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Diff of /v3p/png/pngpread.c [b8853e] .. [1fae15] Maximize Restore

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--- a/v3p/png/pngpread.c
+++ b/v3p/png/pngpread.c
@@ -1,19 +1,21 @@
 
 /* pngpread.c - read a png file in push mode
  *
- * libpng version 1.2.8rc5 - November 29, 2004
- * For conditions of distribution and use, see copyright notice in png.h
- * Copyright (c) 1998-2004 Glenn Randers-Pehrson
+ * Last changed in libpng 1.5.9 [February 18, 2012]
+ * Copyright (c) 1998-2012 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
  */
 
-#define PNG_INTERNAL
-#include "png.h"
+#include "pngpriv.h"
 
 #ifdef PNG_PROGRESSIVE_READ_SUPPORTED
 
-/* push model modes */
+/* Push model modes */
 #define PNG_READ_SIG_MODE   0
 #define PNG_READ_CHUNK_MODE 1
 #define PNG_READ_IDAT_MODE  2
@@ -26,14 +28,75 @@
 
 void PNGAPI
 png_process_data(png_structp png_ptr, png_infop info_ptr,
-   png_bytep buffer, png_size_t buffer_size)
-{
+    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_structp 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_structp 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
@@ -42,6 +105,9 @@
 void /* PRIVATE */
 png_process_some_data(png_structp png_ptr, png_infop info_ptr)
 {
+   if (png_ptr == NULL)
+      return;
+
    switch (png_ptr->process_mode)
    {
       case PNG_READ_SIG_MODE:
@@ -49,42 +115,25 @@
          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;
       }
-#if defined(PNG_READ_tEXt_SUPPORTED)
-      case PNG_READ_tEXt_MODE:
-      {
-         png_push_read_tEXt(png_ptr, info_ptr);
-         break;
-      }
-#endif
-#if defined(PNG_READ_zTXt_SUPPORTED)
-      case PNG_READ_zTXt_MODE:
-      {
-         png_push_read_zTXt(png_ptr, info_ptr);
-         break;
-      }
-#endif
-#if defined(PNG_READ_iTXt_SUPPORTED)
-      case PNG_READ_iTXt_MODE:
-      {
-         png_push_read_iTXt(png_ptr, info_ptr);
-         break;
-      }
-#endif
+
       case PNG_SKIP_MODE:
       {
          png_push_crc_finish(png_ptr);
          break;
       }
+
       default:
       {
          png_ptr->buffer_size = 0;
@@ -103,7 +152,7 @@
 png_push_read_sig(png_structp png_ptr, png_infop info_ptr)
 {
    png_size_t num_checked = png_ptr->sig_bytes,
-             num_to_check = 8 - num_checked;
+       num_to_check = 8 - num_checked;
 
