/* This file is part of the GNU plotutils package.  Copyright (C) 1995,
   1996, 1997, 1998, 1999, 2000, 2005, Free Software Foundation, Inc.

   The GNU plotutils package is free software.  You may 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, or (at your
   option) any later version.

   The GNU plotutils package 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 the GNU plotutils package; see the file COPYING.  If not, write to
   the Free Software Foundation, Inc., 51 Franklin St., Fifth Floor,
   Boston, MA 02110-1301, USA. */

/* This file (i_rle.c) is a module that does run-length encoding on
   a sequence of integers ("pixel values"), and writes the resulting
   encoded sequence to an output stream.  The accompanying header file
   (i_rle.h) defines the external interface.  The encoded sequence
   should be GIF-compatible, even though the compression technique
   is not LZW.

   This module encapsulates the miGIF compression routines, originally
   written by der Mouse and ivo.  Their copyright notice is reproduced
   below. */
   

/*-----------------------------------------------------------------------
 *
 * miGIF Compression - mouse and ivo's GIF-compatible compression
 *
 *          -run length encoding compression routines-
 *
 * Copyright (C) 1998 Hutchison Avenue Software Corporation
 *               http://www.hasc.com
 *               info@hasc.com
 *
 * Permission to use, copy, modify, and distribute this software and its
 * documentation for any purpose and without fee is hereby granted, provided
 * that the above copyright notice appear in all copies and that both that
 * copyright notice and this permission notice appear in supporting
 * documentation.  This software is provided "AS IS." The Hutchison Avenue 
 * Software Corporation disclaims all warranties, either express or implied, 
 * including but not limited to implied warranties of merchantability and 
 * fitness for a particular purpose, with respect to this code and accompanying
 * documentation. 
 * 
 * The miGIF compression routines do not, strictly speaking, generate files 
 * conforming to the GIF spec, since the image data is not LZW-compressed 
 * (this is the point: in order to avoid transgression of the Unisys patent 
 * on the LZW algorithm.)  However, miGIF generates data streams that any 
 * reasonably sane LZW decompresser will decompress to what we want.
 *
 * miGIF compression uses run length encoding. It compresses horizontal runs 
 * of pixels of the same color. This type of compression gives good results
 * on images with many runs, for example images with lines, text and solid 
 * shapes on a solid-colored background. It gives little or no compression 
 * on images with few runs, for example digital or scanned photos.
 *
 *                               der Mouse
 *                      mouse@rodents.montreal.qc.ca
 *            7D C8 61 52 5D E7 2D 39  4E F1 31 3E E8 B3 27 4B
 *
 *                             ivo@hasc.com
 *
 * The Graphics Interchange Format(c) is the Copyright property of
 * CompuServe Incorporated.  GIF(sm) is a Service Mark property of
 * CompuServe Incorporated.
 *
 */

#include "sys-defines.h"	/* libplot-specific */
#include "extern.h"		/* libplot-specific */
#include "i_rle.h"

/* forward references */
static void _block_out (rle_out *rle, unsigned char c);

static void 
_write_block (rle_out *rle)
{
  if (rle->ofile)
    {
      fputc (rle->oblen, rle->ofile);
      fwrite ((void *) &(rle->oblock[0]), 1, rle->oblen, rle->ofile);
    }
#ifdef LIBPLOTTER
  else if (rle->outstream)
    {
      rle->outstream->put ((unsigned char)(rle->oblen));
      rle->outstream->write ((const char *)(&(rle->oblock[0])), rle->oblen);
    }
#endif  

  rle->oblen = 0;
}

static void 
_block_out (rle_out *rle, unsigned char c)
{
  rle->oblock[(rle->oblen)++] = c;
  if (rle->oblen >= 255)
    _write_block (rle);
}

static void 
_block_flush (rle_out *rle)
{
  if (rle->oblen > 0)
    _write_block (rle);
}

static void 
_output (rle_out *rle, int val)
{
  rle->obuf |= val << rle->obits;
  rle->obits += rle->out_bits;
  while (rle->obits >= 8)
    { 
      _block_out (rle, (unsigned char)(rle->obuf & 0xff));
      rle->obuf >>= 8;
      rle->obits -= 8;
    }
}

