/**************************************************************
	lzhuf.c
	written by Haruyasu Yoshizaki 11/20/1988
	some minor changes 4/6/1989
	comments translated by Haruhiko Okumura 4/7/1989

	MSX-C PROFI adaptation by MaxWolf, Aug-Sep 1992
	            EOF bugfix 1st April 1993

	Компиляция:
	cc1 -m -c lzh3.c
	cc2 lzh3
**************************************************************/


#define EOF (-1)

int getc(), putc();
char encount(), deinc(), decount(), memmove();

#pragma nonrec


/********** LZSS compression *************/

#define N		4096		/* размер буфера */
#define F		60		/* предварительный размер буфера */
#define THRESHOLD	2
#define NIL		N		/* лист дерева */


extern char text_buf[N + F - 1];
static int  matchposition, matchlength;
extern int  lson[N + 1], rson[N + 257], dad[N + 1];



/* инициализация дерева(ев) */
static int InitTree()
{
   int *i, n;

   for(i = &rson[N + 1], n = 256; n--;)
        *i++ = NIL;			/* корень */
   for(i = dad, n = N; n--;)
        *i++ = NIL;			/* узел */
}


/* занести (вставить) в дерево */
static int InsertNode(r)
int r;
{
	int  i, p, cmp;
	char  *key;
	unsigned c;

	cmp = 1;
	key = &text_buf[r];
	p = N + 1 + (int)key[0];
	rson[r] = lson[r] = NIL;
	matchlength = 0;
	for (;;) {
		if (cmp >= 0) {
			if (rson[p] != NIL)
				p = rson[p];
			else {
				rson[p] = r;
				goto i1;
			}
		} else {
			if (lson[p] != NIL)
				p = lson[p];
			else {
				lson[p] = r;
i1:				dad[r] = p;
				return;
			}
		}
		for (i = 1; i < F; i++)
			if ((cmp = (int)key[i] - (int)text_buf[p + i]) != 0)
				break;
		if (i > THRESHOLD) {
			if (i > matchlength) {
				matchposition = ((r - p) & (N - 1)) - 1;
				if ((matchlength = i) >= F)
					break;
			}
			if (i == matchlength) {
				if ((c = ((r - p) & (N - 1)) - 1) < matchposition) {
					matchposition = c;
				}
			}
		}
	}
	dad[r] = dad[p];
	dad[ lson[r] = lson[p] ] = r;
	dad[ rson[r] = rson[p] ] = r;
	if (rson[ i = dad[p] ] == p)
		rson[i] = r;
	else
		lson[i] = r;
	dad[p] = NIL;  /* удалить p */
}


/* удалить из дерева */
static int DeleteNode(p) int p;
{
	int  q, i;

	if (dad[p] == NIL)
		return;			/* not registered */
	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);
			dad[ rson[dad[q]] = lson[q] ] = dad[q];
			;
			dad[ lson[q] = lson[p] ] = q;
		}
		dad[ rson[q] = rson[p] ] = q;
	}
	if (rson[ i = dad[q] = dad[p] ] == p)
		rson[i] = q;
	else
		lson[i] = q;
	dad[p] = NIL;
}



/* Кодирование Хаффмана */

#define N_CHAR     (256 - THRESHOLD + F)
			/* kinds of characters (character code = 0..N_CHAR-1) */
#define T          (N_CHAR * 2 - 1)	/* размер таблицы */
#define R          (T - 1)		/* позиция корня */
#define MAX_FREQ   0x8000		/* updates tree when the */
					/* root frequency comes to this value */
typedef char uchar;



/* Таблицы кодирования и декодирования 6-ти верхних (upper) бит позиции */

/* для кодирования */
static uchar p_len[64] = {
	0x03, 0x04, 0x04, 0x04, 0x05, 0x05, 0x05, 0x05,
	0x05, 0x05, 0x05, 0x05, 0x06, 0x06, 0x06, 0x06,
	0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06,
	0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
	0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
	0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
	0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
	0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08
};

static uchar p_code[64] = {
	0x00, 0x20, 0x30, 0x40, 0x50, 0x58, 0x60, 0x68,
	0x70, 0x78, 0x80, 0x88, 0x90, 0x94, 0x98, 0x9C,
	0xA0, 0xA4, 0xA8, 0xAC, 0xB0, 0xB4, 0xB8, 0xBC,
	0xC0, 0xC2, 0xC4, 0xC6, 0xC8, 0xCA, 0xCC, 0xCE,
	0xD0, 0xD2, 0xD4, 0xD6, 0xD8, 0xDA, 0xDC, 0xDE,
	0xE0, 0xE2, 0xE4, 0xE6, 0xE8, 0xEA, 0xEC, 0xEE,
	0xF0, 0xF1, 0xF2, 0xF3, 0xF4, 0xF5, 0xF6, 0xF7,
	0xF8, 0xF9, 0xFA, 0xFB, 0xFC, 0xFD, 0xFE, 0xFF
};


