256 lines
6.1 KiB
C
256 lines
6.1 KiB
C
/* TRAU frame handling according to GSM TS 08.60 */
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/* (C) 2009 by Harald Welte <laforge@gnumonks.org>
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* All Rights Reserved
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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*/
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#include <unistd.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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#include <errno.h>
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#include <openbsc/trau_frame.h>
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#include <openbsc/subchan_demux.h>
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#include <openbsc/debug.h>
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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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for (i = offset; i < offset + num; i++) {
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ret = ret << 1;
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if (bitbuf[i])
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ret |= 1;
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}
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return ret;
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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, 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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/* C1 .. C15 */
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memcpy(fr->c_bits+0, trau_bits+17, 15);
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/* C16 .. C21 */
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memcpy(fr->c_bits+15, trau_bits+310, 6);
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/* T1 .. T4 */
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memcpy(fr->t_bits+0, trau_bits+316, 4);
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/* D1 .. D255 */
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for (i = 32; i < 304; i+= 16) {
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memcpy(fr->d_bits + d_idx, trau_bits+i+1, 15);
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d_idx += 15;
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}
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/* D256 .. D260 */
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memcpy(fr->d_bits + d_idx, trau_bits + 305, 5);
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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, 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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/* C1 .. C15 */
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memcpy(fr->c_bits+0, trau_bits+17, 15);
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/* C16 .. C25 */
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memcpy(fr->c_bits+15, trau_bits+33, 10);
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/* T1 .. T4 */
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memcpy(fr->t_bits+0, trau_bits+316, 4);
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/* D1 .. D5 */
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memcpy(fr->d_bits, trau_bits+43, 5);
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/* D6 .. D245 */
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for (i = 48; i < 304; i += 16) {
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memcpy(fr->d_bits + d_idx, trau_bits+i+1, 15);
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d_idx += 15;
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}
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/* D246 .. D256 */
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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, 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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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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decode_fr(fr, trau_bits);
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break;
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case TRAU_FT_AMR:
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decode_amr(fr, trau_bits);
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break;
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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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DEBUGP(DMUX, "can't decode 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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DEBUGP(DMUX, "can't decode 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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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, 0x01, 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, 0x01, 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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DEBUGP(DMUX, "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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DEBUGP(DMUX, "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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/* FIXME: handle timing adjustment */
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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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DEBUGP(DMUX, "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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DEBUGP(DMUX, "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 struct decoded_trau_frame fr_idle_frame = {
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.c_bits = { 0, 1, 1, 1, 0 }, /* IDLE DOWNLINK 3.5.5 */
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.t_bits = { 1, 1, 1, 1 },
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};
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static u_int8_t encoded_idle_frame[TRAU_FRAME_BITS];
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static int dbits_initted;
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u_int8_t *trau_idle_frame(void)
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{
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/* only initialize during the first call */
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if (!dbits_initted) {
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/* set all D-bits to 1 */
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memset(&fr_idle_frame.d_bits, 0x01, 260);
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encode_fr(encoded_idle_frame, &fr_idle_frame);
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}
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return encoded_idle_frame;
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}
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