blocks.cpp

该源码是JPEG2000的c++源代码,希望对研究JPEG2000标准以及编解码的朋友们有用.

/*****************************************************************************/
/*                         kd_block::read_body_bytes                         */
/*****************************************************************************/

void
  kd_block::read_body_bytes(kd_input *source, kd_buf_server *buf_server)
{
  int body_bytes = this->temp_length; this->temp_length = 0;
  int xfer_bytes;

  if (body_bytes == 0)
    return;

  if (num_passes == 255)
    { // Read and discard the code-bytes.
      assert(first_buf == NULL);
      kd_code_buffer *tmp_buf = buf_server->get();
      while ((body_bytes > 0) && !source->failed())
        {
          xfer_bytes = KD_CODE_BUFFER_LEN;
          xfer_bytes = (body_bytes < xfer_bytes)?body_bytes:xfer_bytes;
          source->read(tmp_buf->buf,xfer_bytes);
          body_bytes -= xfer_bytes;
        }
      buf_server->release(tmp_buf);
      return;
    }

  while (body_bytes > 0)
    {
      xfer_bytes = KD_CODE_BUFFER_LEN - buf_pos;
      if (xfer_bytes == 0)
        {
          current_buf = current_buf->next = buf_server->get();
          buf_pos = 0;
          xfer_bytes = KD_CODE_BUFFER_LEN;
        }
      xfer_bytes = (body_bytes < xfer_bytes)?body_bytes:xfer_bytes;
      xfer_bytes = source->read(current_buf->buf+buf_pos,xfer_bytes);
      if (xfer_bytes == 0)
        break;
      body_bytes -= xfer_bytes;
      buf_pos += xfer_bytes;
      this->num_bytes += xfer_bytes;
    }
}

/*****************************************************************************/
/*                          kd_block::retrieve_data                          */
/*****************************************************************************/

void
  kd_block::retrieve_data(kdu_block *block, int max_layers)
{
  assert(num_passes < 255); // 255 has the special meaning: "discard block"
  block->num_passes = 0; // We will increment this as we read them in.
  block->missing_msbs = msbs_w;
  if (beta == 0)
    return;

  if ((num_bytes+2) > block->max_bytes)
    block->set_max_bytes(((int) num_bytes)+4096,false); // A generous allocation
  if (num_passes > block->max_passes)
    block->set_max_passes(((int) num_passes)+32,false); // A generous allocation

  int remaining_bytes = num_bytes;
  kdu_byte *bp = block->byte_buffer;
  current_buf = first_buf;
  buf_pos = 0;
  for (pass_idx=0; pass_idx < num_passes; )
    {
      // Get the layer index for the next contribution.
      int layer_idx = get_byte();
      layer_idx = (layer_idx<<8) + get_byte();
      if (layer_idx >= max_layers)
        break;

      int new_passes, new_bytes;
      kdu_byte idx = pass_idx;
      bool more_headers=true;

      assert(block->num_passes == (int) pass_idx);
      while (more_headers)
        {
          new_bytes = get_byte();
          new_bytes = (new_bytes << 8) + get_byte();
          new_passes = get_byte();
          more_headers = false;
          if (new_bytes & (1<<15))
            {
              more_headers = true;
              new_bytes &= ~(1<<15);
            }
          for (; new_passes > 0; new_passes--, new_bytes=0, idx++)
            {
              block->pass_lengths[idx] = new_bytes;
              block->pass_slopes[idx] = 0;
            }
          assert(idx <= num_passes);
        }
      assert(idx > 0);
      block->pass_slopes[idx-1] = ((1<<16)-1) - layer_idx;

      for (; pass_idx < idx; pass_idx++)
        {
          new_bytes = block->pass_lengths[pass_idx];
          if (new_bytes > remaining_bytes)
            return;
          block->num_passes = pass_idx+1;
          remaining_bytes -= new_bytes;
          while (new_bytes > 0)
            {
              int xfer_bytes = KD_CODE_BUFFER_LEN - buf_pos;
              if (xfer_bytes == 0)
                {
                  current_buf = current_buf->next;
                  buf_pos = 0;
                  assert(current_buf != NULL);
                  xfer_bytes = KD_CODE_BUFFER_LEN;
                }
              xfer_bytes = (xfer_bytes < new_bytes)?xfer_bytes:new_bytes;
              new_bytes -= xfer_bytes;
              while (xfer_bytes--)
                *(bp++) = current_buf->buf[buf_pos++];
            }
        }
    }
}

