add osmo_cgi_name()

This will be used by cell idenitifier list code, like upcoming neighbor_ident
VTY in osmo-bsc and regression tests.

Change-Id: Iebc5cdf61b697b1603900993fc265af3eca0cedf
diff --git a/src/gsm/gsm23003.c b/src/gsm/gsm23003.c
index 574400d..2c3b21e 100644
--- a/src/gsm/gsm23003.c
+++ b/src/gsm/gsm23003.c
@@ -133,6 +133,33 @@
 	return buf;
 }
 
+static const char *_cgi_name(const struct osmo_cell_global_id *cgi, char *buf, size_t buflen)
+{
+	snprintf(buf, buflen, "%s-%u", osmo_lai_name(&cgi->lai), cgi->cell_identity);
+	return buf;
+}
+
+/*! Return MCC-MNC-LAC-CI as string, in a static buffer.
+ * \param[in] cgi  CGI to encode.
+ * \returns Static string buffer.
+ */
+const char *osmo_cgi_name(const struct osmo_cell_global_id *cgi)
+{
+	static char buf[32];
+	return _cgi_name(cgi, buf, sizeof(buf));
+}
+
+/*! Same as osmo_cgi_name(), but uses a different static buffer.
+ * Useful for printing two distinct CGIs in the same printf format.
+ * \param[in] cgi  CGI to encode.
+ * \returns Static string buffer.
+ */
+const char *osmo_cgi_name2(const struct osmo_cell_global_id *cgi)
+{
+	static char buf[32];
+	return _cgi_name(cgi, buf, sizeof(buf));
+}
+
 static void to_bcd(uint8_t *bcd, uint16_t val)
 {
 	bcd[2] = val % 10;
diff --git a/src/gsm/libosmogsm.map b/src/gsm/libosmogsm.map
index 31717d5..a6ea47d 100644
--- a/src/gsm/libosmogsm.map
+++ b/src/gsm/libosmogsm.map
@@ -277,6 +277,8 @@
 osmo_plmn_name2;
 osmo_lai_name;
 osmo_rai_name;
+osmo_cgi_name;
+osmo_cgi_name2;
 osmo_mnc_from_str;
 osmo_mnc_cmp;
 osmo_plmn_cmp;