libpng/pngpread.c

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

	libpng 1.0 beta 2 - version 0.86
   For conditions of distribution and use, see copyright notice in png.h
	Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
   January 10, 1996
   */

#define PNG_INTERNAL
#include "png.h"

void
png_process_data(png_structp png_ptr, png_infop info,
	png_bytep buffer, png_uint_32 buffer_size)
{
	png_push_restore_buffer(png_ptr, buffer, buffer_size);

	while (png_ptr->buffer_size)
	{
		png_process_some_data(png_ptr, info);
	}
}

void
png_process_some_data(png_structp png_ptr, png_infop info)
{
	switch (png_ptr->process_mode)
	{
		case PNG_READ_SIG_MODE:
		{
			png_push_read_sig(png_ptr);
			break;
		}
		case PNG_READ_CHUNK_MODE:
		{
			png_push_read_chunk(png_ptr, info);
			break;
		}
		case PNG_READ_IDAT_MODE:
		{
			png_push_read_idat(png_ptr);
			break;
		}
		case PNG_READ_PLTE_MODE:
		{
			png_push_read_plte(png_ptr, info);
			break;
		}
#if defined(PNG_READ_tEXt_SUPPORTED)
		case PNG_READ_tEXt_MODE:
		{
			png_push_read_text(png_ptr, info);
			break;
		}
#endif
		case PNG_READ_END_MODE:
		{
			png_push_read_end(png_ptr, info);
			break;
		}
		case PNG_SKIP_MODE:
		{
			png_push_skip(png_ptr);
			break;
		}
		default:
		{
			png_ptr->buffer_size = 0;
			break;
		}
	}
}

void
png_push_read_sig(png_structp png_ptr)
{
	png_byte sig[8];

	if (png_ptr->buffer_size < 8)
	{
		png_push_save_buffer(png_ptr);
		return;
	}

	png_push_fill_buffer(png_ptr, sig, 8);

	if (png_check_sig(sig, 8))
	{
		png_ptr->process_mode = PNG_READ_CHUNK_MODE;
	}
	else
	{
   	png_error(png_ptr, "Not a PNG file");
	}
}

void
png_push_read_chunk(png_structp png_ptr, png_infop info)
{
	if (!png_ptr->have_chunk_header)
	{
		png_byte chunk_start[8];

		if (png_ptr->buffer_size < 8)
		{
			png_push_save_buffer(png_ptr);
			return;
		}

		png_push_fill_buffer(png_ptr, chunk_start, 8);
		png_ptr->push_length = png_get_uint_32(chunk_start);
		memcpy(png_ptr->push_chunk_name, chunk_start + 4, 4);
		png_ptr->have_chunk_header = 1;
		png_reset_crc(png_ptr);
		png_calculate_crc(png_ptr, chunk_start + 4, 4);
	}

	if (!png_memcmp(png_ptr->push_chunk_name, png_IHDR, 4))
	{
		if (png_ptr->mode != PNG_BEFORE_IHDR)
			png_error(png_ptr, "Out of Place IHDR");

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

		png_handle_IHDR(png_ptr, info, png_ptr->push_length);
		png_push_check_crc(png_ptr);
		png_ptr->mode = PNG_HAVE_IHDR;
	}
	else if (!png_memcmp(png_ptr->push_chunk_name, png_PLTE, 4))
	{
		if (png_ptr->mode != PNG_HAVE_IHDR)
			png_error(png_ptr, "Missing IHDR");

