lzari.c

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/* Credits for lzari go to Haruhiko Okumura */

#include <stdio.h>
#include <stdlib.h>

/* #include <string.h>
#include <ctype.h> */

#include "globals.h"


void rewind_buffer(void)
{
  from_pointer = 0;
  return;
}

void Error(char *message)
{
	printf("\n%s\n", message);
	exit(EXIT_FAILURE);
}

void PutBit(int bit)  /* Output one bit (bit = 0,1) */
{
	static unsigned int  buffer = 0, mask = 128;

	if (bit) buffer |= mask;
	if ((mask >>= 1) == 0) {
		if (putc_buffer(buffer) == EOF) Error("Write Error");
		buffer = 0;  mask = 128;  codesize++;
	}
}

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

int GetBit(void)  /* Get one bit (0 or 1) */
{
	static unsigned int  buffer, mask = 0;
	if ((mask >>= 1) == 0) {
		buffer = getc_buffer();  mask = 128;
	}
	return ((buffer & mask) != 0);
}

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

void lzari_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 lzari_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_ARI; 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_ARI) 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 lzari_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 **********/

/*  If you are not familiar with arithmetic compression, you should read
		I. E. Witten, R. M. Neal, and J. G. Cleary,
			Communications of the ACM, Vol. 30, pp. 520-540 (1987),
	from which much have been borrowed.  */

#define M   15

/*	Q1 (= 2 to the M) must be sufficiently large, but not so
	large as the unsigned long 4 * Q1 * (Q1 - 1) overflows.  */

#define Q1  (1UL << M)
#define Q2  (2 * Q1)
#define Q3  (3 * Q1)
#define Q4  (4 * Q1)
#define MAX_CUM (Q1 - 1)
#define N_CHAR  (256 - THRESHOLD + F_ARI)
	/* character code = 0, 1, ..., N_CHAR - 1 */

unsigned long int  low = 0, high = Q4, value = 0;
int  shifts = 0;  /* counts for magnifying low and high around Q2 */
int  char_to_sym[N_CHAR], sym_to_char[N_CHAR + 1];
unsigned int
	sym_freq[N_CHAR + 1],  /* frequency for symbols */
	sym_cum[N_CHAR + 1],   /* cumulative freq for symbols */
	position_cum[N + 1];   /* cumulative freq for positions */

void 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 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]++;
}

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

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

int BinarySearchSym(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 BinarySearchPos(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 StartDecode(void)
{
	int i;

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

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

	range = high - low;
	sym = BinarySearchSym((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 DecodePosition(void)
{
	int position;
	unsigned long int  range;

	range = high - low;
	position = BinarySearchPos((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 lzari_Encode(long real_size)
{
	int  i, c, len, r, s, last_match_length;

	textsize = real_size;
	putc_buffer((textsize & 0xff000000) >> 24);
	putc_buffer((textsize & 0x00ff0000) >> 16);
	putc_buffer((textsize & 0x0000ff00) >> 8);
	putc_buffer(textsize  & 0x000000ff);
	codesize += sizeof textsize;

	if (textsize == 0) return;
	rewind_buffer();  textsize = 0;
	StartModel();  lzari_InitTree();
	s = 0;  r = N - F_ARI;
	for (i = s; i < r; i++) text_buf[i] = ' ';
	for (len = 0; len < F_ARI && (c = getc_buffer()) != EOF; len++)
		text_buf[r + len] = c;
	textsize = len;
	for (i = 1; i <= F_ARI; i++) lzari_InsertNode(r - i);
	lzari_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 &&
				(c = getc_buffer()) != EOF; i++) {
			lzari_DeleteNode(s);  text_buf[s] = c;
			if (s < F_ARI - 1) text_buf[s + N] = c;
			s = (s + 1) & (N - 1);
			r = (r + 1) & (N - 1);
			lzari_InsertNode(r);
		}

		if ((textsize += i) > printcount) {
			printf("%12ld\r", textsize);  printcount += 1024;
		}
		while (i++ < last_match_length) {
			lzari_DeleteNode(s);
			s = (s + 1) & (N - 1);
			r = (r + 1) & (N - 1);
			if (--len) lzari_InsertNode(r);
		}
	} while (len > 0);
	EncodeEnd();

	printf("original data: %ld bytes\n", textsize);
	printf("compressed data: %ld bytes\n", codesize);
}

void lzari_Decode(void)
{
	int  i, j, k, r, c;
	unsigned long int  count;

	textsize = 0;
	textsize |= getc_buffer() << 24;
	textsize |= getc_buffer() << 16;
	textsize |= getc_buffer() << 8;
	textsize |= getc_buffer();

	if (textsize == 0) return;
	StartDecode();  StartModel();
	for (i = 0; i < N - F_ARI; i++) text_buf[i] = ' ';
	r = N - F_ARI;
	for (count = 0; count < textsize; ) {
		c = DecodeChar();
		if (c < 256) {
			putc_buffer(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)];
				putc_buffer(c);  text_buf[r++] = c;
				r &= (N - 1);  count++;
			}
		}
		if (count > printcount) {
			printf("%12lu\r", count);  printcount += 1024;
		}
	}
	printf("%12lu\n", count);
}

long lzari_compress(unsigned char* tbuffer, unsigned char* fbuffer, long real_size)
{
  lz_init();
  from_buffer = fbuffer;
  to_buffer = tbuffer;
  from_max = real_size;
  lzari_Encode(real_size);
  return(codesize);
}

void lzari_decompress(unsigned char* fbuffer, unsigned char* tbuffer, long comp_size)
{
  lz_init();
  from_buffer = fbuffer;
  from_max = comp_size;
  to_buffer = tbuffer;
  lzari_Decode();
  return;
}