pngpread.c

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         }
         png_push_process_row(png_ptr);
         png_ptr->zstream.avail_out = (uInt)png_ptr->irowbytes;
         png_ptr->zstream.next_out = png_ptr->row_buf;
      }
      else
         break;
   }
}

void /* PRIVATE */
png_push_process_row(png_structp png_ptr)
{
   png_ptr->row_info.color_type = png_ptr->color_type;
   png_ptr->row_info.width = png_ptr->iwidth;
   png_ptr->row_info.channels = png_ptr->channels;
   png_ptr->row_info.bit_depth = png_ptr->bit_depth;
   png_ptr->row_info.pixel_depth = png_ptr->pixel_depth;

   png_ptr->row_info.rowbytes = PNG_ROWBYTES(png_ptr->row_info.pixel_depth,
       png_ptr->row_info.width);

   png_read_filter_row(png_ptr, &(png_ptr->row_info),
      png_ptr->row_buf + 1, png_ptr->prev_row + 1,
      (int)(png_ptr->row_buf[0]));

   png_memcpy_check(png_ptr, png_ptr->prev_row, png_ptr->row_buf,
      png_ptr->rowbytes + 1);

   if (png_ptr->transformations || (png_ptr->flags&PNG_FLAG_STRIP_ALPHA))
      png_do_read_transformations(png_ptr);

#if defined(PNG_READ_INTERLACING_SUPPORTED)
   /* blow up interlaced rows to full size */
   if (png_ptr->interlaced && (png_ptr->transformations & PNG_INTERLACE))
   {
      if (png_ptr->pass < 6)
/*       old interface (pre-1.0.9):
         png_do_read_interlace(&(png_ptr->row_info),
            png_ptr->row_buf + 1, png_ptr->pass, png_ptr->transformations);
 */
         png_do_read_interlace(png_ptr);

    switch (png_ptr->pass)
    {
         case 0:
         {
            int i;
            for (i = 0; i < 8 && png_ptr->pass == 0; i++)
            {
               png_push_have_row(png_ptr, png_ptr->row_buf + 1);
               png_read_push_finish_row(png_ptr); /* updates png_ptr->pass */
            }
            if (png_ptr->pass == 2) /* pass 1 might be empty */
            {
               for (i = 0; i < 4 && png_ptr->pass == 2; i++)
               {
                  png_push_have_row(png_ptr, png_bytep_NULL);
                  png_read_push_finish_row(png_ptr);
               }
            }
            if (png_ptr->pass == 4 && png_ptr->height <= 4)
            {
               for (i = 0; i < 2 && png_ptr->pass == 4; i++)
               {
                  png_push_have_row(png_ptr, png_bytep_NULL);
                  png_read_push_finish_row(png_ptr);
               }
            }
            if (png_ptr->pass == 6 && png_ptr->height <= 4)
            {
                png_push_have_row(png_ptr, png_bytep_NULL);
                png_read_push_finish_row(png_ptr);
            }
            break;
         }
         case 1:
         {
            int i;
            for (i = 0; i < 8 && png_ptr->pass == 1; i++)
            {
               png_push_have_row(png_ptr, png_ptr->row_buf + 1);
               png_read_push_finish_row(png_ptr);
            }
            if (png_ptr->pass == 2) /* skip top 4 generated rows */
            {
               for (i = 0; i < 4 && png_ptr->pass == 2; i++)
               {
                  png_push_have_row(png_ptr, png_bytep_NULL);
                  png_read_push_finish_row(png_ptr);
               }
            }
            break;
         }
         case 2:
         {
            int i;
            for (i = 0; i < 4 && png_ptr->pass == 2; i++)
            {
               png_push_have_row(png_ptr, png_ptr->row_buf + 1);
               png_read_push_finish_row(png_ptr);
            }
            for (i = 0; i < 4 && png_ptr->pass == 2; i++)
            {
               png_push_have_row(png_ptr, png_bytep_NULL);
               png_read_push_finish_row(png_ptr);
            }
            if (png_ptr->pass == 4) /* pass 3 might be empty */
            {
               for (i = 0; i < 2 && png_ptr->pass == 4; i++)
               {
                  png_push_have_row(png_ptr, png_bytep_NULL);
                  png_read_push_finish_row(png_ptr);
               }
            }
            break;
         }
         case 3:
         {
            int i;
            for (i = 0; i < 4 && png_ptr->pass == 3; i++)
            {
               png_push_have_row(png_ptr, png_ptr->row_buf + 1);
               png_read_push_finish_row(png_ptr);
            }
            if (png_ptr->pass == 4) /* skip top two generated rows */
            {
               for (i = 0; i < 2 && png_ptr->pass == 4; i++)
               {
                  png_push_have_row(png_ptr, png_bytep_NULL);
                  png_read_push_finish_row(png_ptr);
               }
            }
            break;
         }
         case 4:
         {
            int i;
            for (i = 0; i < 2 && png_ptr->pass == 4; i++)
            {
               png_push_have_row(png_ptr, png_ptr->row_buf + 1);
               png_read_push_finish_row(png_ptr);
            }
            for (i = 0; i < 2 && png_ptr->pass == 4; i++)
            {
               png_push_have_row(png_ptr, png_bytep_NULL);
               png_read_push_finish_row(png_ptr);
            }
            if (png_ptr->pass == 6) /* pass 5 might be empty */
            {
               png_push_have_row(png_ptr, png_bytep_NULL);
               png_read_push_finish_row(png_ptr);
            }
            break;
         }
         case 5:
         {
            int i;
            for (i = 0; i < 2 && png_ptr->pass == 5; i++)
            {
               png_push_have_row(png_ptr, png_ptr->row_buf + 1);
               png_read_push_finish_row(png_ptr);
            }
            if (png_ptr->pass == 6) /* skip top generated row */
            {
               png_push_have_row(png_ptr, png_bytep_NULL);
               png_read_push_finish_row(png_ptr);
            }
            break;
         }
         case 6:
         {
            png_push_have_row(png_ptr, png_ptr->row_buf + 1);
            png_read_push_finish_row(png_ptr);
            if (png_ptr->pass != 6)
               break;
            png_push_have_row(png_ptr, png_bytep_NULL);
            png_read_push_finish_row(png_ptr);
         }
      }
   }
   else
#endif
   {
      png_push_have_row(png_ptr, png_ptr->row_buf + 1);
      png_read_push_finish_row(png_ptr);
   }
}

