commit 98878ed882050bf40b3aab08b4da986876fee0fb
author Paul Elliott <paul.elliott@arm.com> Wed Mar 03 17:11:32 2021 +0000
committer Paul Elliott <paul.elliott@arm.com> Thu Mar 04 10:24:18 2021 +0000
tree 96af085d11cf026e486de9ab48856a1118d3ede3
parent 2f2ec575a5a84e8f7e99024cc02bae2c04693fbe

Fix constant flow mask maths

Signed-off-by: Paul Elliott <paul.elliott@arm.com>

library/base64.c

diff --git a/library/base64.c b/library/base64.c
index 6b0cb71..9bc6a52 100644
--- a/library/base64.c
+++ b/library/base64.c
@@ -110,7 +110,9 @@
 #endif
 
     /* Generate bitmask from condition, mask will either be 0xFFFFFFFF or 0 */
-    unsigned char mask =  -( unsigned char )( ( condition | -condition ) >> 7 );
+    unsigned char mask = ( condition | -condition );
+    mask >>= 7;
+    mask = -mask;
 
 #if defined(_MSC_VER)
 #pragma warning( pop )
@@ -133,7 +135,9 @@
 #endif
 
     /* Generate bitmask from condition, mask will either be 0xFFFFFFFF or 0 */
-    uint32_t mask =  -( uint32_t )( ( condition | -condition ) >> 31 );
+    uint32_t mask = ( condition | -condition );
+    mask >>= 31;
+    mask = -mask;
 
 #if defined(_MSC_VER)
 #pragma warning( pop )
@@ -142,7 +146,6 @@
     *dest = ( src & mask ) | ( ( *dest ) & ~mask );
 }
 
-
 /*
  * Constant flow check for equality
 */