C to PBWin Conversion Problem

[Grant Teakell]

I must admit my C skills are not quite as sharp as they used to
be. I am creating a PowerBasic DLL that is to be called by a
toolkit written in C. Of course, the development information is
in C as well. Here is what I'm trying to convert:

//This is the structure that will be used.
typedef struct
{
char *module_name;
char *func_name;
char *c_func_name;
}CAPIINFO;

//This is an example of data being filled in the structure
CAPIINFO c_api_info[] = {
{"WSOCK32.DLL", "socket(INT, INT, INT)", "cSocket"},
{NULL,NULL,NULL} };

This is the skeleton of the function that I have to export,
and that the 'C' library is trying to call. I think it is
supposed to return a pointer to the structure.

CAPIINFO *GetCAPIINFO()
{ return &c_api_info[0]; }

I've tried creating a structure, and passing the pointer as the
return value. That along with many other things. The toolkit
keeps telling me that invalid data is being returned. I guess
I would like to know exactly what PB code should be generated
that would be equivalent to the above C. Any help would be
greatly appreciated.


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[Kev Peel]

Grant, what do you have so far?, I have translated the code like this (Assuming it is a DLL)...

#Compile Dll
#Dim All
#Register All
 
%USEMACROS = 1
#Include "WIN32API.INC"
 
Type CAPIINFO
     module_name As Asciiz Ptr
     func_name As Asciiz Ptr
     c_func_name As Asciiz Ptr
End Type
 
Global c_api_info() As CAPIINFO      ' Array of UDTs
Global gsModule As String            ' Dynamic string members
Global gsFunc As String              '
Global gsCFunc As String             '
 
Function LibMain(ByVal hInstance As Dword, ByVal lReason As Long, ByVal lReserved As Long) As Long
 
  If lReason = %DLL_PROCESS_ATTACH Then
 
     ' Only 1 element initially specified, second element is blank...
     ReDim c_api_info(0 To 1) As Global CAPIINFO
 
     gsModule = "WSOCK32.DLL"
     gsFunc = "socket(INT, INT, INT)"
     gsCFunc = "cSocket"
     c_api_info(0).module_name = StrPtr(gsModule)
     c_api_info(0).func_name = StrPtr(gsFunc)
     c_api_info(0).c_func_name = StrPtr(gsCFunc)
 
  End If
 
End Function
 
Function GetCAPIINFO Alias "GetCAPIINFO" Export As Dword
  Function = VarPtr(c_api_info(0))
End Function

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email
http://www.kgpsoftware.com

[Charles Dietz]

... or maybe something like this:

TYPE CAPIINFO
  module_name AS STRING PTR
  func_name   AS STRING PTR
  c_func_name AS STRING PTR
END TYPE 

GLOBAL c_api_info() AS CAPIINFO
DECLARE FUNCTION getCAPIINFO() AS DWORD

FUNCTION PBMAIN
   LOCAL pType AS CAPIINFO PTR
   pType = getCAPIINFO
   MSGBOX @pType[0][email protected]_name
END FUNCTION   

FUNCTION getCAPIINFO() AS DWORD
   LOCAL s1 AS STRING, s2 AS STRING, s3 AS STRING
   DIM c_api_info(1) AS CAPIINFO
   s1 = "WSOCK32.DLL"
   s2 = "socket(INT, INT, INT)"
   s3 = "cSocket"
   c_api_info(0).module_name = STRPTR(s1)
   c_api_info(0).func_name   = STRPTR(s2)
   c_api_info(0).c_func_name = STRPTR(s3)
   c_api_info(1).module_name = 0
   c_api_info(1).func_name   = 0
   c_api_info(1).c_func_name = 0
   FUNCTION = VARPTR(c_api_info())
END FUNCTION

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[Cecil L. Williams]

I would stick with ASCIIZ for shoving strings to/from
C/C++ programs in liu of the Basic "STRING".

Grant,

The function is returning an address to the first element of
the C structure!!!!

Cheers,
Cecil

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[This message has been edited by Cecil L. Williams (edited August 18, 2004).]

[Charles Dietz]

My code in the post above is wrong. The 3 strings used in the getCAPIINFO() function
must be global. Also, as Cecil commented, the type declarations should be ASCIIZ PTRs.

TYPE CAPIINFO
  module_name AS ASCIIZ PTR
  func_name   AS ASCIIZ PTR
  c_func_name AS ASCIIZ PTR
END TYPE 

GLOBAL c_api_info() AS CAPIINFO
GLOBAL module_name AS STRING, func_name AS STRING, c_func_name AS STRING
DECLARE FUNCTION getCAPIINFO() AS DWORD

FUNCTION PBMAIN
   LOCAL pType AS CAPIINFO PTR, ps AS STRING PTR, i AS LONG, s AS STRING
   pType = getCAPIINFO
   FOR i = 0 TO 1
      IF (@pType[i].module_name) THEN MSGBOX @pType[i][email protected]_name ELSE MSGBOX "Null pointer" 
   NEXT i
END FUNCTION   

FUNCTION getCAPIINFO() AS DWORD
   DIM c_api_info(1) AS CAPIINFO
   module_name = "WSOCK32.DLL"
   func_name   = "socket(INT, INT, INT)"
   c_func_name = "cSocket"
   c_api_info(0).module_name = STRPTR(module_name)
   c_api_info(0).func_name   = STRPTR(func_name)
   c_api_info(0).c_func_name = STRPTR(c_func_name)
   c_api_info(1).module_name = 0
   c_api_info(1).func_name   = 0
   c_api_info(1).c_func_name = 0
   FUNCTION = VARPTR(c_api_info(0))
END FUNCTION

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[Grant Teakell]

Many thanks to all of you who responded. It was extremely
helpful.

The only modifications I had to make to the code snippets were
the variables pointed to by the ASCIIZ PTR had to be of type
ASCIIZ not string. The code works very well now.

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