/**************************************************************
	LZARI.C -- A Data Compression Program
	(tab = 4 spaces)
***************************************************************
	4/7/1989 Haruhiko Okumura
	Use, distribute, and modify this program freely.
	Please send me your improved versions.
		PC-VAN		SCIENCE
		NIFTY-Serve	PAF01022
		CompuServe	74050,1022
**************************************************************/
#include "LzAri.h"
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

using namespace Framework;

CLzAri::CLzAri()
: putBuffer(0)
, putMask(128)
, getBuffer(0)
, getMask(0)
, low(0)
, high(Q4)
, value(0)
, shifts(0)
, inputStream(nullptr)
, outputStream(nullptr)
{

}

CLzAri::~CLzAri()
{

}

void CLzAri::Decompress(Framework::CStream& dst, Framework::CStream& src)
{
	CLzAri ari;
	ari.inputStream = &src;
	ari.outputStream = &dst;
	ari.Decode();
}

/********** Bit I/O **********/

void CLzAri::PutBit(int bit)  /* Output one bit (bit = 0,1) */
{
	if (bit) putBuffer |= putMask;
	if ((putMask >>= 1) == 0) 
	{
		outputStream->Write8(static_cast<uint8>(putBuffer));
		putBuffer = 0;
		putMask = 128;
	}
}

void CLzAri::FlushBitBuffer(void)  /* Send remaining bits */
{
	for (int i = 0; i < 7; i++) PutBit(0);
}

int CLzAri::GetBit(void)  /* Get one bit (0 or 1) */
{
	if ((getMask >>= 1) == 0)
	{
		if(inputStream->IsEOF())
		{
			getBuffer = 0;
		}
		else
		{
			getBuffer = inputStream->Read8();
		}
		getMask = 128;
	}
	return ((getBuffer & getMask) != 0);
}

/********** LZSS with multiple binary trees **********/

void CLzAri::InitTree(void)  /* Initialize trees */
{
	int  i;

	/* For i = 0 to N - 1, rson[i] and lson[i] will be the right and
	   left children of node i.  These nodes need not be initialized.
	   Also, dad[i] is the parent of node i.  These are initialized to
	   NIL (= N), which stands for 'not used.'
	   For i = 0 to 255, rson[N + i + 1] is the root of the tree
	   for strings that begin with character i.  These are initialized
	   to NIL.  Note there are 256 trees. */

	for (i = N + 1; i <= N + 256; i++) rson[i] = NIL;	/* root */
	for (i = 0; i < N; i++) dad[i] = NIL;	/* node */
}

void CLzAri::InsertNode(int r)
	/* Inserts string of length F, text_buf[r..r+F-1], into one of the
	   trees (text_buf[r]'th tree) and returns the longest-match position
	   and length via the global variables match_position and match_length.
	   If match_length = F, then removes the old node in favor of the new
	   one, because the old one will be deleted sooner.
	   Note r plays double role, as tree node and position in buffer. */
{
	int  i, p, cmp, temp;
	unsigned char  *key;

	cmp = 1;  key = &text_buf[r];  p = N + 1 + key[0];
	rson[r] = lson[r] = NIL;  match_length = 0;
	for ( ; ; ) {
		if (cmp >= 0) {
			if (rson[p] != NIL) p = rson[p];
			else {	rson[p] = r;  dad[r] = p;  return;  }
		} else {
			if (lson[p] != NIL) p = lson[p];
			else {	lson[p] = r;  dad[r] = p;  return;  }
		}
		for (i = 1; i < F; i++)
			if ((cmp = key[i] - text_buf[p + i]) != 0)  break;
		if (i > THRESHOLD) {
			if (i > match_length) {
				match_position = (r - p) & (N - 1);
				if ((match_length = i) >= F) break;
			} else if (i == match_length) {
				if ((temp = (r - p) & (N - 1)) < match_position)
					match_position = temp;
			}
		}
	}
	dad[r] = dad[p];  lson[r] = lson[p];  rson[r] = rson[p];
	dad[lson[p]] = r;  dad[rson[p]] = r;
	if (rson[dad[p]] == p) rson[dad[p]] = r;
	else		       lson[dad[p]] = r;
	dad[p] = NIL;  /* remove p */
}

void CLzAri::DeleteNode(int p)	/* Delete node p from tree */
{
	int  q;

	if (dad[p] == NIL) return;  /* not in tree */
	if (rson[p] == NIL) q = lson[p];
	else if (lson[p] == NIL) q = rson[p];
	else {
		q = lson[p];
		if (rson[q] != NIL) {
			do {  q = rson[q];  } while (rson[q] != NIL);
			rson[dad[q]] = lson[q];  dad[lson[q]] = dad[q];
			lson[q] = lson[p];  dad[lson[p]] = q;
		}
		rson[q] = rson[p];  dad[rson[p]] = q;
	}
	dad[q] = dad[p];
	if (rson[dad[p]] == p) rson[dad[p]] = q;
	else		       lson[dad[p]] = q;
	dad[p] = NIL;
}

