Simple DLL function question--Data type conversion

[Todd Wasson]

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:

 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?

#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



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[Phil Tippit]

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

'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.

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[Todd Wasson]

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.

FUNCTION TestFloattoInt (x AS SINGLE) EXPORT AS LONG   
TestFloattoInt = INT(x)
END FUNCTION

On the other hand, if I do this:

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


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[Michael Mattias]

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

[Todd Wasson]

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




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[This message has been edited by Todd Wasson (edited October 01, 2000).]

[Joseph W Murphy]

I always use FUNCTION = a

not TestFloattoInt = a

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

Joe Murphy

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[Michael Mattias]

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

FUNCTION TestFloatToInt (X AS SINGLE) EXPORT AS LONG
 dim A as LONG
 A = INT(X)
 FUNCTION = A
END FUNCTION

In the using program:

DECLARE FUNCTION TestFloatToInt ALIAS "whateever" LIB "whatever" (X AS SINGLE)AS LONG

MCM

[Todd Wasson]

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


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