/**************************************************************************
 *
 * huffman.c -- Huffman coding functions
 * Copyright (C) 1994  Neil Sharman
 *
 * This program 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.
 *
 * This program 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 this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 **************************************************************************/

#include "sysfuncs.h"
#include "memlib.h"
#include "huffman.h"
#include "messages.h"
#include "netorder.h"  /* [RPAP - Jan 97: Endian Ordering] */

/* ->data on success,  
   NULL on error 
 */
huff_data *
Generate_Huffman_Data (int num, mg_s_long *freqs, huff_data * data,
		       mg_u_long * mem)
{
  int HNum, i, count;
  mg_u_long *heap;
  huff_data *hd = data;
  if (!hd)
    {
      if (!(hd = new huff_data))
	goto error0;
    }
  if (!(heap = new mg_u_long[num * 2]))
    goto error1;
  if (!(hd->clens = new char[num]))
      goto error2;
  hd->num_codes = num;
  if (mem)
    {
      if (hd != data)
	*mem += sizeof (huff_data);
      *mem += num * sizeof (char);
    }
  memcpy (&heap[num], freqs, num * sizeof (*heap));
  memset (heap, '\0', num * sizeof (*heap));

  /* Initialise the pointers to the leaves */
  for (count = i = 0; i < num; ++i)
    if (heap[num + i])
      heap[count++] = num + i;

  /* Reorganise the pointers so that it is a heap */
  HNum = count;
  for (i = HNum / 2; i > 0; --i)
    {
      register int curr, child;
      curr = i;
      child = curr * 2;
      while (child <= HNum)
	{
	  if (child < HNum && heap[heap[child]] < heap[heap[child - 1]])
	    ++child;
	  if (heap[heap[curr - 1]] > heap[heap[child - 1]])
	    {
	      register mg_u_long temp;
	      temp = heap[child - 1];
	      heap[child - 1] = heap[curr - 1];
	      heap[curr - 1] = temp;
	      curr = child;
	      child = 2 * curr;
	    }
	  else
	    break;
	}
    }


  /* Form the huffman tree */
  while (HNum > 1)
    {
      int pos[2];

      for (i = 0; i < 2; ++i)
	{
	  register int curr, child;
	  pos[i] = heap[0];
	  heap[0] = heap[--HNum];
	  curr = 1;
	  child = 2;
	  while (child <= HNum)
	    {
	      if (child < HNum &&
		  heap[heap[child]] < heap[heap[child - 1]])
		++child;
	      if (heap[heap[curr - 1]] > heap[heap[child - 1]])
		{
		  register int temp;
		  temp = heap[child - 1];
		  heap[child - 1] = heap[curr - 1];
		  heap[curr - 1] = temp;
		  curr = child;
		  child = 2 * curr;
		}
	      else
		break;
	    }
	}

      heap[HNum + 1] = heap[pos[0]] + heap[pos[1]];
      heap[pos[0]] = heap[pos[1]] = HNum + 1;

      heap[HNum] = HNum + 1;

      {
	register int parent, curr;
	++HNum;
	curr = HNum;
	parent = curr >> 1;
	while (parent && heap[heap[parent - 1]] > heap[heap[curr - 1]])
	  {
	    register int temp;
	    temp = heap[parent - 1];
	    heap[parent - 1] = heap[curr - 1];
	    heap[curr - 1] = temp;
	    curr = parent;
	    parent = curr >> 1;
	  }
      }
    }


  /* Calculate the code lens */
  heap[0] = -1;
  heap[1] = 0;
  for (i = 2; i < num * 2; ++i)
    heap[i] = heap[heap[i]] + 1;

  /* zero the lencount's array */
  memset (hd->lencount, '\0', sizeof (hd->lencount));
  hd->maxcodelen = 0;
  hd->mincodelen = 100;

