#include "defines.h"
#include <fstream>

static int masks[17]={
	0x0000,
	0x0001,
	0x0003,
	0x0007,
	0x000F,
	0x001F,
	0x003F,
	0x007F,
	0x00FF,
	0x01FF,
	0x03FF,
	0x07FF,
	0x0FFF,
	0x1FFF,
	0x3FFF,
	0x7FFF,
	0xFFFF
};

class CLZWEncoder 
{


	int imgW, imgH;
	byte* pixAry;
	int initCodeSize;
	int remaining;
	int curPixel;

	// GIFCOMPR.C       - GIF Image compression routines
	//
	// Lempel-Ziv compression based on 'compress'.  GIF modifications by
	// David Rowley (mgardi@watdcsu.waterloo.edu)

	// General DEFINEs

	static const int BITS = 12;

	static const int HSIZE = 5003; // 80% occupancy

	// GIF Image compression - modified 'compress'
	//
	// Based on: compress.c - File compression ala IEEE Computer, June 1984.
	//
	// By Authors:  Spencer W. Thomas      (decvax!harpo!utah-cs!utah-gr!thomas)
	//              Jim McKie              (decvax!mcvax!jim)
	//              Steve Davies           (decvax!vax135!petsd!peora!srd)
	//              Ken Turkowski          (decvax!decwrl!turtlevax!ken)
	//              James A. Woods         (decvax!ihnp4!ames!jaw)
	//              Joe Orost              (decvax!vax135!petsd!joe)

	int n_bits; // number of bits/code
	int maxbits; // user settable max # bits/code
	int maxcode; // maximum code, given n_bits
	int maxmaxcode; // should NEVER generate this code

	int htab[HSIZE];
	int codetab[HSIZE];

	int hsize; // for dynamic table sizing

	int free_ent; // first unused entry

	// block compression parameters -- after all codes are used up,
	// and compression rate changes, start over.
	bool clear_flg;

	// Algorithm:  use open addressing double hashing (no chaining) on the
	// prefix code / next character combination.  We do a variant of Knuth's
	// algorithm D (vol. 3, sec. 6.4) along with G. Knott's relatively-prime
	// secondary probe.  Here, the modular division first probe is gives way
	// to a faster exclusive-or manipulation.  Also do block compression with
	// an adaptive reset, whereby the code table is cleared when the compression
	// ratio decreases, but after the table fills.  The variable-length output
	// codes are re-sized at this point, and a special CLEAR code is generated
	// for the decompressor.  Late addition:  construct the table according to
	// file size for noticeable speed improvement on small files.  Please direct
	// questions about this implementation to ames!jaw.

	int g_init_bits;

	int ClearCode;
	int EOFCode;
	// Number of characters so far in this 'packet'
	int a_count;

	// Define the storage for the packet accumulator
	byte accum[256];

	// output
	//
	// Output the given code.
	// Inputs:
	//      code:   A n_bits-bit integer.  If == -1, then EOF.  This assumes
	//              that n_bits =< wordsize - 1.
	// Outputs:
	//      Outputs code to the file.
	// Assumptions:
	//      Chars are 8 bits long.
	// Algorithm:
	//      Maintain a BITS character long buffer (so that 8 codes will
	// fit in it exactly).  Use the VAX insv instruction to insert each
	// code in turn.  When the buffer fills up empty it and start over.

	int cur_accum;
	int cur_bits;



	// Add a character to the end of the current packet, and if it is 254
	// characters, flush the packet to disk.
	void Add(byte c, fstream* outs)
	{
		accum[a_count++] = c;
		if (a_count >= 254)
			Flush(outs);
	}

	// Clear out the hash table

	// table clear for block compress
	void ClearTable(fstream* outs)
	{
		ResetCodeTable(hsize);
		free_ent = ClearCode + 2;
		clear_flg = true;

		Output(ClearCode, outs);
	}

	// reset code table
	void ResetCodeTable(int hsize) 
	{
		for (int i = 0; i < hsize; ++i)
			htab[i] = -1;
	}

	void Compress(int init_bits, fstream* outs)
	{
		int fcode;
		int i /* = 0 */;
		int c;
		int ent;
		int disp;
		int hsize_reg;
		int hshift;

		// Set up the globals:  g_init_bits - initial number of bits
		g_init_bits = init_bits;

		// Set up the necessary values
		clear_flg = false;
		n_bits = g_init_bits;
		maxcode = MaxCode(n_bits);

