c++ check if file is empty - c++

Question

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

Answer 1

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);

Answer 2

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)
}