/********** Arithmetic Compression **********/

void CLzAri::StartModel(void)  /* Initialize model */
{
	int ch, sym, i;

	sym_cum[N_CHAR] = 0;
	for (sym = N_CHAR; sym >= 1; sym--) {
		ch = sym - 1;
		char_to_sym[ch] = sym;	sym_to_char[sym] = ch;
		sym_freq[sym] = 1;
		sym_cum[sym - 1] = sym_cum[sym] + sym_freq[sym];
	}
	sym_freq[0] = 0;  /* sentinel (!= sym_freq[1]) */
	position_cum[N] = 0;
	for (i = N; i >= 1; i--)
		position_cum[i - 1] = position_cum[i] + 10000 / (i + 200);
			/* empirical distribution function (quite tentative) */
			/* Please devise a better mechanism! */
}

void CLzAri::UpdateModel(int sym)
{
	int i, c, ch_i, ch_sym;

	if (sym_cum[0] >= MAX_CUM) {
		c = 0;
		for (i = N_CHAR; i > 0; i--) {
			sym_cum[i] = c;
			c += (sym_freq[i] = (sym_freq[i] + 1) >> 1);
		}
		sym_cum[0] = c;
	}
	for (i = sym; sym_freq[i] == sym_freq[i - 1]; i--) ;
	if (i < sym) {
		ch_i = sym_to_char[i];	  ch_sym = sym_to_char[sym];
		sym_to_char[i] = ch_sym;  sym_to_char[sym] = ch_i;
		char_to_sym[ch_i] = sym;  char_to_sym[ch_sym] = i;
	}
	sym_freq[i]++;
	while (--i >= 0) sym_cum[i]++;
}

void CLzAri::Output(int bit)  /* Output 1 bit, followed by its complements */
{
	PutBit(bit);
	for ( ; shifts > 0; shifts--) PutBit(! bit);
}

void CLzAri::EncodeChar(int ch)
{
	int  sym;
	unsigned long int  range;

	sym = char_to_sym[ch];
	range = high - low;
	high = low + (range * sym_cum[sym - 1]) / sym_cum[0];
	low +=	     (range * sym_cum[sym    ]) / sym_cum[0];
	for ( ; ; ) {
		if (high <= Q2) Output(0);
		else if (low >= Q2) {
			Output(1);  low -= Q2;	high -= Q2;
		} else if (low >= Q1 && high <= Q3) {
			shifts++;  low -= Q1;  high -= Q1;
		} else break;
		low += low;  high += high;
	}
	UpdateModel(sym);
}

void CLzAri::EncodePosition(int position)
{
	unsigned long int  range;

	range = high - low;
	high = low + (range * position_cum[position    ]) / position_cum[0];
	low +=	     (range * position_cum[position + 1]) / position_cum[0];
	for ( ; ; ) {
		if (high <= Q2) Output(0);
		else if (low >= Q2) {
			Output(1);  low -= Q2;	high -= Q2;
		} else if (low >= Q1 && high <= Q3) {
			shifts++;  low -= Q1;  high -= Q1;
		} else break;
		low += low;  high += high;
	}
}

void CLzAri::EncodeEnd(void)
{
	shifts++;
	if (low < Q1) Output(0);  else Output(1);
	FlushBitBuffer();  /* flush bits remaining in buffer */
}

int CLzAri::BsrcSym(unsigned int x)
	/* 1	  if x >= sym_cum[1],
	   N_CHAR if sym_cum[N_CHAR] > x,
	   i such that sym_cum[i - 1] > x >= sym_cum[i] otherwise */
{
	int i, j, k;

	i = 1;	j = N_CHAR;
	while (i < j) {
		k = (i + j) / 2;
		if (sym_cum[k] > x) i = k + 1;	else j = k;
	}
	return i;
}

int CLzAri::BsrcPos(unsigned int x)
	/* 0 if x >= position_cum[1],
	   N - 1 if position_cum[N] > x,
	   i such that position_cum[i] > x >= position_cum[i + 1] otherwise */
{
	int i, j, k;

