Backport PNG output format to origin/master branch.

samples/fx_lpng/lpng_v163/fx_pngpread.c

+/* 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, /* 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))
+   {
+      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 */