text: 
  /* pngpread.c - read a png file in push mode
   *
   * Last changed in libpng 1.6.0 [February 14, 2013]
   * Copyright (c) 1998-2013 Glenn Randers-Pehrson
   * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
   * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
   *
   * This code is released under the libpng license.
   * For conditions of distribution and use, see the disclaimer
   * and license in png.h
   */
  
  #include "pngpriv.h"
  
  #ifdef PNG_PROGRESSIVE_READ_SUPPORTED
  
  /* Push model modes */
  #define PNG_READ_SIG_MODE   0
  #define PNG_READ_CHUNK_MODE 1
  #define PNG_READ_IDAT_MODE  2
  #define PNG_SKIP_MODE       3
  #define PNG_READ_tEXt_MODE  4
  #define PNG_READ_zTXt_MODE  5
  #define PNG_READ_DONE_MODE  6
  #define PNG_READ_iTXt_MODE  7
  #define PNG_ERROR_MODE      8
  
  void PNGAPI
  png_process_data(png_structrp png_ptr, png_inforp info_ptr,
      png_bytep buffer, png_size_t buffer_size)
  {
     if (png_ptr == NULL || info_ptr == NULL)
        return;
  
     png_push_restore_buffer(png_ptr, buffer, buffer_size);
  
     while (png_ptr->buffer_size)
     {
        png_process_some_data(png_ptr, info_ptr);
     }
  }
  
  png_size_t PNGAPI
  png_process_data_pause(png_structrp png_ptr, int save)
  {
     if (png_ptr != NULL)
     {
        /* It's easiest for the caller if we do the save, then the caller doesn't
         * have to supply the same data again:
         */
        if (save)
           png_push_save_buffer(png_ptr);
        else
        {
           /* This includes any pending saved bytes: */
           png_size_t remaining = png_ptr->buffer_size;
           png_ptr->buffer_size = 0;
  
           /* So subtract the saved buffer size, unless all the data
            * is actually 'saved', in which case we just return 0
            */
           if (png_ptr->save_buffer_size < remaining)
              return remaining - png_ptr->save_buffer_size;
        }
     }
  
     return 0;
  }
  
  png_uint_32 PNGAPI
  png_process_data_skip(png_structrp png_ptr)
  {
     png_uint_32 remaining = 0;
  
     if (png_ptr != NULL && png_ptr->process_mode == PNG_SKIP_MODE &&
        png_ptr->skip_length > 0)
     {
        /* At the end of png_process_data the buffer size must be 0 (see the loop
         * above) so we can detect a broken call here:
         */
        if (png_ptr->buffer_size != 0)
           png_error(png_ptr,
              "png_process_data_skip called inside png_process_data");
  
        /* If is impossible for there to be a saved buffer at this point -
         * otherwise we could not be in SKIP mode.  This will also happen if
         * png_process_skip is called inside png_process_data (but only very
         * rarely.)
         */
        if (png_ptr->save_buffer_size != 0)
           png_error(png_ptr, "png_process_data_skip called with saved data");
  
        remaining = png_ptr->skip_length;
        png_ptr->skip_length = 0;
        png_ptr->process_mode = PNG_READ_CHUNK_MODE;
     }
  
     return remaining;
  }
  
  /* What we do with the incoming data depends on what we were previously
   * doing before we ran out of data...
   */
  void /* PRIVATE */
  png_process_some_data(png_structrp png_ptr, png_inforp info_ptr)
  {
     if (png_ptr == NULL)
        return;
  
     switch (png_ptr->process_mode)
     {
        case PNG_READ_SIG_MODE:
        {
           png_push_read_sig(png_ptr, info_ptr);
           break;
        }
  
        case PNG_READ_CHUNK_MODE:
        {
           png_push_read_chunk(png_ptr, info_ptr);
           break;
        }
  
        case PNG_READ_IDAT_MODE:
        {
           png_push_read_IDAT(png_ptr);
           break;
        }
  
        case PNG_SKIP_MODE:
        {
           png_push_crc_finish(png_ptr);
           break;
        }
  
        default:
        {
           png_ptr->buffer_size = 0;
           break;
        }
     }
  }
  