/*****************************************************************************/
/*                           kd_block::store_data                            */
/*****************************************************************************/

void
  kd_block::store_data(kdu_block *block, kd_buf_server *buf_server)
{
  assert(block->modes == (int) modes);
  assert(block->missing_msbs < 255);
  assert(block->num_passes <= 255);
  assert(first_buf == NULL);

  // Now copy the coding pass summary information.
  int n, val, total_bytes;

  msbs_w = (kdu_byte) block->missing_msbs;
  start_buffering(buf_server);
  num_passes = (kdu_byte) block->num_passes;
  total_bytes = 0;
  for (n=0; n < block->num_passes; n++)
    {
      val = block->pass_slopes[n];
      assert(val >= 0);
      put_byte((kdu_byte)(val>>8),buf_server);
      put_byte((kdu_byte) val,buf_server);
      val = block->pass_lengths[n];
      assert((val >= 0) && (val < (1<<16)));
      total_bytes += val;
      put_byte((kdu_byte)(val>>8),buf_server);
      put_byte((kdu_byte) val,buf_server);
    }
  assert(total_bytes <= block->max_bytes);

  // Finally, copy the code-bytes.
  kdu_byte *bp = block->byte_buffer;
  while (total_bytes > 0)
    {
      int xfer_bytes = KD_CODE_BUFFER_LEN - buf_pos;
      if (xfer_bytes == 0)
        {
          current_buf = current_buf->next = buf_server->get();
          buf_pos = 0;
          xfer_bytes = KD_CODE_BUFFER_LEN;
        }
      xfer_bytes = (xfer_bytes < total_bytes)?xfer_bytes:total_bytes;
      total_bytes -= xfer_bytes;
      while (xfer_bytes--)
        current_buf->buf[buf_pos++] = *(bp++);
    }
  current_buf = first_buf;
  buf_pos = 0;
}

/*****************************************************************************/
/*                           kd_block::trim_data                             */
/*****************************************************************************/

bool
  kd_block::trim_data(kdu_uint16 slope_threshold, kd_buf_server *buf_server)
{
  if (num_passes == 0)
    return false;

  // Find the number of passes we can keep.
  int n;
  int potential_body_bytes = 0;
  int max_body_bytes = 0;
  int max_passes = 0;
  kd_code_buffer *save_current_buf = current_buf;
  kdu_byte save_buf_pos = buf_pos;

  current_buf = first_buf;
  buf_pos = 0;
  for (n=0; n < num_passes; n++)
    {
      kdu_uint16 slope = get_byte();
      slope = (slope<<8) + get_byte();
      if ((slope != 0) && (slope <= slope_threshold))
        break; // Need to discard this one.
      kdu_uint16 length = get_byte();
      length = (length<<8) + get_byte();
      potential_body_bytes += length;
      if (slope != 0)
        {
          max_body_bytes = potential_body_bytes;
          max_passes = n+1;
        }
    }

  // Restore the counters.
  current_buf = save_current_buf;
  buf_pos = save_buf_pos;

  // Now go back through the data setting additional pass slopes to 0.

     /* Notice that we do not change `num_passes' for that would prevent
        us from later locating the body bytes. */

  if (n == num_passes)
    return false;
  kd_code_buffer *buf_ptr = first_buf;
  int pos = max_passes << 2;
  while (pos > KD_CODE_BUFFER_LEN)
    { buf_ptr = buf_ptr->next; pos -= KD_CODE_BUFFER_LEN; }
  n = (num_passes-max_passes)<<2; // Number of bytes to set to 0
  while (n--)
    {
      if (pos == KD_CODE_BUFFER_LEN)
        { buf_ptr = buf_ptr->next; pos = 0; }
      buf_ptr->buf[pos++] = 0;
    }

  // Now remove the unwanted body bytes.

  buf_ptr = first_buf;
  pos = (num_passes<<2) + max_body_bytes;
  while (pos > KD_CODE_BUFFER_LEN)
    { buf_ptr = buf_ptr->next; pos -= KD_CODE_BUFFER_LEN; }
  kd_code_buffer *tmp;
  while ((tmp=buf_ptr->next) != NULL)
    {
      buf_ptr->next = tmp->next;
      buf_server->release(tmp);
    }
  return true;
}

