CODEWITHSUNDEEP
c++filewinapi
ilija veselica
ilija veselica

Reputation: 9574

c++ check if file is empty

I got a project in C++ which I need to edit. This is a declaration of variable:

// Attachment
    OFSTRUCT ofstruct;
    HFILE hFile = OpenFile( mmsHandle->hTemporalFileName , &ofstruct , OF_READ );
    DWORD hFileSize = GetFileSize( (HANDLE) hFile , NULL );
    LPSTR hFileBuffer = (LPSTR)GlobalAlloc(GPTR, sizeof(CHAR) * hFileSize );
    DWORD hFileSizeReaded = 0;
    ReadFile( (HANDLE) hFile , hFileBuffer, hFileSize, &hFileSizeReaded, NULL );
    CloseHandle( (HANDLE) hFile );

I need to check if the file is attached (I suppose I need to check if hFile has any value), but don't know how. I tried with hFile == NULL but this doesn't do the job.

Thanks,
Ile

Upvotes: 1

Views: 3043

Answers (2)

Mark Ransom
Mark Ransom

Reputation: 308520

Before you open the file you can try this:

WIN32_FIND_DATA wfd;
HANDLE h = FindFirstFile(filename, &wfd);
if (h != INVALID_FILE_HANDLE)
{
    // file exists
    if (wfd.nFileSizeHigh != 0 || wfd.nFileSizeLow != 0)
    {
        // file is not empty
    }
    FindClose(h)
}

Upvotes: 1

Michael Goldshteyn
Michael Goldshteyn

Reputation: 74450

Compare hFile with HFILE_ERROR (not with NULL!). Also, you should change OpenFile to CreateFile and call it properly, OpenFile has long been deprecated. In fact MSDN clearly states:

OpenFile Function

Only use this function with 16-bit versions of Windows. For newer applications, use the CreateFile function.

When you make this change, you will get a HANDLE back, which you should compare with INVALID_HANDLE_VALUE.

Update: Correct way to get a file's size:

LARGE_INTEGER fileSize={0};

// You may want to use a security descriptor, tweak file sharing, etc...
// But this is a boiler plate file open
HANDLE hFile=CreateFile(mmsHandle->hTemporalFileName,GENERIC_READ,0,NULL,
                        OPEN_EXISTING,FILE_ATTRIBUTE_NORMAL,NULL);

if (hFile!=INVALID_HANDLE_VALUE && GetFileSizeEx(hFile,&fileSize) && 
    fileSize.QuadPart!=0)
{
  // The file has size
}
else
{
  // The file is missing or size==0 (or an error occurred getting its size)
}

// Do whatever else and don't forget to close the file handle when done!
if (hFile!=INVALID_HANDLE_VALUE)
  CloseHandle(hFile);

Upvotes: 6

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