* add function to change c-bits in TRAU frame from uplink to downlink
* add function to re-encode an exploded TRAU frame into a bit-per-byte stream
diff --git a/src/trau_frame.c b/src/trau_frame.c
index 8eb2b45..9d7e517 100644
--- a/src/trau_frame.c
+++ b/src/trau_frame.c
@@ -27,7 +27,7 @@
#include <openbsc/trau_frame.h>
-static u_int32_t get_bits(u_int8_t *bitbuf, int offset, int num)
+static u_int32_t get_bits(const u_int8_t *bitbuf, int offset, int num)
{
int i;
u_int32_t ret = 0;
@@ -41,7 +41,7 @@
}
/* Decode according to 3.1.1 */
-static void decode_fr(struct decoded_trau_frame *fr, u_int8_t *trau_bits)
+static void decode_fr(struct decoded_trau_frame *fr, const u_int8_t *trau_bits)
{
int i;
int d_idx = 0;
@@ -62,7 +62,7 @@
}
/* Decode according to 3.1.2 */
-static void decode_amr(struct decoded_trau_frame *fr, u_int8_t *trau_bits)
+static void decode_amr(struct decoded_trau_frame *fr, const u_int8_t *trau_bits)
{
int i;
int d_idx = 0;
@@ -84,7 +84,7 @@
memcpy(fr->d_bits + d_idx, trau_bits + 305, 11);
}
-int decode_trau_frame(struct decoded_trau_frame *fr, u_int8_t *trau_bits)
+int decode_trau_frame(struct decoded_trau_frame *fr, const u_int8_t *trau_bits)
{
u_int8_t cbits5 = get_bits(trau_bits, 17, 5);
@@ -116,3 +116,117 @@
return 0;
}
+
+const u_int8_t ft_fr_down_bits[] = { 1, 1, 1, 0, 0 };
+const u_int8_t ft_idle_down_bits[] = { 0, 1, 1, 1, 0 };
+
+/* modify an uplink TRAU frame so we can send it downlink */
+int trau_frame_up2down(struct decoded_trau_frame *fr)
+{
+ u_int8_t cbits5 = get_bits(fr->c_bits, 0, 5);
+
+ switch (cbits5) {
+ case TRAU_FT_FR_UP:
+ memcpy(fr->c_bits, ft_fr_down_bits, 5);
+ /* clear time alignment */
+ memset(fr->c_bits+5, 0, 6);
+ /* FIXME: SP / BFI in case of DTx */
+ /* C12 .. C21 are spare and coded as '1' */
+ memset(fr->c_bits+11, 0, 10);
+ break;
+ case TRAU_FT_EFR:
+ /* clear time alignment */
+ memset(fr->c_bits+5, 0, 6);
+ /* FIXME: set UFE appropriately */
+ /* FIXME: SP / BFI in case of DTx */
+ break;
+ case TRAU_FT_IDLE_UP:
+ memcpy(fr->c_bits, ft_idle_down_bits, 5);
+ /* clear time alignment */
+ memset(fr->c_bits+5, 0, 6);
+ /* FIXME: SP / BFI in case of DTx */
+ /* C12 .. C21 are spare and coded as '1' */
+ memset(fr->c_bits+11, 0, 10);
+ break;
+ case TRAU_FT_FR_DOWN:
+ case TRAU_FT_IDLE_DOWN:
+ case TRAU_FT_OM_DOWN:
+ case TRAU_FT_DATA_DOWN:
+ /* we cannot convert a downlink to a downlink frame */
+ return -EINVAL;
+ break;
+ case TRAU_FT_AMR:
+ case TRAU_FT_OM_UP:
+ case TRAU_FT_DATA_UP:
+ case TRAU_FT_D145_SYNC:
+ case TRAU_FT_EDATA:
+ fprintf(stderr, "unimplemented TRAU Frame Type 0x%02x\n", cbits5);
+ return -1;
+ break;
+ default:
+ fprintf(stderr, "unknown TRAU Frame Type 0x%02x\n", cbits5);
+ return -1;
+ break;
+ }
+
+ return 0;
+
+}
+
+static void encode_fr(u_int8_t *trau_bits, const struct decoded_trau_frame *fr)
+{
+ int i;
+ int d_idx = 0;
+
+ trau_bits[16] = 1;
+ /* C1 .. C15 */
+ memcpy(trau_bits+17, fr->c_bits+0, 15);
+ /* D1 .. D255 */
+ for (i = 32; i < 304; i+= 16) {
+ trau_bits[i] = 1;
+ memcpy(trau_bits+i+1, fr->d_bits + d_idx, 15);
+ d_idx += 15;
+ }
+ /* D256 .. D260 */
+ trau_bits[304] = 1;
+ memcpy(trau_bits + 305, fr->d_bits + d_idx, 5);
+ /* C16 .. C21 */
+ memcpy(trau_bits+310, fr->c_bits+15, 6);
+ /* T1 .. T4 */
+ memcpy(trau_bits+316, fr->t_bits+0, 4);
+}
+
+
+int encode_trau_frame(u_int8_t *trau_bits, const struct decoded_trau_frame *fr)
+{
+ u_int8_t cbits5 = get_bits(fr->c_bits, 0, 5);
+
+ /* 16 bits of sync header */
+ memset(trau_bits, 0, 16);
+
+ switch (cbits5) {
+ case TRAU_FT_FR_UP:
+ case TRAU_FT_FR_DOWN:
+ case TRAU_FT_IDLE_UP:
+ case TRAU_FT_IDLE_DOWN:
+ case TRAU_FT_EFR:
+ encode_fr(trau_bits, fr);
+ break;
+ case TRAU_FT_AMR:
+ case TRAU_FT_OM_UP:
+ case TRAU_FT_OM_DOWN:
+ case TRAU_FT_DATA_UP:
+ case TRAU_FT_DATA_DOWN:
+ case TRAU_FT_D145_SYNC:
+ case TRAU_FT_EDATA:
+ fprintf(stderr, "unimplemented TRAU Frame Type 0x%02x\n", cbits5);
+ return -1;
+ break;
+ default:
+ fprintf(stderr, "unknown TRAU Frame Type 0x%02x\n", cbits5);
+ return -1;
+ break;
+ }
+
+ return 0;
+}