hello monks
There is the GetPrinter Win32 api function (which retrieves information on a printer)
that requires a pointer to a PRINTER_INFO_2 structure.

The structure is defined as : 
typedef struct _PRINTER_INFO_2 { 
  LPTSTR    pServerName; 
  LPTSTR    pPrinterName; 
  LPTSTR    pShareName; 
  LPTSTR    pPortName; 
  LPTSTR    pDriverName; 
  LPTSTR    pComment; 
  LPTSTR    pLocation; 
  LPDEVMODE pDevMode; 
  LPTSTR    pSepFile; 
  LPTSTR    pPrintProcessor; 
  LPTSTR    pDatatype; 
  LPTSTR    pParameters; 
  PSECURITY_DESCRIPTOR pSecurityDescriptor; 
  DWORD     Attributes; 
  DWORD     Priority; 
  DWORD     DefaultPriority; 
  DWORD     StartTime; 
  DWORD     UntilTime; 
  DWORD     Status; 
  DWORD     cJobs; 
  DWORD     AveragePPM; 
} PRINTER_INFO_2, *PPRINTER_INFO_2;

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which I packed it into $printer_info_2 variable as : 
$a="\0";
$printer_info_2=pack('PPPPPPPPPPPPPLLLLLLLL',$a,$a,$a,$a,$a,$a,$a,$a,$
+a,$a,$a,$a,$a,0,0,0,0,0,0,0,0);

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then I load and call the function : 
$GetPrinter=new Win32::API('winspool.drv','GetPrinterA','NNPNP','N');
$GetPrinter->Call($handle,2,$printer_info_2,10000,$bytesgot);

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and then unpack as : 
@a=unpack('P32P32P32P32P32P32P32P32P32P32P32P32P32LLLLLLLL',$printer_i
+nfo_2);

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I do get data,but they are mixed or overlap hence they cannot lead to a solid view of the printer's details

data output : 
\\http://192.168.4.98\Lexmark T4
  \\http://192.168.4.98\Lexmark 
http://192.168.4.98 . 1 6 8 . 4 
Lexmark T430    T 4 3 0   http:/
comments go here  g o   h e r e 
  comments go here  g o   h e r 
\\http://192.168.4.98\Lexmark   
    comments go here  g o   h e 
WinPrint  i n t       comments g
RAW W   WinPrint  i n t       co
  RAW W   WinPrint  i n t       
  €                \ \ h t t p 
2128
1
0
1380
1380
0
0
0

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So this raises the question:
Is that the correct way to define and unpack pointers to strings? I don't know the length of the string that is why I use a number like 32.
I tried to pack and unpack using 'p' instead of 'P' but it makes the application crash!
Plus,how do I implement a pointer to a structure,where the pointer itself is part of another structure? (such as LPDEVMODE)
During my research I've seen pointers to strings being packed as 'L' and unpacked as 'p'.But it is all so confusing!

Any answers or any hints to get me started are gladly appreciated!Thanks!

In reply to Packing a c structure when using the win32api by omikron1

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