    if (png_ptr->buffer_size < num_to_check)
    {
@@ -111,17 +160,19 @@
    }
 
    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);
+       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)
@@ -134,63 +185,8 @@
 void /* PRIVATE */
 png_push_read_chunk(png_structp png_ptr, png_infop info_ptr)
 {
-#ifdef PNG_USE_LOCAL_ARRAYS
-      PNG_IHDR;
-      PNG_IDAT;
-      PNG_IEND;
-      PNG_PLTE;
-#if defined(PNG_READ_bKGD_SUPPORTED)
-      PNG_bKGD;
-#endif
-#if defined(PNG_READ_cHRM_SUPPORTED)
-      PNG_cHRM;
-#endif
-#if defined(PNG_READ_gAMA_SUPPORTED)
-      PNG_gAMA;
-#endif
-#if defined(PNG_READ_hIST_SUPPORTED)
-      PNG_hIST;
-#endif
-#if defined(PNG_READ_iCCP_SUPPORTED)
-      PNG_iCCP;
-#endif
-#if defined(PNG_READ_iTXt_SUPPORTED)
-      PNG_iTXt;
-#endif
-#if defined(PNG_READ_oFFs_SUPPORTED)
-      PNG_oFFs;
-#endif
-#if defined(PNG_READ_pCAL_SUPPORTED)
-      PNG_pCAL;
-#endif
-#if defined(PNG_READ_pHYs_SUPPORTED)
-      PNG_pHYs;
-#endif
-#if defined(PNG_READ_sBIT_SUPPORTED)
-      PNG_sBIT;
-#endif
-#if defined(PNG_READ_sCAL_SUPPORTED)
-      PNG_sCAL;
-#endif
-#if defined(PNG_READ_sRGB_SUPPORTED)
-      PNG_sRGB;
-#endif
-#if defined(PNG_READ_sPLT_SUPPORTED)
-      PNG_sPLT;
-#endif
-#if defined(PNG_READ_tEXt_SUPPORTED)
-      PNG_tEXt;
-#endif
-#if defined(PNG_READ_tIME_SUPPORTED)
-      PNG_tIME;
-#endif
-#if defined(PNG_READ_tRNS_SUPPORTED)
-      PNG_tRNS;
-#endif
-#if defined(PNG_READ_zTXt_SUPPORTED)
-      PNG_zTXt;
-#endif
-#endif /* PNG_USE_LOCAL_ARRAYS */
+   png_uint_32 chunk_name;
+
    /* 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
@@ -200,6 +196,7 @@
    if (!(png_ptr->mode & PNG_HAVE_CHUNK_HEADER))
    {
       png_byte chunk_length[4];
+      png_byte chunk_tag[4];
 
       if (png_ptr->buffer_size < 8)
       {
@@ -208,57 +205,86 @@
       }
 
       png_push_fill_buffer(png_ptr, chunk_length, 4);
-      png_ptr->push_length = png_get_uint_31(png_ptr,chunk_length);
+      png_ptr->push_length = png_get_uint_31(png_ptr, chunk_length);
       png_reset_crc(png_ptr);
-      png_crc_read(png_ptr, png_ptr->chunk_name, 4);
+      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;
    }
 
-   if (!png_memcmp(png_ptr->chunk_name, png_IHDR, 4))
-   {
-      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
-      {
-         png_push_save_buffer(png_ptr);
-         return;
-      }
+   chunk_name = png_ptr->chunk_name;
+
+   if (chunk_name == png_IDAT)
+   {
+      /* This is here above the if/else case statement below because if the
+       * unknown handling marks 'IDAT' as unknown then the IDAT handling case is
+       * completely skipped.
+       *
+       * TODO: there must be a better way of doing this.
+       */
+      if (png_ptr->mode & PNG_AFTER_IDAT)
+         png_ptr->mode |= PNG_HAVE_CHUNK_AFTER_IDAT;
+   }
+
+   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 (!png_memcmp(png_ptr->chunk_name, png_IEND, 4))
-   {
-      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
-      {
-         png_push_save_buffer(png_ptr);
-         return;
-      }
+
+   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 (png_handle_as_unknown(png_ptr, png_ptr->chunk_name))
-   {
-      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
-      {
-         png_push_save_buffer(png_ptr);
-         return;
-      }
-      if (!png_memcmp(png_ptr->chunk_name, png_IDAT, 4))
+   else if (png_chunk_unknown_handling(png_ptr, chunk_name))
+   {
+      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
+      {
+         png_push_save_buffer(png_ptr);
+         return;
+      }
+
+      if (chunk_name == png_IDAT)
          png_ptr->mode |= PNG_HAVE_IDAT;
+
       png_handle_unknown(png_ptr, info_ptr, png_ptr->push_length);
-      if (!png_memcmp(png_ptr->chunk_name, png_PLTE, 4))
+
+      if (chunk_name == png_PLTE)
          png_ptr->mode |= PNG_HAVE_PLTE;
-      else if (!png_memcmp(png_ptr->chunk_name, png_IDAT, 4))
+
+      else if (chunk_name == png_IDAT)
       {
          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_ptr->mode & PNG_HAVE_PLTE))
             png_error(png_ptr, "Missing PLTE before IDAT");
       }
    }
-#endif
-   else if (!png_memcmp(png_ptr->chunk_name, png_PLTE, 4))
+
+#endif
+   else if (chunk_name == png_PLTE)
    {
       if (png_ptr->push_length + 4 > png_ptr->buffer_size)
       {
@@ -267,221 +293,262 @@
       }
       png_handle_PLTE(png_ptr, info_ptr, png_ptr->push_length);
    }
-   else if (!png_memcmp(png_ptr->chunk_name, (png_bytep)png_IDAT, 4))
+
+   else if (chunk_name == png_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");
+
+      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");
 
