/* pngpread.c - read a png file in push mode

 *

 * Last changed in libpng 1.6.18 [July 23, 2015]

 * Copyright (c) 1998-2002,2004,2006-2015 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_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

#define PNG_PUSH_SAVE_BUFFER_IF_FULL \

if (png_ptr->push_length + 4 > png_ptr->buffer_size) \

   { png_push_save_buffer(png_ptr); return; }

#define PNG_PUSH_SAVE_BUFFER_IF_LT(N) \

if (png_ptr->buffer_size < N) \

   { png_push_save_buffer(png_ptr); return; }

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 != 0)

         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)

{

  /* TODO: Deprecate and remove this API.

   * Somewhere the implementation of this seems to have been lost,

   * or abandoned.  It was only to support some internal back-door access

   * to png_struct) in libpng-1.4.x.

   */

   png_app_warning(png_ptr,

"png_process_data_skip is not implemented in any current version of libpng");

   return 0;

}

/* 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;

      }

      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, /* SAFE, does not exceed 8 */

       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) == 0)

   {

      png_byte chunk_length[4];

      png_byte chunk_tag[4];

      PNG_PUSH_SAVE_BUFFER_IF_LT(8)

      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) != 0)

         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) == 0)

         png_error(png_ptr, "Missing IHDR before IDAT");

      else if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&

          (png_ptr->mode & PNG_HAVE_PLTE) == 0)

         png_error(png_ptr, "Missing PLTE before IDAT");

      png_ptr->mode |= PNG_HAVE_IDAT;

      png_ptr->process_mode = PNG_READ_IDAT_MODE;

      if ((png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT) == 0)

         if (png_ptr->push_length == 0)

            return;

      if ((png_ptr->mode & PNG_AFTER_IDAT) != 0)

         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");

      PNG_PUSH_SAVE_BUFFER_IF_FULL

      png_handle_IHDR(png_ptr, info_ptr, png_ptr->push_length);

   }

   else if (chunk_name == png_IEND)

   {

      PNG_PUSH_SAVE_BUFFER_IF_FULL

      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)

   {

      PNG_PUSH_SAVE_BUFFER_IF_FULL

      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)

   {

      PNG_PUSH_SAVE_BUFFER_IF_FULL

      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)

   {

      PNG_PUSH_SAVE_BUFFER_IF_FULL

      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)

   {

      PNG_PUSH_SAVE_BUFFER_IF_FULL

      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)

   {

      PNG_PUSH_SAVE_BUFFER_IF_FULL

      png_handle_cHRM(png_ptr, info_ptr, png_ptr->push_length);

   }

#endif

#ifdef PNG_READ_sRGB_SUPPORTED

   else if (chunk_name == png_sRGB)

   {

      PNG_PUSH_SAVE_BUFFER_IF_FULL

      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)

   {

      PNG_PUSH_SAVE_BUFFER_IF_FULL

      png_handle_iCCP(png_ptr, info_ptr, png_ptr->push_length);

   }

#endif

#ifdef PNG_READ_sPLT_SUPPORTED

   else if (chunk_name == png_sPLT)

   {

      PNG_PUSH_SAVE_BUFFER_IF_FULL

      png_handle_sPLT(png_ptr, info_ptr, png_ptr->push_length);

   }

#endif

#ifdef PNG_READ_tRNS_SUPPORTED

   else if (chunk_name == png_tRNS)

   {

      PNG_PUSH_SAVE_BUFFER_IF_FULL

      png_handle_tRNS(png_ptr, info_ptr, png_ptr->push_length);

   }

#endif

#ifdef PNG_READ_bKGD_SUPPORTED

   else if (chunk_name == png_bKGD)

   {

      PNG_PUSH_SAVE_BUFFER_IF_FULL

      png_handle_bKGD(png_ptr, info_ptr, png_ptr->push_length);

   }

#endif

#ifdef PNG_READ_hIST_SUPPORTED

   else if (chunk_name == png_hIST)

