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DLL returning an integer
Posted: Tue Apr 09, 2024 1:51 pm
by charvista
Hello again,
I am studying the DLL concept and I am doing some try-and-error's.
Returning a value with String, it works fine.
But apparently not with integers.... (see MyFourthFunction())
Is string the only way to return something from a DLL function call ?
Code: Select all
; My first DLL's => to be saved as "PureBasic.dll"
ProcedureDLL MyFirstFunction()
MessageRequester("Hello","This is a PureBasic DLL !",0)
EndProcedure
ProcedureDLL MySecondFunction()
MessageRequester("Hello","This is my second function, working fine together",0)
EndProcedure
ProcedureDLL.s MyThirdFunction()
ProcedureReturn "returned-some-string"
EndProcedure
ProcedureDLL.i MyFourthFunction()
ProcedureReturn 103
EndProcedure
Code: Select all
EnableExplicit
Define.s string
Define.i integ
If OpenLibrary(0, "PureBasic.dll")
CallFunction(0, "MyFunction")
CallFunction(0, "MySecondFunction")
string.s=PeekS(CallFunction(0,"MyThirdFunction"))
MessageRequester("Returned value:",string)
integ.i=PeekI(CallFunction(0,"MyFourthFunction"))
MessageRequester("Returned value:",Str(integ))
CloseLibrary(0)
EndIf
Re: DLL returning an integer
Posted: Tue Apr 09, 2024 2:09 pm
by infratec
Read the help for CallFunction()
Code: Select all
integ.i=CallFunction(0,"MyFourthFunction")
But you should use Import or Prototypes and not CallFunction.
Re: DLL returning an integer
Posted: Tue Apr 09, 2024 3:32 pm
by charvista
Ok, no PeekI() needed, thanks.
Ok, use of Import or Prototypes are recommended instead of CallFunction.
So, Prototypes handles .dll files so I think it is the same way to create the .dll (with Compiler set to Executable Format: Shared DLL)
But Import handles .lib files instead of .dll. How do we create a .lib file? By writing the name of the lib in the field "Library Subsystem:"?
Re: DLL returning an integer
Posted: Tue Apr 09, 2024 3:56 pm
by AZJIO
It happened
Code: Select all
EnableExplicit
; It's like the contents of structures
Prototype.i MyThirdFunction(string.p-unicode)
Prototype.i MyFourthFunction(*i.Integer)
Define String$
Define num
; It's like declaring structures
Define My3Function.MyThirdFunction
Define My4Function.MyFourthFunction
If OpenLibrary(0, "PureBasic.dll")
My3Function = GetFunction(0, "MyThirdFunction") ; gets a pointer to a function
My4Function = GetFunction(0, "MyFourthFunction")
Debug My4Function(@num) ; Call
MessageRequester("", Str(num))
String$ = Space(256)
Debug My3Function(String$) ; a pointer to a string of size 256 is passed
MessageRequester("", String$)
CloseLibrary(0)
EndIf
DLL
Code: Select all
ProcedureDLL MyThirdFunction(*s.String)
PokeS(*s, "returned-some-string")
ProcedureReturn 32
EndProcedure
ProcedureDLL MyFourthFunction(*i.Integer)
; PokeI(@*i\i, 104)
; PokeI(*i, 104)
*i\i = 104
ProcedureReturn 103
EndProcedure
Re: DLL returning an integer
Posted: Tue Apr 09, 2024 4:28 pm
by charvista
Nice example, thank you AZJIO.
Through your code, I have seen that Debug and MessageRequester give different return values, so the string is returned ByRef.
For now, a real "Chinese puzzle", but I understand perfectly what is happening.
I only need to get accustomed....
Edit: I saw your edit - better example, also showing how to return 103/104. Super!
Re: DLL returning an integer
Posted: Wed Apr 10, 2024 8:52 am
by AZJIO
Building a DLL
When using CallFunction() (or one of its similar CallXXX functions) on a DLL function you will get a pointer on the return string, which you could read with PeekS().
Using a pointer to the structure *s.String is not relevant, replace it with a pointer *s. I did some tests and I couldn't use *s\s.
In the reference file in the DLL description, it is useful to make a reference to Prototype, and in the Prototype description make a reference to "Building a DLL".
Re: DLL returning an integer
Posted: Wed Apr 10, 2024 9:48 am
by mk-soft
Normally you pass the buffer size for the string
Code: Select all
ProcedureDLL MyThirdFunction(*sResult, cntChar)
Protected r1.s, len
r1 = "returned-some-string"
len = Len(r1)
If *sResult
If len > cntChar
len = cntChar
EndIf
PokeS(*sResult, "returned-some-string", len)
EndIf
ProcedureReturn len
EndProcedure
; Main
cnt = MyThirdFunction(0, 0)
Debug cnt
Result.s = Space(cnt)
cnt = MyThirdFunction(@Result, cnt)
Debug Result
Re: DLL returning an integer
Posted: Wed Apr 10, 2024 6:02 pm
by charvista
Thanks mk-soft for the trick.
Question for having the confirmation:
If a ProcedureDLL is used in the local program (thus not as an extern DLL file), is it working 100% like a standard Procedure?
Code: Select all
ProcedureDLL.s Software()
ProcedureReturn "PBM-Software"
EndProcedure
v1.s=Software()
Debug v1
Re: DLL returning an integer
Posted: Wed Apr 10, 2024 10:42 pm
by mk-soft
Yes