core/msgb.h: introduce msgb_l4len() helper
There is already a group of similar functions for L1, L2 and L3,
but L4 was missing. The L4 is usually used for parsing of complex
L3 messages, such as SS/USSD and SMS.
This change introduces a similar halper for L4.
Change-Id: I755f2d654bbdad2a8b4f94df9023bdd370b07ae6
diff --git a/include/osmocom/core/msgb.h b/include/osmocom/core/msgb.h
index b1cb6ec..8843db0 100644
--- a/include/osmocom/core/msgb.h
+++ b/include/osmocom/core/msgb.h
@@ -169,6 +169,18 @@
return msgb->tail - (uint8_t *)msgb_l3(msgb);
}
+/*! determine length of L4 message
+ * \param[in] msgb message buffer
+ * \returns size of L4 message in bytes
+ *
+ * This function computes the number of bytes between the tail of the
+ * message and the layer 4 header.
+ */
+static inline unsigned int msgb_l4len(const struct msgb *msgb)
+{
+ return msgb->tail - (uint8_t *)msgb_sms(msgb);
+}
+
/*! determine the length of the header
* \param[in] msgb message buffer
* \returns number of bytes between start of buffer and start of msg