Move mbedtls_cf_size_mask_ge function to the constant-time module
Signed-off-by: gabor-mezei-arm <gabor.mezei@arm.com>
diff --git a/library/constant_time.c b/library/constant_time.c
index 928b9b7..b53d06b 100644
--- a/library/constant_time.c
+++ b/library/constant_time.c
@@ -161,3 +161,19 @@
return( mask );
}
+
+/*
+ * Constant-flow mask generation for "greater or equal" comparison:
+ * - if x >= y, return all bits 1, that is (size_t) -1
+ * - otherwise, return all bits 0, that is 0
+ *
+ * This function can be used to write constant-time code by replacing branches
+ * with bit operations using masks.
+ *
+ * This function is implemented without using comparison operators, as those
+ * might be translated to branches by some compilers on some platforms.
+ */
+size_t mbedtls_cf_size_mask_ge( size_t x, size_t y )
+{
+ return( ~mbedtls_cf_size_mask_lt( x, y ) );
+}