MdePkg/BaseLib: Refine (Ascii)StrnLenS functions logic

This commit refines the logic for AsciiStrnLenS and StrnLenS. It makes the
logic more straightforward to prevent possible mis-reports by static code
checkers.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

1 files changed, 12 insertions, 4 deletions

diff --git a/MdePkg/Library/BaseLib/SafeString.c b/MdePkg/Library/BaseLib/SafeString.c
index ede2f4c5b4..e4c0759c70 100644
--- a/MdePkg/Library/BaseLib/SafeString.c
+++ b/MdePkg/Library/BaseLib/SafeString.c
@@ -143,8 +143,12 @@ StrnLenS (
   // String then StrnLenS returns MaxSize. At most the first MaxSize characters of String shall

   // be accessed by StrnLenS.

   //

-  for (Length = 0; (Length < MaxSize) && (*String != 0); String++, Length++) {

-    ;

+  Length = 0;

+  while (String[Length] != 0) {

+    if (Length >= MaxSize - 1) {

+      return MaxSize;

+    }

+    Length++;

   }

   return Length;

 }

@@ -571,8 +575,12 @@ AsciiStrnLenS (
   // String then AsciiStrnLenS returns MaxSize. At most the first MaxSize characters of String shall

   // be accessed by AsciiStrnLenS.

   //

-  for (Length = 0; (Length < MaxSize) && (*String != 0); String++, Length++) {

-    ;

+  Length = 0;

+  while (String[Length] != 0) {

+    if (Length >= MaxSize - 1) {

+      return MaxSize;

+    }

+    Length++;

   }

   return Length;

 }