#if !defined(PNG_READ_OPT_PLTE_SUPPORTED)
		if (png_ptr->color_type != PNG_COLOR_TYPE_PALETTE)
			png_push_crc_skip(png_ptr, length);
		else
#else
		{
			png_push_handle_PLTE(png_ptr, info, png_ptr->push_length);
		}
#endif
		png_ptr->mode = PNG_HAVE_PLTE;
	}
	else if (!png_memcmp(png_ptr->push_chunk_name, png_IDAT, 4))
	{
		png_ptr->idat_size = png_ptr->push_length;
		png_ptr->mode = PNG_HAVE_IDAT;
		png_ptr->process_mode = PNG_READ_IDAT_MODE;
		png_push_have_info(png_ptr, info);
		png_ptr->zstream->avail_out = (uInt)png_ptr->irowbytes;
		png_ptr->zstream->next_out = png_ptr->row_buf;
		return;
	}
	else if (!png_memcmp(png_ptr->push_chunk_name, png_IEND, 4))
	{
		png_error(png_ptr, "No Image in File");
	}
#if defined(PNG_READ_gAMA_SUPPORTED)
	else if (!png_memcmp(png_ptr->push_chunk_name, png_gAMA, 4))
	{
		if (png_ptr->push_length + 4 > png_ptr->buffer_size)
		{
			png_push_save_buffer(png_ptr);
			return;
		}

		if (png_ptr->mode != PNG_HAVE_IHDR)
			png_error(png_ptr, "Out of Place PLTE");

		png_handle_gAMA(png_ptr, info, png_ptr->push_length);
		png_push_check_crc(png_ptr);
	}
#endif
#if defined(PNG_READ_sBIT_SUPPORTED)
	else if (!png_memcmp(png_ptr->push_chunk_name, png_sBIT, 4))
	{
		if (png_ptr->push_length + 4 > png_ptr->buffer_size)
		{
			png_push_save_buffer(png_ptr);
			return;
		}

		if (png_ptr->mode != PNG_HAVE_IHDR)
			png_error(png_ptr, "Out of Place sBIT");

		png_handle_sBIT(png_ptr, info, png_ptr->push_length);
		png_push_check_crc(png_ptr);
	}
#endif
#if defined(PNG_READ_cHRM_SUPPORTED)
	else if (!png_memcmp(png_ptr->push_chunk_name, png_cHRM, 4))
	{
		if (png_ptr->push_length + 4 > png_ptr->buffer_size)
		{
			png_push_save_buffer(png_ptr);
			return;
		}

		if (png_ptr->mode != PNG_HAVE_IHDR)
			png_error(png_ptr, "Out of Place cHRM");

		png_handle_cHRM(png_ptr, info, png_ptr->push_length);
		png_push_check_crc(png_ptr);
	}
#endif
#if defined(PNG_READ_tRNS_SUPPORTED)
	else if (!png_memcmp(png_ptr->push_chunk_name, png_tRNS, 4))
	{
		if (png_ptr->push_length + 4 > png_ptr->buffer_size)
		{
			png_push_save_buffer(png_ptr);
			return;
		}
		if (png_ptr->mode != PNG_HAVE_IHDR &&
			png_ptr->mode != PNG_HAVE_PLTE)
			png_error(png_ptr, "Out of Place tRNS");

		png_handle_tRNS(png_ptr, info, png_ptr->push_length);
		png_push_check_crc(png_ptr);
	}
#endif
#if defined(PNG_READ_bKGD_SUPPORTED)
	else if (!png_memcmp(png_ptr->push_chunk_name, png_bKGD, 4))
	{
		if (png_ptr->push_length + 4 > png_ptr->buffer_size)
		{
			png_push_save_buffer(png_ptr);
			return;
		}

		if (png_ptr->mode != PNG_HAVE_IHDR &&
			png_ptr->mode != PNG_HAVE_PLTE)
			png_error(png_ptr, "Out of Place bKGD");

		png_handle_bKGD(png_ptr, info, png_ptr->push_length);
		png_push_check_crc(png_ptr);
	}
#endif
#if defined(PNG_READ_hIST_SUPPORTED)
	else if (!png_memcmp(png_ptr->push_chunk_name, png_hIST, 4))
	{
		if (png_ptr->push_length + 4 > png_ptr->buffer_size)
		{
			png_push_save_buffer(png_ptr);
			return;
		}

		if (png_ptr->mode != PNG_HAVE_PLTE)
			png_error(png_ptr, "Out of Place hIST");

