Add osmo_gsm48_si1ro_nch_pos_{encode,decode} functions
These functions encode/decode the NCH position field within the SI1
rest octets. This is used within ASCI (VBS/VGCS).
Change-Id: I24a0095ac6eee0197f9d9ef9895c7795df6cdc49
Related: OS#5781
diff --git a/include/osmocom/gsm/gsm48_rest_octets.h b/include/osmocom/gsm/gsm48_rest_octets.h
index c8d63b2..cdb2e80 100644
--- a/include/osmocom/gsm/gsm48_rest_octets.h
+++ b/include/osmocom/gsm/gsm48_rest_octets.h
@@ -13,6 +13,9 @@
/* generate SI1 rest octets */
int osmo_gsm48_rest_octets_si1_encode(uint8_t *data, uint8_t *nch_pos, int is1800_net);
+int osmo_gsm48_si1ro_nch_pos_decode(uint8_t value, uint8_t *num_blocks, uint8_t *first_block);
+int osmo_gsm48_si1ro_nch_pos_encode(uint8_t num_blocks, uint8_t first_block);
+
int osmo_gsm48_rest_octets_si2quater_encode(uint8_t *data, uint8_t si2q_index, uint8_t si2q_count,
const uint16_t *uarfcn_list, size_t *u_offset,
size_t uarfcn_length, uint16_t *scramble_list,
diff --git a/src/gsm/gsm48_rest_octets.c b/src/gsm/gsm48_rest_octets.c
index 77fd349..b63c63f 100644
--- a/src/gsm/gsm48_rest_octets.c
+++ b/src/gsm/gsm48_rest_octets.c
@@ -59,6 +59,82 @@
return bv.data_len;
}
+struct nch_pos {
+ uint8_t num_blocks;
+ uint8_t first_block;
+};
+
+/* 3GPP TS 44.010 Table 10.5.2.32.1b */
+static const struct nch_pos si1ro_nch_positions[] = {
+ [0x00] = {1, 0},
+ [0x01] = {1, 1},
+ [0x02] = {1, 2},
+ [0x03] = {1, 3},
+ [0x04] = {1, 4},
+ [0x05] = {1, 5},
+ [0x06] = {1, 6},
+
+ [0x07] = {2, 0},
+ [0x08] = {2, 1},
+ [0x08] = {2, 2},
+ [0x0a] = {2, 3},
+ [0x0b] = {2, 4},
+ [0x0c] = {2, 5},
+
+ [0x0d] = {3, 0},
+ [0x0e] = {3, 1},
+ [0x0f] = {3, 2},
+ [0x10] = {3, 3},
+ [0x11] = {3, 4},
+
+ [0x12] = {4, 0},
+ [0x13] = {4, 1},
+ [0x14] = {4, 2},
+ [0x15] = {4, 3},
+
+ [0x16] = {5, 0},
+ [0x17] = {5, 1},
+ [0x18] = {5, 2},
+
+ [0x19] = {6, 0},
+ [0x1a] = {6, 1},
+
+ [0x1b] = {7, 0},
+};
+
+/*! Decode the 5-bit 'NCH position' field within SI1 Rest Octets.
+ * \param[in] value 5-bit value from SI1 rest octets
+ * \param[out] num_blocks Number of CCCH used for NCH
+ * \param[out] first_block First CCCH block used for NCH
+ * \returns 0 on success; negative in case of error */
+int osmo_gsm48_si1ro_nch_pos_decode(uint8_t value, uint8_t *num_blocks, uint8_t *first_block)
+{
+ if (value >= ARRAY_SIZE(si1ro_nch_positions))
+ return -EINVAL;
+
+ *num_blocks = si1ro_nch_positions[value].num_blocks;
+ *first_block = si1ro_nch_positions[value].first_block;
+
+ return 0;
+}
+
+/*! Encode the 5-bit 'NCH position' field within SI1 Rest Octets.
+ * \param[in] num_blocks Number of CCCH used for NCH
+ * \param[in] first_block First CCCH block used for NCH
+ * \returns 5-bit value for SI1 rest octets on success; negative in case of error */
+int osmo_gsm48_si1ro_nch_pos_encode(uint8_t num_blocks, uint8_t first_block)
+{
+ unsigned int i;
+
+ for (i = 0; i < ARRAY_SIZE(si1ro_nch_positions); i++) {
+ if (si1ro_nch_positions[i].num_blocks == num_blocks &&
+ si1ro_nch_positions[i].first_block == first_block) {
+ return i;
+ }
+ }
+ return -EINVAL;
+}
+
/* Append Repeated E-UTRAN Neighbour Cell to bitvec: see 3GPP TS 44.018 Table 10.5.2.33b.1 */
static inline bool append_eutran_neib_cell(struct bitvec *bv, const struct osmo_earfcn_si2q *e, size_t *e_offset,
uint8_t budget)
diff --git a/src/gsm/libosmogsm.map b/src/gsm/libosmogsm.map
index 0018e1c..003d6e8 100644
--- a/src/gsm/libosmogsm.map
+++ b/src/gsm/libosmogsm.map
@@ -336,6 +336,8 @@
osmo_gsm48_rest_octets_si13_encode;
osmo_gsm48_rest_octets_si3_decode;
osmo_gsm48_rest_octets_si4_decode;
+osmo_gsm48_si1ro_nch_pos_encode;
+osmo_gsm48_si1ro_nch_pos_decode;
gsm48_rr_short_pd_msg_name;
gsm48_rr_msg_name;
gsm48_cc_state_name;