gsm0808_utils: Add gsm0808_decode_cell_id_u()
This function parses a single Cell ID list element into a
'union gsm0808_cell_id_u'. This function is going to be used
by the upcoming CBSP support.
Related: OS#3537
Change-Id: I08b33881667aa32f01e53ccb70d44d5b79c7c986
diff --git a/src/gsm/gsm0808_utils.c b/src/gsm/gsm0808_utils.c
index 70eed15..afff59a 100644
--- a/src/gsm/gsm0808_utils.c
+++ b/src/gsm/gsm0808_utils.c
@@ -193,6 +193,17 @@
#endif /* HAVE_SYS_SOCKET_H */
+/* Decode 5-byte LAI list element data (see TS 08.08 3.2.2.27) into MCC/MNC/LAC. */
+static void decode_lai(const uint8_t *data, struct osmo_location_area_id *decoded)
+{
+ struct gsm48_loc_area_id lai;
+
+ /* Copy data to stack to prevent unaligned access in gsm48_decode_lai2(). */
+ memcpy(&lai, data, sizeof(lai)); /* don't byte swap yet */
+
+ gsm48_decode_lai2(&lai, decoded);
+}
+
/* Helper function for gsm0808_enc_speech_codec()
* and gsm0808_enc_speech_codec_list() */
static uint8_t enc_speech_codec(struct msgb *msg,
@@ -756,6 +767,53 @@
return (int)(elem - old_elem);
}
+/*! Decode a single GSM 08.08 Cell ID list element payload
+ * \param[out] out caller-provided output union
+ * \param[in] discr Cell ID discriminator describing type to be decoded
+ * \param[in] buf User-provided input buffer containing binary Cell ID list element
+ * \param[in] len Length of buf
+ * \returns 0 on success; negative on error */
+int gsm0808_decode_cell_id_u(union gsm0808_cell_id_u *out, enum CELL_IDENT discr, const uint8_t *buf, unsigned int len)
+{
+ switch (discr) {
+ case CELL_IDENT_WHOLE_GLOBAL:
+ if (len < 7)
+ return -EINVAL;
+ decode_lai(buf, &out->global.lai);
+ out->global.cell_identity = osmo_load16be(buf + sizeof(struct gsm48_loc_area_id));
+ break;
+ case CELL_IDENT_LAC_AND_CI:
+ if (len < 4)
+ return -EINVAL;
+ out->lac_and_ci.lac = osmo_load16be(buf);
+ out->lac_and_ci.ci = osmo_load16be(buf + sizeof(uint16_t));
+ break;
+ case CELL_IDENT_CI:
+ if (len < 2)
+ return -EINVAL;
+ out->ci = osmo_load16be(buf);
+ break;
+ case CELL_IDENT_LAI_AND_LAC:
+ if (len < 5)
+ return -EINVAL;
+ decode_lai(buf, &out->lai_and_lac);
+ break;
+ case CELL_IDENT_LAC:
+ if (len < 2)
+ return -EINVAL;
+ out->lac = osmo_load16be(buf);
+ break;
+ case CELL_IDENT_BSS:
+ case CELL_IDENT_NO_CELL:
+ /* Does not have any list items */
+ break;
+ default:
+ /* Remaining cell identification types are not implemented. */
+ return -EINVAL;
+ }
+ return 0;
+}
+
void gsm0808_msgb_put_cell_id_u(struct msgb *msg, enum CELL_IDENT id_discr, const union gsm0808_cell_id_u *u)
{
switch (id_discr) {
@@ -865,17 +923,6 @@
return *tlv_len + 2;
}
-/* Decode 5-byte LAI list element data (see TS 08.08 3.2.2.27) into MCC/MNC/LAC. */
-static void decode_lai(const uint8_t *data, struct osmo_location_area_id *decoded)
-{
- struct gsm48_loc_area_id lai;
-
- /* Copy data to stack to prevent unaligned access in gsm48_decode_lai2(). */
- memcpy(&lai, data, sizeof(lai)); /* don't byte swap yet */
-
- gsm48_decode_lai2(&lai, decoded);
-}
-
static int parse_cell_id_global_list(struct gsm0808_cell_id_list2 *cil, const uint8_t *data, size_t remain,
size_t *consumed)
{