		png_handle_hIST(png_ptr, info, png_ptr->push_length);
		png_push_check_crc(png_ptr);
	}
#endif
#if defined(PNG_READ_pHYs_SUPPORTED)
	else if (!png_memcmp(png_ptr->push_chunk_name, png_pHYs, 4))
	{
		if (png_ptr->push_length + 4 > png_ptr->buffer_size)
		{
			png_push_save_buffer(png_ptr);
			return;
		}

		if (png_ptr->mode != PNG_HAVE_IHDR &&
			png_ptr->mode != PNG_HAVE_PLTE)
			png_error(png_ptr, "Out of Place pHYs");

		png_handle_pHYs(png_ptr, info, png_ptr->push_length);
		png_push_check_crc(png_ptr);
	}
#endif
#if defined(PNG_READ_oFFs_SUPPORTED)
	else if (!png_memcmp(png_ptr->push_chunk_name, png_oFFs, 4))
	{
		if (png_ptr->push_length + 4 > png_ptr->buffer_size)
		{
			png_push_save_buffer(png_ptr);
			return;
		}

		if (png_ptr->mode != PNG_HAVE_IHDR &&
			png_ptr->mode != PNG_HAVE_PLTE)
			png_error(png_ptr, "Out of Place oFFs");

		png_handle_oFFs(png_ptr, info, png_ptr->push_length);
		png_push_check_crc(png_ptr);
	}
#endif
#if defined(PNG_READ_tIME_SUPPORTED)
	else if (!png_memcmp(png_ptr->push_chunk_name, png_tIME, 4))
	{
		if (png_ptr->push_length + 4 > png_ptr->buffer_size)
		{
			png_push_save_buffer(png_ptr);
			return;
		}

		if (png_ptr->mode == PNG_BEFORE_IHDR ||
			png_ptr->mode == PNG_AFTER_IEND)
			png_error(png_ptr, "Out of Place tIME");

		png_handle_tIME(png_ptr, info, png_ptr->push_length);
		png_push_check_crc(png_ptr);
	}
#endif
#if defined(PNG_READ_tEXt_SUPPORTED)
	else if (!png_memcmp(png_ptr->push_chunk_name, png_tEXt, 4))
	{
		if (png_ptr->mode == PNG_BEFORE_IHDR ||
			png_ptr->mode == PNG_AFTER_IEND)
			png_error(png_ptr, "Out of Place tEXt");

		png_push_handle_tEXt(png_ptr, info, png_ptr->push_length);
	}
#endif
#if defined(PNG_READ_zTXt_SUPPORTED)
	else if (!png_memcmp(png_ptr->push_chunk_name, png_zTXt, 4))
	{
		if (png_ptr->mode == PNG_BEFORE_IHDR ||
			png_ptr->mode == PNG_AFTER_IEND)
			png_error(png_ptr, "Out of Place zTXt");

		png_push_handle_zTXt(png_ptr, info, png_ptr->push_length);
	}
#endif
	else
	{
		if ((png_ptr->push_chunk_name[0] & 0x20) == 0)
			png_error(png_ptr, "Unknown Critical Chunk");

		png_push_crc_skip(png_ptr, png_ptr->push_length);
	}
	png_ptr->have_chunk_header = 0;
}

void
png_push_check_crc(png_structp png_ptr)
{
	png_byte crc_buf[4];
	png_uint_32 crc;

	png_push_fill_buffer(png_ptr, crc_buf, 4);
	crc = png_get_uint_32(crc_buf);
	if (((crc ^ 0xffffffffL) & 0xffffffffL) !=
		(png_ptr->crc & 0xffffffffL))
		png_error(png_ptr, "Bad CRC value");
}

void
png_push_crc_skip(png_structp png_ptr, png_uint_32 length)
{
	png_ptr->process_mode = PNG_SKIP_MODE;
	png_ptr->skip_length = length;
}

void
png_push_skip(png_structp png_ptr)
{
	if (png_ptr->skip_length && png_ptr->save_buffer_size)
	{
		png_uint_32 save_size;