void /* PRIVATE */
png_read_push_finish_row(png_structp png_ptr)
{
#ifdef PNG_USE_LOCAL_ARRAYS
   /* arrays to facilitate easy interlacing - use pass (0 - 6) as index */

   /* start of interlace block */
   const int FARDATA png_pass_start[] = {0, 4, 0, 2, 0, 1, 0};

   /* offset to next interlace block */
   const int FARDATA png_pass_inc[] = {8, 8, 4, 4, 2, 2, 1};

   /* start of interlace block in the y direction */
   const int FARDATA png_pass_ystart[] = {0, 0, 4, 0, 2, 0, 1};

   /* offset to next interlace block in the y direction */
   const int FARDATA png_pass_yinc[] = {8, 8, 8, 4, 4, 2, 2};

   /* Width of interlace block.  This is not currently used - if you need
    * it, uncomment it here and in png.h
   const int FARDATA png_pass_width[] = {8, 4, 4, 2, 2, 1, 1};
   */

   /* Height of interlace block.  This is not currently used - if you need
    * it, uncomment it here and in png.h
   const int FARDATA png_pass_height[] = {8, 8, 4, 4, 2, 2, 1};
   */
#endif

   png_ptr->row_number++;
   if (png_ptr->row_number < png_ptr->num_rows)
      return;

   if (png_ptr->interlaced)
   {
      png_ptr->row_number = 0;
      png_memset_check(png_ptr, png_ptr->prev_row, 0,
         png_ptr->rowbytes + 1);
      do
      {
         png_ptr->pass++;
         if ((png_ptr->pass == 1 && png_ptr->width < 5) ||
             (png_ptr->pass == 3 && png_ptr->width < 3) ||
             (png_ptr->pass == 5 && png_ptr->width < 2))
           png_ptr->pass++;

         if (png_ptr->pass > 7)
            png_ptr->pass--;
         if (png_ptr->pass >= 7)
            break;

         png_ptr->iwidth = (png_ptr->width +
            png_pass_inc[png_ptr->pass] - 1 -
            png_pass_start[png_ptr->pass]) /
            png_pass_inc[png_ptr->pass];

         png_ptr->irowbytes = PNG_ROWBYTES(png_ptr->pixel_depth,
            png_ptr->iwidth) + 1;

         if (png_ptr->transformations & PNG_INTERLACE)
            break;

         png_ptr->num_rows = (png_ptr->height +
            png_pass_yinc[png_ptr->pass] - 1 -
            png_pass_ystart[png_ptr->pass]) /
            png_pass_yinc[png_ptr->pass];