/* для декодирования */
static uchar d_code[256] = {
	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
	0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01,
	0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01,
	0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02,
	0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02,
	0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03,
	0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03,
	0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
	0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05,
	0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06,
	0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
	0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
	0x09, 0x09, 0x09, 0x09, 0x09, 0x09, 0x09, 0x09,
	0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A,
	0x0B, 0x0B, 0x0B, 0x0B, 0x0B, 0x0B, 0x0B, 0x0B,
	0x0C, 0x0C, 0x0C, 0x0C, 0x0D, 0x0D, 0x0D, 0x0D,
	0x0E, 0x0E, 0x0E, 0x0E, 0x0F, 0x0F, 0x0F, 0x0F,
	0x10, 0x10, 0x10, 0x10, 0x11, 0x11, 0x11, 0x11,
	0x12, 0x12, 0x12, 0x12, 0x13, 0x13, 0x13, 0x13,
	0x14, 0x14, 0x14, 0x14, 0x15, 0x15, 0x15, 0x15,
	0x16, 0x16, 0x16, 0x16, 0x17, 0x17, 0x17, 0x17,
	0x18, 0x18, 0x19, 0x19, 0x1A, 0x1A, 0x1B, 0x1B,
	0x1C, 0x1C, 0x1D, 0x1D, 0x1E, 0x1E, 0x1F, 0x1F,
	0x20, 0x20, 0x21, 0x21, 0x22, 0x22, 0x23, 0x23,
	0x24, 0x24, 0x25, 0x25, 0x26, 0x26, 0x27, 0x27,
	0x28, 0x28, 0x29, 0x29, 0x2A, 0x2A, 0x2B, 0x2B,
	0x2C, 0x2C, 0x2D, 0x2D, 0x2E, 0x2E, 0x2F, 0x2F,
	0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37,
	0x38, 0x39, 0x3A, 0x3B, 0x3C, 0x3D, 0x3E, 0x3F,
};

static uchar d_len[256] = {
	0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03,
	0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03,
	0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03,
	0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03,
	0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
	0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
	0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
	0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
	0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
	0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
	0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05,
	0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05,
	0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05,
	0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05,
	0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05,
	0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05,
	0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05,
	0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05,
	0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06,
	0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06,
	0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06,
	0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06,
	0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06,
	0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06,
	0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
	0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
	0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
	0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
	0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
	0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
	0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
	0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
};


extern unsigned freq[T + 1];	/* таблица частоты */

extern int prnt[T + N_CHAR];	/* pointers to parent nodes, except for the */
                      /* elements [T..T + N_CHAR - 1] which are used to get */
                      /* the positions of leaves corresponding to the codes. */

extern int son[T];    /* pointers to child nodes (son[], son[] + 1) */

static unsigned getbuf;
static uchar getlen;


#define GetBit()	_GetBit((char)0)
#define GetByte()	_GetBit((char)1)



/* получить один/восемь бит */
/* get one/eight bit(s) */
static int _GetBit(f)
char f;
{
	unsigned i;

	while (getlen <= 8) {
		if ((int)(i = getc()) == EOF) break; /* i = 0; */
		getbuf |= i << (8 - getlen);
		getlen += 8;
	}
	i = getbuf;
	if (f) {
		getbuf <<= 8;
		getlen -= 8;
		return i >> 8;
	} else {
		getbuf <<= 1;
		--getlen;
		return ((int)i < 0);
	}
}


/*int GetByte()
{
	unsigned i;

	while (getlen <= 8) {
		if ((i = getc()) == EOF) i = 0;
		getbuf |= i << (8 - getlen);
		getlen += 8;
	}
	i = getbuf;
	getbuf <<= 8;
	getlen -= 8;
	return i >> 8;
}*/


static unsigned putbuf;
static uchar putlen;


static int Putcode(l,c) int l;unsigned c;		/* output c bits of code */
{
	putbuf |= c >> putlen;
	if ((putlen += l) >= 8) {
		putc(putbuf >> 8);
		if ((putlen -= 8) >= 8) {
			putc(putbuf);
			putlen -= 8;
			putbuf = c << (l - putlen);
		} else {
			putbuf <<= 8;
		}
	}
}


/* initialization of tree */

static int StartHuff()
{
	int i, j;

	for (i = 0; i < N_CHAR; i++) {
		freq[i] = 1;
		son[i] = i + T;
		prnt[i + T] = i;
	}
	i = 0; j = N_CHAR;
	while (j <= R) {
		freq[j] = freq[i] + freq[i + 1];
		son[j] = i;
		prnt[i] = prnt[i + 1] = j;
		i += 2; j++;
	}
	freq[T] = 0xFFFF;
	prnt[R] = 0;
}


/* reconstruction of tree */

static int reconst()
{
	int i, j, k;
	unsigned f, l;

	/* collect leaf nodes in the first half of the table */
	/* and replace the freq by (freq + 1) / 2. */
	j = 0;
	for (i = 0; i < T; i++) {
		if (son[i] >= T) {
			freq[j] = (freq[i] + 1) / 2;
			son[j] = son[i];
			j++;
		}
	}
	/* begin constructing tree by connecting sons */
	for (i = 0, j = N_CHAR; j < T; i += 2, j++) {
		k = i + 1;
		f = freq[j] = freq[i] + freq[k];
		for (k = j - 1; f < freq[k]; k--);
		k++;
		l = (j - k) * 2;
		memmove(&freq[k + 1], &freq[k], l);
		freq[k] = f;
		memmove(&son[k + 1], &son[k], l);
		son[k] = i;
	}
	/* connect prnt */
	for (i = 0; i < T; i++) {
		if ((k = son[i]) >= T) {
			prnt[k] = i;
		} else {
			prnt[k] = prnt[k + 1] = i;
		}
	}
}



