/* ScummVM - Scumm Interpreter
 * Copyright (C) 2003 The ScummVM project
 *
 * 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., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 * $Header$
 *
 */

#include <string.h>
#include "common/scummsys.h"
#include "sky/rnc_deco.h"

#define ROL(x, n) (((x) << (n)) | ((x) >> (16 - (n))))
#define ROR(x, n) (((x) << (16 - (n))) | ((x) >> (n)))
#define XCHG(a, b) (a ^=b, b ^= a, a ^= b)

//conditional flags
#define CHECKSUMS	   1
#define PROTECTED	   0

//return codes
#define NOT_PACKED	  0
#define PACKED_CRC	  -1
#define UNPACKED_CRC	-2

//other defines
#define TABLE_SIZE	  (16 * 8)
#define MIN_LENGTH	  2
#define HEADER_LEN	  18

RncDecoder::RncDecoder()
{
	_bitBuffl = 0;
	_bitBuffh = 0;
	_bitCount = 0;
}

RncDecoder::~RncDecoder()
{

}

void RncDecoder::initCrc()
{
	uint16 cnt = 0;
	uint16 tmp1 = 0;
	uint16 tmp2 = 0;

	for (tmp2 = 0; tmp2 < 0x100; tmp2++) {
		tmp1 = tmp2; 
		for (cnt = 8; cnt > 0; cnt--) {
			if (tmp1 % 2) {
				tmp1 /= 2;
				tmp1 ^= 0x0a001;
			} else
				tmp1 /= 2;
		}
		_crcTable[tmp2] = tmp1;
	}
}

//calculate 16 bit crc of a block of memory
uint16 RncDecoder::crcBlock(uint8 *block, uint32 size)
{
	uint16 crc = 0;
	uint8 *crcTable8 = (uint8 *)_crcTable; //make a uint8* to crc_table
	uint8 tmp;
	uint32 i;

	for (i = 0; i < size; i++) {
		tmp = *block++;
		crc ^= tmp; 
		tmp = (uint8)((crc >> 8) & 0x00FF); 
		crc &= 0x00FF;  
		crc = crc << 1; 
		crc = *(uint16 *)&crcTable8[crc];
		crc ^= tmp;
	}

	return crc;
}

uint16 RncDecoder::inputBits(uint8 amount)
{
	uint16 newBitBuffh = _bitBuffh;
	uint16 newBitBuffl = _bitBuffl;
	int16 newBitCount = _bitCount;
	uint16 remBits, returnVal;

	returnVal = ((1 << amount) - 1) & newBitBuffl;	
	newBitCount -= amount;

	if (newBitCount < 0) {
		newBitCount += amount;
		XCHG(newBitCount, amount);
		remBits = ROR((uint16)(((1 << amount) - 1) & newBitBuffh), amount);
		newBitBuffh >>= amount;
		newBitBuffl >>= amount;
		newBitBuffl |= remBits;	
		_srcPtr += 2;
		newBitBuffh = READ_LE_UINT16(_srcPtr);
		XCHG(newBitCount, amount);
		amount -= newBitCount;
		newBitCount = 16 - amount;
	}
	remBits = ROR((uint16)(((1 << amount) - 1) & newBitBuffh), amount);
	_bitBuffh = newBitBuffh >> amount;
	_bitBuffl = (newBitBuffl >> amount) | remBits;
	_bitCount = (uint8)newBitCount;

	return returnVal;
}

void RncDecoder::makeHufftable(uint16 *table) 
{
	uint16 bitLength, i, j;
	uint16 numCodes = inputBits(5);

	if (!numCodes)
		return;

	uint8 huffLength[16];
	for (i = 0; i < numCodes; i++)
		huffLength[i] = (uint8)(inputBits(4) & 0x00FF);

	uint16 huffCode = 0;

	for (bitLength = 1; bitLength < 17; bitLength++) {
		for (i = 0; i < numCodes; i++) {
			if (huffLength[i] == bitLength) {
				*table++ = (1 << bitLength) - 1;

				uint16 b = huffCode >> (16 - bitLength);
				uint16 a = 0;

				for (j = 0; j < bitLength; j++)
					a |= ((b >> j) & 1) << (bitLength - j - 1);
				*table++ = a;

