code:
    'your code
    FUNCTION TestFloattoInt (x AS SINGLE) EXPORT AS SINGLE
       DIM a AS LONG
       MSGBOX "PowerBasic DLL Message: Input value is " + STR$(x)
        a=x  
       TestFloattoInt = a
    END FUNCTION
    'new code
    
    FUNCTION TestFloattoInt (x AS SINGLE) EXPORT AS LONG
       TestFloattoInt = INT(x)
    END FUNCTION
    
    ' but why not just do
    a&=INT(x!) in your main program.
    ------------------
    E-Mail:
    pt AT pursuersoft DOT com

    Comment


    • #3
      Phil,

      This DLL function also returns 0. I need to send a number like 17.3
      defined as a SINGLE, and return 17 to a LONG variable.

      Code:
      FUNCTION TestFloattoInt (x AS SINGLE) EXPORT AS LONG   
      TestFloattoInt = INT(x)
      END FUNCTION
      On the other hand, if I do this:

      Code:
      FUNCTION TestFloattoInt (x AS SINGLE) EXPORT AS SINGLE   
      TestFloattoInt = INT(x)
      END FUNCTION
      the code returns the correct number, but isn't it just a SINGLE with
      the .3 cut off? Or is it truly a LONG now?

      The reason for this is to create a DLL that a Pascal programmer will use.
      We need to make sure our data types mix correctly and compatability won't be
      a problem.

      Thanks


      ------------------
      Todd Wasson
      http://PerformanceSimulations.Com
      PowerBasic Racing Simulator (October 2007 clip - 15.1MB wmv file) http:http://www.performancesimulations.co...m-GenIV-12.wmv

      Comment


      • #4
        Might be a bit easier to just use the Cxxx, INT, FIX, and CEIL functions and eschew the DLL.

        DIM A AS LONG, B AS SINGLE
        A = CLNG(B)
        A = CEIL(B)
        A = INT(B)
        A = FIX(B)

        MCM


        Michael Mattias
        Tal Systems Inc. (retired)
        Racine WI USA
        [email protected]
        http://www.talsystems.com

        Comment


        • #5
          Thank you for your reply, Michael. The DLL will be necessary for my
          purposes. A Pascal or other language program will be calling my DLL.
          One basic thing I need to do here is pass and convert parameters the way
          the customer wants. The final purpose of the DLL will not be to convert
          SINGLEs to LONGs, but it will be necessary to do at some point. Unfortunately, I've
          never created a DLL, have always used Subs and Globals instead of Function
          calls, and have never had a need to do this type of thing before. Can anyone
          answer my original question?

          Thanks for your assistance,
          Todd Wasson




          ------------------


          [This message has been edited by Todd Wasson (edited October 01, 2000).]
          Todd Wasson
          http://PerformanceSimulations.Com
          PowerBasic Racing Simulator (October 2007 clip - 15.1MB wmv file) http:http://www.performancesimulations.co...m-GenIV-12.wmv

          Comment


          • #6
            I always use FUNCTION = a

            not TestFloattoInt = a

            to set the value of a function in PowerBasic. This is different from VB

            Joe Murphy

            ------------------

            Comment


            • #7
              On your first effort you had testfloattoint returing a single because your DECLARE did not specify an AS [type] for the return, so it was returing a SINGLE because a DEFSNG was in effect.

              in DLL
              Code:
              FUNCTION TestFloatToInt (X AS SINGLE) EXPORT AS LONG
               dim A as LONG
               A = INT(X)
               FUNCTION = A
              END FUNCTION
              In the using program:
              Code:
              DECLARE FUNCTION TestFloatToInt ALIAS "whateever" LIB "whatever" (X AS SINGLE)AS LONG
              MCM


              Michael Mattias
              Tal Systems Inc. (retired)
              Racine WI USA
              [email protected]
              http://www.talsystems.com

              Comment


              • #8
                Excellent, Michael, thank you very much I never would have noticed the
                misplaced (totally absent) AS LONG. Now I understand that this defines the type
                of the return value. Exactly what I needed to know. Thanks again!


                Joseph, I just noticed how "FUNCTION = x" could be used instead of F
                FunctionName = x. That will speed things up a little on my end. Thank you.

                Todd Wasson
                Performance Simulations
                Drag Racing and Top Speed Prediction
                Software http://PerformanceSimulations.Com


                ------------------
                Todd Wasson
                http://PerformanceSimulations.Com
                PowerBasic Racing Simulator (October 2007 clip - 15.1MB wmv file) http:http://www.performancesimulations.co...m-GenIV-12.wmv

                Comment

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