static void 
_output_flush (rle_out *rle)
{
  if (rle->obits > 0)
    _block_out (rle, (unsigned char)(rle->obuf));
  _block_flush (rle);
}

static void 
_did_clear (rle_out *rle)
{
  rle->out_bits = rle->out_bits_init;
  rle->out_bump = rle->out_bump_init;
  rle->out_clear = rle->out_clear_init;
  rle->out_count = 0;
  rle->rl_table_max = 0;
  rle->just_cleared = true;
}

static void 
_output_plain (rle_out *rle, int c)
{
  rle->just_cleared = false;
  _output (rle, c);
  rle->out_count++;
  if (rle->out_count >= rle->out_bump)
    { 
      rle->out_bits++;
      rle->out_bump += 1 << (rle->out_bits - 1);
    }
  if (rle->out_count >= rle->out_clear)
    { 
      _output (rle, rle->code_clear);
      _did_clear (rle);
    }
}

static unsigned int 
_isqrt (unsigned int x)
{
  unsigned int r;
  unsigned int v;

  if (x < 2)
    return x;
  for (v=x, r=1; v; v>>=2, r<<=1)
    ;
  for ( ; ; )
    { 
      v = ((x / r) + r) / 2;
      if ((v == r) || (v == r+1))
	return r;
      r = v;
    }
}

static unsigned int 
_compute_triangle_count (unsigned int count, unsigned int nrepcodes)
{
  unsigned int perrep, cost;

  cost = 0;
  perrep = (nrepcodes * (nrepcodes+1)) / 2;
  while (count >= perrep)
    { 
      cost += nrepcodes;
      count -= perrep;
    }
  if (count > 0)
    { 
      unsigned int n;

      n = _isqrt (count);
      while ((n*(n+1)) >= 2*count)
	n--;
      while ((n*(n+1)) < 2*count)
	n++;
      cost += n;
    }
  return cost;
}

static void 
_max_out_clear (rle_out *rle)
{
  rle->out_clear = rle->max_ocodes;
}

static void 
_reset_out_clear (rle_out *rle)
{
  rle->out_clear = rle->out_clear_init;
  if (rle->out_count >= rle->out_clear)
    { 
      _output (rle, rle->code_clear);
      _did_clear (rle);
    }
}

static void 
_rl_flush_fromclear (rle_out *rle, int count)
{
  int n;

  _max_out_clear (rle);
  rle->rl_table_pixel = rle->rl_pixel;
  n = 1;
  while (count > 0)
    { 
      if (n == 1)
	{ 
	  rle->rl_table_max = 1;
	  _output_plain (rle, rle->rl_pixel);
	  count--;
	}
      else if (count >= n)
	{ 
	  rle->rl_table_max = n;
	  _output_plain (rle, rle->rl_basecode + n - 2);
	  count -= n;
	}
      else if (count == 1)
	{ 
	  (rle->rl_table_max)++;
	  _output_plain (rle, rle->rl_pixel);
	  count = 0;
	}
      else
	{ 
	  rle->rl_table_max++;
	  _output_plain (rle, rle->rl_basecode+count-2);
	  count = 0;
	}
      if (rle->out_count == 0)
	n = 1;
      else 
	n++;
    }
  _reset_out_clear (rle);
}

static void 
_rl_flush_clearorrep (rle_out *rle, int count)
{
  int withclr;

  withclr = 1 + _compute_triangle_count ((unsigned int)count, 
					 (unsigned int)(rle->max_ocodes));
  if (withclr < count)
    { 
      _output (rle, rle->code_clear);
      _did_clear (rle);
      _rl_flush_fromclear (rle, count);
    }
  else
    for ( ; count>0; count--)
      _output_plain (rle, rle->rl_pixel);
}

static void 
_rl_flush_withtable (rle_out *rle, int count)
{
  int repmax;
  int repleft;
  int leftover;

