+
−/*
+
− * The function implemented in this module takes whatever HRv1 payload format
+
− * came in from RTP (can be RFC 5993 with or without TW-TS-002 extensions,
+
− * can be bare TS 101 318, can be zero-length or missing payload) and turns it
+
− * into canonical TW-TS-002 format, be it for storage or for immediate
+
− * further processing.
+
− */
+
−
+
−#include <stdint.h>
+
−#include <string.h>
+
−#include "tw_gsmhr.h"
+
−
+
−int gsmhr_rtp_in_preen(const uint8_t *rtp_in, unsigned rtp_in_len,
+
−			uint8_t *canon_pl)
+
−{
+
−	int ft;
+
−
+
−	switch (rtp_in_len) {
+
−	case 0:
+
−		/* BFI-no-data, but not an invalid RTP input per se */
+
−		canon_pl[0] = 0x70;
+
−		return 0;
+
−	case 1:
+
−		/*
+
−		 * This length is valid only if the payload is in
+
−		 * RFC 5993 or TW-TS-002 format with FT=1 or FT=7.
+
−		 */
+
−		if (rtp_in[0] & 0x80)
+
−			goto bad_rtp_input;
+
−		ft = rtp_in[0] >> 4;
+
−		switch (ft) {
+
−		case 1:
+
−			if (rtp_in[0] & 0x04)
+
−				goto bad_rtp_input;
+
−			/* FALL THRU */
+
−		case 7:
+
−			canon_pl[0] = rtp_in[0];
+
−			return 0;
+
−		default:
+
−			goto bad_rtp_input;
+
−		}
+
−	case GSMHR_FRAME_LEN_RPF:
+
−		/*
+
−		 * The length is that of a TS 101 318 payload.
+
−		 * No further checks can be done: every possible
+
−		 * bit pattern is a valid payload in this format.
+
−		 * But we do need to check for a perfect SID
+
−		 * (the only kind of SID this format allows)
+
−		 * and mark it accordingly in the output.
+
−		 */
+
−		canon_pl[0] = gsmhr_ts101318_is_perfect_sid(rtp_in) << 4;
+
−		memcpy(canon_pl + 1, rtp_in, GSMHR_FRAME_LEN_RPF);
+
−		return 0;
+
−	case GSMHR_FRAME_LEN_5993:
+
−		/*
+
−		 * This length is valid only if the payload is in
+
−		 * RFC 5993 or TW-TS-002 format with FT=0, FT=2 or FT=6.
+
−		 */
+
−		if (rtp_in[0] & 0x80)
+
−			goto bad_rtp_input;
+
−		ft = rtp_in[0] >> 4;
+
−		switch (ft) {
+
−		case 1:
+
−			if (!(rtp_in[0] & 0x04))
+
−				goto bad_rtp_input;
+
−			/* FALL THRU */
+
−		case 0:
+
−		case 2:
+
−		case 6:
+
−			memcpy(canon_pl, rtp_in, GSMHR_FRAME_LEN_5993);
+
−			return 0;
+
−		default:
+
−			goto bad_rtp_input;
+
−		}
+
−	default:
+
−	bad_rtp_input:
+
−		/*
+
−		 * Treat it like BFI-no-data, and tell the caller
+
−		 * that we received an invalid RTP payload.
+
−		 */
+
−		canon_pl[0] = 0x70;
+
−		return -1;
+
−	}
+
−}