Many times in our job, we need to work with files and need to know file properties.
One of the most important properties is file size. Of course, there are a lot of API that allows finding this property, but most of them needs additional file operations: open file, find file size and close file.

A direct and fast way in order to detect the file size without these operations means the CRT run-time library’s function _tstat64() and stuff.

#define __S_ISTYPE(mode, mask)  (((mode) & _S_IFMT) == (mask))
#define S_ISDIR(mode)    __S_ISTYPE((mode), _S_IFDIR)

Then, write next function:

long long GetFileSizeFast(const TCHAR *szFilePath) {
  if (!szFilePath || !szFilePath[0] || !PathFileExists(szFilePath))
    return -1;

  long long nSize = -1;
  struct __stat64 buf;
  nSize  = (_tstat64( szFilePath, &buf ) == 0) 
           ? buf.st_size : -1;
  if (S_ISDIR(buf.st_mode)) nSize = -1;

  return nSize;
}

If you’re using WinAPI there is an even faster way in order to get file size.

long long GetFileSizeFastest(const TCHAR* szFilePath) {
  if (!szFilePath || !szFilePath[0] || !PathFileExists(szFilePath))
    return -1;

  WIN32_FIND_DATA sFileData;
  HANDLE hFind = FindFirstFile(szFilePath, &sFileData);
  if (hFind == INVALID_HANDLE_VALUE)
    return -1;

  FindClose(hFind);

  return  (sFileData.nFileSizeHigh * (MAXDWORD+1LL)) + sFileData.nFileSizeLow;
}

Finally, call these functions wherever you need.