Move mbedtls_cf_uint_if 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 b513c6a..6d53134 100644
--- a/library/constant_time.c
+++ b/library/constant_time.c
@@ -273,3 +273,19 @@
}
#endif /* MBEDTLS_BIGNUM_C */
+
+/** Choose between two integer values, without branches.
+ *
+ * This is equivalent to `cond ? if1 : if0`, but is likely to be compiled
+ * to code using bitwise operation rather than a branch.
+ *
+ * \param cond Condition to test.
+ * \param if1 Value to use if \p cond is nonzero.
+ * \param if0 Value to use if \p cond is zero.
+ * \return \c if1 if \p cond is nonzero, otherwise \c if0.
+ */
+unsigned mbedtls_cf_uint_if( unsigned cond, unsigned if1, unsigned if0 )
+{
+ unsigned mask = mbedtls_cf_uint_mask( cond );
+ return( ( mask & if1 ) | (~mask & if0 ) );
+}