/*
 *   Copyright (C) 2015,2016 by Jonathan Naylor G4KLX
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include "CRC.h"

#include "Utils.h"
#include "Log.h"

#include <cstdint>
#include <cstdio>
#include <cassert>
#include <cmath>

const uint16_t CCITT16_TABLE[] = {
	0x0000U, 0x1189U, 0x2312U, 0x329bU, 0x4624U, 0x57adU, 0x6536U, 0x74bfU,
	0x8c48U, 0x9dc1U, 0xaf5aU, 0xbed3U, 0xca6cU, 0xdbe5U, 0xe97eU, 0xf8f7U,
	0x1081U, 0x0108U, 0x3393U, 0x221aU, 0x56a5U, 0x472cU, 0x75b7U, 0x643eU,
	0x9cc9U, 0x8d40U, 0xbfdbU, 0xae52U, 0xdaedU, 0xcb64U, 0xf9ffU, 0xe876U,
	0x2102U, 0x308bU, 0x0210U, 0x1399U, 0x6726U, 0x76afU, 0x4434U, 0x55bdU,
	0xad4aU, 0xbcc3U, 0x8e58U, 0x9fd1U, 0xeb6eU, 0xfae7U, 0xc87cU, 0xd9f5U,
	0x3183U, 0x200aU, 0x1291U, 0x0318U, 0x77a7U, 0x662eU, 0x54b5U, 0x453cU,
	0xbdcbU, 0xac42U, 0x9ed9U, 0x8f50U, 0xfbefU, 0xea66U, 0xd8fdU, 0xc974U,
	0x4204U, 0x538dU, 0x6116U, 0x709fU, 0x0420U, 0x15a9U, 0x2732U, 0x36bbU,
	0xce4cU, 0xdfc5U, 0xed5eU, 0xfcd7U, 0x8868U, 0x99e1U, 0xab7aU, 0xbaf3U,
	0x5285U, 0x430cU, 0x7197U, 0x601eU, 0x14a1U, 0x0528U, 0x37b3U, 0x263aU,
	0xdecdU, 0xcf44U, 0xfddfU, 0xec56U, 0x98e9U, 0x8960U, 0xbbfbU, 0xaa72U,
	0x6306U, 0x728fU, 0x4014U, 0x519dU, 0x2522U, 0x34abU, 0x0630U, 0x17b9U,
	0xef4eU, 0xfec7U, 0xcc5cU, 0xddd5U, 0xa96aU, 0xb8e3U, 0x8a78U, 0x9bf1U,
	0x7387U, 0x620eU, 0x5095U, 0x411cU, 0x35a3U, 0x242aU, 0x16b1U, 0x0738U,
	0xffcfU, 0xee46U, 0xdcddU, 0xcd54U, 0xb9ebU, 0xa862U, 0x9af9U, 0x8b70U,
	0x8408U, 0x9581U, 0xa71aU, 0xb693U, 0xc22cU, 0xd3a5U, 0xe13eU, 0xf0b7U,
	0x0840U, 0x19c9U, 0x2b52U, 0x3adbU, 0x4e64U, 0x5fedU, 0x6d76U, 0x7cffU,
	0x9489U, 0x8500U, 0xb79bU, 0xa612U, 0xd2adU, 0xc324U, 0xf1bfU, 0xe036U,
	0x18c1U, 0x0948U, 0x3bd3U, 0x2a5aU, 0x5ee5U, 0x4f6cU, 0x7df7U, 0x6c7eU,
	0xa50aU, 0xb483U, 0x8618U, 0x9791U, 0xe32eU, 0xf2a7U, 0xc03cU, 0xd1b5U,
	0x2942U, 0x38cbU, 0x0a50U, 0x1bd9U, 0x6f66U, 0x7eefU, 0x4c74U, 0x5dfdU,
	0xb58bU, 0xa402U, 0x9699U, 0x8710U, 0xf3afU, 0xe226U, 0xd0bdU, 0xc134U,
	0x39c3U, 0x284aU, 0x1ad1U, 0x0b58U, 0x7fe7U, 0x6e6eU, 0x5cf5U, 0x4d7cU,
	0xc60cU, 0xd785U, 0xe51eU, 0xf497U, 0x8028U, 0x91a1U, 0xa33aU, 0xb2b3U,
	0x4a44U, 0x5bcdU, 0x6956U, 0x78dfU, 0x0c60U, 0x1de9U, 0x2f72U, 0x3efbU,
	0xd68dU, 0xc704U, 0xf59fU, 0xe416U, 0x90a9U, 0x8120U, 0xb3bbU, 0xa232U,
	0x5ac5U, 0x4b4cU, 0x79d7U, 0x685eU, 0x1ce1U, 0x0d68U, 0x3ff3U, 0x2e7aU,
	0xe70eU, 0xf687U, 0xc41cU, 0xd595U, 0xa12aU, 0xb0a3U, 0x8238U, 0x93b1U,
	0x6b46U, 0x7acfU, 0x4854U, 0x59ddU, 0x2d62U, 0x3cebU, 0x0e70U, 0x1ff9U,
	0xf78fU, 0xe606U, 0xd49dU, 0xc514U, 0xb1abU, 0xa022U, 0x92b9U, 0x8330U,
	0x7bc7U, 0x6a4eU, 0x58d5U, 0x495cU, 0x3de3U, 0x2c6aU, 0x1ef1U, 0x0f78U };