  /* Read any remaining signature bytes from the stream and compare them with
   * the correct PNG signature.  It is possible that this routine is called
   * with bytes already read from the signature, either because they have been
   * checked by the calling application, or because of multiple calls to this
   * routine.
   */
  void /* PRIVATE */
  png_push_read_sig(png_structrp png_ptr, png_inforp info_ptr)
  {
     png_size_t num_checked = png_ptr->sig_bytes,
               num_to_check = 8 - num_checked;
  
     if (png_ptr->buffer_size < num_to_check)
     {
        num_to_check = png_ptr->buffer_size;
     }
  
     png_push_fill_buffer(png_ptr, &(info_ptr->signature[num_checked]),
         num_to_check);
     png_ptr->sig_bytes = (png_byte)(png_ptr->sig_bytes + num_to_check);
  
     if (png_sig_cmp(info_ptr->signature, num_checked, num_to_check))
     {
        if (num_checked < 4 &&
            png_sig_cmp(info_ptr->signature, num_checked, num_to_check - 4))
           png_error(png_ptr, "Not a PNG file");
  
        else
           png_error(png_ptr, "PNG file corrupted by ASCII conversion");
     }
     else
     {
        if (png_ptr->sig_bytes >= 8)
        {
           png_ptr->process_mode = PNG_READ_CHUNK_MODE;
        }
     }
  }
  
  void /* PRIVATE */
  png_push_read_chunk(png_structrp png_ptr, png_inforp info_ptr)
  {
     png_uint_32 chunk_name;
  #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
     int keep; /* unknown handling method */
  #endif
  
     /* First we make sure we have enough data for the 4 byte chunk name
      * and the 4 byte chunk length before proceeding with decoding the
      * chunk data.  To fully decode each of these chunks, we also make
      * sure we have enough data in the buffer for the 4 byte CRC at the
      * end of every chunk (except IDAT, which is handled separately).
      */
     if (!(png_ptr->mode & PNG_HAVE_CHUNK_HEADER))
     {
        png_byte chunk_length[4];
        png_byte chunk_tag[4];
  
        if (png_ptr->buffer_size < 8)
        {
           png_push_save_buffer(png_ptr);
           return;
        }
  
        png_push_fill_buffer(png_ptr, chunk_length, 4);
        png_ptr->push_length = png_get_uint_31(png_ptr, chunk_length);
        png_reset_crc(png_ptr);
        png_crc_read(png_ptr, chunk_tag, 4);
        png_ptr->chunk_name = PNG_CHUNK_FROM_STRING(chunk_tag);
        png_check_chunk_name(png_ptr, png_ptr->chunk_name);
        png_ptr->mode |= PNG_HAVE_CHUNK_HEADER;
     }
  
     chunk_name = png_ptr->chunk_name;
  
     if (chunk_name == png_IDAT)
     {
        if (png_ptr->mode & PNG_AFTER_IDAT)
           png_ptr->mode |= PNG_HAVE_CHUNK_AFTER_IDAT;
  
        /* If we reach an IDAT chunk, this means we have read all of the
         * header chunks, and we can start reading the image (or if this
         * is called after the image has been read - we have an error).
         */
        if (!(png_ptr->mode & PNG_HAVE_IHDR))
           png_error(png_ptr, "Missing IHDR before IDAT");
  
        else if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
            !(png_ptr->mode & PNG_HAVE_PLTE))
           png_error(png_ptr, "Missing PLTE before IDAT");
  
        png_ptr->mode |= PNG_HAVE_IDAT;
  
        if (!(png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT))
           if (png_ptr->push_length == 0)
              return;
  
        if (png_ptr->mode & PNG_AFTER_IDAT)
           png_benign_error(png_ptr, "Too many IDATs found");
     }
  
     if (chunk_name == png_IHDR)
     {
        if (png_ptr->push_length != 13)
           png_error(png_ptr, "Invalid IHDR length");
  
        if (png_ptr->push_length + 4 > png_ptr->buffer_size)
        {
           png_push_save_buffer(png_ptr);
           return;
        }
  
        png_handle_IHDR(png_ptr, info_ptr, png_ptr->push_length);
     }
  
     else if (chunk_name == png_IEND)
     {
        if (png_ptr->push_length + 4 > png_ptr->buffer_size)
        {
           png_push_save_buffer(png_ptr);
           return;
        }
  
        png_handle_IEND(png_ptr, info_ptr, png_ptr->push_length);
  
        png_ptr->process_mode = PNG_READ_DONE_MODE;
        png_push_have_end(png_ptr, info_ptr);
     }
  
