CODEWITHSUNDEEP
c++filewinapisizedesktop-application
liu ziaoming218
liu ziaoming218

Reputation: 27

How to get file size for Huge file(10GB) in c++?

I tried to get file size for 16 GB txt file. but I got different size with real size. who can help me?

HANDLE FileHandle = INVALID_HANDLE_VALUE;
long long FileSize;
FileHandle = CreateFileA(szInputFileName, GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, NULL, NULL);
if(FileHandle == INVALID_HANDLE_VALUE)
    return;

FileSize = GetFileSize(FileHandle, NULL);

Upvotes: 1

Views: 578

Answers (3)

Remy Lebeau
Remy Lebeau

Reputation: 598134

If you don't really need an open HANDLE to the actual file itself, you can instead use FindFirstFile() or GetFileAttributesEx() to query the file size from the filesystem, eg:

WIN32_FIND_DATA fd;
HANDLE FindHandle = FindFirstFile(szInputFileName, &fd);
if (FindHandle == INVALID_HANDLE_VALUE)
    return;
FindClose(FindHandle);

ULONGLONG FileSize = (static_cast<ULONGLONG>(fd.nFileSizeHigh) << 32) + fd.nFileSizeLow;

WIN32_FILE_ATTRIBUTE_DATA fad;
if (!GetFileAttributesEx(szInputFileName, GetFileExInfoStandard, &fad))
    return;

ULONGLONG FileSize = (static_cast<ULONGLONG>(fad.nFileSizeHigh) << 32) + fad.nFileSizeLow;

Upvotes: 2

wohlstad
wohlstad

Reputation: 29287

As you can see in the GetFileSize documentation:
If the file size exceeds 32bit, you must provide the 2nd argument, to be filled with the 32 high bits of the size.
Then you can combine the 2 in order to get the final file size.

Code example:

HANDLE FileHandle = INVALID_HANDLE_VALUE;
// ... (initialize FileHandle)

DWORD FileSizeLow;
DWORD FileSizeHigh;
//------------------------------------vvvvvvvvvvvvvv-
FileSizeLow = GetFileSize(FileHandle, &FileSizeHigh);
// Handle error case (see documentation link above) ...
uint64_t FileSize = ((uint64_t)FileSizeHigh << 32) + FileSizeLow;
// ...

Alternatively, as @IInspectable commented, you can use GetFileSizeEx:

LARGE_INTEGER FileSizeL;
if (GetFileSizeEx(FileHandle, &FileSizeL))
{
    LONGLONG FileSize = FileSizeL.QuadPart;  // 64bit signed
    // ...
}
else
{
    // Handle error ...
}

Note: Using GetFileSizeEx is actually the recomended way (the documentation above mentions it explicitly) thanks to a 64bit single result and easier error handling.

Upvotes: 7

Alan Birtles
Alan Birtles

Reputation: 36578

The GetFileSize documentation recommends using GetFileSizeEx instead which is simpler:

LARGE_INTEGER FileSize;
if (!GetFileSizeEx(FileHandle, &FileSize))
{
  std::cout << "error getting file size\n";
}
else
{
  std::cout << "file size: " << FileSize.QuadPart << "\n";
}

for a more c++ solution std::filesystem::file_size (though this only works with a path, not a handle):

auto FileSize = std::filesystem::file_size(szInputFileName)

Upvotes: 4

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