grafX2/src/packbits.c

/* vim:expandtab:ts=2 sw=2:
*/
/*  Grafx2 - The Ultimate 256-color bitmap paint program

	Copyright owned by various GrafX2 authors, see COPYRIGHT.txt for details.

    Grafx2 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; version 2
    of the License.

    Grafx2 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 Grafx2; if not, see <http://www.gnu.org/licenses/>
*/

///@file packbits.c
/// Packbits compression as used in IFF etc.
/// see http://fileformats.archiveteam.org/wiki/PackBits

#include <stdio.h>
#include <string.h>
#include "struct.h"
#include "io.h"
#include "gfx2log.h"
#include "packbits.h"

int PackBits_unpack_from_file(FILE * f, byte * dest, unsigned int count)
{
  unsigned int i = 0;
  while (i < count)
  {
    byte cmd;
    if (fread(&cmd, 1, 1, f) != 1)
      return PACKBITS_UNPACK_READ_ERROR;
    if (cmd > 128)
    {
      // cmd > 128 => repeat (257 - cmd) the next byte
      byte v;
      if (fread(&v, 1, 1, f) != 1)
        return PACKBITS_UNPACK_READ_ERROR;
      if (count < (i + 257 - cmd))
        return PACKBITS_UNPACK_OVERFLOW_ERROR;
      memset(dest + i, v, (257 - cmd));
      i += (257 - cmd);
    }
    else if (cmd < 128)
    {
      // cmd < 128 => copy (cmd + 1) bytes
      if (count < (i + cmd + 1))
        return PACKBITS_UNPACK_OVERFLOW_ERROR;
      if (fread(dest + i, 1, (cmd + 1), f) != (unsigned)(cmd + 1))
        return PACKBITS_UNPACK_READ_ERROR;
      i += (cmd + 1);
    }
    else
    {
      // 128 = NOP
      GFX2_Log(GFX2_WARNING, "NOP in packbits stream\n");
    }
  }
  return PACKBITS_UNPACK_OK;
}

void PackBits_pack_init(T_PackBits_data * data, FILE * f)
{
  memset(data, 0, sizeof(T_PackBits_data));
  data->f = f;
}

int PackBits_pack_add(T_PackBits_data * data, byte b)
{
  switch (data->list_size)
  {
    case 0 : // First color
      data->list[0] = b;
      data->list_size = 1;
      break;
    case 1 : // second color
      data->repetition_mode = (data->list[0] == b);
      data->list[1] = b;
      data->list_size = 2;
      break;
    default: // next colors
      if (data->list[data->list_size - 1] == b)  // repeat detected
      {
        if ( !data->repetition_mode && data->list_size >= 127)
        {
          // diff mode with 126 bytes then 2 identical bytes
          data->list_size--;
          if (PackBits_pack_flush(data) < 0)
            return -1;
          data->list[0] = b;
          data->list[1] = b;
          data->list_size = 2;
          data->repetition_mode = 1;
        }
        else if ((data->repetition_mode) || (data->list[data->list_size - 2] != b))
        {
          // same mode is kept
          if (data->list_size == 128)
          {
            if (PackBits_pack_flush(data) < 0)
              return -1;
          }
          data->list[data->list_size++] = b;
        }
        else
        {
          // diff mode and 3 identical bytes
          data->list_size -= 2;
          if (PackBits_pack_flush(data) < 0)
            return -1;
          data->list[0] = b;
          data->list[1] = b;
          data->list[2] = b;
          data->list_size = 3;
          data->repetition_mode = 1;
        }
      }
      else // the color is different from the previous one
      {
        if (!data->repetition_mode)                 // keep mode
        {
          if (data->list_size == 128)
          {
            if (PackBits_pack_flush(data) < 0)
              return -1;
          }
          data->list[data->list_size++] = b;
        }
        else                                        // change mode
        {
          if (PackBits_pack_flush(data) < 0)
            return -1;
          data->list[data->list_size++] = b;
        }
      }
  }
  return 0; // OK
}

int PackBits_pack_flush(T_PackBits_data * data)
{
  if (data->list_size > 0)
  {
    if (data->list_size > 128)
    {
      GFX2_Log(GFX2_ERROR, "PackBits_pack_flush() list_size=%d !\n", data->list_size);
    }
    if (data->repetition_mode)
    {
      if (data->f != NULL)
      {
        if (!Write_byte(data->f, 257 - data->list_size) ||
            !Write_byte(data->f, data->list[0]))
          return -1;
      }
      data->output_count += 2;
    }
    else
    {
      if (data->f != NULL)
      {
        if (!Write_byte(data->f, data->list_size - 1) ||
            !Write_bytes(data->f, data->list, data->list_size))
          return -1;
      }
      data->output_count += 1 + data->list_size;
    }
    data->list_size = 0;
    data->repetition_mode = 0;
  }
  return data->output_count;
}

int PackBits_pack_buffer(FILE * f, const byte * buffer, size_t size)
{
  T_PackBits_data pb_data;

  PackBits_pack_init(&pb_data, f);
  while (size-- > 0)
  {
    if (PackBits_pack_add(&pb_data, *buffer++))
      return -1;
  }
  return PackBits_pack_flush(&pb_data);
}