msgb: introduce msgb_trim() and msgb_l3trim() to trim msgb's
diff --git a/include/osmocom/core/msgb.h b/include/osmocom/core/msgb.h
index 9f46e6c..ea2ee53 100644
--- a/include/osmocom/core/msgb.h
+++ b/include/osmocom/core/msgb.h
@@ -312,6 +312,34 @@
msg->tail += len;
}
+/*! \brief Trim the msgb to a given absolute length
+ * \param[in] msg message buffer
+ * \param[in] len new total length of buffer
+ * \returns 0 in case of success, negative in case of error
+ */
+static inline int msgb_trim(struct msgb *msg, int len)
+{
+ if (msg->len < len)
+ return -1;
+
+ msg->len -= len;
+ msg->tail -= len;
+ if (msg->tail < msg->data)
+ msg->tail = msg->data;
+
+ return 0;
+}
+
+/*! \brief Trim the msgb to a given layer3 length
+ * \pram[in] msg message buffer
+ * \param[in] l3len new layer3 length
+ * \returns 0 in case of success, negative in case of error
+ */
+static inline int msgb_l3trim(struct msgb *msg, int l3len)
+{
+ return msgb_trim(msg, (msg->l3h - msg->data) + l3len);
+}
+
/*! \brief Allocate message buffer with specified headroom
* \param[in] size size in bytes, including headroom
* \param[in] headroom headroom in bytes