[PATCH] MdePkg/BaseLib: Fix PathRemoveLastItem to ignore consecutive '\'

[Jeff Westfahl <jeff.westfahl@ni.com>]

This patch makes PathRemoveLastItem ignore consecutive occurrences of the
'\' path separator.

Consider a path like "FS0:\ABC\DEF\\", noting the consecutive '\' path
separator characters at the end. The expected result of PathRemoveLastItem
on such a path is "FS0:\ABC\". However, what we get is "FS0:\ABC\DEF\".

We can see the result of this behavior with 'ls' in the EFI shell. Go a
couple of folders deep into a filesystem and try 'ls ..\..'. Here's an
example, with a filesystem with folder ABC in the root, with subfolder
DEF.

    FS0:\ABC\DEF\> ls ..
    Directory of: FS0:\ABC\
    05/12/2017  15:46 <DIR>         8,192  .
    05/12/2017  15:46 <DIR>             0  ..
    05/12/2017  15:46 <DIR>         8,192  DEF
              0 File(s)           0 bytes
              3 Dir(s)
    FS0:\ABC\DEF\> ls ..\..
    Directory of: FS0:\ABC\
    05/12/2017  15:46 <DIR>         8,192  .
    05/12/2017  15:46 <DIR>             0  ..
    05/12/2017  15:46 <DIR>         8,192  DEF
              0 File(s)           0 bytes
              3 Dir(s)
    fs0:\ABC\DEF\>

As you can see, 'ls ..\..' lists only the parent folder. This patch
resolves the issue so that 'ls ..\..' lists the grandparent folder.

Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Jaben Carsey <jaben.carsey@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jeff Westfahl <jeff.westfahl@ni.com>
---
 MdePkg/Library/BaseLib/FilePaths.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/MdePkg/Library/BaseLib/FilePaths.c b/MdePkg/Library/BaseLib/FilePaths.c
index 203045c..bbaf140 100644
--- a/MdePkg/Library/BaseLib/FilePaths.c
+++ b/MdePkg/Library/BaseLib/FilePaths.c
@@ -37,9 +37,7 @@ PathRemoveLastItem(
       ; Walker != NULL && *Walker != CHAR_NULL
       ; Walker++
      ){
-    if (*Walker == L'\\' && *(Walker + 1) != CHAR_NULL) {
-      LastSlash = Walker+1;
-    } else if (*Walker == L':' && *(Walker + 1) != L'\\' && *(Walker + 1) != CHAR_NULL) {
+    if ((*Walker == L'\\' || *Walker == L':') && *(Walker + 1) != L'\\' && *(Walker + 1) != CHAR_NULL) {
       LastSlash = Walker+1;
     }
   }
-- 
2.7.4