		if (png_ptr->skip_length < png_ptr->save_buffer_size)
			save_size = png_ptr->skip_length;
		else
			save_size = png_ptr->save_buffer_size;

		png_calculate_crc(png_ptr, png_ptr->save_buffer_ptr, save_size);

		png_ptr->skip_length -= save_size;
		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_uint_32 save_size;

		if (png_ptr->skip_length < png_ptr->current_buffer_size)
			save_size = png_ptr->skip_length;
		else
			save_size = png_ptr->current_buffer_size;

		png_calculate_crc(png_ptr, png_ptr->current_buffer_ptr, save_size);

		png_ptr->skip_length -= save_size;
		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 && png_ptr->buffer_size >= 4)
	{
		png_push_check_crc(png_ptr);
		png_ptr->process_mode = PNG_READ_CHUNK_MODE;
	}
}

void
png_push_fill_buffer(png_structp png_ptr, png_bytep buffer,
	png_uint_32 length)
{
	png_byte * ptr;

	ptr = buffer;
	if (png_ptr->save_buffer_size)
	{
		png_uint_32 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_uint_32 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
png_push_save_buffer(png_structp png_ptr)
{
	if (png_ptr->save_buffer_size)
	{
		if (png_ptr->save_buffer_ptr != png_ptr->save_buffer)
		{
			int i;
			png_byte * sp;
			png_byte * dp;

			for (i = 0, sp = png_ptr->save_buffer_ptr, dp = png_ptr->save_buffer;
				i < png_ptr->save_buffer_size;
				i++, sp++, dp++)
			{
         	*dp = *sp;
			}
		}
	}
	if (png_ptr->save_buffer_size + png_ptr->current_buffer_size >
		png_ptr->save_buffer_max)
	{
		int new_max;
		png_byte * old_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_byte *)
			png_large_malloc(png_ptr, new_max);
		memcpy(png_ptr->save_buffer, old_buffer,
			png_ptr->save_buffer_size);
		png_large_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
png_push_restore_buffer(png_structp png_ptr, png_bytep buffer,
	png_uint_32 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
png_push_read_idat(png_structp png_ptr)
{
	if (!png_ptr->have_chunk_header)
	{
		png_byte chunk_start[8];

		if (png_ptr->buffer_size < 8)
		{
			png_push_save_buffer(png_ptr);
			return;
		}

		png_push_fill_buffer(png_ptr, chunk_start, 8);
		png_ptr->push_length = png_get_uint_32(chunk_start);
		memcpy(png_ptr->push_chunk_name, chunk_start + 4, 4);
		png_ptr->have_chunk_header = 1;
		png_reset_crc(png_ptr);
		png_calculate_crc(png_ptr, chunk_start + 4, 4);
		if (png_memcmp(png_ptr->push_chunk_name, png_IDAT, 4))
		{
			png_ptr->process_mode = PNG_READ_END_MODE;
			if (!png_ptr->zlib_finished)
				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_uint_32 save_size;

		if (png_ptr->idat_size < png_ptr->save_buffer_size)
			save_size = png_ptr->idat_size;
		else
			save_size = png_ptr->save_buffer_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 -= save_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_uint_32 save_size;

		if (png_ptr->idat_size < png_ptr->current_buffer_size)
			save_size = png_ptr->idat_size;
		else
			save_size = png_ptr->current_buffer_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 -= save_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 && png_ptr->buffer_size >= 4)
	{
		png_push_check_crc(png_ptr);
		png_ptr->have_chunk_header = 0;
	}
}

void
png_process_IDAT_data(png_structp png_ptr, png_bytep buffer,
	png_uint_32 buffer_length)
{
	int ret;

	if (png_ptr->zlib_finished && buffer_length)
   	png_error(png_ptr, "Extra compression data");

