Passing Strings by Reference with DllCall using Binary Buffers

Keywords: 	 Passing Strings by Reference  DllCall  Binary Buffers

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Question:

I have several scripts that rely entirely on OLE, with the exception of checking for the availability of a driver. I realize I can add the ODBC Extender and call qDrivers(), but would rather use a DLLCall, something like:

cString = StrCat(strfill(" ",4000),Num2Char(0) )
nLen = 4000
nBuffer= BinaryAlloc(8)
BinaryPoke4(nBuffer,1,0)

x = DllCall("ODBCCP32.DLL", long:"SQLGetInstalledDrivers",lpstr:cString,long:nLen,lpbinary:nBuffer)

If x<>0
Message("SQL Driver Call",Strcat("FAILED! ",x))
Else
cString = StrReplace(cString,Num2Char(0),@CRLF )
Message("Installed Drivers",cString)
Endif
exit

Problem is, it doesn't seem to work, though I remember it working back when. Where did I screw up?

Answer:

I did some research at:

http://doc.ddart.net/msdn/header/include/odbcinst.h.html

and with some trial and error ... and I've got something working ...

BufMax=4000
Buf=BinaryAlloc(BufMax)
BufOut=BinaryAlloc(4)
pBufOut=IntControl(42,BufOut,0,0,0)

bool = DllCall("ODBCCP32.DLL", long:"SQLGetInstalledDrivers",lpbinary:Buf,long:BufMax,long:pBufOut)

BinaryEodSet(Buf,BinaryPeek4(BufOut,0)-1)
BinaryFree(BufOut)
BinaryReplace(Buf,"",@lf,@false)

;BinaryWrite(Buf,"C:\TEMP\TEST.BIN") ; test

list=BinaryPeekStr(Buf,0,BinaryEodGet(Buf))
BinaryFree(Buf)
item = AskItemList("ODBC Installed Drivers",list,@lf,@unsorted,@single)

:cancel
exit

and here is a UDF to do it. This code retrieves driver information.

 ;----------------------------------------------------------------------------------------------------
 ; udfGetODBCDriverList(DriverPattern) ; DD.2001:11:13:20:40:06 ;
 udfIsODBCDriverInstalled(DriverPattern) ; DD.2001:11:13:20:40:06
 ;----------------------------------------------------------------------------------------------------
 If itemlocate("udfgetodbcdriverlist",IntControl(77,103,0,0,0),@tab) then goto skip_udfgetodbcdriverlist 
 
 #DefineFunction udfGetODBCDriverList(DriverPattern) 
	 DriverList="" 
	 BufMax=4000
	 Buf=BinaryAlloc(BufMax) 
	 BufEod=BinaryAlloc(4)
	 pBufEod=IntControl(42,BufEod,0,0,0) 
	 
	 If DllCall("ODBCCP32.DLL",long:"SQLGetInstalledDrivers",lpbinary:Buf,long:BufMax,long:pBufEod)
		 BinaryEodSet(Buf,BinaryPeek4(BufEod,0)-1) 
		 BinaryFree(BufEod)
		 BinaryReplace(Buf,"",@tab,@false)
		 DriverList=BinaryPeekStr(Buf,0,BinaryEodGet(Buf)-1)
		 BinaryFree(Buf) 
		 
		 If (DriverPattern!="")
			 icount=ItemCount(DriverList,@tab) 
			 i=1 
			 
			 While (i<=icount)
				 DriverItem=ItemExtract(i,DriverList,@tab) 
				 
				 If !StrIndexWild(DriverItem,DriverPattern,1)
				 DriverList=ItemRemove(i,DriverList,@tab) 
				 icount=icount-1 
				 else
				 i=i+1 
				 EndIf 
			 EndWhile 
		 EndIf 
	 EndIf 
	 
	 Return (DriverList) 

	 ;udfGetODBCDriverList() returns a tab delimited list of installed ODBC drivers 
	 ; DD.20011113, Thanks to Stan Littlefield's request. ; 
	 
	 ; this udf replaces WIL's ODBC extender routine: ;
	 AddExtender("wwodb34i.dll") ; 
	 list=qDriverList() ; 
 #EndFunction

 :skip_udfgetodbcdriverlist 
 
 If itemlocate("udfisodbcdriverinstalled", IntControl(77,103,0,0,0), @tab) then goto skip_udfisodbcdriverinstalled 
 
 #DefineFunction udfIsODBCDriverInstalled(DriverPattern) 
 	Return(udfGetODBCDriverList(DriverPattern)!="") 
 #EndFunction

 :skip_udfisodbcdriverinstalled 
 ;--- test --- 
 item = AskItemList("ODBC Installed Drivers",udfGetODBCDriverList(""),@tab,@unsorted,@single) 

 ; all drivers
 item = AskItemList("ODBC Installed Drivers",udfGetODBCDriverList("*sql*"),@tab,@unsorted,@single) 

 ;only SQL 
 item = AskItemList("ODBC Installed Drivers",udfGetODBCDriverList("*soft*"),@tab,@unsorted,@single)

 ; only Microsoft item = AskItemList("ODBC Installed Drivers",udfGetODBCDriverList("*DBF*"),@tab,@unsorted,@single) 
 
 ;only DBF DriverPattern = "*foxpro*"
 noyes=ItemExtract(udfIsODBCDriverInstalled(DriverPattern)+1,"not","") 
 
 message("Demo udfIsODBCDriverInstalled('%DriverPattern%')","Driver is %noyes%installed.") 
 
 DriverPattern = "*profox*"
 noyes=ItemExtract(udfIsODBCDriverInstalled(DriverPattern)+1,"not","") 
 
 message("Demo udfIsODBCDriverInstalled('%DriverPattern%')","Driver is %noyes%installed.") 
 
 :cancel 
 Exit 

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Article ID:   W15136