thirtyflightsofloving/game/acebot_compress.c

/*
===========================================================================
Copyright (C) 1998 Steve Yeager

This file is part of ACE Bot source code.

ACE Bot source code is free software; you can redistribute it
and/or modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of the License,
or (at your option) any later version.

ACE Bot source code is distributed in the hope that it will be
useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with ACE Bot source code; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
===========================================================================
*/

///////////////////////////////////////////////////////////
//
//  ACE - Quake II Bot
//
//  Copyright (c) Steve Yeager 1998
//
//
//  acebot_compress.c - Data compress based on LZSS
//
//  Not sure where I got this code, but thanks go to the
//  author. I just rewote it to allow the use of buffers
//  instead of files.
//
///////////////////////////////////////////////////////////

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

#define N		 4096	/* size of ring buffer */
#define F		   18	/* upper limit for match_length */
#define THRESHOLD	2   /* encode string into position and length
						   if match_length is greater than this */
#define NIL			N	/* index for root of binary search trees */

unsigned /*long*/ int
		textsize = 0,	/* text size counter */
		codesize = 0,	/* code size counter */
		printcount = 0;	/* counter for reporting progress every 1K bytes */
unsigned char
		text_buf[N + F - 1];	/* ring buffer of size N,
			with extra F-1 bytes to facilitate string comparison */
int		match_position, match_length,  /* of longest match.  These are
			set by the InsertNode() procedure. */
		lson[N + 1], rson[N + 257], dad[N + 1];  /* left & right children &
			parents -- These constitute binary search trees. */

void 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;
	for (i = 0; i < N; i++) dad[i] = NIL;
}

void 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;
	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 > match_length) {
			match_position = p;
			if ((match_length = i) >= F)  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] = NIL;  /* remove p */
}

void DeleteNode(int p)  /* deletes 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;
}

int Encode(char *filename, unsigned char *buffer, int bufsize, int version)
{
	int  i, c, len, r, s, last_match_length, code_buf_ptr;
	unsigned char  code_buf[17], mask;
	int bufptr = 0;
	FILE *pOut;
	//int version;
	
	pOut  = fopen(filename, "wb");
	if(pOut == NULL)
		return -1; // bail

	//version = 2; // compressed version

	// Read version info (uneeded here, but moves file ptr)
	fwrite(&version,sizeof(int),1,pOut); // write version
	fwrite(&bufsize,sizeof(int),1,pOut); // write out the size of the buffer
	
	InitTree();  /* initialize trees */
	code_buf[0] = 0;  /* 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_ptr = mask = 1;
	s = 0;  r = N - F;
	for (i = s; i < r; i++) text_buf[i] = ' ';  /* Clear the buffer with
		any character that will appear often. */
	for (len = 0; len < F &&  bufptr < bufsize; len++)
	{	
		c = buffer[bufptr++];
		text_buf[r + len] = c;  /* Read F bytes into the last F bytes of
			the buffer */
	}
	if ((textsize = len) == 0) return -1;  /* text of size zero */
	for (i = 1; i <= F; i++) InsertNode(r - i);  /* 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. */
	InsertNode(r);  /* Finally, insert the whole string just read.  The
		global variables match_length and match_position are set. */
	do {
		if (match_length > len) match_length = len;  /* match_length
			may be spuriously long near the end of text. */
		if (match_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. */
		} else {
			code_buf[code_buf_ptr++] = (unsigned char) match_position;
			code_buf[code_buf_ptr++] = (unsigned char)
				(((match_position >> 4) & 0xf0)
			  | (match_length - (THRESHOLD + 1)));  /* Send position and
					length pair. Note match_length > THRESHOLD. */
		}
		if ((mask <<= 1) == 0) {  /* Shift mask left one bit. */
			for (i = 0; i < code_buf_ptr; i++)  /* Send at most 8 units of */
				putc(code_buf[i], pOut);     /* code together */
			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 &&
				bufptr < bufsize; i++) 
		{
			c = buffer[bufptr++];
			DeleteNode(s);		/* Delete old strings and */
			text_buf[s] = c;	/* read new bytes */
			if (s < F - 1) text_buf[s + N] = c;  /* If the position is
				near the end of buffer, extend the buffer to make
				string comparison easier. */
			s = (s + 1) & (N - 1);  r = (r + 1) & (N - 1);
				/* Since this is a ring buffer, increment the position
				   modulo N. */
			InsertNode(r);	/* Register the string in text_buf[r..r+F-1] */
		}
//		if ((textsize += i) > printcount) {
//			printf("%12ld\r", textsize);  printcount += 1024;
//				/* Reports progress each time the textsize exceeds
//				   multiples of 1024. */
//		}
		while (i++ < last_match_length) {	/* After the end of text, */
			DeleteNode(s);					/* no need to read, but */
			s = (s + 1) & (N - 1);  r = (r + 1) & (N - 1);
			if (--len) InsertNode(r);		/* buffer may not be empty. */
		}
	} while (len > 0);	/* until length of string to be processed is zero */
	if (code_buf_ptr > 1) {		/* Send remaining code. */
		for (i = 0; i < code_buf_ptr; i++) putc(code_buf[i], pOut);
		codesize += code_buf_ptr;
	}
//	printf("In : %ld bytes\n", textsize);	/* Encoding is done. */
//	printf("Out: %ld bytes\n", codesize);
//	printf("Out/In: %.3f\n", (double)codesize / textsize);	
	fclose(pOut);

