Best way to get volume name of symbolic link target [NTFS] - c++

Question

I want a reliable way to get the volume name of a symbolic link's target that isn't super complicated.
So it looks like the FILE_NAME_INFO structure does not contain any info about the volume the file resides on. I am able to obtain the path of symlink targets from this structure, but for now I just assume the target resides on the same volume. However, I know symlinks permit targets on other volumes.
#include <windows.h>
#include <stdio.h>
#include <tchar.h>
#include <ole2.h>
struct FILE_NAME_INFO_AND_BUF {
FILE_NAME_INFO fni;
WCHAR buf[260];
};
WCHAR* getReparseTarget(WCHAR* linkFileName) {
HANDLE hFile;
WCHAR *szGuid = (WCHAR *)malloc(sizeof(WCHAR) * MAX_PATH);
BOOL result;
FILE_NAME_INFO_AND_BUF fnib = { 0 };
hFile = ::CreateFile(linkFileName, FILE_READ_ATTRIBUTES,
FILE_SHARE_READ |
FILE_SHARE_WRITE,
0,
OPEN_EXISTING,
FILE_FLAG_BACKUP_SEMANTICS, 0);
if (hFile == INVALID_HANDLE_VALUE) {
::CloseHandle(hFile);
return NULL;
}
result = ::GetFileInformationByHandleEx(hFile, FileNameInfo, &fnib, sizeof(fnib));
if (!result) {
fprintf(stderr, "GetFileInformationByHandleEx Error %d\n", ::GetLastError());
::CloseHandle(hFile);
return NULL;
}
WCHAR *targetFileName = (WCHAR *)malloc(sizeof(WCHAR) * MAX_PATH);
wmemset(targetFileName, 0, MAX_PATH);
wcsncpy(targetFileName, linkFileName, 2);
wcscat(targetFileName, fnib.fni.FileName);
return targetFileName;
}
As you can see I'm cheating and getting the volume name, in this case the drive letter, from the input string, but this wouldn't work if the target was on another volume. Also I'd prefer obtaining the volume name with the GUID e.g. \\?\Volume{f993747a-5d7a-4de1-a97a-c20c1af1ba02}\ in it than the drive letter e.g. C:\

Answer 1

The absolute simplest way, as long as you can target Vista or later, is to use the GetFinalPathNameByHandle function.
If you need to target XP as well then you can find a symlink's target by opening the link itself (not the file it points to) using the FILE_FLAG_OPEN_REPARSE_POINT flag, and then use the FSCTL_GET_REPARSE_POINT IO control code to find the target of the link.
Because a link's target can potentially contain other links (up to a maximum of 31 I believe), you have to do this on every element of the path to be sure you've found the final target.