      } while (png_ptr->iwidth == 0 || png_ptr->num_rows == 0);
   }
}

#if defined(PNG_READ_tEXt_SUPPORTED)
void /* PRIVATE */
png_push_handle_tEXt(png_structp png_ptr, png_infop info_ptr, png_uint_32
   length)
{
   if (!(png_ptr->mode & PNG_HAVE_IHDR) || (png_ptr->mode & PNG_HAVE_IEND))
      {
         png_error(png_ptr, "Out of place tEXt");
         /* to quiet some compiler warnings */
         if(info_ptr == NULL) return;
      }

#ifdef PNG_MAX_MALLOC_64K
   png_ptr->skip_length = 0;  /* This may not be necessary */

   if (length > (png_uint_32)65535L) /* Can't hold entire string in memory */
   {
      png_warning(png_ptr, "tEXt chunk too large to fit in memory");
      png_ptr->skip_length = length - (png_uint_32)65535L;
      length = (png_uint_32)65535L;
   }
#endif

   png_ptr->current_text = (png_charp)png_malloc(png_ptr,
         (png_uint_32)(length+1));
   png_ptr->current_text[length] = '\0';
   png_ptr->current_text_ptr = png_ptr->current_text;
   png_ptr->current_text_size = (png_size_t)length;
   png_ptr->current_text_left = (png_size_t)length;
   png_ptr->process_mode = PNG_READ_tEXt_MODE;
}

void /* PRIVATE */
png_push_read_tEXt(png_structp png_ptr, png_infop info_ptr)
{
   if (png_ptr->buffer_size && png_ptr->current_text_left)
   {
      png_size_t text_size;

      if (png_ptr->buffer_size < png_ptr->current_text_left)
         text_size = png_ptr->buffer_size;
      else
         text_size = png_ptr->current_text_left;
      png_crc_read(png_ptr, (png_bytep)png_ptr->current_text_ptr, text_size);
      png_ptr->current_text_left -= text_size;
      png_ptr->current_text_ptr += text_size;
   }
   if (!(png_ptr->current_text_left))
   {
      png_textp text_ptr;
      png_charp text;
      png_charp key;
      int ret;

      if (png_ptr->buffer_size < 4)
      {
         png_push_save_buffer(png_ptr);
         return;
      }

      png_push_crc_finish(png_ptr);

#if defined(PNG_MAX_MALLOC_64K)
      if (png_ptr->skip_length)
         return;
#endif

      key = png_ptr->current_text;

      for (text = key; *text; text++)
         /* empty loop */ ;

      if (text != key + png_ptr->current_text_size)
         text++;

      text_ptr = (png_textp)png_malloc(png_ptr,
         (png_uint_32)png_sizeof(png_text));
      text_ptr->compression = PNG_TEXT_COMPRESSION_NONE;
      text_ptr->key = key;
#ifdef PNG_iTXt_SUPPORTED
      text_ptr->lang = NULL;
      text_ptr->lang_key = NULL;
#endif
      text_ptr->text = text;

      ret = png_set_text_2(png_ptr, info_ptr, text_ptr, 1);

      png_free(png_ptr, key);
      png_free(png_ptr, text_ptr);
      png_ptr->current_text = NULL;

      if (ret)
        png_warning(png_ptr, "Insufficient memory to store text chunk.");
   }
}
#endif

#if defined(PNG_READ_zTXt_SUPPORTED)
void /* PRIVATE */
png_push_handle_zTXt(png_structp png_ptr, png_infop info_ptr, png_uint_32
   length)
{
   if (!(png_ptr->mode & PNG_HAVE_IHDR) || (png_ptr->mode & PNG_HAVE_IEND))
      {
         png_error(png_ptr, "Out of place zTXt");
         /* to quiet some compiler warnings */
         if(info_ptr == NULL) return;
      }

#ifdef PNG_MAX_MALLOC_64K
   /* We can't handle zTXt chunks > 64K, since we don't have enough space
    * to be able to store the uncompressed data.  Actually, the threshold
    * is probably around 32K, but it isn't as definite as 64K is.
    */
   if (length > (png_uint_32)65535L)
   {
      png_warning(png_ptr, "zTXt chunk too large to fit in memory");
      png_push_crc_skip(png_ptr, length);
      return;
   }
#endif

   png_ptr->current_text = (png_charp)png_malloc(png_ptr,
       (png_uint_32)(length+1));
   png_ptr->current_text[length] = '\0';
   png_ptr->current_text_ptr = png_ptr->current_text;
   png_ptr->current_text_size = (png_size_t)length;
   png_ptr->current_text_left = (png_size_t)length;
   png_ptr->process_mode = PNG_READ_zTXt_MODE;
}

void /* PRIVATE */
png_push_read_zTXt(png_structp png_ptr, png_infop info_ptr)
{