       if (png_ptr->mode & PNG_HAVE_IDAT)
       {
-         if (png_ptr->push_length == 0)
-            return;
+         if (!(png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT))
+            if (png_ptr->push_length == 0)
+               return;
 
          if (png_ptr->mode & PNG_AFTER_IDAT)
-            png_error(png_ptr, "Too many IDAT's found");
+            png_benign_error(png_ptr, "Too many IDATs found");
       }
 
       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_ptr);
-      png_ptr->zstream.avail_out = (uInt)png_ptr->irowbytes;
+      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;
    }
-#if defined(PNG_READ_gAMA_SUPPORTED)
-   else if (!png_memcmp(png_ptr->chunk_name, png_gAMA, 4))
-   {
-      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
-      {
-         png_push_save_buffer(png_ptr);
-         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
-#if defined(PNG_READ_sBIT_SUPPORTED)
-   else if (!png_memcmp(png_ptr->chunk_name, png_sBIT, 4))
-   {
-      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
-      {
-         png_push_save_buffer(png_ptr);
-         return;
-      }
+
+#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
-#if defined(PNG_READ_cHRM_SUPPORTED)
-   else if (!png_memcmp(png_ptr->chunk_name, png_cHRM, 4))
-   {
-      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
-      {
-         png_push_save_buffer(png_ptr);
-         return;
-      }
+
+#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
-#if defined(PNG_READ_sRGB_SUPPORTED)
-   else if (!png_memcmp(png_ptr->chunk_name, png_sRGB, 4))
-   {
-      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
-      {
-         png_push_save_buffer(png_ptr);
-         return;
-      }
+
+#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
-#if defined(PNG_READ_iCCP_SUPPORTED)
-   else if (!png_memcmp(png_ptr->chunk_name, png_iCCP, 4))
-   {
-      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
-      {
-         png_push_save_buffer(png_ptr);
-         return;
-      }
+
+#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
-#if defined(PNG_READ_sPLT_SUPPORTED)
-   else if (!png_memcmp(png_ptr->chunk_name, png_sPLT, 4))
-   {
-      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
-      {
-         png_push_save_buffer(png_ptr);
-         return;
-      }
+
+#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
-#if defined(PNG_READ_tRNS_SUPPORTED)
-   else if (!png_memcmp(png_ptr->chunk_name, png_tRNS, 4))
-   {
-      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
-      {
-         png_push_save_buffer(png_ptr);
-         return;
-      }
+
+#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
-#if defined(PNG_READ_bKGD_SUPPORTED)
-   else if (!png_memcmp(png_ptr->chunk_name, png_bKGD, 4))
-   {
-      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
-      {
-         png_push_save_buffer(png_ptr);
-         return;
-      }
+
+#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
-#if defined(PNG_READ_hIST_SUPPORTED)
-   else if (!png_memcmp(png_ptr->chunk_name, png_hIST, 4))
-   {
-      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
-      {
-         png_push_save_buffer(png_ptr);
-         return;
-      }
+
+#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
-#if defined(PNG_READ_pHYs_SUPPORTED)
-   else if (!png_memcmp(png_ptr->chunk_name, png_pHYs, 4))
-   {
-      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
-      {
-         png_push_save_buffer(png_ptr);
-         return;
-      }
+
+#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
-#if defined(PNG_READ_oFFs_SUPPORTED)
-   else if (!png_memcmp(png_ptr->chunk_name, png_oFFs, 4))
-   {
-      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
-      {
-         png_push_save_buffer(png_ptr);
-         return;
-      }
+
+#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
-#if defined(PNG_READ_pCAL_SUPPORTED)
-   else if (!png_memcmp(png_ptr->chunk_name, png_pCAL, 4))
-   {
-      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
-      {
-         png_push_save_buffer(png_ptr);
-         return;
-      }
+
+#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
-#if defined(PNG_READ_sCAL_SUPPORTED)
-   else if (!png_memcmp(png_ptr->chunk_name, png_sCAL, 4))
-   {
-      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
-      {
-         png_push_save_buffer(png_ptr);
-         return;
-      }
+
+#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
-#if defined(PNG_READ_tIME_SUPPORTED)
-   else if (!png_memcmp(png_ptr->chunk_name, png_tIME, 4))
-   {
-      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
-      {
-         png_push_save_buffer(png_ptr);
-         return;
-      }
+
+#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
-#if defined(PNG_READ_tEXt_SUPPORTED)
-   else if (!png_memcmp(png_ptr->chunk_name, png_tEXt, 4))
-   {
-      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
-      {
-         png_push_save_buffer(png_ptr);
-         return;
-      }
-      png_push_handle_tEXt(png_ptr, info_ptr, png_ptr->push_length);
-   }
-#endif
-#if defined(PNG_READ_zTXt_SUPPORTED)
-   else if (!png_memcmp(png_ptr->chunk_name, png_zTXt, 4))
-   {
-      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
-      {
-         png_push_save_buffer(png_ptr);
-         return;
-      }
-      png_push_handle_zTXt(png_ptr, info_ptr, png_ptr->push_length);
-   }
-#endif
-#if defined(PNG_READ_iTXt_SUPPORTED)
-   else if (!png_memcmp(png_ptr->chunk_name, png_iTXt, 4))
-   {
-      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
-      {
-         png_push_save_buffer(png_ptr);
-         return;
-      }
-      png_push_handle_iTXt(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
    {
@@ -490,7 +557,7 @@
          png_push_save_buffer(png_ptr);
          return;
       }
-      png_push_handle_unknown(png_ptr, info_ptr, png_ptr->push_length);
+      png_handle_unknown(png_ptr, info_ptr, png_ptr->push_length);
    }
 