/* increment frequency of given code by one, and update tree */

static int update(c) int c;
{
	int i, j, k, l;

	if (freq[R] == MAX_FREQ) {
		reconst();
	}
	c = prnt[c + T];
	do {
		k = ++freq[c];

		/* if the order is disturbed, exchange nodes */
		if (k > freq[l = c + 1]) {
			while (k > freq[++l]);
			l--;
			freq[c] = freq[l];
			freq[l] = k;

			i = son[c];
			prnt[i] = l;
			if (i < T) prnt[i + 1] = l;

			j = son[l];
			son[l] = i;

			prnt[j] = c;
			if (j < T) prnt[j + 1] = c;
			son[c] = j;

			c = l;
		}
	} while ((c = prnt[c]) != 0);	/* repeat up to root */
}


static EncodeChar(c) unsigned c;
{
	unsigned i;
	int j, k;
#ifdef DEBUG
	printf("char[%x]\n",c);
#endif
	i = j = 0;
	k = prnt[c + T];

	/* travel from leaf to root */
	do {
		i >>= 1;

		/* if node's address is odd-numbered, choose bigger brother node */
		if (k & 1) i += 0x8000;

		j++;
	} while ((k = prnt[k]) != R);
	Putcode(j, i);
	update(c);
}


static EncodePosition(c) unsigned c;
{
	unsigned i;
#ifdef DEBUG
	printf("pos[%x]\n",c);
#endif
	/* output upper 6 bits by table lookup */
	i = c >> 6;
	Putcode((int)p_len[i], (unsigned)p_code[i] << 8);

	/* output lower 6 bits verbatim */
	Putcode(6, (c & 0x3f) << 10);
}


static EncodeEnd()
{
	if (putlen) {
		putc(putbuf >> 8);
	}
}


static int DecodeChar()
{
	unsigned c;

	c = son[R];

	/* travel from root to leaf, */
	/* choosing the smaller child node (son[]) if the read bit is 0, */
	/* the bigger (son[]+1} if 1 */
	while (c < T) {
		c += GetBit();
		c = son[c];
	}
	c -= T;
	update(c);
#ifdef DEBUG
	printf("char[%x]\n",c);
#endif
	return c;
}


static int DecodePosition()
{
	unsigned i, j, c;

	/* recover upper 6 bits from table */
	i = GetByte();
	c = (unsigned)d_code[i] << 6;
	j = d_len[i] - 2;

	/* read lower 6 bits verbatim */
	while (j--) {
		i = (i << 1) + GetBit();
	}
	c |= (i & 0x3F);
#ifdef DEBUG
	printf("pos[%x]\n",c);
#endif
	return c;
}


/*-- Упаковка/Распаковка --*/

/* Упаковка */
char Encode()
{
	int  i, c, len, r, s, last_matchlength;

	StartHuff();
	InitTree();
	putbuf = putlen = 0;
	s = 0;
	r = N - F;
	for (i = s; i < r; i++)
		text_buf[i] = ' ';
	for (len = 0; len < F && (c = getc()) != EOF; len++)
		text_buf[r + len] = c;
	encount(len);
	for (i = 1; i <= F; i++)
		InsertNode(r - i);
	InsertNode(r);
	do {
		if (matchlength > len)
			matchlength = len;
		if (matchlength <= THRESHOLD) {
			matchlength = 1;
			EncodeChar((int)text_buf[r]);
		} else {
			EncodeChar(255 - THRESHOLD + matchlength);
			EncodePosition(matchposition);
		}
		last_matchlength = matchlength;
		for (i = 0; i < last_matchlength &&
				(c = getc()) != EOF; i++) {
			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);
		}
		encount(i);
		while (i++ < last_matchlength) {
			DeleteNode(s);
			s = (s + 1) & (N - 1);
			r = (r + 1) & (N - 1);
			if (--len) InsertNode(r);
		}
	} while (len > 0);
	EncodeEnd();
}


/* Распаковка */
char Decode()
{
	int i, j, k, r, c;

	StartHuff();
	getbuf = getlen = 0;
	for (i = 0; i < N - F; i++)
		text_buf[i] = ' ';
	r = N - F;
	while (decount() || getlen) {
		c = DecodeChar();
		if (c < 256) {
			putc(c);
			text_buf[r++] = c;
			r &= (N - 1);
			deinc();
		} else {
			i = (r - DecodePosition() - 1) & (N - 1);
			j = c - 255 + THRESHOLD;
			for (k = 0; k < j; k++) {
				c = text_buf[(i + k) & (N - 1)];
				putc(c);
				text_buf[r++] = c;
				r &= (N - 1);
				deinc();
			}
		}
	}
}