	return codesize;
}

// Be careful with your buffersize, will return an exit of -1 if failure
int Decode(char *filename, unsigned char *buffer, int bufsize)	/* Just the reverse of Encode(). */
{
	int  i, j, k, r, c;
	unsigned int  flags;
	int bufptr=0;
	FILE *pIn;
	int version;
	
	pIn  = fopen(filename, "rb");
	if(pIn == NULL)
		return -1; // bail

	// Read version info (uneeded here, but moves file ptr)
	fread(&version,sizeof(int),1,pIn); // read version
	fread(&version,sizeof(int),1,pIn); // read buffersize (not needed, so repeat into version)

	
	for (i = 0; i < N - F; i++) text_buf[i] = ' ';
	r = N - F;  flags = 0;
	for ( ; ; ) {
		if (((flags >>= 1) & 256) == 0) {
			if ((c = getc(pIn)) == EOF) break;
			flags = c | 0xff00;		/* uses higher byte cleverly */
		}							/* to count eight */
		if (flags & 1) {
			if ((c = getc(pIn)) == EOF) break;
			buffer[bufptr++] = c;	
			if(bufptr > bufsize)
				return -1; // check for overflow
			text_buf[r++] = c;  
			r &= (N - 1);
		} else {
			if ((i = getc(pIn)) == EOF) break;
			if ((j = getc(pIn)) == EOF) break;
			i |= ((j & 0xf0) << 4);  j = (j & 0x0f) + THRESHOLD;
			for (k = 0; k <= j; k++) {
				c = text_buf[(i + k) & (N - 1)];
				buffer[bufptr++] = c;
				if(bufptr > bufsize)
					return -1; // check for overflow
				text_buf[r++] = c;  
				r &= (N - 1);
			}
		}
	}
	
	fclose(pIn);
	return bufptr; // return uncompressed size
}
/*
// tester
int main(int argc, char *argv[])
{
	//char  *s;
	unsigned char i;
	int csize,ucsize;
	unsigned char *buffer1;
	int bufsize = 20000;
	
	buffer1 = (unsigned char *)malloc(bufsize);

	buffer1[500] = 'c';
	buffer1[785] = 's';
	
	csize = Encode("testbuf.bin", buffer1, bufsize);//sizeof(buffer1));
	
	buffer1[500] = 0;
	buffer1[785] = 0;
	
	ucsize = Decode("testbuf.bin", buffer1, bufsize);
		
	printf("Output: %c %c\n",buffer1[500],buffer1[785]);
	printf("Compressed: %d Uncompressed:%d\n",csize,ucsize);

	free(buffer1);

	return EXIT_SUCCESS;
}
*/