Question

I’m working on some code that needs to run on every version of windows since WIN2000 and also needs to work with wide file paths.

I need to call some variant of stat to get the file length. The file may be larger than 4GB.

Here’s the relevant section from the MSDN Visual Studio .NET 2003[1] documentation:

int _stat(
   const char *path,
   struct _stat *buffer 
);
int _stat64(
   const char *path,
   struct __stat64 *buffer 
);
int _stati64(
   const char *path,
   struct _stati64 *buffer 
);
int _wstat(
   const wchar_t *path,
   struct _stat *buffer 
);
int _wstat64(
   const wchar_t *path,
   struct __stat64 *buffer 
);
int _wstati64(
   const wchar_t *path,
   struct _stati64 *buffer 
);

[1] https://web.archive.org/web/20110506201149/http://msdn.microsoft.com/en-us/library/14h5k7ff(v=VS.71).aspx

I can’t figure out the difference between the __stat64 structure and the _stati64 structure. I know that I want to use _wstat64 or _wstati64 but MSDN is silent on which is better.

Any suggestions?

Answer 1

Here are the __stat64 and the _stati64 structures from the mingw wchar.h #include file:

#if defined (__MSVCRT__)
struct _stati64 {
    _dev_t st_dev;
    _ino_t st_ino;
    unsigned short st_mode;
    short st_nlink;
    short st_uid;
    short st_gid;
    _dev_t st_rdev;
    __int64 st_size;
    time_t st_atime;
    time_t st_mtime;
    time_t st_ctime;
};

#if __MSVCRT_VERSION__ >= 0x0601
struct __stat64
{
    _dev_t st_dev;
    _ino_t st_ino;
    _mode_t st_mode;
    short st_nlink;
    short st_uid;
    short st_gid;
    _dev_t st_rdev;
    __int64 st_size;
    __time64_t st_atime;
    __time64_t st_mtime;
    __time64_t st_ctime;
};

According to these structures, it seems that _stat64 is a better choice than stati64 because:

1. st_mode is _mode_t and not unsigned short
2. Time is expressed as a _time64_t and not a time_t, so it has the same range that can be expressed by the NTFS file system, and is not crippled to the 32-bit time_t.

I’m still confused, but this seems closer to the correct answer.

Notice also that the _stat64 requires MSVCRT_VERSION > 0x0601, which implies that it is more modern.