DOS路径转化为NT路径

ReactOS里面给的源码
真是碉堡了
 1 NTSTATUS NTAPI RtlpWin32NTNameToNtPathName_U    (    IN PUNICODE_STRING     DosPath,
 2                                                     OUT PUNICODE_STRING     NtPath,
 3                                                     OUT PCWSTR *     PartName,
 4                                                     OUT PRTL_RELATIVE_NAME_U     RelativeName )    
 5 {
 6     ULONG DosLength;
 7     PWSTR NewBuffer, p;
 8 
 9     /* Validate the input */
10     if (!DosPath) return STATUS_OBJECT_NAME_INVALID;
11 
12     /* Validate the DOS length */
13     DosLength = DosPath->Length;
14     if (DosLength >= UNICODE_STRING_MAX_BYTES) return STATUS_NAME_TOO_LONG;
15 
16     /* Make space for the new path */
17     NewBuffer = RtlAllocateHeap(RtlGetProcessHeap(),
18                                 0,
19                                 DosLength + sizeof(UNICODE_NULL));
20     if (!NewBuffer) return STATUS_NO_MEMORY;
21 
22     /* Copy the prefix, and then the rest of the DOS path, and NULL-terminate */
23     RtlCopyMemory(NewBuffer, RtlpDosDevicesPrefix.Buffer, RtlpDosDevicesPrefix.Length);
24     RtlCopyMemory((PCHAR)NewBuffer + RtlpDosDevicesPrefix.Length,
25                   DosPath->Buffer + RtlpDosDevicesPrefix.Length / sizeof(WCHAR),
26                   DosPath->Length - RtlpDosDevicesPrefix.Length);
27     NewBuffer[DosLength / sizeof(WCHAR)] = UNICODE_NULL;
28 
29     /* Did the caller send a relative name? */
30     if (RelativeName)
31     {
32         /* Zero initialize it */
33         RtlInitEmptyUnicodeString(&RelativeName->RelativeName, NULL, 0);
34         RelativeName->ContainingDirectory = NULL;
35         RelativeName->CurDirRef = 0;
36     }
37 
38     /* Did the caller request a partial name? */
39     if (PartName)
40     {
41         /* Loop from the back until we find a path separator */
42         p = &NewBuffer[(DosLength - 1) / sizeof (WCHAR)];
43         while (p > NewBuffer) if (*p-- == '\\') break;
44 
45         /* Was one found? */
46         if (p > NewBuffer)
47         {
48             /* Move past it -- anything left? */
49             p++;
50             if (!*p)
51             {
52                 /* The path ends with a path separator, no part name */
53                 *PartName = NULL;
54             }
55             else
56             {
57                 /* What follows the path separator is the part name */
58                 *PartName = p;
59             }
60         }
61     }
62 
63     /* Build the final NT path string */
64     NtPath->Length = (USHORT)DosLength;
65     NtPath->Buffer = NewBuffer;
66     NtPath->MaximumLength = (USHORT)DosLength + sizeof(UNICODE_NULL);
67     return STATUS_SUCCESS;
68 }