* 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
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418f5a4e25
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@ -56,6 +56,9 @@ struct decoded_trau_frame {
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#define TRAU_FT_IDLE_DOWN 0x0e /* 0 1 1 1 0 - 3.5.5 */
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int decode_trau_frame(struct decoded_trau_frame *fr, u_int8_t *trau_bits);
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int decode_trau_frame(struct decoded_trau_frame *fr, const u_int8_t *trau_bits);
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int encode_trau_frame(u_int8_t *trau_bits, const struct decoded_trau_frame *fr);
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int trau_frame_up2down(struct decoded_trau_frame *fr);
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#endif /* _TRAU_FRAME_H */
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122
src/trau_frame.c
122
src/trau_frame.c
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@ -27,7 +27,7 @@
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#include <openbsc/trau_frame.h>
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static u_int32_t get_bits(u_int8_t *bitbuf, int offset, int num)
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static u_int32_t get_bits(const u_int8_t *bitbuf, int offset, int num)
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{
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int i;
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u_int32_t ret = 0;
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@ -41,7 +41,7 @@ static u_int32_t get_bits(u_int8_t *bitbuf, int offset, int num)
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}
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/* Decode according to 3.1.1 */
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static void decode_fr(struct decoded_trau_frame *fr, u_int8_t *trau_bits)
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static void decode_fr(struct decoded_trau_frame *fr, const u_int8_t *trau_bits)
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{
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int i;
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int d_idx = 0;
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@ -62,7 +62,7 @@ static void decode_fr(struct decoded_trau_frame *fr, u_int8_t *trau_bits)
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}
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/* Decode according to 3.1.2 */
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static void decode_amr(struct decoded_trau_frame *fr, u_int8_t *trau_bits)
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static void decode_amr(struct decoded_trau_frame *fr, const u_int8_t *trau_bits)
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{
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int i;
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int d_idx = 0;
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@ -84,7 +84,7 @@ static void decode_amr(struct decoded_trau_frame *fr, u_int8_t *trau_bits)
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memcpy(fr->d_bits + d_idx, trau_bits + 305, 11);
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}
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int decode_trau_frame(struct decoded_trau_frame *fr, u_int8_t *trau_bits)
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int decode_trau_frame(struct decoded_trau_frame *fr, const u_int8_t *trau_bits)
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{
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u_int8_t cbits5 = get_bits(trau_bits, 17, 5);
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@ -116,3 +116,117 @@ int decode_trau_frame(struct decoded_trau_frame *fr, u_int8_t *trau_bits)
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return 0;
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}
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const u_int8_t ft_fr_down_bits[] = { 1, 1, 1, 0, 0 };
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const u_int8_t ft_idle_down_bits[] = { 0, 1, 1, 1, 0 };
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/* modify an uplink TRAU frame so we can send it downlink */
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int trau_frame_up2down(struct decoded_trau_frame *fr)
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{
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u_int8_t cbits5 = get_bits(fr->c_bits, 0, 5);
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switch (cbits5) {
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case TRAU_FT_FR_UP:
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memcpy(fr->c_bits, ft_fr_down_bits, 5);
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/* clear time alignment */
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memset(fr->c_bits+5, 0, 6);
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/* FIXME: SP / BFI in case of DTx */
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/* C12 .. C21 are spare and coded as '1' */
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memset(fr->c_bits+11, 0, 10);
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break;
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case TRAU_FT_EFR:
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/* clear time alignment */
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memset(fr->c_bits+5, 0, 6);
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/* FIXME: set UFE appropriately */
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/* FIXME: SP / BFI in case of DTx */
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break;
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case TRAU_FT_IDLE_UP:
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memcpy(fr->c_bits, ft_idle_down_bits, 5);
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/* clear time alignment */
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memset(fr->c_bits+5, 0, 6);
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/* FIXME: SP / BFI in case of DTx */
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/* C12 .. C21 are spare and coded as '1' */
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memset(fr->c_bits+11, 0, 10);
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break;
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case TRAU_FT_FR_DOWN:
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case TRAU_FT_IDLE_DOWN:
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case TRAU_FT_OM_DOWN:
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case TRAU_FT_DATA_DOWN:
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/* we cannot convert a downlink to a downlink frame */
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return -EINVAL;
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break;
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case TRAU_FT_AMR:
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case TRAU_FT_OM_UP:
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case TRAU_FT_DATA_UP:
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case TRAU_FT_D145_SYNC:
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case TRAU_FT_EDATA:
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fprintf(stderr, "unimplemented TRAU Frame Type 0x%02x\n", cbits5);
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return -1;
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break;
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default:
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fprintf(stderr, "unknown TRAU Frame Type 0x%02x\n", cbits5);
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return -1;
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break;
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}
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return 0;
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}
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static void encode_fr(u_int8_t *trau_bits, const struct decoded_trau_frame *fr)
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{
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int i;
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int d_idx = 0;
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trau_bits[16] = 1;
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/* C1 .. C15 */
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memcpy(trau_bits+17, fr->c_bits+0, 15);
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/* D1 .. D255 */
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for (i = 32; i < 304; i+= 16) {
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trau_bits[i] = 1;
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memcpy(trau_bits+i+1, fr->d_bits + d_idx, 15);
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d_idx += 15;
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}
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/* D256 .. D260 */
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trau_bits[304] = 1;
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memcpy(trau_bits + 305, fr->d_bits + d_idx, 5);
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/* C16 .. C21 */
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memcpy(trau_bits+310, fr->c_bits+15, 6);
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/* T1 .. T4 */
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memcpy(trau_bits+316, fr->t_bits+0, 4);
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}
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int encode_trau_frame(u_int8_t *trau_bits, const struct decoded_trau_frame *fr)
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{
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u_int8_t cbits5 = get_bits(fr->c_bits, 0, 5);
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/* 16 bits of sync header */
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memset(trau_bits, 0, 16);
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switch (cbits5) {
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case TRAU_FT_FR_UP:
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case TRAU_FT_FR_DOWN:
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case TRAU_FT_IDLE_UP:
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case TRAU_FT_IDLE_DOWN:
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case TRAU_FT_EFR:
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encode_fr(trau_bits, fr);
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break;
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case TRAU_FT_AMR:
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case TRAU_FT_OM_UP:
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case TRAU_FT_OM_DOWN:
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case TRAU_FT_DATA_UP:
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case TRAU_FT_DATA_DOWN:
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case TRAU_FT_D145_SYNC:
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case TRAU_FT_EDATA:
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fprintf(stderr, "unimplemented TRAU Frame Type 0x%02x\n", cbits5);
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return -1;
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break;
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default:
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fprintf(stderr, "unknown TRAU Frame Type 0x%02x\n", cbits5);
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return -1;
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break;
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}
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return 0;
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}
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