  #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
     else if ((keep = png_chunk_unknown_handling(png_ptr, chunk_name)) != 0)
     {
        if (png_ptr->push_length + 4 > png_ptr->buffer_size)
        {
           png_push_save_buffer(png_ptr);
           return;
        }
  
        png_handle_unknown(png_ptr, info_ptr, png_ptr->push_length, keep);
  
        if (chunk_name == png_PLTE)
           png_ptr->mode |= PNG_HAVE_PLTE;
     }
  
  #endif
     else if (chunk_name == png_PLTE)
     {
        if (png_ptr->push_length + 4 > png_ptr->buffer_size)
        {
           png_push_save_buffer(png_ptr);
           return;
        }
        png_handle_PLTE(png_ptr, info_ptr, png_ptr->push_length);
     }
  
     else if (chunk_name == png_IDAT)
     {
        png_ptr->idat_size = png_ptr->push_length;
        png_ptr->process_mode = PNG_READ_IDAT_MODE;
        png_push_have_info(png_ptr, info_ptr);
        png_ptr->zstream.avail_out =
            (uInt) PNG_ROWBYTES(png_ptr->pixel_depth,
            png_ptr->iwidth) + 1;
        png_ptr->zstream.next_out = png_ptr->row_buf;
        return;
     }
  
  #ifdef PNG_READ_gAMA_SUPPORTED
     else if (png_ptr->chunk_name == png_gAMA)
     {
        if (png_ptr->push_length + 4 > png_ptr->buffer_size)
        {
           png_push_save_buffer(png_ptr);
           return;
        }
  
        png_handle_gAMA(png_ptr, info_ptr, png_ptr->push_length);
     }
  
  #endif
  #ifdef PNG_READ_sBIT_SUPPORTED
     else if (png_ptr->chunk_name == png_sBIT)
     {
        if (png_ptr->push_length + 4 > png_ptr->buffer_size)
        {
           png_push_save_buffer(png_ptr);
           return;
        }
  
        png_handle_sBIT(png_ptr, info_ptr, png_ptr->push_length);
     }
  
  #endif
  #ifdef PNG_READ_cHRM_SUPPORTED
     else if (png_ptr->chunk_name == png_cHRM)
     {
        if (png_ptr->push_length + 4 > png_ptr->buffer_size)
        {
           png_push_save_buffer(png_ptr);
           return;
        }
  
        png_handle_cHRM(png_ptr, info_ptr, png_ptr->push_length);
     }
  
  #endif
  #ifdef PNG_READ_sRGB_SUPPORTED
     else if (chunk_name == png_sRGB)
     {
        if (png_ptr->push_length + 4 > png_ptr->buffer_size)
        {
           png_push_save_buffer(png_ptr);
           return;
        }
  
        png_handle_sRGB(png_ptr, info_ptr, png_ptr->push_length);
     }
  
  #endif
  #ifdef PNG_READ_iCCP_SUPPORTED
     else if (png_ptr->chunk_name == png_iCCP)
     {
        if (png_ptr->push_length + 4 > png_ptr->buffer_size)
        {
           png_push_save_buffer(png_ptr);
           return;
        }
  
        png_handle_iCCP(png_ptr, info_ptr, png_ptr->push_length);
     }
  
  #endif
  #ifdef PNG_READ_sPLT_SUPPORTED
     else if (chunk_name == png_sPLT)
     {
        if (png_ptr->push_length + 4 > png_ptr->buffer_size)
        {
           png_push_save_buffer(png_ptr);
           return;
        }
  
        png_handle_sPLT(png_ptr, info_ptr, png_ptr->push_length);
     }
  
  #endif
  #ifdef PNG_READ_tRNS_SUPPORTED
     else if (chunk_name == png_tRNS)
     {
        if (png_ptr->push_length + 4 > png_ptr->buffer_size)
        {
           png_push_save_buffer(png_ptr);
           return;
        }
  
        png_handle_tRNS(png_ptr, info_ptr, png_ptr->push_length);
     }
  
  #endif
  #ifdef PNG_READ_bKGD_SUPPORTED
     else if (chunk_name == png_bKGD)
     {
        if (png_ptr->push_length + 4 > png_ptr->buffer_size)
        {
           png_push_save_buffer(png_ptr);
           return;
        }
  
        png_handle_bKGD(png_ptr, info_ptr, png_ptr->push_length);
     }
  
  #endif
  #ifdef PNG_READ_hIST_SUPPORTED
     else if (chunk_name == png_hIST)
     {
        if (png_ptr->push_length + 4 > png_ptr->buffer_size)
        {
           png_push_save_buffer(png_ptr);
           return;
        }
  
        png_handle_hIST(png_ptr, info_ptr, png_ptr->push_length);
     }
  
  #endif
  #ifdef PNG_READ_pHYs_SUPPORTED
     else if (chunk_name == png_pHYs)
     {
        if (png_ptr->push_length + 4 > png_ptr->buffer_size)
        {
           png_push_save_buffer(png_ptr);
           return;
        }
  