		ClearCode = 1 << (init_bits - 1);
		EOFCode = ClearCode + 1;
		free_ent = ClearCode + 2;

		a_count = 0; // clear packet

		ent = NextPixel();

		hshift = 0;
		for (fcode = hsize; fcode < 65536; fcode *= 2)
			++hshift;
		hshift = 8 - hshift; // set hash code range bound

		hsize_reg = hsize;
		ResetCodeTable(hsize_reg); // clear hash table

		Output(ClearCode, outs);

outer_loop : 
		while ((c = NextPixel()) != EOF) 
			{
				fcode = (c << maxbits) + ent;
				i = (c << hshift) ^ ent; // xor hashing

				if (htab[i] == fcode) 
				{
					ent = codetab[i];
					continue;
				} 
				else if (htab[i] >= 0) // non-empty slot
				{
					disp = hsize_reg - i; // secondary hash (after G. Knott)
					if (i == 0)
						disp = 1;
					do 
					{
						if ((i -= disp) < 0)
							i += hsize_reg;

						if (htab[i] == fcode) 
						{
							ent = codetab[i];
							goto outer_loop;
						}
					} while (htab[i] >= 0);
				}
				Output(ent, outs);
				ent = c;
				if (free_ent < maxmaxcode) 
				{
					codetab[i] = free_ent++; // code -> hashtable
					htab[i] = fcode;
				} 
				else
					ClearTable(outs);
			}
			// Put out the final code.
			Output(ent, outs);
			Output(EOFCode, outs);
	}

	// Flush the packet to disk, and reset the accumulator
	void Flush(fstream* outs)
	{
		if (a_count > 0) 
		{
			outs->write((char*)&a_count, 1);
			outs->write((char*)&(accum[0]), a_count);
			a_count = 0;
		}
	}

	int MaxCode(int n_bits) 
	{
		return (1 << n_bits) - 1;
	}

	//----------------------------------------------------------------------------
	// Return the next pixel from the image
	//----------------------------------------------------------------------------
	int NextPixel() 
	{
		if (remaining == 0)
			return EOF;

		--remaining;

		int temp = curPixel + 1;
		if ( temp < imgW * imgH)
		{
			byte pix = pixAry[curPixel++];

			return (int)pix & 0xff;
		}
		return 0xff;
	}

	void Output(int code, fstream* outs)
	{
		cur_accum &= masks[cur_bits];

		if (cur_bits > 0)
			cur_accum |= (code << cur_bits);
		else
			cur_accum = code;

		cur_bits += n_bits;

		while (cur_bits >= 8) 
		{
			Add(*((byte*) &cur_accum), outs);
			cur_accum >>= 8;
			cur_bits -= 8;
		}

		// If the next entry is going to be too big for the code size,
		// then increase it, if possible.
		if (free_ent > maxcode || clear_flg) 
		{
			if (clear_flg) 
			{
				maxcode = MaxCode(n_bits = g_init_bits);
				clear_flg = false;
			} 
			else 
			{
				++n_bits;
				if (n_bits == maxbits)
					maxcode = maxmaxcode;
				else
					maxcode = MaxCode(n_bits);
			}
		}

		if (code == EOFCode) 
		{
			// At EOF, write the rest of the buffer.
			while (cur_bits > 0) 
			{
				Add(*((byte*) &cur_accum), outs);
				cur_accum >>= 8;
				cur_bits -= 8;
			}

			Flush(outs);
		}
	}

public:
	//----------------------------------------------------------------------------
	CLZWEncoder(int width, int height, byte* pixels, int color_depth) 
		:imgW(width), 
		imgH(height),
		pixAry(pixels),
		initCodeSize(max(2, color_depth)),
		remaining(0),
		curPixel(0),

		n_bits(0),
		maxbits(BITS),
		maxcode(0),
		maxmaxcode(1 << BITS),
		hsize(HSIZE),
		free_ent(0),
		clear_flg(false),
		g_init_bits(0),
		ClearCode(0),
		EOFCode(0),
		a_count(0),
		cur_accum(0),
		cur_bits(0)
	{
		memset(codetab, 0, sizeof(int)*HSIZE);
	}

	~CLZWEncoder(){}

	//----------------------------------------------------------------------------
	void Encode( fstream* os)
	{
		os->write((char*)&initCodeSize, 1); // write "initial code size" byte
		//os<<(byte) (initCodeSize & 0xff);

		remaining = imgW * imgH; // reset navigation variables
		curPixel = 0;

		Compress(initCodeSize + 1, os); // compress and write the pixel data

		int a = 0;
		os->write((char*)&a, 1); // write block terminator
	}
};

