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osmo-mgw
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* 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
This commit is contained in:
Harald Welte 2009-01-05 20:12:47 +00:00
parent 38e04372e5
commit 418f5a4e25
2 changed files with 122 additions and 5 deletions
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5
include/openbsc/trau_frame.h
View File

@ -56,6 +56,9 @@ struct decoded_trau_frame {
#define TRAU_FT_IDLE_DOWN 0x0e /* 0 1 1 1 0 - 3.5.5 */
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);
int encode_trau_frame(u_int8_t *trau_bits, const struct decoded_trau_frame *fr);
int trau_frame_up2down(struct decoded_trau_frame *fr);
#endif /* _TRAU_FRAME_H */

122
src/trau_frame.c
View File

@ -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 @@ static u_int32_t get_bits(u_int8_t *bitbuf, int offset, int num)
}
/* 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 @@ static void decode_fr(struct decoded_trau_frame *fr, u_int8_t *trau_bits)
}
/* 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 @@ static void decode_amr(struct decoded_trau_frame *fr, u_int8_t *trau_bits)
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 @@ int decode_trau_frame(struct decoded_trau_frame *fr, u_int8_t *trau_bits)
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;
}