windows.h FindFirstFile help

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4.00/5 (1 vote)

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VS2010

Hi,

I am new to using win32 and I am having some issues trying to get the function FindFirstFile to work.

I am wondering if someone can point out what I am doing wrong with the following code:

LPCTSTR lpFileName = L"C:\\temp.txt";
LPWIN32_FIND_DATA lpFindFileData = {0};
		
		if( INVALID_HANDLE_VALUE == FindFirstFile(lpFileName, lpFindFileData))
		{
				cerr << "error:" << GetLastError() ;
		}

The previous code compiles, however, I get a access violation exception for the address of the variable lpFindFileData.

I have also tried using the address of lpFindFileData like this:

if( INVALID_HANDLE_VALUE == FindFirstFile(lpFileName, &lpFindFileData))

The previous code, however, will not build. I get the error message:

CSS

error C2664: 'FindFirstFileW' : cannot convert parameter 2 from 'LPWIN32_FIND_DATA *' to 'LPWIN32_FIND_DATAW'
1>          Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast

If anyone is willing to help me overcome this learning curve it will be greatly appreciated!!!

robNo.

Edit: Perhaps it would be beneficial to mention that I am using Visual Studio 2010 to compile and build this code.

Posted 20-May-11 17:35pm

RobNO

Updated 20-May-11 18:02pm

v2

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Richard MacCutchan 21-May-11 4:36am

The version of Visual Studio is irrelevant, it's the programming language and version that matters.

3 solutions

Solution 1

i do not work that much with c/c++ but it look like pointer porblem. Try the code below

//LPWIN32_FIND_DATA lpFindFileData
LPWIN32_FIND_DATA *lpFindFileData

Posted 20-May-11 18:04pm

CS2011

Comments

RobNO 21-May-11 0:13am

Thanks for your reply!
trying this:
LPWIN32_FIND_DATAW* lpFindFileData = {0};
if( INVALID_HANDLE_VALUE == FindFirstFile(lpFileName, lpFindFileData)) ..
, gives me the error message:
cannot convert parameter 2 from 'LPWIN32_FIND_DATAW *' to 'LPWIN32_FIND_DATAW'

trying this:
LPWIN32_FIND_DATAW* lpFindFileData = {0};

if( INVALID_HANDLE_VALUE == FindFirstFile(lpFileName, &lpFindFileData))

gives me the error message:
cannot convert parameter 2 from 'LPWIN32_FIND_DATAW **' to 'LPWIN32_FIND_DATAW'

and trying this:
LPWIN32_FIND_DATAW* lpFindFileData = {0};
if( INVALID_HANDLE_VALUE == FindFirstFile(lpFileName, *lpFindFileData))

compiles! However, i get the exception: Access violation reading location 0x00000000.
Which, is the address of lpFindFileData.

Thanks for the idea!

CS2011 21-May-11 0:36am

not sure about this exception. but look like you are trying to read some other memory location(it just my view i might be wrong)

Richard MacCutchan 21-May-11 4:30am

You created a pointer but did not initialise it; see my answer below.

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ix12 · Accepted Answer · 2011-05-20T20:07:00

Solution 2

NOOO, you are using a NULL pointer there: lpFindFileData = {0}; You either (probably) need to do lpFindFileData = new WIN32_FIND_DATA (I didn't try this personally), OR declare a WIN32_FIND_DATA structure and use its address in the call for FindFirstFile(), like this:

WIN32_FILE_DATA fdata;
FindFirstFile(lpFileName, &fdata);

The rest remains the same.
Hope you understand my english :)

Posted 20-May-11 20:07pm

ix12

Comments

RobNO 21-May-11 11:03am

Thanks for your reply!

Your English was great, I understood what you meant perfectly and it worked. So far I have just tried using new and delete. Once i get some more time ill try to declare the whole structure and pass it by the address. I will let you know the outcome!

Thanks for everything! your help is greatly appreciated!

Richard MacCutchan · Accepted Answer · 2011-05-20T22:35:00

C++

LPCTSTR lpFileName = L"C:\\temp.txt";
LPWIN32_FIND_DATA lpFindFileData = {0};
		
		if( INVALID_HANDLE_VALUE == FindFirstFile(lpFileName, lpFindFileData))
		{
				cerr << "error:" << GetLastError() ;
		}

LPWIN32_FIND_DATA is a pointer to a WIN32_FIND_DATA structure so it needs to point to something; you have initialised it to NULL. Try adding before your if statement:

C++

lpFindFileData = new WIN32_FIND_DATA;

alternatively you could instantiate the structure on the stack and reference it by address thus:

C++

WIN32_FIND_DATA findFileData;
		
	if(INVALID_HANDLE_VALUE == FindFirstFile(lpFileName, &findFileData))
...

windows.h FindFirstFile help

3 solutions

Solution 2

Solution 1

Solution 3

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