st_error() will be &quot;BAD_MESSAGE_VERSION&quot;. If the message couldn't be decoded then olm_session_last_error() will be &quot;BAD_MESSAGE_FORMAT&quot;. If the MAC on the message was invalid then olm_session_last_error() will be &quot;BAD_MESSAGE_MAC&quot;.</p></dd></dl><dl><dt class="spec value" id="val-sha256_length"><a href="#val-sha256_length" class="anchor"></a><code><span class="keyword">val</span> sha256_length : <span><a href="../Types/Utility/index.html#type-t">Types.Utility.t</a> Ctypes_static