gsm0808: Add utils for Channel Type
The planned support for true A over IP requires the encoding of
the a Channel Type element (see also ASSIGNMENT REQUEST).
This commt adds encoding/decoding functionality and tests for
the element mentioned above, however, it is not yet actively used.
Change-Id: Id0e2164d84b8cbcc6fe6a090fc7f40a1251421d7
diff --git a/src/gsm/gsm0808_utils.c b/src/gsm/gsm0808_utils.c
index eef6146..ef0f943 100644
--- a/src/gsm/gsm0808_utils.c
+++ b/src/gsm/gsm0808_utils.c
@@ -31,6 +31,8 @@
#define IP_V6_ADDR_LEN 16
#define IP_PORT_LEN 2
+#define CHANNEL_TYPE_ELEMENT_MAXLEN 11
+#define CHANNEL_TYPE_ELEMENT_MINLEN 3
/* Encode AoIP transport address element */
uint8_t gsm0808_enc_aoip_trasp_addr(struct msgb *msg,
@@ -306,3 +308,74 @@
return (int)(elem - old_elem);
}
+
+/* Encode Channel Type element */
+uint8_t gsm0808_enc_channel_type(struct msgb *msg,
+ const struct gsm0808_channel_type *ct)
+{
+ unsigned int i;
+ uint8_t byte;
+ uint8_t *old_tail;
+ uint8_t *tlv_len;
+
+ OSMO_ASSERT(msg);
+ OSMO_ASSERT(ct);
+ OSMO_ASSERT(ct->perm_spch_len <= CHANNEL_TYPE_ELEMENT_MAXLEN - 2);
+
+ /* FIXME: Implement encoding support for Data
+ * and Speech + CTM Text Telephony */
+ if ((ct->ch_indctr & 0x0f) != GSM0808_CHAN_SPEECH
+ && (ct->ch_indctr & 0x0f) != GSM0808_CHAN_SIGN)
+ OSMO_ASSERT(false);
+
+ msgb_put_u8(msg, GSM0808_IE_CHANNEL_TYPE);
+ tlv_len = msgb_put(msg, 1);
+ old_tail = msg->tail;
+
+ msgb_put_u8(msg, ct->ch_indctr & 0x0f);
+ msgb_put_u8(msg, ct->ch_rate_type);
+
+ for (i = 0; i < ct->perm_spch_len; i++) {
+ byte = ct->perm_spch[i];
+
+ if (i < ct->perm_spch_len - 1)
+ byte |= 0x80;
+ msgb_put_u8(msg, byte);
+ }
+
+ *tlv_len = (uint8_t) (msg->tail - old_tail);
+ return *tlv_len + 2;
+}
+
+/* Decode Channel Type element */
+int gsm0808_dec_channel_type(struct gsm0808_channel_type *ct,
+ const uint8_t *elem, uint8_t len)
+{
+ unsigned int i;
+ uint8_t byte;
+ const uint8_t *old_elem = elem;
+
+ OSMO_ASSERT(ct);
+ if (!elem)
+ return -EINVAL;
+ if (len <= 0)
+ return -EINVAL;
+
+ memset(ct, 0, sizeof(*ct));
+
+ ct->ch_indctr = (*elem) & 0x0f;
+ elem++;
+ ct->ch_rate_type = (*elem) & 0x0f;
+ elem++;
+
+ for (i = 0; i < ARRAY_SIZE(ct->perm_spch); i++) {
+ byte = *elem;
+ elem++;
+ ct->perm_spch[i] = byte & 0x7f;
+ if ((byte & 0x80) == 0x00)
+ break;
+ }
+ ct->perm_spch_len = i + 1;
+
+ return (int)(elem - old_elem);
+}