// ####################################
// #                                  #
// #       Ping of Death - Bot        #
// #                by                #
// #    Markus Klinge aka Count Floyd #
// #                                  #
// ####################################
//
// Started from the HPB-Bot Alpha Source
// by Botman so Credits for a lot of the basic
// HL Server/Client Stuff goes to him
//
// compress.cpp
//
// POD Data Compress Routines based on LZSS
//
// Actually I ripped this out of the AceBot Source and
// modified it to suit my needs.
// This is what the original (?) Author writes:
//
// Original file is Copyright(c), Steve Yeager 1998
//
// 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>
#include <malloc.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 index for root of binary search trees
#define NIL N


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 of longest match. Set by the InsertNode() procedure.
int   match_position, match_length,
      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* header, int headersize, unsigned char *buffer, int bufsize)
{
   int i, c, len, r, s, last_match_length, code_buf_ptr;
   unsigned char code_buf[17], mask;
   int bufptr = 0;
   FILE *pOut;

   pOut  = fopen (filename, "wb");
   if (pOut == NULL)
      return (-1); // bail

   // Write Header first
   fwrite (header, headersize, 1, pOut);

   InitTree (); // initialize trees

   // 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 = 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

   // 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.
   for (i = 1; i <= F; i++)
      InsertNode (r - i);

   // Finally, insert the whole string just read. The global variables
   // match_length and match_position are set.
   InsertNode (r);

   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
      {
         // Send position and length pair. Note match_length > THRESHOLD.
         code_buf[code_buf_ptr++] = (unsigned char) match_position;
         code_buf[code_buf_ptr++] = (unsigned char) (((match_position >> 4) & 0xf0) | (match_length - (THRESHOLD + 1)));
      }

      if ((mask <<= 1) == 0)
      {
         // Shift mask left one bit.
         for (i = 0; i < code_buf_ptr; i++)
            putc (code_buf[i], pOut); // Send at most 8 units of 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 the position is near the end of buffer, extend the buffer to make
         // string comparison easier.
         if (s < F - 1)
            text_buf[s + N] = c;

         // Since this is a ring buffer, increment the position modulo N.
         s = (s + 1) & (N - 1);
         r = (r + 1) & (N - 1);
         InsertNode (r); // Register the string in text_buf[r..r+F-1]
      }

      while (i++ < last_match_length)
      {
         // After the end of text, no need to read, but buffer may not be empty.
         DeleteNode (s);

         s = (s + 1) & (N - 1);
         r = (r + 1) & (N - 1);

         if (--len)
            InsertNode (r);
      }
   } 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;
   }

   fclose (pOut);

   return (codesize);
}


int Decode (char *filename, int headersize, unsigned char *buffer, int bufsize)
{
   // Be careful with your buffersize, will return an exit of -1 if failure

   int i, j, k, r, c;
   unsigned int flags;
   int bufptr = 0;
   FILE *pIn;

   pIn  = fopen (filename, "rb");
   if (pIn == NULL)
      return (-1); // bail

   // Skip Header
   fseek (pIn, headersize, SEEK_SET);

   r = N - F;
   for (i = 0; i < r; i++)
      text_buf[i] = ' ';

   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
}
