/*
 * This module implements the EFR decoding part of trau-parse.
 */

#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <gsm_efr.h>
#include "osmo_bits.h"

/*
 * EFR TRAU parity
 *
 * g(x) = x^3 + x^1 + 1
 */
static const struct osmo_crc8gen_code gsm0860_efr_crc3 = {
	.bits = 3,
	.poly = 0x3,
	.init = 0x0,
	.remainder = 0x7,
};

/* re-combine EFR parity bits */
static inline void efr_parity_bits_1(ubit_t *check_bits, const ubit_t *d_bits)
{
	memcpy(check_bits + 0 , d_bits + 0, 22);
	memcpy(check_bits + 22 , d_bits + 24, 3);
	check_bits[25] = d_bits[28];
}

static inline void efr_parity_bits_2(ubit_t *check_bits, const ubit_t *d_bits)
{
	memcpy(check_bits + 0 , d_bits + 42, 10);
	memcpy(check_bits + 10 , d_bits + 90, 2);
}

static inline void efr_parity_bits_3(ubit_t *check_bits, const ubit_t *d_bits)
{
	memcpy(check_bits + 0 , d_bits + 98, 5);
	check_bits[5] = d_bits[104];
	memcpy(check_bits + 6 , d_bits + 143, 2);
}

static inline void efr_parity_bits_4(ubit_t *check_bits, const ubit_t *d_bits)
{
	memcpy(check_bits + 0 , d_bits + 151, 10);
	memcpy(check_bits + 10 , d_bits + 199, 2);
}

static inline void efr_parity_bits_5(ubit_t *check_bits, const ubit_t *d_bits)
{
	memcpy(check_bits + 0 , d_bits + 207, 5);
	check_bits[5] = d_bits[213];
	memcpy(check_bits + 6 , d_bits + 252, 2);
}

void
check_efr_crc(d_bits)
	ubit_t *d_bits;
{
	ubit_t check_bits[26];
	int rc1, rc2, rc3, rc4, rc5;

	efr_parity_bits_1(check_bits, d_bits);
	rc1 = osmo_crc8gen_check_bits(&gsm0860_efr_crc3, check_bits, 26,
					d_bits + 39);
	efr_parity_bits_2(check_bits, d_bits);
	rc2 = osmo_crc8gen_check_bits(&gsm0860_efr_crc3, check_bits, 12,
					d_bits + 95);
	efr_parity_bits_3(check_bits, d_bits);
	rc3 = osmo_crc8gen_check_bits(&gsm0860_efr_crc3, check_bits, 8,
					d_bits + 148);
	efr_parity_bits_4(check_bits, d_bits);
	rc4 = osmo_crc8gen_check_bits(&gsm0860_efr_crc3, check_bits, 12,
					d_bits + 204);
	efr_parity_bits_5(check_bits, d_bits);
	rc5 = osmo_crc8gen_check_bits(&gsm0860_efr_crc3, check_bits, 8,
					d_bits + 257);
	printf("  D1=%u CRC: %s %s %s %s %s\n", d_bits[0],
		rc1 ? "bad" : "good", rc2 ? "bad" : "good",
		rc3 ? "bad" : "good", rc4 ? "bad" : "good",
		rc5 ? "bad" : "good");
}