				*(table + 0x1e) = (huffLength[i] << 8)|(i & 0x00FF);
				huffCode += 1 << (16 - bitLength);
			}
		}
	}
}

uint16 RncDecoder::inputValue(uint16 *table)
{
	uint16 valOne, valTwo, value = _bitBuffl;

	do {
		valTwo = (*table++) & value;
		valOne = *table++;

	} while (valOne != valTwo);

	value = *(table + 0x1e);
	inputBits((uint8)((value>>8) & 0x00FF));
	value &= 0x00FF;

	if (value >= 2) {
		value--;
		valOne = inputBits((uint8)value & 0x00FF);
		valOne |= (1 << value);
		value = valOne;
	}

	return value;
}

int32 RncDecoder::unpackM1(void *input, void *output, uint16 key)
{
	uint8 *inputHigh, *outputLow, *outputHigh;
	uint8 *inputptr = (uint8 *)input;

	uint32 unpackLen = 0;
	uint32 packLen = 0;
	uint16 counts = 0;

#ifdef CHECKSUMS
	uint16 crcUnpacked = 0;
	uint16 crcPacked = 0;
#endif
	
	if (CHECKSUMS)
		initCrc();

	//Check for "RNC "
	if (READ_BE_UINT32(inputptr) != 0x524e4301)
		return NOT_PACKED;

	inputptr += 4;

	// read unpacked/packed file length
	unpackLen = READ_BE_UINT32(inputptr); inputptr += 4;
	packLen = READ_BE_UINT32(inputptr); inputptr += 4;

	uint8 blocks = *(inputptr + 5);

	if (CHECKSUMS) {
		//read CRC's
		crcUnpacked = READ_BE_UINT16(inputptr); inputptr += 2;
		crcPacked = READ_BE_UINT16(inputptr); inputptr += 2;
		inputptr = (inputptr + HEADER_LEN - 16);

		if (crcBlock(inputptr, packLen) != crcPacked)
			return PACKED_CRC;

		inputptr = (((uint8 *)input) + HEADER_LEN); 
		_srcPtr = inputptr;
	}

	// inputLow = *input
	inputHigh = ((uint8 *)input) + packLen + HEADER_LEN;;
	outputLow = (uint8 *)output;
	outputHigh = *(((uint8 *)input) + 16) + unpackLen + outputLow;

	if (! ((inputHigh <= outputLow) || (outputHigh <= inputHigh)) ) {
		_srcPtr = inputHigh;
		_dstPtr = outputHigh;
		memcpy((_dstPtr-packLen), (_srcPtr-packLen), packLen);
		_srcPtr = (_dstPtr-packLen);
	}

	_dstPtr = (uint8 *)output;
	_bitCount = 0;

	_bitBuffl = READ_LE_UINT16(_srcPtr);
	inputBits(2);
	
	do {
		makeHufftable(_rawTable);
		makeHufftable(_posTable);
		makeHufftable(_lenTable);

		counts = inputBits(16);

		for (;;) {
			uint32 inputBytes = inputValue(_rawTable);

			if (inputBytes) {
				memcpy(_dstPtr, _srcPtr, inputBytes); //memcpy is allowed here
				_dstPtr += inputBytes;
				_srcPtr += inputBytes;
				uint16 b = READ_LE_UINT16(_srcPtr);
				uint16 a = ROL(b, _bitCount);
				uint16 d = ((1 << _bitCount) - 1);
				_bitBuffl &= d;
				d &= a;

				a = READ_LE_UINT16((_srcPtr + 2));
				b = (b << _bitCount);
				a = (a << _bitCount);
				a |= d;
				_bitBuffl |= b;
				_bitBuffh = a;
			}

			if (--counts) {
				uint32 inputOffset = inputValue(_posTable) + 1;
				uint32 inputLength = inputValue(_lenTable) + MIN_LENGTH;

				inputHigh = _srcPtr;
				_srcPtr = (_dstPtr-inputOffset);

				//Don't use memcpy here! because input and output overlap	
				while (inputLength--)
					*_dstPtr++ = *_srcPtr++;

				_srcPtr = inputHigh;
			} else
				break;

		}
	} while (--blocks);

	if (CHECKSUMS) {
		if (crcBlock((uint8 *)output, unpackLen) != crcUnpacked)
			return UNPACKED_CRC;
	}

	// all is done..return the amount of unpacked bytes
	return unpackLen;
}