        png_handle_pHYs(png_ptr, info_ptr, png_ptr->push_length);
     }
  
  #endif
  #ifdef PNG_READ_oFFs_SUPPORTED
     else if (chunk_name == png_oFFs)
     {
        if (png_ptr->push_length + 4 > png_ptr->buffer_size)
        {
           png_push_save_buffer(png_ptr);
           return;
        }
  
        png_handle_oFFs(png_ptr, info_ptr, png_ptr->push_length);
     }
  #endif
  
  #ifdef PNG_READ_pCAL_SUPPORTED
     else if (chunk_name == png_pCAL)
     {
        if (png_ptr->push_length + 4 > png_ptr->buffer_size)
        {
           png_push_save_buffer(png_ptr);
           return;
        }
  
        png_handle_pCAL(png_ptr, info_ptr, png_ptr->push_length);
     }
  
  #endif
  #ifdef PNG_READ_sCAL_SUPPORTED
     else if (chunk_name == png_sCAL)
     {
        if (png_ptr->push_length + 4 > png_ptr->buffer_size)
        {
           png_push_save_buffer(png_ptr);
           return;
        }
  
        png_handle_sCAL(png_ptr, info_ptr, png_ptr->push_length);
     }
  
  #endif
  #ifdef PNG_READ_tIME_SUPPORTED
     else if (chunk_name == png_tIME)
     {
        if (png_ptr->push_length + 4 > png_ptr->buffer_size)
        {
           png_push_save_buffer(png_ptr);
           return;
        }
  
        png_handle_tIME(png_ptr, info_ptr, png_ptr->push_length);
     }
  
  #endif
  #ifdef PNG_READ_tEXt_SUPPORTED
     else if (chunk_name == png_tEXt)
     {
        if (png_ptr->push_length + 4 > png_ptr->buffer_size)
        {
           png_push_save_buffer(png_ptr);
           return;
        }
  
        png_handle_tEXt(png_ptr, info_ptr, png_ptr->push_length);
     }
  
  #endif
  #ifdef PNG_READ_zTXt_SUPPORTED
     else if (chunk_name == png_zTXt)
     {
        if (png_ptr->push_length + 4 > png_ptr->buffer_size)
        {
           png_push_save_buffer(png_ptr);
           return;
        }
  
        png_handle_zTXt(png_ptr, info_ptr, png_ptr->push_length);
     }
  
  #endif
  #ifdef PNG_READ_iTXt_SUPPORTED
     else if (chunk_name == png_iTXt)
     {
        if (png_ptr->push_length + 4 > png_ptr->buffer_size)
        {
           png_push_save_buffer(png_ptr);
           return;
        }
  
        png_handle_iTXt(png_ptr, info_ptr, png_ptr->push_length);
     }
  
  #endif
     else
     {
        if (png_ptr->push_length + 4 > png_ptr->buffer_size)
        {
           png_push_save_buffer(png_ptr);
           return;
        }
        png_handle_unknown(png_ptr, info_ptr, png_ptr->push_length,
           PNG_HANDLE_CHUNK_AS_DEFAULT);
     }
  
     png_ptr->mode &= ~PNG_HAVE_CHUNK_HEADER;
  }
  
  void /* PRIVATE */
  png_push_crc_skip(png_structrp png_ptr, png_uint_32 skip)
  {
     png_ptr->process_mode = PNG_SKIP_MODE;
     png_ptr->skip_length = skip;
  }
  
  void /* PRIVATE */
  png_push_crc_finish(png_structrp png_ptr)
  {
     if (png_ptr->skip_length && png_ptr->save_buffer_size)
     {
        png_size_t save_size = png_ptr->save_buffer_size;
        png_uint_32 skip_length = png_ptr->skip_length;
  
        /* We want the smaller of 'skip_length' and 'save_buffer_size', but
         * they are of different types and we don't know which variable has the
         * fewest bits.  Carefully select the smaller and cast it to the type of
         * the larger - this cannot overflow.  Do not cast in the following test
         * - it will break on either 16 or 64 bit platforms.
         */
        if (skip_length < save_size)
           save_size = (png_size_t)skip_length;
  
        else
           skip_length = (png_uint_32)save_size;
  
        png_calculate_crc(png_ptr, png_ptr->save_buffer_ptr, save_size);
  
        png_ptr->skip_length -= skip_length;
        png_ptr->buffer_size -= save_size;
        png_ptr->save_buffer_size -= save_size;
        png_ptr->save_buffer_ptr += save_size;
     }
     if (png_ptr->skip_length && png_ptr->current_buffer_size)
     {
        png_size_t save_size = png_ptr->current_buffer_size;
        png_uint_32 skip_length = png_ptr->skip_length;
  