	png_ptr->zstream->next_in = buffer;
	png_ptr->zstream->avail_in = (uInt)buffer_length;
	do
	{
		ret = inflate(png_ptr->zstream, Z_PARTIAL_FLUSH);
		if (ret == Z_STREAM_END)
		{
			if (png_ptr->zstream->avail_in)
				png_error(png_ptr, "Extra compressed data");
			if (!png_ptr->zstream->avail_out)
			{
				png_push_process_row(png_ptr);
			}
			png_ptr->mode = PNG_AT_LAST_IDAT;
			png_ptr->zlib_finished = 1;
			break;
		}
		if (ret != Z_OK)
			png_error(png_ptr, "Compression Error");
		if (!(png_ptr->zstream->avail_out))
		{
			png_push_process_row(png_ptr);
			png_ptr->zstream->avail_out = (uInt)png_ptr->irowbytes;
			png_ptr->zstream->next_out = png_ptr->row_buf;
		}

	} while (png_ptr->zstream->avail_in);
}

void
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_ptr->row_info.width *
      (png_uint_32)png_ptr->row_info.pixel_depth + 7) >> 3);

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

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

   if (png_ptr->transformations)
      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)
			png_do_read_interlace(&(png_ptr->row_info),
				png_ptr->row_buf + 1, png_ptr->pass);

		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);
				}
				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)
				{
					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);
				}
				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)
				{
					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);
				}
				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)
				{
					png_push_have_row(png_ptr, 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, 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
png_read_push_finish_row(png_structp png_ptr)
{
   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(png_ptr->prev_row, 0, (png_size_t)png_ptr->rowbytes + 1);
      do
      {
         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_ptr->iwidth *
            png_ptr->pixel_depth + 7) >> 3) + 1;
         if (!(png_ptr->transformations & PNG_INTERLACE))
			{
            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];
            if (!(png_ptr->num_rows))
               continue;
         }
         if (png_ptr->transformations & PNG_INTERLACE)
            break;
      } while (png_ptr->iwidth == 0);
   }
}


void
png_push_handle_PLTE(png_structp png_ptr, png_infop info, png_uint_32 length)
{
	if (length % 3)
		png_error(png_ptr, "Invalid Palette Chunk");

	png_ptr->num_palette = length / 3;
	png_ptr->cur_palette = 0;
	png_ptr->palette = (png_colorp)png_malloc(png_ptr,
		png_ptr->num_palette * sizeof (png_color));
	png_ptr->process_mode = PNG_READ_PLTE_MODE;
}

void
png_push_read_plte(png_structp png_ptr, png_infop info)
{
	while (png_ptr->cur_palette < png_ptr->num_palette &&
		png_ptr->buffer_size >= 3)
	{
		png_byte buf[3];
		png_push_fill_buffer(png_ptr, buf, 3);
		png_calculate_crc(png_ptr, buf, 3);

		/* don't depend upon png_color being any order */
		png_ptr->palette[png_ptr->cur_palette].red = buf[0];
		png_ptr->palette[png_ptr->cur_palette].green = buf[1];
		png_ptr->palette[png_ptr->cur_palette].blue = buf[2];
		png_ptr->cur_palette++;
	}
	if (png_ptr->cur_palette == png_ptr->num_palette &&
		png_ptr->buffer_size >= 4)
	{
		png_push_check_crc(png_ptr);
		png_read_PLTE(png_ptr, info, png_ptr->palette, png_ptr->num_palette);
		png_ptr->process_mode = PNG_READ_CHUNK_MODE;
	}
	else
	{
		png_push_save_buffer(png_ptr);
	}
}

#if defined(PNG_READ_tEXt_SUPPORTED)
void
png_push_handle_tEXt(png_structp png_ptr, png_infop info,
	png_uint_32 length)
{
	png_ptr->current_text = (png_charp)png_large_malloc(png_ptr, length + 1);
	png_ptr->current_text[(png_size_t)length] = '\0';
	png_ptr->current_text_ptr = png_ptr->current_text;
	png_ptr->current_text_size = length;
	png_ptr->current_text_left = length;
	png_ptr->process_mode = PNG_READ_tEXt_MODE;
}

void
png_push_read_text(png_structp png_ptr, png_infop info)
{
	if (png_ptr->buffer_size && png_ptr->current_text_left)
	{
		png_uint_32 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_push_fill_buffer(png_ptr, (png_bytep)png_ptr->current_text_ptr,
			text_size);
		png_calculate_crc(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_ptr->buffer_size >= 4)
	{
		png_charp text;
		png_charp key;

		png_push_check_crc(png_ptr);

		key = png_ptr->current_text;
		png_ptr->current_text = 0;

