dos33fsprogs/mockingboard/lzss_compress.c

/**************************************************************
	LZSS.C -- A Data Compression Program
	(tab = 4 spaces)
***************************************************************
	4/6/1989 Haruhiko Okumura
	Use, distribute, and modify this program freely.
	Please send me your improved versions.
		PC-VAN		SCIENCE
		NIFTY-Serve	PAF01022
		CompuServe	74050,1022
**************************************************************
         WARNING: order of match_position and match_lenght changed!
         see lines 178 to 182
         Mofication by <stephan.walter@gmx.ch>

         Also modified to have N,F,etc, etc to be parameters, not
         hard-coded  -- vmw
 */

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


/* output types */
#define NORMAL_ASM 0

#define num_trees 256

	/* initialize trees */
static void newInitTree(int ring_buffer_size,int binary_search_index,
		 int *rson, int *dad) {

	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=ring_buffer_size+1; i<=ring_buffer_size+num_trees; i++) {
		rson[i] = binary_search_index;
	}
	for (i=0; i<ring_buffer_size; i++) {
		dad[i] = binary_search_index;
	}
}

static void newInsertNode(
		int r, int ring_buffer_size, int binary_search_index,
		int match_length_limit,
		unsigned char *text_buf, int *rson,int *lson, int *dad,
		int *match_length, int *match_position) {
	/* 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;
	unsigned char  *key;

	cmp = 1;
	key = text_buf+r;
	p = ring_buffer_size + 1 + key[0];
	rson[r] = lson[r] = binary_search_index;
	*match_length = 0;

	for( ; ; ) {

		if (cmp >= 0) {
			if (rson[p] != binary_search_index) p = rson[p];
			else {
				rson[p] = r;
				dad[r] = p;
				return;
			}
		}
		else {
			if (lson[p] != binary_search_index) p = lson[p];
			else {
				lson[p] = r;
				dad[r] = p;
				return;
			}
		}

		for(i = 1; i < match_length_limit; i++)
			if ((cmp = key[i] - text_buf[p + i]) != 0)  break;
		if (i > *match_length) {
			*match_position = p;
			if ((*match_length = i) >= match_length_limit)  break;
		}
	}

	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] = binary_search_index;  /* remove p */

}

	/* deletes node p from tree */
static void newDeleteNode(int p, int binary_search_index,
		   int *dad, int *rson, int *lson) {

	int  q;

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

static int lzss_encode_better(
		FILE *infile,
		unsigned char frequent_char,
		int ring_buffer_size, int position_length_threshold,
		int output_type) {

//	unsigned char frequent_char='#';
//	int ring_buffer_size=1024;  /* N */
	int match_length_limit;  //=64;  /* F */
	/*int position_length_threshold=2;  THRESHOLD */
	int binary_search_index=ring_buffer_size;  /* NIL */
	int position_bits; //=10;
//	int length_bits=16-position_bits;

	unsigned long int codesize = 0;	/* code size counter */

	int  i, c, len, r, s, last_match_length, code_buf_ptr;

	unsigned char  code_buf[8*2+1], mask;

	unsigned char *text_buf;

	int match_position, match_length;  /* of longest match.  These are
			                 set by the InsertNode() procedure. */
	int *lson, *rson, *dad;  /* left & right children &
			                        parents -- These constitute
					        binary search trees. */

	/* determine stuff from ring_buffer_size */
	/* fake log2 algorithm */

	i=1;
	while (((ring_buffer_size-1)>>i) >=1) {
		i++;
	};

	position_bits=i;
	match_length_limit=1<<(16-position_bits);
//	printf("%i, %i %i %i '%c'\n",ring_buffer_size,position_bits,match_length_limit
//		,position_length_threshold,frequent_char);

                                   /* ring buffer of size N, with extra F-1
				      bytes to facilitate string comparison */
	text_buf=calloc(ring_buffer_size+match_length_limit-1,sizeof(unsigned char));
	lson=calloc(ring_buffer_size+1,sizeof(int));
	rson=calloc(ring_buffer_size+num_trees+1,sizeof(int));
	dad=calloc(ring_buffer_size+1,sizeof(int));

	/* initialize trees */
	newInitTree(ring_buffer_size,binary_search_index,rson,dad);



	/* code_buf[1..16] saves eight units of code, and
	   code_buf[0] works as eight flags, "1" representing
	   that the unit is an unencoded letter (1 byte),
	   "0" a position-and-length pair (2 bytes).
	   Thus, eight units require at most 16 bytes of code. */

	code_buf[0] = 0;

	code_buf_ptr = mask = 1;
	s = 0;
	r = ring_buffer_size - match_length_limit;

	if (frequent_char<32) {
		printf(";FREQUENT_CHAR EQU %d\n",frequent_char);
	}
	else {
		printf(";FREQUENT_CHAR EQU '%c'\n",frequent_char);
	}
	printf(";N EQU %i\n",ring_buffer_size);
	printf(";F EQU %i\n",match_length_limit);
	printf(";THRESHOLD EQU %i\n",position_length_threshold);
	printf(";P_BITS EQU %i\n",position_bits);
	printf(";POSITION_MASK EQU %i\n",(0xff>>(8-(position_bits-8))));

	printf("logo:\n");

	/* Clear the buffer with any character that will appear often. */
	for(i=0; i<(ring_buffer_size-match_length_limit); i++) {
		text_buf[i]=frequent_char;
	}

