Is there a Windows API for converting File ID and Volume Serial to a unique path? - c++

Question

Background: I know that in Windows, two volumes with the same serial cannot be mounted at the same time. Moreover, there cannot exist two files within a single mounted volume with the same file ID. EDIT: this may not be the case. Then, given any volume handle or drive letter, the file_id maps to a unique file path. Is there a Windows API that can do this for any volume?
Progress: Here's how far I got:
#import <Windows.h>
...
FILE_ID_DESCRIPTOR file_id;
file_id.dwSize = 24;
file_id.Type = FileIdType;
file_id.QuadPart = /* file reference number */;
...
BOOL File::open(HANDLE *volume) {
file = OpenFileById(*volume, &file_id, SYNCHRONIZE | FILE_READ_ATTRIBUTES
| READ_CONTROL | ACCESS_SYSTEM_SECURITY,
SHARE_MODE, NULL, OPEN_FLAGS);
if (file == INVALID_HANDLE_VALUE) {
if (GetLastError() == 1314UL) { /* SACL permissions denied */
file = OpenFileById(*volume, &file_id, SYNCHRONIZE | FILE_READ_ATTRIBUTES
| READ_CONTROL, SHARE_MODE, NULL, OPEN_FLAGS);
perms = 0x4 | 0x2 | 0x1;
}
if (GetLastError() == 5UL) { /* Security permissions denied */
file = OpenFileById(*volume, &file_id, SYNCHRONIZE | FILE_READ_ATTRIBUTES,
SHARE_MODE, NULL, OPEN_FLAGS);
perms = 0x2 | 0x1;
}
if (file == INVALID_HANDLE_VALUE) { /* All permissions denied */
file = OpenFileById(*volume, &file_id, SYNCHRONIZE,
SHARE_MODE, NULL, OPEN_FLAGS);
perms = 0x1;
}
if (file == INVALID_HANDLE_VALUE) /* File name denied|file doesn't exist */
perms = 0;
} else {
perms = 0x8 | 0x4 | 0x2 | 0x1;
}
return file != INVALID_HANDLE_VALUE;
}
...
if (perms) {
path = new WCHAR[260]; /* expected file length */
l = GetFinalPathNameByHandle(file, path, 260, 0);
if (l >= 260) {
delete[] path;
path = new WCHAR[l];
GetFinalPathNameByHandle(file, path, l, 0);
} else if (l <= 0) {
delete[] path;
path = NULL;
}
}
In the first part of the code, I open a handle to the file, using an already-open handle to the volume, which is easy to do given the mounted drive letter. file is a handle to the file I am about to open.
In the second part, I use the handle to acquire the full name including DOS-style drive name (for example, C:\Users\rmanne\Downloads\test.txt). As long as perms is non-zero, I am guaranteed a human-readable absolute path in the second part of the code. However, I have only tested this with NTFS. According to the API, it will work with CsvFS and ReFS as well, but I haven't had a chance to test it with these yet.
The two functions are provided here:
http://msdn.microsoft.com/en-us/library/windows/desktop/aa364962%28v=vs.85%29.aspx
http://msdn.microsoft.com/en-us/library/windows/desktop/aa365432%28v=vs.85%29.aspx
As you can see, GetFinalPathNameByHandle is well-defined for all filesystems that Windows can mount and read without extra drivers or work-arounds. However, OpenFileByFileId is only defined for NTFS, ReFS, and CsvFS. I do not know whether or not it is defined for FAT or exFAT drives. However, it will, by specification, not work with network shared drives (SMB).
I have the option to just cache the file name because of the way I traverse all of the files, but caching these is incredibly memory-inefficient, taking up to 500MB of memory, whereas, not caching takes about 100MB of memory. Is there a different api that would enable me to get the name of a file given the file_id?