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

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

		png_read_tEXt(png_ptr, info, key, text,
			png_ptr->current_text_size - (text - key));
		png_ptr->process_mode = PNG_READ_CHUNK_MODE;
	}
}
#endif

#if defined(PNG_READ_zTXt_SUPPORTED)
void
png_push_handle_zTXt(png_structp png_ptr, png_infop info,
	png_uint_32 length)
{
	png_ptr->current_text = (png_charp)png_large_malloc(png_ptr, length + 1);
	png_ptr->current_text[(png_size_t)length] = '\0';
	png_ptr->current_text_ptr = png_ptr->current_text;
	png_ptr->current_text_size = length;
	png_ptr->current_text_left = length;
	png_ptr->process_mode = PNG_READ_zTXt_MODE;
}

void
png_push_read_ztxt(png_structp png_ptr, png_infop info)
{
	if (png_ptr->buffer_size && png_ptr->current_text_left)
	{
		png_uint_32 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_push_fill_buffer(png_ptr, (png_bytep)png_ptr->current_text_ptr,
			text_size);
		png_calculate_crc(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_ptr->buffer_size >= 4)
	{
		png_charp text;
		png_charp key;
		int ret;
		png_uint_32 text_size, key_size;

		png_push_check_crc(png_ptr);

		key = png_ptr->current_text;
		png_ptr->current_text = 0;

		text = NULL;

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

		/* zTXt can't have zero text */
		if (text == key + (png_size_t)png_ptr->current_text_size)
		{
			png_large_free(png_ptr, key);
			return;
		}

		text++;

		if (*text) /* check compression byte */
		{
			png_large_free(png_ptr, key);
			return;
		}

		text++;

		png_ptr->zstream->next_in = (png_bytep )text;
		png_ptr->zstream->avail_in = (uInt)(png_ptr->current_text_size -
			(text - key));
		png_ptr->zstream->next_out = png_ptr->zbuf;
		png_ptr->zstream->avail_out = (png_size_t)png_ptr->zbuf_size;

		key_size = text - key;
		text_size = 0;
		text = NULL;
      ret = Z_STREAM_END;

		while (png_ptr->zstream->avail_in)
		{
			ret = inflate(png_ptr->zstream, Z_PARTIAL_FLUSH);
			if (ret != Z_OK && ret != Z_STREAM_END)
			{
				inflateReset(png_ptr->zstream);
				png_ptr->zstream->avail_in = 0;
				png_large_free(png_ptr, key);
				png_large_free(png_ptr, text);
				return;
			}
			if (!png_ptr->zstream->avail_out || ret == Z_STREAM_END)
			{
				if (!text)
				{
					text = (png_charp)png_malloc(png_ptr,
						png_ptr->zbuf_size - png_ptr->zstream->avail_out +
							key_size + 1);
					png_memcpy(text + (png_size_t)key_size, png_ptr->zbuf,
						(png_size_t)(png_ptr->zbuf_size - png_ptr->zstream->avail_out));
					png_memcpy(text, key, (png_size_t)key_size);
					text_size = key_size + (png_size_t)png_ptr->zbuf_size -
						png_ptr->zstream->avail_out;
					*(text + (png_size_t)text_size) = '\0';
				}
				else
				{
					png_charp tmp;

