+/**
+ Given Cwd expand Path to remove .. and replace them with real
+ directory names.
+
+ @param Cwd Current Working Directory
+ @param Path Path to expand
+
+ @return NULL Cwd or Path are not valid
+ @return 'other' Path with .. expanded
+
+**/
+CHAR8 *
+ExpandPath (
+ IN CHAR8 *Cwd,
+ IN CHAR8 *Path
+ )
+{
+ CHAR8 *NewPath;
+ CHAR8 *Work, *Start, *End;
+ UINTN StrLen;
+ UINTN i;
+
+ if (Cwd == NULL || Path == NULL) {
+ return NULL;
+ }
+
+ StrLen = AsciiStrSize (Cwd);
+ if (StrLen <= 2) {
+ // Smallest valid path is 1 char and a null
+ return NULL;
+ }
+
+ StrLen = AsciiStrSize (Path);
+ NewPath = AllocatePool (AsciiStrSize (Cwd) + StrLen + 1);
+ if (NewPath == NULL) {
+ return NULL;
+ }
+ AsciiStrCpy (NewPath, Cwd);
+
+ End = Path + StrLen;
+ for (Start = Path ;;) {
+ Work = AsciiStrStr (Start, "..") ;
+ if (Work == NULL) {
+ // Remaining part of Path contains no more ..
+ break;
+ }
+
+ // append path prior to ..
+ AsciiStrnCat (NewPath, Start, Work - Start);
+ StrLen = AsciiStrLen (NewPath);
+ for (i = StrLen; i >= 0; i--) {
+ if (NewPath[i] == ':') {
+ // too many ..
+ return NULL;
+ }
+ if (NewPath[i] == '/' || NewPath[i] == '\\') {
+ if ((i > 0) && (NewPath[i-1] == ':')) {
+ // leave the / before a :
+ NewPath[i+1] = '\0';
+ } else {
+ // replace / will Null to remove trailing file/dir reference
+ NewPath[i] = '\0';
+ }
+ break;
+ }
+ }
+
+ Start = Work + 3;
+ }
+
+ // Handle the path that remains after the ..
+ AsciiStrnCat (NewPath, Start, End - Start);
+
+ return NewPath;
+}
+