gsm0808: Add utils for Cell Identifier List

The planned support for true A over IP requires the encoding of
the a Cell Identifier List element (see also BSS_MAP_MSG_PAGING).

This commt adds encoding/decoding functionality and tests for
the element mentioned above, however, it is not yet actively used.

Change-Id: I625245dd1dd396fc2bc189e8cd2c444a33042528
diff --git a/tests/gsm0808/gsm0808_test.c b/tests/gsm0808/gsm0808_test.c
index 5fe9c87..af457b4 100644
--- a/tests/gsm0808/gsm0808_test.c
+++ b/tests/gsm0808/gsm0808_test.c
@@ -610,6 +610,88 @@
 	msgb_free(msg);
 }
 
+static void test_gsm0808_enc_dec_cell_id_list_lac()
+{
+	struct gsm0808_cell_id_list enc_cil;
+	struct gsm0808_cell_id_list dec_cil;
+	struct msgb *msg;
+	uint8_t rc_enc;
+	int rc_dec;
+
+	memset(&enc_cil, 0, sizeof(enc_cil));
+	enc_cil.id_discr = CELL_IDENT_LAC;
+	enc_cil.id_list_lac[0] = 0x0124;
+	enc_cil.id_list_lac[1] = 0xABCD;
+	enc_cil.id_list_lac[2] = 0x5678;
+	enc_cil.id_list_len = 3;
+
+	msg = msgb_alloc(1024, "output buffer");
+	rc_enc = gsm0808_enc_cell_id_list(msg, &enc_cil);
+	OSMO_ASSERT(rc_enc == 9);
+
+	rc_dec = gsm0808_dec_cell_id_list(&dec_cil, msg->data + 2,
+					  msg->len - 2);
+	OSMO_ASSERT(rc_dec == 7);
+
+	OSMO_ASSERT(memcmp(&enc_cil, &dec_cil, sizeof(enc_cil)) == 0);
+
+	msgb_free(msg);
+}
+
+static void test_gsm0808_enc_dec_cell_id_list_single_lac()
+{
+	struct gsm0808_cell_id_list enc_cil;
+	struct gsm0808_cell_id_list dec_cil;
+	struct msgb *msg;
+	uint8_t cil_enc_expected[] = { GSM0808_IE_CELL_IDENTIFIER_LIST, 0x03,
+		0x05, 0x23, 0x42
+	};
+	uint8_t rc_enc;
+	int rc_dec;
+
+	memset(&enc_cil, 0, sizeof(enc_cil));
+	enc_cil.id_discr = CELL_IDENT_LAC;
+	enc_cil.id_list_lac[0] = 0x2342;
+	enc_cil.id_list_len = 1;
+
+	msg = msgb_alloc(1024, "output buffer");
+	rc_enc = gsm0808_enc_cell_id_list(msg, &enc_cil);
+	OSMO_ASSERT(rc_enc == 5);
+	OSMO_ASSERT(memcmp(cil_enc_expected, msg->data, msg->len) == 0);
+
+	rc_dec = gsm0808_dec_cell_id_list(&dec_cil, msg->data + 2,
+					  msg->len - 2);
+	OSMO_ASSERT(rc_dec == 3);
+
+	OSMO_ASSERT(memcmp(&enc_cil, &dec_cil, sizeof(enc_cil)) == 0);
+
+	msgb_free(msg);
+}
+
+static void test_gsm0808_enc_dec_cell_id_list_bss()
+{
+	struct gsm0808_cell_id_list enc_cil;
+	struct gsm0808_cell_id_list dec_cil;
+	struct msgb *msg;
+	uint8_t rc_enc;
+	int rc_dec;
+
+	memset(&enc_cil, 0, sizeof(enc_cil));
+	enc_cil.id_discr = CELL_IDENT_LAC;
+
+	msg = msgb_alloc(1024, "output buffer");
+	rc_enc = gsm0808_enc_cell_id_list(msg, &enc_cil);
+	OSMO_ASSERT(rc_enc == 3);
+
+	rc_dec = gsm0808_dec_cell_id_list(&dec_cil, msg->data + 2,
+					  msg->len - 2);
+	OSMO_ASSERT(rc_dec == 1);
+
+	OSMO_ASSERT(memcmp(&enc_cil, &dec_cil, sizeof(enc_cil)) == 0);
+
+	msgb_free(msg);
+}
+
 int main(int argc, char **argv)
 {
 	printf("Testing generation of GSM0808 messages\n");
@@ -637,6 +719,9 @@
 	test_gsm0808_enc_dec_speech_codec_list();
 	test_gsm0808_enc_dec_channel_type();
 	test_gsm0808_enc_dec_encrypt_info();
+	test_gsm0808_enc_dec_cell_id_list_lac();
+	test_gsm0808_enc_dec_cell_id_list_single_lac();
+	test_gsm0808_enc_dec_cell_id_list_bss();
 
 	printf("Done\n");
 	return EXIT_SUCCESS;