Re: Create a file larger than 3 gb

From:
Norbert Unterberg <nunterberg@newsgroups.nospam>
Newsgroups:
microsoft.public.vc.language,microsoft.public.vc.mfc
Date:
Wed, 16 Jul 2008 07:46:37 +0200
Message-ID:
<O3J8Sdw5IHA.1428@TK2MSFTNGP06.phx.gbl>
CodeTestDummy schrieb:

I am having an issue create a file larger than 3 GB. I am using
CreateFile and WriteFile. Any ideas how to create one past 3 GB? Here
is what I am doing. Thanks in advance...

               BOOL bWrite = TRUE;
    HANDLE hFile = CreateFile("c:\\test.dat", GENERIC_WRITE,
             FILE_SHARE_WRITE, 0, CREATE_ALWAYS, FILE_ATTRIBUTE_HIDDEN, 0);

    while(bWrite == TRUE)
    {
        memset(szData, 0, sizeof(szData));

        WriteFile(hFile, szData, sizeof(szData), &dwBytesWrite, NULL);

        Sleep(.5);

*****
Any reason to sleep here? Once WriteFile returns, the file size has already
changed, no need to sleep.
In addition, Sleep takes an unsigned integer as argument, not a floating point
value. A Sleep(.5) is the same as Sleep(0).
******

        dwSize = GetFileSize(hFile, NULL);

******
Alle the "standard" file api only uses a DWORD for file size. For files of your
size use the "Ex" functions like GetFileSizeEx, GetFileAttributesEx etc.
******

        if(dwSize >= (1024 * 1024 * 1024 * 5))

****
As already said, the interger expressen overflows, so you need to compare to a
64 bit integer.
****

        {
            bWrite = FALSE;
        }
    }
    CloseHandle(hFile);


Norbert

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