					tmp = text;
					text = png_large_malloc(png_ptr, text_size +
						png_ptr->zbuf_size - png_ptr->zstream->avail_out + 1);
					png_memcpy(text, tmp, (png_size_t)text_size);
					png_large_free(png_ptr, tmp);
					png_memcpy(text + (png_size_t)text_size, png_ptr->zbuf,
						(png_size_t)(png_ptr->zbuf_size - png_ptr->zstream->avail_out));
					text_size += png_ptr->zbuf_size - png_ptr->zstream->avail_out;
					*(text + (png_size_t)text_size) = '\0';
				}
				if (ret != Z_STREAM_END)
				{
					png_ptr->zstream->next_out = png_ptr->zbuf;
					png_ptr->zstream->avail_out = (uInt)png_ptr->zbuf_size;
				}
			}
			else
			{
				break;
			}

			if (ret == Z_STREAM_END)
				break;
		}

		inflateReset(png_ptr->zstream);
		png_ptr->zstream->avail_in = 0;

		if (ret != Z_STREAM_END)
		{
			png_large_free(png_ptr, key);
			png_large_free(png_ptr, text);
			return;
		}

		png_large_free(png_ptr, key);
		key = text;
		text += (png_size_t)key_size;
		text_size -= key_size;

		png_read_zTXt(png_ptr, info, key, text, text_size, 0);
	}
}
#endif

void
png_push_have_info(png_structp png_ptr, png_infop info)
{
	if (png_ptr->info_fn)
		(*(png_ptr->info_fn))(png_ptr, info);
}

void
png_push_have_end(png_structp png_ptr, png_infop info)
{
	if (png_ptr->end_fn)
		(*(png_ptr->end_fn))(png_ptr, info);
}

void
png_push_have_row(png_structp png_ptr, png_bytep row)
{
	if (png_ptr->row_fn)
		(*(png_ptr->row_fn))(png_ptr, row, png_ptr->row_number,
			(int)png_ptr->pass);
}

png_voidp
png_get_progressive_ptr(png_structp png_ptr)
{
	return png_ptr->push_ptr;
}

void
png_push_read_end(png_structp png_ptr, png_infop info)
{
	if (!png_ptr->have_chunk_header)
	{
		png_byte chunk_start[8];

		if (png_ptr->buffer_size < 8)
		{
			png_push_save_buffer(png_ptr);
			return;
		}

		png_push_fill_buffer(png_ptr, chunk_start, 8);
		png_ptr->push_length = png_get_uint_32(chunk_start);
		memcpy(png_ptr->push_chunk_name, chunk_start + 4, 4);
		png_ptr->have_chunk_header = 1;
		png_reset_crc(png_ptr);
		png_calculate_crc(png_ptr, chunk_start + 4, 4);
	}

	if (!png_memcmp(png_ptr->push_chunk_name, png_IHDR, 4))
	{
		png_error(png_ptr, "invalid chunk after IDAT");
	}
	else if (!png_memcmp(png_ptr->push_chunk_name, png_PLTE, 4))
	{
		png_error(png_ptr, "invalid chunk after IDAT");
	}
	else if (!png_memcmp(png_ptr->push_chunk_name, png_IDAT, 4))
	{
		if (png_ptr->push_length > 0 || png_ptr->mode != PNG_AT_LAST_IDAT)
			png_error(png_ptr, "too many IDAT's found");
	}
	else if (!png_memcmp(png_ptr->push_chunk_name, png_IEND, 4))
	{
		if (png_ptr->push_length)
      	png_error(png_ptr, "Invalid IEND chunk");
		png_push_check_crc(png_ptr);
		png_ptr->mode = PNG_AFTER_IEND;
		png_ptr->process_mode = PNG_READ_DONE_MODE;
		png_push_have_end(png_ptr, info);
	}
#if defined(PNG_READ_gAMA_SUPPORTED)
	else if (!png_memcmp(png_ptr->push_chunk_name, png_gAMA, 4))
	{
		png_error(png_ptr, "invalid chunk after IDAT");
	}
#endif
#if defined(PNG_READ_sBIT_SUPPORTED)
	else if (!png_memcmp(png_ptr->push_chunk_name, png_sBIT, 4))
	{
		png_error(png_ptr, "invalid chunk after IDAT");
	}
#endif
#if defined(PNG_READ_cHRM_SUPPORTED)
	else if (!png_memcmp(png_ptr->push_chunk_name, png_cHRM, 4))
	{
		png_error(png_ptr, "invalid chunk after IDAT");
	}
#endif
#if defined(PNG_READ_tRNS_SUPPORTED)
	else if (!png_memcmp(png_ptr->push_chunk_name, png_tRNS, 4))
	{
		png_error(png_ptr, "invalid chunk after IDAT");
	}
#endif
#if defined(PNG_READ_bKGD_SUPPORTED)
	else if (!png_memcmp(png_ptr->push_chunk_name, png_bKGD, 4))
	{
		png_error(png_ptr, "invalid chunk after IDAT");
	}
#endif
#if defined(PNG_READ_hIST_SUPPORTED)
	else if (!png_memcmp(png_ptr->push_chunk_name, png_hIST, 4))
	{
		png_error(png_ptr, "invalid chunk after IDAT");
	}
#endif
#if defined(PNG_READ_pHYs_SUPPORTED)
	else if (!png_memcmp(png_ptr->push_chunk_name, png_pHYs, 4))
	{
		png_error(png_ptr, "invalid chunk after IDAT");
	}
#endif
#if defined(PNG_READ_oFFs_SUPPORTED)
	else if (!png_memcmp(png_ptr->push_chunk_name, png_oFFs, 4))
	{
		png_error(png_ptr, "invalid chunk after IDAT");
	}
#endif
#if defined(PNG_READ_tIME_SUPPORTED)
	else if (!png_memcmp(png_ptr->push_chunk_name, png_tIME, 4))
	{
		if (png_ptr->push_length + 4 > png_ptr->buffer_size)
		{
			png_push_save_buffer(png_ptr);
			return;
		}