        /* We want the smaller of 'skip_length' and 'current_buffer_size', here,
         * the same problem exists as above and the same solution.
         */
        if (skip_length < save_size)
           save_size = (png_size_t)skip_length;
  
        else
           skip_length = (png_uint_32)save_size;
  
        png_calculate_crc(png_ptr, png_ptr->current_buffer_ptr, save_size);
  
        png_ptr->skip_length -= skip_length;
        png_ptr->buffer_size -= save_size;
        png_ptr->current_buffer_size -= save_size;
        png_ptr->current_buffer_ptr += save_size;
     }
     if (!png_ptr->skip_length)
     {
        if (png_ptr->buffer_size < 4)
        {
           png_push_save_buffer(png_ptr);
           return;
        }
  
        png_crc_finish(png_ptr, 0);
        png_ptr->process_mode = PNG_READ_CHUNK_MODE;
     }
  }
  
  void PNGCBAPI
  png_push_fill_buffer(png_structp png_ptr, png_bytep buffer, png_size_t length)
  {
     png_bytep ptr;
  
     if (png_ptr == NULL)
        return;
  
     ptr = buffer;
     if (png_ptr->save_buffer_size)
     {
        png_size_t save_size;
  
        if (length < png_ptr->save_buffer_size)
           save_size = length;
  
        else
           save_size = png_ptr->save_buffer_size;
  
        memcpy(ptr, png_ptr->save_buffer_ptr, save_size);
        length -= save_size;
        ptr += save_size;
        png_ptr->buffer_size -= save_size;
        png_ptr->save_buffer_size -= save_size;
        png_ptr->save_buffer_ptr += save_size;
     }
     if (length && png_ptr->current_buffer_size)
     {
        png_size_t save_size;
  
        if (length < png_ptr->current_buffer_size)
           save_size = length;
  
        else
           save_size = png_ptr->current_buffer_size;
  
        memcpy(ptr, png_ptr->current_buffer_ptr, save_size);
        png_ptr->buffer_size -= save_size;
        png_ptr->current_buffer_size -= save_size;
        png_ptr->current_buffer_ptr += save_size;
     }
  }
  
  void /* PRIVATE */
  png_push_save_buffer(png_structrp png_ptr)
  {
     if (png_ptr->save_buffer_size)
     {
        if (png_ptr->save_buffer_ptr != png_ptr->save_buffer)
        {
           png_size_t i, istop;
           png_bytep sp;
           png_bytep dp;
  
           istop = png_ptr->save_buffer_size;
           for (i = 0, sp = png_ptr->save_buffer_ptr, dp = png_ptr->save_buffer;
               i < istop; i++, sp++, dp++)
           {
              *dp = *sp;
           }
        }
     }
     if (png_ptr->save_buffer_size + png_ptr->current_buffer_size >
         png_ptr->save_buffer_max)
     {
        png_size_t new_max;
        png_bytep old_buffer;
  
        if (png_ptr->save_buffer_size > PNG_SIZE_MAX -
            (png_ptr->current_buffer_size + 256))
        {
           png_error(png_ptr, "Potential overflow of save_buffer");
        }
  
        new_max = png_ptr->save_buffer_size + png_ptr->current_buffer_size + 256;
        old_buffer = png_ptr->save_buffer;
        png_ptr->save_buffer = (png_bytep)png_malloc_warn(png_ptr,
            (png_size_t)new_max);
  
        if (png_ptr->save_buffer == NULL)
        {
           png_free(png_ptr, old_buffer);
           png_error(png_ptr, "Insufficient memory for save_buffer");
        }
  
        memcpy(png_ptr->save_buffer, old_buffer, png_ptr->save_buffer_size);
        png_free(png_ptr, old_buffer);
        png_ptr->save_buffer_max = new_max;
     }
     if (png_ptr->current_buffer_size)
     {
        memcpy(png_ptr->save_buffer + png_ptr->save_buffer_size,
           png_ptr->current_buffer_ptr, png_ptr->current_buffer_size);
        png_ptr->save_buffer_size += png_ptr->current_buffer_size;
        png_ptr->current_buffer_size = 0;
     }
     png_ptr->save_buffer_ptr = png_ptr->save_buffer;
     png_ptr->buffer_size = 0;
  }
  
  void /* PRIVATE */
  png_push_restore_buffer(png_structrp png_ptr, png_bytep buffer,
     png_size_t buffer_length)
  {
     png_ptr->current_buffer = buffer;
     png_ptr->current_buffer_size = buffer_length;
     png_ptr->buffer_size = buffer_length + png_ptr->save_buffer_size;
     png_ptr->current_buffer_ptr = png_ptr->current_buffer;
  }
  
  void /* PRIVATE */
  png_push_read_IDAT(png_structrp png_ptr)
  {
     if (!(png_ptr->mode & PNG_HAVE_CHUNK_HEADER))
     {
        png_byte chunk_length[4];
        png_byte chunk_tag[4];
  