//	printf("%i to %i = %i\n",0,ring_buffer_size-match_length_limit,frequent_char);

//	printf("%i to %i = ",r,r+match_length_limit);
	for(len=0; len<match_length_limit && (c=getc(infile))!=EOF; len++) {
		/* Read F bytes into the last F bytes of the buffer */
		text_buf[r+len]=c;
//		printf("%i ",text_buf[r+len]);
	}
//	printf("\n");
	if (len== 0) return 0;  /* trying to compress empty file */

	for(i = 1; i <= match_length_limit; i++) {
		newInsertNode(r-i,ring_buffer_size,binary_search_index,
			match_length_limit,text_buf,rson,lson,dad,
			&match_length,&match_position);
	}

	/* Insert the F strings,
		each of which begins with one or more 'space' characters.  Note
		the order in which these strings are inserted.  This way,
		degenerate trees will be less likely to occur. */
	newInsertNode(r,ring_buffer_size,binary_search_index,
			match_length_limit,text_buf,rson,lson,dad,
			&match_length,&match_position);
	/* Finally, insert the whole string just read.  The
		global variables match_length and match_position are set. */
	do {
		/* match_length may be spuriously long near the end of text. */
		if (match_length > len) match_length = len;

		if (match_length <= position_length_threshold) {
			match_length=1;  /* Not long enough match.  Send one byte. */
			code_buf[0] |= mask;  /* 'send one byte' flag */
			code_buf[code_buf_ptr++] = text_buf[r];  /* Send uncoded. */
//			printf("single: %i @ %i\n",text_buf[r],r);
		} else {
//			printf("pos : %i\tlen : %i\n",match_position,match_length);

			code_buf[code_buf_ptr++] = (unsigned char) match_position;

			code_buf[code_buf_ptr++] = (unsigned char)
				( ((match_position>>8) & (0xff >> (8-(position_bits-8)))) |
				((match_length-(position_length_threshold+1))<<(position_bits-8)) );

//			code_buf[code_buf_ptr++] = (unsigned char)
//					(((match_position >> 8) & 7) |
//					(match_length - (position_length_threshold+1))<<3);
		}
		if ((mask <<= 1) == 0) {  /* Shift mask left one bit. */
			printf("\t.byte\t");
			for(i=0; i<code_buf_ptr; i++) { /* Send at most 8 units of */
				printf("$%02X%c",code_buf[i],(i==code_buf_ptr-1)?'\n':',');
			}
			codesize += code_buf_ptr;
			code_buf[0] = 0;  code_buf_ptr = mask = 1;
		}

		last_match_length = match_length;
		for (i = 0; i < last_match_length && (c = getc(infile)) != EOF; i++) {
			/* Delete old strings and */
			newDeleteNode(s,binary_search_index,dad,rson,lson);
			/* read new bytes */
			text_buf[s] = c;

			/* If the position is near the end of buffer,
				extend the buffer to make string comparison easier. */
			if (s < match_length_limit - 1) {
				text_buf[s + ring_buffer_size] = c;
			}

			s = (s + 1) & (ring_buffer_size - 1);
			r = (r + 1) & (ring_buffer_size - 1);
			/* Since this is a ring buffer, increment the position
			modulo N. */
			newInsertNode(r,ring_buffer_size,binary_search_index,
				match_length_limit,text_buf,rson,lson,dad,
				&match_length,&match_position);
			/* Register the string in text_buf[r..r+F-1] */
		}

		/* After the end of text, */
		while (i++ < last_match_length) {

			/* no need to read, but */
			newDeleteNode(s,binary_search_index,dad,rson,lson);

			s = (s + 1) & (ring_buffer_size - 1);
			r = (r + 1) & (ring_buffer_size - 1);
			if (--len) {
				newInsertNode(r,ring_buffer_size,binary_search_index,
					match_length_limit,text_buf,rson,lson,dad,
					&match_length,&match_position);
			}
			/* buffer may not be empty. */
		}
		/* until length of string to be processed is zero */
	} while (len > 0);


	/* Send remaining code. */
	if (code_buf_ptr > 1) {


		printf("\t.byte\t");

		for(i=0; i<code_buf_ptr; i++) {
			printf("$%02x",code_buf[i]);

			if (i==code_buf_ptr-1) {
				printf("\n");
			} else {
				printf(",");
			}
		}
		codesize += code_buf_ptr;
	}

	printf("logo_end:\n");

	free(text_buf);
	free(lson);
	free(rson);
	free(dad);
	return codesize;
}

int main(int argc, char **argv) {

	FILE *input;
	int ch,byte_count=0,orig_byte_count=0;

	/* Check command line arguments */
	if (argc<2) {
		printf("\nUsage:\n\t%s file_to_compress\n\n",argv[0]);
		return 3;
	}

	/* Open input file */
	input=fopen(argv[1],"r");
	if (input==NULL) {
		printf("Could not open \"%s\"\n",argv[1]);
		return 2;
	}

	byte_count=lzss_encode_better(input,'\0',1024,2,NORMAL_ASM);

	rewind(input);

	/* calculate size of original */
	/* Why aren't we using stat()? */
	while((ch=fgetc(input))!=EOF) {
		orig_byte_count++;
	}

	fclose(input);

	printf("; Size of original version: %i\n",orig_byte_count);
	printf("; Size of compressed version: %i\n",byte_count);

	return 0;

}