82 lines
1.8 KiB
C
82 lines
1.8 KiB
C
/* AMR support for OsmoBTS-TRX */
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/* (C) 2013 by Andreas Eversberg <jolly@eversberg.eu>
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*
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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 Affero General Public License as published by
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* the Free Software Foundation; either version 3 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 Affero General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <errno.h>
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#include <stdint.h>
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static int amr_len_by_ft[16] = {
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12, 13, 15, 17, 19, 20, 26, 31,
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0, 0, 0, 0, 0, 0, 0, 0
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};
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int amr_decompose_payload(uint8_t *payload, int payload_len, uint8_t *_cmr,
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uint8_t *_ft, uint8_t *_bfi)
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{
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uint8_t cmr, f, ft, q;
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if (payload_len < 2)
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return -EINVAL;
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cmr = payload[0] >> 4;
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if (_cmr)
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*_cmr = cmr;
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f = payload[1] >> 7;
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ft = (payload[1] >> 3) & 0xf;
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if (_ft)
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*_ft = ft;
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q = (payload[1] >> 2) & 0x1;
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if (_bfi)
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*_bfi = !q;
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if (f) {
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fprintf(stderr, "%s: multiple payloads not supported\n",
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__func__);
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return -ENOTSUP;
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}
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if (payload_len - 2 < amr_len_by_ft[ft])
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return -EINVAL;
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return 2 + amr_len_by_ft[ft];
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}
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int amr_compose_payload(uint8_t *payload, uint8_t cmr, uint8_t ft, uint8_t bfi)
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{
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if (cmr >= 16)
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return -EINVAL;
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if (ft >= 16)
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return -EINVAL;
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payload[0] = cmr << 4;
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payload[1] = (ft << 3) | ((!bfi) << 2); /* F = 0 */
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return 2 + amr_len_by_ft[ft];
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}
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