/*****************************************************************************/
/*                          kd_block::start_packet                           */
/*****************************************************************************/

int
  kd_block::start_packet(int layer_idx, kdu_uint16 slope_threshold)
{
  if (layer_idx == 0)
    {
      pass_idx = 0;
      current_buf = first_buf;
      buf_pos = 0;
      layer_w = 0xFFFF;
      if (num_passes == 0)
        msbs_w = 0xFF; /* We will never include this block.  Make sure its
                          `msbs_w' value does not damage the efficiency with
                          with the neighbouring blocks are represented. */

      // Reflect `msbs_w' value into higher nodes in the tag tree.
      for (kd_block *scan=this->up_down; scan != NULL; scan=scan->up_down)
        if (scan->msbs_w > msbs_w)
          scan->msbs_w = msbs_w;
        else
          break; // No point in going further up the tree.
    }

  // Find number of new passes.

  pending_new_passes = 0;
  temp_length = 0;
  if (pass_idx == num_passes)
    {
      layer_w = 0xFFFF; // `save_beta' may have been reset by `save_output_tree
      return 0;
    }

  kd_code_buffer *save_current_buf = current_buf;
  kdu_byte save_buf_pos = buf_pos;
  int test_length = 0;
  int test_passes = 0;
  for (int n=(num_passes-pass_idx); n > 0; n--)
    {
      kdu_uint16 slope = get_byte();
      slope = (slope<<8) + get_byte();
      if ((slope != 0) && (slope <= slope_threshold))
        break;
      kdu_uint16 length = get_byte();
      length = (length<<8) + get_byte();
      test_passes++;
      test_length += length;
      if (slope != 0)
        {
          pending_new_passes = test_passes;
          assert(test_length < (1<<16));
          temp_length = (kdu_uint16) test_length;
        }
    }
  current_buf = save_current_buf;
  buf_pos = save_buf_pos;

  // See if we need to update tag tree nodes.

  if (pass_idx == 0)
    {
      if (pending_new_passes)
        {
          layer_w  = (kdu_uint16) layer_idx;
          for (kd_block *scan=up_down; scan != NULL; scan=scan->up_down)
            if (scan->layer_w > layer_w)
              scan->layer_w = layer_w;
            else
              break; // No point in going further up the tree.
        }
      else
        layer_w = 0xFFFF;
    }
  return temp_length;
}

/*****************************************************************************/
/*                       kd_block::write_packet_header                       */
/*****************************************************************************/

void
  kd_block::write_packet_header(kd_header_out &head, int layer_idx,
                                 bool simulate)
{
  // Process inclusion information first

  bool included = (pending_new_passes > 0);
  if (pass_idx == 0)
    { // First time inclusion.
      assert((included && (layer_w < 0xFFFF)) ||
             ((!included) && (layer_w == 0xFFFF)));
      kdu_byte save_new_passes=pending_new_passes; // Shares layer_wbar storage
      layer_wbar = (kdu_uint16) layer_idx;
      kd_block *scan, *prev, *next;

      // Walk up to the root node in the tree.
      scan=this; prev=NULL;
      while ((next=scan->up_down) != NULL)
        { scan->up_down=prev; prev=scan; scan=next; }
      scan->up_down = prev;

      // Walk back down the tree, performing the encoding steps.

      kdu_uint16 wbar_min = 0;
      kdu_uint16 threshold = layer_wbar+1;
      prev = NULL;
      while (scan != NULL)
        {
          if (scan->layer_wbar < wbar_min)
            scan->layer_wbar = wbar_min;
          while ((scan->layer_w >= scan->layer_wbar) &&
                 (scan->layer_wbar < threshold))
            {
              scan->layer_wbar++;
              head.put_bit((scan->layer_w >= scan->layer_wbar)?0:1);
            }
          wbar_min =
            (scan->layer_w<scan->layer_wbar)?scan->layer_w:scan->layer_wbar;
          next=scan->up_down; scan->up_down=prev; prev=scan; scan=next;
        }
      pending_new_passes = save_new_passes; // Finished using layer_wbar now
    }
  else