DynamicTablesPkg: Add AsciiFromHex helper function

AsciiFromHex is a function converts a hex number to an
ASCII character. This function is used across multiple
generators, so add it to the TableHelperLib.

Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
Signed-off-by: Sami Mujawar <sami.mujawar@arm.com>
Reviewed-by: Alexei Fedorov <Alexei.Fedorov@arm.com>

DynamicTablesPkg/Include/Library/TableHelperLib.h

@@ -1,6 +1,6 @@
 /** @file
 
-  Copyright (c) 2017 - 2019, ARM Limited. All rights reserved.
+  Copyright (c) 2017 - 2020, Arm Limited. All rights reserved.<BR>
 
   SPDX-License-Identifier: BSD-2-Clause-Patent
 
@@ -107,4 +107,17 @@ FindDuplicateValue (
   IN        PFN_IS_EQUAL    EqualTestFunction
   );
 
+/** Convert a hex number to its ASCII code.
+
+ @param [in]  x   Hex number to convert.
+                  Must be 0 <= x < 16.
+
+ @return The ASCII code corresponding to x.
+**/
+UINT8
+EFIAPI
+AsciiFromHex (
+  IN  UINT8   x
+  );
+
 #endif // TABLE_HELPER_LIB_H_

DynamicTablesPkg/Library/Common/TableHelperLib/TableHelper.c

@@ -1,7 +1,8 @@
 /** @file
   Table Helper
 
-Copyright (c) 2017 - 2019, ARM Limited. All rights reserved.
+  Copyright (c) 2017 - 2020, Arm Limited. All rights reserved.<BR>
+
   SPDX-License-Identifier: BSD-2-Clause-Patent
 **/
 
@@ -244,3 +245,28 @@ FindDuplicateValue (
   }
   return FALSE;
 }
+
+/** Convert a hex number to its ASCII code.
+
+ @param [in]  x   Hex number to convert.
+                  Must be 0 <= x < 16.
+
+ @return The ASCII code corresponding to x.
+**/
+UINT8
+EFIAPI
+AsciiFromHex (
+  IN  UINT8   x
+  )
+{
+  if (x < 10) {
+    return (UINT8)(x + '0');
+  }
+
+  if (x < 16) {
+    return (UINT8)(x - 10 + 'A');
+  }
+
+  ASSERT (FALSE);
+  return (UINT8)0;
+}