  /* Set the code length of each leaf in the huffman tree */
  for (i = 0; i < num; ++i)
    {
      register mg_u_long codelen = heap[i + num];
      hd->clens[i] = (char) codelen;
      if (!codelen)
	continue;
      if (codelen > hd->maxcodelen)
	hd->maxcodelen = codelen;
      if (codelen < hd->mincodelen)
	hd->mincodelen = codelen;
      ++hd->lencount[codelen];
    }


  if (hd->maxcodelen == 0 && hd->mincodelen == 100)
    {
      hd->num_codes = 0;
    }
  else
    {
      /* Calculate the current codes for each different code length */
      hd->min_code[hd->maxcodelen] = 0;
      for (i = hd->maxcodelen - 1; i>=0; --i)
	hd->min_code[i] = (hd->min_code[i + 1] + hd->lencount[i + 1]) >> 1;
    }
  delete []heap;
  return (hd);

error2:
  delete []heap;
error1:
  if (!data)
    delete hd;
error0:
  return (NULL);

}

mg_u_long *
Generate_Huffman_Codes (huff_data * data, mg_u_long * mem)
{
  int i;
  mg_u_long *codes;
  mg_u_long mc[MAX_HUFFCODE_LEN + 1];

  if (!data)
    return (NULL);
  if (!(codes = new mg_u_long[data->num_codes]))
    return (NULL);
  if (mem)
    *mem += data->num_codes * sizeof (*codes);
  memcpy (mc, data->min_code, sizeof (mc));
  for (i = 0; i < data->num_codes; ++i)
    if (data->clens[i])
      codes[i] = mc[(int) (data->clens[i])]++;

  return (codes);
}


mg_u_long **
Generate_Huffman_Vals (huff_data * data, mg_u_long * mem)
{
  int i;
  mg_u_long *fcode[MAX_HUFFCODE_LEN + 1];
  mg_u_long **values;
  mg_u_long *vals;

  if (!data)
    return (NULL);
  if (!(vals = new mg_u_long[data->num_codes]))
    return (NULL);
  if (!(values = new mg_u_long *[MAX_HUFFCODE_LEN + 1]))
    {
      delete []vals;
      return (NULL);
    }

  memset (values, '\0', (MAX_HUFFCODE_LEN + 1) * sizeof (mg_u_long *));

  if (mem)
    *mem += data->num_codes * sizeof (*vals) +
      (MAX_HUFFCODE_LEN + 1) * sizeof (mg_u_long *);

  fcode[0] = values[0] = &vals[0];
  for (i = 1; i <= data->maxcodelen; ++i)
    fcode[i] = values[i] = &vals[(values[i - 1] - vals) + data->lencount[i - 1]];

  for (i = 0; i < data->num_codes; ++i)
    if (data->clens[i])
      *fcode[(int) (data->clens[i])]++ = i;
  return (values);
}



double 
Calculate_Huffman_Size (int num, mg_s_long *freqs, mg_s_long *counts)
{
  double size = 0;
  huff_data hd;
  int i;
  if (!Generate_Huffman_Data (num, freqs, &hd, NULL))
    return -1;
  for (i = 0; i < num; ++i)
    size += counts[i] * hd.clens[i];
  delete []hd.clens;
  return size;
}



int 
Write_Huffman_Data (FILE * f, huff_data * hd)
{
  /* [RPAP - Jan 97: Endian Ordering] */
  HTONSI(hd->num_codes);
  HTONSI(hd->mincodelen);
  HTONSI(hd->maxcodelen);

  if (fwrite (&hd->num_codes, sizeof (hd->num_codes), 1, f) != 1)
    return -1;

  if (fwrite (&hd->mincodelen, sizeof (hd->mincodelen), 1, f) != 1)
    return -1;

  if (fwrite (&hd->maxcodelen, sizeof (hd->maxcodelen), 1, f) != 1)
    return -1;