        /* TODO: this code can be commoned up with the same code in push_read */
        if (png_ptr->buffer_size < 8)
        {
           png_push_save_buffer(png_ptr);
           return;
        }
  
        png_push_fill_buffer(png_ptr, chunk_length, 4);
        png_ptr->push_length = png_get_uint_31(png_ptr, chunk_length);
        png_reset_crc(png_ptr);
        png_crc_read(png_ptr, chunk_tag, 4);
        png_ptr->chunk_name = PNG_CHUNK_FROM_STRING(chunk_tag);
        png_ptr->mode |= PNG_HAVE_CHUNK_HEADER;
  
        if (png_ptr->chunk_name != png_IDAT)
        {
           png_ptr->process_mode = PNG_READ_CHUNK_MODE;
  
           if (!(png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED))
              png_error(png_ptr, "Not enough compressed data");
  
           return;
        }
  
        png_ptr->idat_size = png_ptr->push_length;
     }
  
     if (png_ptr->idat_size && png_ptr->save_buffer_size)
     {
        png_size_t save_size = png_ptr->save_buffer_size;
        png_uint_32 idat_size = png_ptr->idat_size;
  
        /* We want the smaller of 'idat_size' and 'current_buffer_size', but they
         * are of different types and we don't know which variable has the fewest
         * bits.  Carefully select the smaller and cast it to the type of the
         * larger - this cannot overflow.  Do not cast in the following test - it
         * will break on either 16 or 64 bit platforms.
         */
        if (idat_size < save_size)
           save_size = (png_size_t)idat_size;
  
        else
           idat_size = (png_uint_32)save_size;
  
        png_calculate_crc(png_ptr, png_ptr->save_buffer_ptr, save_size);
  
        png_process_IDAT_data(png_ptr, png_ptr->save_buffer_ptr, save_size);
  
        png_ptr->idat_size -= idat_size;
        png_ptr->buffer_size -= save_size;
        png_ptr->save_buffer_size -= save_size;
        png_ptr->save_buffer_ptr += save_size;
     }
  
     if (png_ptr->idat_size && png_ptr->current_buffer_size)
     {
        png_size_t save_size = png_ptr->current_buffer_size;
        png_uint_32 idat_size = png_ptr->idat_size;
  
        /* We want the smaller of 'idat_size' and 'current_buffer_size', but they
         * are of different types and we don't know which variable has the fewest
         * bits.  Carefully select the smaller and cast it to the type of the
         * larger - this cannot overflow.
         */
        if (idat_size < save_size)
           save_size = (png_size_t)idat_size;
  
        else
           idat_size = (png_uint_32)save_size;
  
        png_calculate_crc(png_ptr, png_ptr->current_buffer_ptr, save_size);
  
        png_process_IDAT_data(png_ptr, png_ptr->current_buffer_ptr, save_size);
  
        png_ptr->idat_size -= idat_size;
        png_ptr->buffer_size -= save_size;
        png_ptr->current_buffer_size -= save_size;
        png_ptr->current_buffer_ptr += save_size;
     }
     if (!png_ptr->idat_size)
     {
        if (png_ptr->buffer_size < 4)
        {
           png_push_save_buffer(png_ptr);
           return;
        }
  
        png_crc_finish(png_ptr, 0);
        png_ptr->mode &= ~PNG_HAVE_CHUNK_HEADER;
        png_ptr->mode |= PNG_AFTER_IDAT;
        png_ptr->zowner = 0;
     }
  }
  
  void /* PRIVATE */
  png_process_IDAT_data(png_structrp png_ptr, png_bytep buffer,
     png_size_t buffer_length)
  {
     /* The caller checks for a non-zero buffer length. */
     if (!(buffer_length > 0) || buffer == NULL)
        png_error(png_ptr, "No IDAT data (internal error)");
  
     /* This routine must process all the data it has been given
      * before returning, calling the row callback as required to
      * handle the uncompressed results.
      */
     png_ptr->zstream.next_in = buffer;
     /* TODO: WARNING: TRUNCATION ERROR: DANGER WILL ROBINSON: */
     png_ptr->zstream.avail_in = (uInt)buffer_length;
  
     /* Keep going until the decompressed data is all processed
      * or the stream marked as finished.
      */
     while (png_ptr->zstream.avail_in > 0 &&
        !(png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED))
     {
        int ret;
  
