/*
 * 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 the internal input form for the HRv1 decoder.  It is logically
 * equivalent to calling gsmhr_rtp_in_preen() followed by
 * gsmhr_decoder_twts002_in(), but is more efficient by avoiding the extra
 * intermediate buffer and copying.
 */

#include <stdint.h>
#include <string.h>
#include "tw_gsmhr.h"

static void emit_bfi_nodata(int16_t *params)
{
	memset(params, 0, sizeof(int16_t) * GSMHR_NUM_PARAMS);
	params[18] = 2;		/* BFI with no data */
	params[19] = 0;		/* UFI */
	params[20] = 0;		/* SID */
	params[21] = 0;		/* TAF */
}

int gsmhr_rtp_in_direct(const uint8_t *rtp_in, unsigned rtp_in_len,
			int16_t *params)
{
	int ft;

	switch (rtp_in_len) {
	case 0:
		/* BFI-no-data, but not an invalid RTP input per se */
		emit_bfi_nodata(params);
		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:
			gsmhr_decoder_twts002_in(rtp_in, params);
			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.
		 */
		gsmhr_unpack_ts101318(rtp_in, params);
		params[18] = 0;		/* BFI */
		params[19] = 0;		/* UFI */
		params[20] = gsmhr_ts101318_is_perfect_sid(rtp_in);
		params[21] = 0;		/* TAF */
		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:
			gsmhr_decoder_twts002_in(rtp_in, params);
			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.
		 */
		emit_bfi_nodata(params);
		return -1;
	}
}