		if (png_ptr->mode == PNG_BEFORE_IHDR ||
			png_ptr->mode == PNG_AFTER_IEND)
			png_error(png_ptr, "Out of Place tIME");

		png_handle_tIME(png_ptr, info, png_ptr->push_length);
		png_push_check_crc(png_ptr);
	}
#endif
#if defined(PNG_READ_tEXt_SUPPORTED)
	else if (!png_memcmp(png_ptr->push_chunk_name, png_tEXt, 4))
	{
		if (png_ptr->mode == PNG_BEFORE_IHDR ||
			png_ptr->mode == PNG_AFTER_IEND)
			png_error(png_ptr, "Out of Place tEXt");

		png_push_handle_tEXt(png_ptr, info, png_ptr->push_length);
	}
#endif
#if defined(PNG_READ_zTXt_SUPPORTED)
	else if (!png_memcmp(png_ptr->push_chunk_name, png_zTXt, 4))
	{
		if (png_ptr->mode == PNG_BEFORE_IHDR ||
			png_ptr->mode == PNG_AFTER_IEND)
			png_error(png_ptr, "Out of Place zTXt");

		png_push_handle_zTXt(png_ptr, info, png_ptr->push_length);
	}
#endif
	else
	{
		if ((png_ptr->push_chunk_name[0] & 0x20) == 0)
			png_error(png_ptr, "Unknown Critical Chunk");

		png_push_crc_skip(png_ptr, png_ptr->push_length);
	}
	if (png_ptr->mode == PNG_AT_LAST_IDAT)
		png_ptr->mode = PNG_AFTER_IDAT;
	png_ptr->have_chunk_header = 0;
}

void
png_set_progressive_read_fn(png_structp png_ptr, png_voidp progressive_ptr,
	png_progressive_info_ptr info_fn, png_progressive_row_ptr row_fn,
	png_progressive_end_ptr end_fn)
{
	png_ptr->info_fn = info_fn;
	png_ptr->row_fn = row_fn;
	png_ptr->push_ptr = progressive_ptr;
   png_ptr->end_fn = end_fn;
	png_ptr->read_mode = PNG_READ_PUSH_MODE;
}

void
png_progressive_combine_row (png_structp png_ptr,
	png_bytep old_row, png_bytep new_row)
{
	png_combine_row(png_ptr, old_row, png_pass_dsp_mask[png_ptr->pass]);
}