Subject; DLL function calls callback function in callee (parent)

like
// MyDLL a Dll written in D
export bool dfunc(char[] s,extern (Windows)char[] function() cb)
{
   while ( char[] t = tokenize(s)) cb(t);
   return true;
}

I have to use some 4GL code to explain:


FUNCTION GetResult(StringToAnanlyse is string = "Hello from 4GL")
// Call dfunc , pass StringToAnalyse, and address of CallBack Function
  IF API("MyDLL", "dfunc", StringToAnanlyse, &ReceiveResult)
  END

// The CallBack Function
PRIVATE FUNCTION ReceiveResult(token is string)
  WHILE token <> ""
    Trace(token)
    newString += (token + ",") // defined elsewhere
  END
  RESULT newString
// Output
Hello
from
4GL
newString == "Hello,from,4GL,"
---------------------------------------------------
I ask here instead of D.lean because I mean the official "DLLs in D" documents should explain this functionality too.

Oh, the question :)

export bool dfunc(char[] s, extern (Windows) char[] function() cb)

I think at least my intention is clear , so I hope somebody is willing to  show me how to implement such a DLL function.

Many thanks in advance, Bjoern

"Bjoern" <nanali@nospam-wanadoo.fr> wrote in message news:fmiien$14cf$1@digitalmars.com...

>
> export bool dfunc(char[] s, extern (Windows) char[] function() cb)
>
> I think at least my intention is clear , so I hope somebody is willing to show me how to implement such a DLL function.
>

I'm guessing that 4GL expects DLL functions to use either C or Windows calling conventions.  Secondly AFAIK there's no way to indicate the calling convention of a function pointer inline; it has to be done as an alias/typedef and then used.

alias extern(Windows) char[] function() MyFuncType;

// Don't know if it's extern(C) or extern(Windows)
extern(Windows) export bool dfunc(char[] s, MyFuncType cb)
{
    ...
}

Jarrett Billingsley schrieb:
> I'm guessing that 4GL expects DLL functions to use either C or Windows calling conventions.  Secondly AFAIK there's no way to indicate the calling convention of a function pointer inline; it has to be done as an alias/typedef and then used.
> 
> alias extern(Windows) char[] function() MyFuncType;
> 
> // Don't know if it's extern(C) or extern(Windows)
> extern(Windows) export bool dfunc(char[] s, MyFuncType cb)
> {
>     ...
> } 

Thanks Jarret!,
yes the 4GL expects Windows calling convention. (and uses just the .DLL, no .LIB)
Using an alias instead of inlining is okay, not to say smarter!

In reality I have to use :

alias extern(Windows) void function(char[] token, bool eof) MyFuncType;

extern(Windows) export bool dfunc(char[] s, MyFuncType cb)
{
  // do something and call cb, (exists in a secondary thread)
 cb(token, false)
}
I hope this is correct ?

However, thanks to your help I should be able to solve the problem(s) :) by myself. Bjoern

"Bjoern" <nanali@nospam-wanadoo.fr> wrote in message news:fmja4s$11rq$1@digitalmars.com...

> alias extern(Windows) void function(char[] token, bool eof) MyFuncType;
>
> extern(Windows) export bool dfunc(char[] s, MyFuncType cb)
> {
>   // do something and call cb, (exists in a secondary thread)
>  cb(token, false)
> }
> I hope this is correct ?

That looks perfectly fine.  Only thing I wonder is, does 4GL support D-style char[]?  Or will it be passing/expecting C-style zero-terminated char*?

Jarrett Billingsley schrieb:
> "Bjoern" <nanali@nospam-wanadoo.fr> wrote in message news:fmja4s$11rq$1@digitalmars.com...
> 
>> alias extern(Windows) void function(char[] token, bool eof) MyFuncType;
>>
>> extern(Windows) export bool dfunc(char[] s, MyFuncType cb)
>> {
>>   // do something and call cb, (exists in a secondary thread)
>>  cb(token, false)
>> }
>> I hope this is correct ?
> 
> That looks perfectly fine.  Only thing I wonder is, does 4GL support D-style char[]?  Or will it be passing/expecting C-style zero-terminated char*? 
> 
> 

Thanks for confirming Jarret,

Yes it supports D style char with a little effort :

MyString is string  // dynamic ANSI string
MyUTF8String = StringToUTF8(MyString) // toUTF16 et vice versa

Heh, I still have to make  tests :)

But you are right, most probabely it is more economic to pass the string
as pointer to C string.
( because this string could contain the contents of an complete D source file ;) )
Due to the fact that my tool is garbage collected too, passing a dynamic string's address is not secure because this address may change. A dynamic string can contain 2 GB. here (in theory ...), so using standard C string is most probabely what I have to choose. Let's see.

Bjoern
OT , in case that you are courious what 4GL I am using , here a link. You can download full working express copy . version 10, ( most current is 12) -- A 4GL + matrix - financial - statistic - array, dyn array, asso. array, runtime compiler,threads, outstanding GUI designer .... have fun.
http://www.windev.com/windev/quick-overview-WD.html

// HERE I /most probabely/ can use char[]
alias extern(Windows) void function(char[] token, bool eof) MyFuncType;
// Here of course NOT !
extern(Windows) export bool dfunc(char* s, MyFuncType cb)
{
  char[] tok;
  // do something and call cb, (exists in a secondary thread)
  cb(tok, false);
}


Sorry. Next time, I'll think twice. Bjoern