    png_ptr->mode &= ~PNG_HAVE_CHUNK_HEADER;
@@ -508,36 +575,51 @@
 {
    if (png_ptr->skip_length && png_ptr->save_buffer_size)
    {
-      png_size_t save_size;
-
-      if (png_ptr->skip_length < (png_uint_32)png_ptr->save_buffer_size)
-         save_size = (png_size_t)png_ptr->skip_length;
+      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
-         save_size = png_ptr->save_buffer_size;
+         skip_length = (png_uint_32)save_size;
 
       png_calculate_crc(png_ptr, png_ptr->save_buffer_ptr, save_size);
 
-      png_ptr->skip_length -= 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;
-
-      if (png_ptr->skip_length < (png_uint_32)png_ptr->current_buffer_size)
-         save_size = (png_size_t)png_ptr->skip_length;
+      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
-         save_size = png_ptr->current_buffer_size;
+         skip_length = (png_uint_32)save_size;
 
       png_calculate_crc(png_ptr, png_ptr->current_buffer_ptr, save_size);
 
-      png_ptr->skip_length -= 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)
@@ -551,18 +633,23 @@
    }
 }
 
-void PNGAPI
+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;
 
@@ -573,12 +660,14 @@
       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;
 
@@ -596,37 +685,47 @@
    {
       if (png_ptr->save_buffer_ptr != png_ptr->save_buffer)
       {
-         png_size_t i,istop;
+         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++)
+             i < istop; i++, sp++, dp++)
          {
             *dp = *sp;
          }
       }
    }
+
    if (png_ptr->save_buffer_size + png_ptr->current_buffer_size >
-      png_ptr->save_buffer_max)
+       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");
-      }
+      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(png_ptr,
-         (png_uint_32)new_max);
+      png_ptr->save_buffer = (png_bytep)png_malloc_warn(png_ptr, new_max);
+
+      if (png_ptr->save_buffer == NULL)
+      {
+         png_free(png_ptr, old_buffer);
+         png_error(png_ptr, "Insufficient memory for save_buffer");
+      }
+
       png_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)
    {
       png_memcpy(png_ptr->save_buffer + png_ptr->save_buffer_size,
@@ -634,6 +733,7 @@
       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;
 }
@@ -651,13 +751,12 @@
 void /* PRIVATE */
 png_push_read_IDAT(png_structp png_ptr)
 {
-#ifdef PNG_USE_LOCAL_ARRAYS
-   PNG_IDAT;
-#endif
    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);
@@ -665,66 +764,78 @@
       }
 