        /* We have data for zlib, but we must check that zlib
         * has someplace to put the results.  It doesn't matter
         * if we don't expect any results -- it may be the input
         * data is just the LZ end code.
         */
        if (!(png_ptr->zstream.avail_out > 0))
        {
           /* TODO: WARNING: TRUNCATION ERROR: DANGER WILL ROBINSON: */
           png_ptr->zstream.avail_out = (uInt)(PNG_ROWBYTES(png_ptr->pixel_depth,
               png_ptr->iwidth) + 1);
  
           png_ptr->zstream.next_out = png_ptr->row_buf;
        }
  
        /* Using Z_SYNC_FLUSH here means that an unterminated
         * LZ stream (a stream with a missing end code) can still
         * be handled, otherwise (Z_NO_FLUSH) a future zlib
         * implementation might defer output and therefore
         * change the current behavior (see comments in inflate.c
         * for why this doesn't happen at present with zlib 1.2.5).
         */
        ret = inflate(&png_ptr->zstream, Z_SYNC_FLUSH);
  
        /* Check for any failure before proceeding. */
        if (ret != Z_OK && ret != Z_STREAM_END)
        {
           /* Terminate the decompression. */
           png_ptr->flags |= PNG_FLAG_ZSTREAM_ENDED;
           png_ptr->zowner = 0;
  
           /* This may be a truncated stream (missing or
            * damaged end code).  Treat that as a warning.
            */
           if (png_ptr->row_number >= png_ptr->num_rows ||
               png_ptr->pass > 6)
              png_warning(png_ptr, "Truncated compressed data in IDAT");
  
           else
              png_error(png_ptr, "Decompression error in IDAT");
  
           /* Skip the check on unprocessed input */
           return;
        }
  
        /* Did inflate output any data? */
        if (png_ptr->zstream.next_out != png_ptr->row_buf)
        {
           /* Is this unexpected data after the last row?
            * If it is, artificially terminate the LZ output
            * here.
            */
           if (png_ptr->row_number >= png_ptr->num_rows ||
               png_ptr->pass > 6)
           {
              /* Extra data. */
              png_warning(png_ptr, "Extra compressed data in IDAT");
              png_ptr->flags |= PNG_FLAG_ZSTREAM_ENDED;
              png_ptr->zowner = 0;
  
              /* Do no more processing; skip the unprocessed
               * input check below.
               */
              return;
           }
  
           /* Do we have a complete row? */
           if (png_ptr->zstream.avail_out == 0)
              png_push_process_row(png_ptr);
        }
  
        /* And check for the end of the stream. */
        if (ret == Z_STREAM_END)
           png_ptr->flags |= PNG_FLAG_ZSTREAM_ENDED;
     }
  
     /* All the data should have been processed, if anything
      * is left at this point we have bytes of IDAT data
      * after the zlib end code.
      */
     if (png_ptr->zstream.avail_in > 0)
        png_warning(png_ptr, "Extra compression data in IDAT");
  }
  
  void /* PRIVATE */
  png_push_process_row(png_structrp png_ptr)
  {
     /* 1.5.6: row_info moved out of png_struct to a local here. */
     png_row_info row_info;
  
     row_info.width = png_ptr->iwidth; /* NOTE: width of current interlaced row */
     row_info.color_type = png_ptr->color_type;
     row_info.bit_depth = png_ptr->bit_depth;
     row_info.channels = png_ptr->channels;
     row_info.pixel_depth = png_ptr->pixel_depth;
     row_info.rowbytes = PNG_ROWBYTES(row_info.pixel_depth, row_info.width);
  
     if (png_ptr->row_buf[0] > PNG_FILTER_VALUE_NONE)
     {
        if (png_ptr->row_buf[0] < PNG_FILTER_VALUE_LAST)
           png_read_filter_row(png_ptr, &row_info, png_ptr->row_buf + 1,
              png_ptr->prev_row + 1, png_ptr->row_buf[0]);
        else
           png_error(png_ptr, "bad adaptive filter value");
     }
  
     /* libpng 1.5.6: the following line was copying png_ptr->rowbytes before
      * 1.5.6, while the buffer really is this big in current versions of libpng
      * it may not be in the future, so this was changed just to copy the
      * interlaced row count:
      */
     memcpy(png_ptr->prev_row, png_ptr->row_buf, row_info.rowbytes + 1);
  
  #ifdef PNG_READ_TRANSFORMS_SUPPORTED
     if (png_ptr->transformations)
        png_do_read_transformations(png_ptr, &row_info);
  #endif
  