   {

      PNG_PUSH_SAVE_BUFFER_IF_FULL

      png_handle_hIST(png_ptr, info_ptr, png_ptr->push_length);

   }

#endif

#ifdef PNG_READ_pHYs_SUPPORTED

   else if (chunk_name == png_pHYs)

   {

      PNG_PUSH_SAVE_BUFFER_IF_FULL

      png_handle_pHYs(png_ptr, info_ptr, png_ptr->push_length);

   }

#endif

#ifdef PNG_READ_oFFs_SUPPORTED

   else if (chunk_name == png_oFFs)

   {

      PNG_PUSH_SAVE_BUFFER_IF_FULL

      png_handle_oFFs(png_ptr, info_ptr, png_ptr->push_length);

   }

#endif

#ifdef PNG_READ_pCAL_SUPPORTED

   else if (chunk_name == png_pCAL)

   {

      PNG_PUSH_SAVE_BUFFER_IF_FULL

      png_handle_pCAL(png_ptr, info_ptr, png_ptr->push_length);

   }

#endif

#ifdef PNG_READ_sCAL_SUPPORTED

   else if (chunk_name == png_sCAL)

   {

      PNG_PUSH_SAVE_BUFFER_IF_FULL

      png_handle_sCAL(png_ptr, info_ptr, png_ptr->push_length);

   }

#endif

#ifdef PNG_READ_tIME_SUPPORTED

   else if (chunk_name == png_tIME)

   {

      PNG_PUSH_SAVE_BUFFER_IF_FULL

      png_handle_tIME(png_ptr, info_ptr, png_ptr->push_length);

   }

#endif

#ifdef PNG_READ_tEXt_SUPPORTED

   else if (chunk_name == png_tEXt)

   {

      PNG_PUSH_SAVE_BUFFER_IF_FULL

      png_handle_tEXt(png_ptr, info_ptr, png_ptr->push_length);

   }

#endif

#ifdef PNG_READ_zTXt_SUPPORTED

   else if (chunk_name == png_zTXt)

   {

      PNG_PUSH_SAVE_BUFFER_IF_FULL

      png_handle_zTXt(png_ptr, info_ptr, png_ptr->push_length);

   }

#endif

#ifdef PNG_READ_iTXt_SUPPORTED

   else if (chunk_name == png_iTXt)

   {

      PNG_PUSH_SAVE_BUFFER_IF_FULL

      png_handle_iTXt(png_ptr, info_ptr, png_ptr->push_length);

   }

#endif

   else

   {

      PNG_PUSH_SAVE_BUFFER_IF_FULL

      png_handle_unknown(png_ptr, info_ptr, png_ptr->push_length,

         PNG_HANDLE_CHUNK_AS_DEFAULT);

   }

   png_ptr->mode &= ~PNG_HAVE_CHUNK_HEADER;

}

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 != 0)

   {

      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 != 0 && png_ptr->current_buffer_size != 0)

   {

      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 != 0)

   {

      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) == 0)

   {

      png_byte chunk_length[4];

      png_byte chunk_tag[4];

      /* TODO: this code can be commoned up with the same code in push_read */

      PNG_PUSH_SAVE_BUFFER_IF_LT(8)

      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) == 0)

            png_error(png_ptr, "Not enough compressed data");

         return;

      }

      png_ptr->idat_size = png_ptr->push_length;

   }

   if (png_ptr->idat_size != 0 && png_ptr->save_buffer_size != 0)

   {

      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-bit 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 != 0 && png_ptr->current_buffer_size != 0)

   {

      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 == 0)

   {

      PNG_PUSH_SAVE_BUFFER_IF_LT(4)

      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) == 0)

   {

      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 = PNG_INFLATE(png_ptr, 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 != 0)

      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

   /* Expand interlaced rows to full size */

   if (png_ptr->interlaced != 0 &&

       (png_ptr->transformations & PNG_INTERLACE) != 0)

   {

      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 */