How do I use C++ datatype "LPBYTE" in installshield

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I was trying to use enumprinters function in installshield to get the list of printer names.

One of the enumprinters parameter is of LPBYTE type, i couldnt get the datatype LPBYTE in installshield, if i use pointer type the function is crashing.

BOOL EnumPrinters(
_In_ DWORD Flags,
_In_ LPTSTR Name,
_In_ DWORD Level,
_Out_ LPBYTE pPrinterEnum,
_In_ DWORD cbBuf,
_Out_ LPDWORD pcbNeeded,
_Out_ LPDWORD pcReturned
);

Could any one please let me know how could i use the datatype LPBYTE in installshield

Thanks in advance.

What I have tried:

I was trying to use enumprinters function in installshield to get the list of printer names.

One of the enumprinters parameter is of LPBYTE type, i couldnt get the datatype LPBYTE in installshield, if i use pointer type the function is crashing.

Posted 29-Apr-21 3:33am

karthik836

Updated 1-May-21 4:16am

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Richard MacCutchan · Answer 1 · 2021-04-29T03:40:00

Solution 1

The LPBYTE type is just a pointer to a byte array; you can use unsigned char * instead. And the EnumPrinters function (Winspool.h) - Win32 apps | Microsoft Docs[^] explains the requirements for each of the parameters.

Posted 29-Apr-21 3:40am

Richard MacCutchan

Comments

karthik836 29-Apr-21 10:02am

Hi Richard,

How would i use unsigend char * in installshield, as i could see the datatype Char is only allowed.

Can i get an example of declaring the variable as unsigned char * in installshield

Thanks in advance

Richard MacCutchan 29-Apr-21 11:06am

Sorry, I have not used installshield so I do not know the answer. Exactly how are you calling the EnumPrinters function?

karthik836 1-May-21 9:35am

Hi Richard,

sorry for the delay

Please find the below code,
export prototype INT winspool.EnumPrintersA(LONG, BYREF STRING, LONG, BYREF POINTER, LONG, BYREF LONG, BYREF LONG);
prototype NUMBER KERNEL.LocalAlloc ( NUMBER, NUMBER );
prototype NUMBER KERNEL.LocalFree(NUMBER);
#define LPTR 0X0040

function enumtest()

NUMBER nResult;
STRING svName;

BOOL resa;

LONG neededa;
LONG returneda;

POINTER structpinfo;

LONG n;

begin
svName = "";

neededa = 0;
returneda = 0;

nResult = UseDLL("winspool.drv");
if (nResult < 0 ) then
return ERROR_FUNCTION_FAILED;
endif;

resa = EnumPrintersA(6, svName, 4, structpinfo, neededa, neededa, returneda);

LocalFree(structpinfo);
structpinfo = LocalAlloc(LPTR,neededa);

if(!structpinfo == NULL)then
SprintfBox(INFORMATION,"start buffering","[%d]", structpinfo);

endif;

resa = EnumPrintersA(6, svName, 4, structpinfo, neededa, neededa, returneda);

if(!resa)then
SprintfBox(INFORMATION,"buffering size","[%d]", neededa);
endif;

After allocation of memory the below line is getting crash
resa = EnumPrintersA(6, svName, 4, structpinfo, neededa, neededa, returneda)

I have followed the reference link from flexera community
https://community.flexera.com/t5/InstallShield-Forum/Enumerate-printers/td-p/97983

Richard MacCutchan · Answer 2 · 2021-05-01T04:16:00

C++

resa = EnumPrintersA(6, svName, 4, structpinfo, neededa, neededa, returneda);

The last two parameters must be pointers to variables, but you are using the values. Also with level = 4, the name field should be NULL. It should be:

C++

resa = EnumPrintersA(6, NULL, 4, structpinfo, neededa, &neededa, &returneda);

Check EnumPrinters function (Winspool.h) - Win32 apps | Microsoft Docs[^] carefully.

And you should avoid calling

C++

LocalFree(structpinfo);

before you have allocated any space to it, as that may try to free some random address.