bool CCRC::checkFiveBit(bool* in, unsigned int tcrc)
{
	assert(in != NULL);

	unsigned int crc;
	encodeFiveBit(in, crc);

	return crc == tcrc;
}

void CCRC::encodeFiveBit(const bool* in, unsigned int& tcrc)
{
	assert(in != NULL);

	unsigned short total = 0U;
	for (unsigned int i = 0U; i < 72U; i += 8U) {
		unsigned char c;
		CUtils::bitsToByteBE(in + i, c);
		total += c;
	}

	total %= 31U;

	tcrc = total;
}

unsigned char CCRC::encodeEightBit(const unsigned char *in, unsigned int length)
{
	assert(in != NULL);

	unsigned char crc = 0x00U;

	for (unsigned int i = 0U; i < length; i++) {
		crc ^= in[i];
	
		for (unsigned int j = 0U; j < 8U; j++) {
			if ((crc & 0x80U) == 0x80U) {
				crc <<= 1;
				crc ^= 0x07U;
			} else {
				crc <<= 1;
			}
		}
	}

	return crc;
}

bool CCRC::checkCCITT16(const unsigned char *in, unsigned int length)
{
	assert(in != NULL);
	assert(length > 2U);

	unsigned short crc16 = 0U;

	for (unsigned int a = 0; a < (length - 2U); a++)	{
		unsigned char val = in[a];

		for (unsigned int i = 0U; i < 8U; i++) {
			bool c15 = (crc16 >> 15 & 0x01U) == 0x01U;
			bool bit = (val >> (7 - i) & 0x01U) == 0x01U;
			crc16 <<= 1;
			if (c15 ^ bit)
				crc16 ^= 0x1021U;
		}
	}

	LogMessage("CCITT16, %04X == %02X %02X", crc16, in[length - 2U], in[length - 1U]);

	return crc16 == (in[length - 2U] << 8 | in[length - 1U]);
}

void CCRC::addCCITT16(unsigned char *in, unsigned int length)
{
	assert(in != NULL);
	assert(length > 2U);

	union {
		uint16_t crc16;
		uint8_t  crc8[2U];
	};

	crc16 = 0xFFFFU;
	for (unsigned int i = 0U; i < (length - 2U); i++)
		crc16 = uint16_t(crc8[1U]) ^ CCITT16_TABLE[crc8[0U] ^ in[i]];

	crc16 = ~crc16;

	in[length - 2U] = crc8[0U];
	in[length - 1U] = crc8[1U];
}

unsigned char CCRC::crc8(const unsigned char *in, unsigned int length)
{
	unsigned int crc = 0U;

	for (unsigned int j = 0U; j < length; j++, in++) {
		crc ^= (*in << 8);

		for (unsigned int i = 0U; i < 8U; i++) {
			if (crc & 0x8000U)
				crc ^= (0x1070U << 3);
			crc <<= 1;
		}
	}

	return crc >> 8;
}