/* $XConsortium: lzss.cc /main/5 1996/07/18 16:00:08 drk $ */

#include "compression/lzss.h"

/*

Adapted from LDS (lossless datacompression sources) Version 1.1 by 
Nico E. de Vries.

qfc. 12-8-93.

*/

/**************************************************************
	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
**************************************************************/
#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. */
//FILE	*infile, *outfile;  /* input & output files */

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;
}

void lzss::compress(const buffer& uncompressed, buffer& compressed) 
{
   if ( compressed.buf_sz() < uncompressed.buf_sz() )
      compressed.expand_chunk(uncompressed.buf_sz());

////////////////////////////////////////////
////////////////////////////////////////////
   int  i, c, len, r, s, last_match_length, code_buf_ptr;
   unsigned char  code_buf[17], mask;
	
   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. */

   char* unc_str = uncompressed.get_base();
   int  unc_str_len = uncompressed.content_sz();
   int  unc_str_ptr = 0;

   for (len = 0; len < F; len++) {

      if ( unc_str_ptr == unc_str_len )
         break;

      c = unc_str[unc_str_ptr++];
//cerr << char(c);

      text_buf[r + len] = c;  /* Read F bytes into the last F bytes of
			         the buffer */
   }

   if ((textsize = len) == 0) return;  /* 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], outfile);     /* code together */
//           }

             compressed.put((char*)code_buf, code_buf_ptr, true);  

	     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; i++) {

            if ( unc_str_ptr == unc_str_len )
               break;

            c = unc_str[unc_str_ptr++];

	    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);
            s++; s &= (N - 1);  r++; r &= (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);
         s++; s &= (N - 1);  r++; r &= (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], outfile);
//                  compressed.put(code_buf[i], true);
//                }

      compressed.put((char*)code_buf, code_buf_ptr, true);
      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);
}

void lzss::decompress(buffer& compressed, buffer& uncompressed) 
{
   int  i, j, k, r, c;
   unsigned int flags;

   for (i = 0; i < N - F; i++) text_buf[i] = ' ';
   r = N - F;  flags = 0;
   for (;;) {
      if (((flags >>= 1) & 256) == 0) {

         // if ((c = getc(infile)) == EOF) break;

         if ( compressed.content_sz() == 0 )
            break;

         compressed.getusc(c);

	 flags = c | 0xff00;  /* uses higher byte cleverly */
      }		     	     /* to count eight */

      if (flags & 1) {
	//if ((c = getc(infile)) == EOF) break;
	//putc(c, outfile);  text_buf[r++] = c;  r &= (N - 1);

        if ( compressed.content_sz() == 0 )
           break;

        compressed.getusc(c);

//debug(cerr, char(c));
	uncompressed.put(char(c), true);  text_buf[r++] = c;  r &= (N - 1);

      } else {
	//if ((i = getc(infile)) == EOF) break;
	//if ((j = getc(infile)) == EOF) break;

       if ( compressed.content_sz() == 0 )
          break;
       else { 
          compressed.getusc(i); 
       }

       if ( compressed.content_sz() == 0 )
          break;
       else 
          compressed.getusc(j); 

			
       i |= ((j & 0xf0) << 4);  j = (j & 0x0f) + THRESHOLD;

       for (k = 0; k <= j; k++) {
          c = text_buf[(i + k) & (N - 1)];

	   //putc(c, outfile);  
//debug(cerr, char(c));
	  uncompressed.put(char(c), true);  

          text_buf[r++] = c;  r &= (N - 1);

        }

      }
   }
}


io_status lzss::build_dict(lex_func_t, getchar_func_t)
{
   return done;
}

MMDB_BODIES(lzss)