	i = 1;	j = N;
	while (i < j) {
		k = (i + j) / 2;
		if (position_cum[k] > x) i = k + 1;  else j = k;
	}
	return i - 1;
}

void CLzAri::StartDecode(void)
{
	int i;

	for (i = 0; i < M + 2; i++)
		value = 2 * value + GetBit();
}

int CLzAri::DecodeChar(void)
{
	int	 sym, ch;
	unsigned long int  range;

	range = high - low;
	sym = BsrcSym((unsigned int)
		(((value - low + 1) * sym_cum[0] - 1) / range));
	high = low + (range * sym_cum[sym - 1]) / sym_cum[0];
	low +=	     (range * sym_cum[sym    ]) / sym_cum[0];
	for ( ; ; ) {
		if (low >= Q2) {
			value -= Q2;  low -= Q2;  high -= Q2;
		} else if (low >= Q1 && high <= Q3) {
			value -= Q1;  low -= Q1;  high -= Q1;
		} else if (high > Q2) break;
		low += low;  high += high;
		value = 2 * value + GetBit();
	}
	ch = sym_to_char[sym];
	UpdateModel(sym);
	return ch;
}

int CLzAri::DecodePosition(void)
{
	int position;
	unsigned long int  range;

	range = high - low;
	position = BsrcPos((unsigned int)
		(((value - low + 1) * position_cum[0] - 1) / range));
	high = low + (range * position_cum[position    ]) / position_cum[0];
	low +=	     (range * position_cum[position + 1]) / position_cum[0];
	for ( ; ; ) {
		if (low >= Q2) {
			value -= Q2;  low -= Q2;  high -= Q2;
		} else if (low >= Q1 && high <= Q3) {
			value -= Q1;  low -= Q1;  high -= Q1;
		} else if (high > Q2) break;
		low += low;  high += high;
		value = 2 * value + GetBit();
	}
	return position;
}

/********** Encode and Decode **********/

void CLzAri::Encode(void)
{
	int  i, len, r, s, last_match_length;
	uint32 textsize = static_cast<uint32>(inputStream->GetLength());
	outputStream->Write32(textsize);
	if (textsize == 0) return;
	inputStream->Seek(0, Framework::STREAM_SEEK_SET);
	textsize = 0;
	StartModel();
	InitTree();
	s = 0;	r = N - F;
	for (i = s; i < r; i++) 
	{
		text_buf[i] = ' ';
	}
	for (len = 0; len < F && !inputStream->IsEOF(); len++)
	{
		text_buf[r + len] = inputStream->Read8();
	}
	textsize = len;
	for (i = 1; i <= F; i++) InsertNode(r - i);
	InsertNode(r);
	do
	{
		if (match_length > len) match_length = len;
		if (match_length <= THRESHOLD) 
		{
			match_length = 1;  EncodeChar(text_buf[r]);
		}
		else 
		{
			EncodeChar(255 - THRESHOLD + match_length);
			EncodePosition(match_position - 1);
		}
		last_match_length = match_length;
		for (i = 0; i < last_match_length && !inputStream->IsEOF(); i++) 
		{
			uint8 c = inputStream->Read8();
			DeleteNode(s);	text_buf[s] = c;
			if (s < F - 1) text_buf[s + N] = c;
			s = (s + 1) & (N - 1);
			r = (r + 1) & (N - 1);
			InsertNode(r);
		}
		while (i++ < last_match_length) 
		{
			DeleteNode(s);
			s = (s + 1) & (N - 1);
			r = (r + 1) & (N - 1);
			if (--len) InsertNode(r);
		}
	} 
	while (len > 0);
	EncodeEnd();
}

void CLzAri::Decode(void)
{
	int  i, j, k, r, c;
	uint32 count;
	uint32 textsize = inputStream->Read32();
	if (textsize == 0) return;
	StartDecode();
	StartModel();
	for (i = 0; i < N - F; i++) text_buf[i] = ' ';
	r = N - F;
	for (count = 0; count < textsize; ) 
	{
		c = DecodeChar();
		if (c < 256) 
		{
			outputStream->Write8(c);
			text_buf[r++] = c;
			r &= (N - 1);  count++;
		} 
		else 
		{
			i = (r - DecodePosition() - 1) & (N - 1);
			j = c - 255 + THRESHOLD;
			for (k = 0; k < j; k++) 
			{
				c = text_buf[(i + k) & (N - 1)];
				outputStream->Write8(c);
				text_buf[r++] = c;
				r &= (N - 1);  count++;
			}
		}
	}
}
