Add mbedtls_ct_error_if, with tests
Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/library/constant_time_internal.h b/library/constant_time_internal.h
index d3d8945..3731107 100644
--- a/library/constant_time_internal.h
+++ b/library/constant_time_internal.h
@@ -411,6 +411,35 @@
unsigned char c,
unsigned char t);
+/** Choose between two error values. The values must be in the range [-32767..0].
+ *
+ * Functionally equivalent to:
+ *
+ * condition ? if1 : if0.
+ *
+ * \param condition Condition to test.
+ * \param if1 Value to use if \p condition == MBEDTLS_CT_TRUE.
+ * \param if0 Value to use if \p condition == MBEDTLS_CT_FALSE.
+ *
+ * \return \c if1 if \p condition == MBEDTLS_CT_TRUE, otherwise \c if0.
+ */
+static inline int mbedtls_ct_error_if(mbedtls_ct_condition_t condition, int if1, int if0);
+
+/** Choose between an error value and 0. The error value must be in the range [-32767..0].
+ *
+ * Functionally equivalent to:
+ *
+ * condition ? if1 : 0.
+ *
+ * Functionally equivalent to mbedtls_ct_error_if(condition, if1, 0) but
+ * results in smaller code size.
+ *
+ * \param condition Condition to test.
+ * \param if1 Value to use if \p condition == MBEDTLS_CT_TRUE.
+ *
+ * \return \c if1 if \p condition == MBEDTLS_CT_TRUE, otherwise 0.
+ */
+static inline int mbedtls_ct_error_if_else_0(mbedtls_ct_condition_t condition, int if1);
/* ============================================================================
* Block memory operations