  /* [RPAP - Jan 97: Endian Ordering] */
  NTOHSI(hd->num_codes);
  NTOHSI(hd->mincodelen);
  NTOHSI(hd->maxcodelen);

  if (hd->num_codes)
    {
      /* [RPAP - Jan 97: Endian Ordering] */
      int i;
      for (i = hd->mincodelen; i < hd->maxcodelen + 1; ++i)
	HTONSI(hd->lencount[i]);
      for (i = 0; i < hd->maxcodelen + 1; ++i)
	HTONUL(hd->min_code[i]);

      if (fwrite (hd->lencount + hd->mincodelen, sizeof (*hd->lencount),
		  hd->maxcodelen - hd->mincodelen + 1, f) !=
	  hd->maxcodelen - hd->mincodelen + 1)
	return -1;

      if (fwrite (hd->min_code, sizeof (*hd->min_code), hd->maxcodelen + 1, f) !=
	  hd->maxcodelen + 1)
	return -1;

      if (fwrite (hd->clens, sizeof (*hd->clens), hd->num_codes, f) != hd->num_codes)
	return -1;

      /* [RPAP - Jan 97: Endian Ordering] */
      for (i = hd->mincodelen; i < hd->maxcodelen + 1; ++i)
	NTOHSI(hd->lencount[i]);
      for (i = 0; i < hd->maxcodelen + 1; ++i)
	NTOHUL(hd->min_code[i]);
    }
  return 0;
}



int Read_Huffman_Data (FILE * f, huff_data * hd, mg_u_long * mem, mg_u_long * disk) {
  if (fread (&hd->num_codes, sizeof (hd->num_codes), 1, f) != 1)
    return -1;

  if (fread (&hd->mincodelen, sizeof (hd->mincodelen), 1, f) != 1)
    return -1;

  if (fread (&hd->maxcodelen, sizeof (hd->maxcodelen), 1, f) != 1)
    return -1;

  /* [RPAP - Jan 97: Endian Ordering] */
  NTOHSI(hd->num_codes);
  NTOHSI(hd->mincodelen);
  NTOHSI(hd->maxcodelen);

  if (disk)
    (*disk) += sizeof (hd->num_codes) + sizeof (hd->mincodelen) +
      sizeof (hd->maxcodelen);

  hd->clens = NULL;

  if (hd->num_codes)
    {
      int i;  /* [RPAP - Jan 97: Endian Ordering] */

      memset (hd->lencount, '\0', sizeof (hd->lencount));
      if (fread (hd->lencount + hd->mincodelen, sizeof (*hd->lencount),
	      hd->maxcodelen - hd->mincodelen + 1, f) !=
	  hd->maxcodelen - hd->mincodelen + 1)
	return -1;

      /* [RPAP - Jan 97: Endian Ordering] */
      for (i = hd->mincodelen; i < hd->maxcodelen + 1; ++i)
	NTOHSI(hd->lencount[i]);

      if (disk)
	(*disk) += sizeof (*hd->lencount) * (hd->maxcodelen - hd->mincodelen + 1);

      memset (hd->min_code, '\0', sizeof (hd->min_code));

      if (fread (hd->min_code, sizeof (*hd->min_code), hd->maxcodelen + 1, f) !=
	  hd->maxcodelen + 1)
	return -1;

      /* [RPAP - Jan 97: Endian Ordering] */
      for (i = 0; i < hd->maxcodelen + 1; ++i)
	NTOHUL(hd->min_code[i]);

      if (disk)
	(*disk) += sizeof (*hd->min_code) * (hd->maxcodelen + 1);

      if (!(hd->clens = new char[hd->num_codes]))
	return -1;


      if (fread (hd->clens, sizeof (*hd->clens), hd->num_codes, f) != hd->num_codes)
	return -1;

      if (disk)
	(*disk) += sizeof (*hd->clens) * hd->num_codes;
    }

  if (mem)
    *mem += sizeof (*hd->clens) * hd->num_codes;
  return 0;
}