     /* The transformed pixel depth should match the depth now in row_info. */
     if (png_ptr->transformed_pixel_depth == 0)
     {
        png_ptr->transformed_pixel_depth = row_info.pixel_depth;
        if (row_info.pixel_depth > png_ptr->maximum_pixel_depth)
           png_error(png_ptr, "progressive row overflow");
     }
  
     else if (png_ptr->transformed_pixel_depth != row_info.pixel_depth)
        png_error(png_ptr, "internal progressive row size calculation error");
  
  
  #ifdef 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)
           png_do_read_interlace(&row_info, png_ptr->row_buf + 1, png_ptr->pass,
              png_ptr->transformations);
  
      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, 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, NULL);
                    png_read_push_finish_row(png_ptr);
                 }
              }
  
              if (png_ptr->pass == 6 && png_ptr->height <= 4)
              {
                  png_push_have_row(png_ptr, 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, 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, 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, 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, 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, NULL);
                 png_read_push_finish_row(png_ptr);
              }
  
              if (png_ptr->pass == 6) /* Pass 5 might be empty */
              {
                 png_push_have_row(png_ptr, 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, NULL);
                 png_read_push_finish_row(png_ptr);
              }
  
              break;
           }
  
           default:
           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, 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_structrp png_ptr)
  {
  #ifdef PNG_READ_INTERLACING_SUPPORTED
     /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
  
     /* Start of interlace block */
     static PNG_CONST png_byte png_pass_start[] = {0, 4, 0, 2, 0, 1, 0};
  
     /* Offset to next interlace block */
     static PNG_CONST png_byte png_pass_inc[] = {8, 8, 4, 4, 2, 2, 1};
  
     /* Start of interlace block in the y direction */
     static PNG_CONST png_byte png_pass_ystart[] = {0, 0, 4, 0, 2, 0, 1};
  
     /* Offset to next interlace block in the y direction */
     static PNG_CONST png_byte png_pass_yinc[] = {8, 8, 8, 4, 4, 2, 2};
  
     /* Height of interlace block.  This is not currently used - if you need
      * it, uncomment it here and in png.h
     static PNG_CONST png_byte 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;
  
  #ifdef PNG_READ_INTERLACING_SUPPORTED
     if (png_ptr->interlaced)
     {
        png_ptr->row_number = 0;
        memset(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];
  
           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);
     }
  #endif /* PNG_READ_INTERLACING_SUPPORTED */
  }
  
  void /* PRIVATE */
  png_push_have_info(png_structrp png_ptr, png_inforp info_ptr)
  {
     if (png_ptr->info_fn != NULL)
        (*(png_ptr->info_fn))(png_ptr, info_ptr);
  }
  
  void /* PRIVATE */
  png_push_have_end(png_structrp png_ptr, png_inforp info_ptr)
  {
     if (png_ptr->end_fn != NULL)
        (*(png_ptr->end_fn))(png_ptr, info_ptr);
  }
  
  void /* PRIVATE */
  png_push_have_row(png_structrp png_ptr, png_bytep row)
  {
     if (png_ptr->row_fn != NULL)
        (*(png_ptr->row_fn))(png_ptr, row, png_ptr->row_number,
           (int)png_ptr->pass);
  }
  
  #ifdef PNG_READ_INTERLACING_SUPPORTED
  void PNGAPI
  png_progressive_combine_row(png_const_structrp png_ptr, png_bytep old_row,
      png_const_bytep new_row)
  {
     if (png_ptr == NULL)
        return;
  
     /* new_row is a flag here - if it is NULL then the app callback was called
      * from an empty row (see the calls to png_struct::row_fn below), otherwise
      * it must be png_ptr->row_buf+1
      */
     if (new_row != NULL)
        png_combine_row(png_ptr, old_row, 1/*display*/);
  }
  #endif /* PNG_READ_INTERLACING_SUPPORTED */
  
  void PNGAPI
  png_set_progressive_read_fn(png_structrp png_ptr, png_voidp progressive_ptr,
      png_progressive_info_ptr info_fn, png_progressive_row_ptr row_fn,
      png_progressive_end_ptr end_fn)
  {
     if (png_ptr == NULL)
        return;
  
     png_ptr->info_fn = info_fn;
     png_ptr->row_fn = row_fn;
     png_ptr->end_fn = end_fn;
  
     png_set_read_fn(png_ptr, progressive_ptr, png_push_fill_buffer);
  }
  
  png_voidp PNGAPI
  png_get_progressive_ptr(png_const_structrp png_ptr)
  {
     if (png_ptr == NULL)
        return (NULL);
  
     return png_ptr->io_ptr;
  }
  #endif /* PNG_PROGRESSIVE_READ_SUPPORTED */
  