  repmax = count / rle->rl_table_max;
  leftover = count % rle->rl_table_max;
  repleft = (leftover ? 1 : 0);
  if (rle->out_count + repmax + repleft > rle->max_ocodes)
    { 
      repmax = rle->max_ocodes - rle->out_count;
      leftover = count - (repmax * rle->rl_table_max);
      repleft = 1 + _compute_triangle_count ((unsigned int)leftover,
					     (unsigned int)(rle->max_ocodes));
    }
  if (1 + _compute_triangle_count ((unsigned int)count, 
				   (unsigned int)(rle->max_ocodes)) 
      < repmax + repleft)
    { 
      _output (rle, rle->code_clear);
      _did_clear (rle);
      _rl_flush_fromclear (rle, count);
      return;
    }
  _max_out_clear (rle);
  for ( ; repmax>0; repmax--)
    _output_plain (rle, rle->rl_basecode + rle->rl_table_max - 2);
  if (leftover)
    { 
      if (rle->just_cleared)
	_rl_flush_fromclear (rle, leftover);
      else if (leftover == 1)
	_output_plain (rle, rle->rl_pixel);
      else
	_output_plain (rle, rle->rl_basecode + leftover - 2);
    }
  _reset_out_clear (rle);
}

/* end a run in progress */
static void 
_rl_flush (rle_out *rle)
{
  if (rle->rl_count == 1)	/* not a real run, just output pixel */
    _output_plain (rle, rle->rl_pixel);
  else
    {
      if (rle->just_cleared)
	_rl_flush_fromclear (rle, rle->rl_count);
      else if ((rle->rl_table_max < 2) 
	       || (rle->rl_table_pixel != rle->rl_pixel))
	_rl_flush_clearorrep (rle, rle->rl_count);
      else
	_rl_flush_withtable (rle, rle->rl_count);
    }

  rle->rl_count = 0;
}

/***********************************************************************/
/* 			EXTERNAL INTERFACE			       */
/***********************************************************************/

/* create new RLE struct, which writes to a specified stream */
rle_out *
#ifdef LIBPLOTTER
_rle_init (FILE *fp, ostream *out, int bit_depth)
#else
_rle_init (FILE *fp, int bit_depth)
#endif
{
  int init_bits;
  rle_out *rle;

  /* Initial length for compression codes, one bit longer than the minimum
     number of bits needed to represent the set of pixel values.  The
     IMAX() and the addition of 1 bit are "because of some algorithmic
     constraints". */
  init_bits = IMAX(bit_depth, 2) + 1;

  rle = (rle_out *)_pl_xmalloc(sizeof(rle_out));
  rle->ofile = fp;
#ifdef LIBPLOTTER
  rle->outstream = out;
#endif
  rle->obuf = 0;
  rle->obits = 0;
  rle->oblen = 0;
  rle->code_clear = 1 << (init_bits - 1); 	   /* 100..000 */
  rle->code_eof = rle->code_clear + 1;    	   /* 100..001 */
  rle->rl_basecode = rle->code_eof + 1;   	   /* 100..010 */
  rle->out_bump_init = (1 << (init_bits - 1)) - 1; /* 011..111 */
  /* for images with a lot of runs, making out_clear_init larger will
     give better compression. */ 
						   /* 011..110 */
  rle->out_clear_init = (init_bits <= 3) ? 9 : (rle->out_bump_init - 1);
  rle->out_bits_init = init_bits;
  rle->max_ocodes = (1 << GIFBITS) - ((1 << (rle->out_bits_init - 1)) + 3);

  _did_clear (rle);
  _output (rle, rle->code_clear);
  rle->rl_count = 0;

  return rle;
}

/* send one pixel to the RLE */
void
_rle_do_pixel (rle_out *rle, int c)
{
  /* if a run needs to be terminated by being written out, do so */
  if ((rle->rl_count > 0) && (c != rle->rl_pixel))
    _rl_flush (rle);
  /* if current run can be continued, do so (internally) */
  if (rle->rl_pixel == c)
    rle->rl_count++;
  /* otherwise start a new one */
  else
    { 
      rle->rl_pixel = c;
      rle->rl_count = 1;
    }
}

/* flush out any data remaining in RLE; write EOF and deallocate RLE */
void
_rle_terminate (rle_out *rle)
{
  /* if a run in progress, end it */
  if (rle->rl_count > 0)
    _rl_flush (rle);
  _output (rle, rle->code_eof);
  _output_flush (rle);
  /* deallocate */
  free (rle);
}