       png_push_fill_buffer(png_ptr, chunk_length, 4);
-      png_ptr->push_length = png_get_uint_31(png_ptr,chunk_length);
+      png_ptr->push_length = png_get_uint_31(png_ptr, chunk_length);
       png_reset_crc(png_ptr);
-      png_crc_read(png_ptr, png_ptr->chunk_name, 4);
+      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_memcmp(png_ptr->chunk_name, (png_bytep)png_IDAT, 4))
+      if (png_ptr->chunk_name != png_IDAT)
       {
          png_ptr->process_mode = PNG_READ_CHUNK_MODE;
+
          if (!(png_ptr->flags & PNG_FLAG_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_size_t save_size;
-
-      if (png_ptr->idat_size < (png_uint_32)png_ptr->save_buffer_size)
-      {
-         save_size = (png_size_t)png_ptr->idat_size;
-         /* check for overflow */
-         if((png_uint_32)save_size != png_ptr->idat_size)
-            png_error(png_ptr, "save_size overflowed in pngpread");
-      }
+      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
-         save_size = png_ptr->save_buffer_size;
+         idat_size = (png_uint_32)save_size;
 
       png_calculate_crc(png_ptr, png_ptr->save_buffer_ptr, save_size);
-      if (!(png_ptr->flags & PNG_FLAG_ZLIB_FINISHED))
-         png_process_IDAT_data(png_ptr, png_ptr->save_buffer_ptr, save_size);
-      png_ptr->idat_size -= 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;
-
-      if (png_ptr->idat_size < (png_uint_32)png_ptr->current_buffer_size)
-      {
-         save_size = (png_size_t)png_ptr->idat_size;
-         /* check for overflow */
-         if((png_uint_32)save_size != png_ptr->idat_size)
-            png_error(png_ptr, "save_size overflowed in pngpread");
-      }
+      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
-         save_size = png_ptr->current_buffer_size;
+         idat_size = (png_uint_32)save_size;
 
       png_calculate_crc(png_ptr, png_ptr->current_buffer_ptr, save_size);
-      if (!(png_ptr->flags & PNG_FLAG_ZLIB_FINISHED))
-        png_process_IDAT_data(png_ptr, png_ptr->current_buffer_ptr, save_size);
-
-      png_ptr->idat_size -= 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)
@@ -743,91 +854,159 @@
 png_process_IDAT_data(png_structp png_ptr, png_bytep buffer,
    png_size_t buffer_length)
 {
-   int ret;
-
-   if ((png_ptr->flags & PNG_FLAG_ZLIB_FINISHED) && buffer_length)
-      png_error(png_ptr, "Extra compression data");
-
+   /* 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;
    png_ptr->zstream.avail_in = (uInt)buffer_length;
-   for(;;)
-   {
-      ret = inflate(&png_ptr->zstream, Z_PARTIAL_FLUSH);
-      if (ret != Z_OK)
-      {
-         if (ret == Z_STREAM_END)
+
+   /* 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_ZLIB_FINISHED))
+   {
+      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))
+      {
+         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_ZLIB_FINISHED;
+
+         /* 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)
          {
-            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_AFTER_IDAT;
+            /* Extra data. */
+            png_warning(png_ptr, "Extra compressed data in IDAT");
             png_ptr->flags |= PNG_FLAG_ZLIB_FINISHED;
-            break;
+
+            /* Do no more processing; skip the unprocessed
+             * input check below.
+             */
+            return;
          }
-         else if (ret == Z_BUF_ERROR)
-            break;
-         else
-            png_error(png_ptr, "Decompression Error");
-      }
-      if (!(png_ptr->zstream.avail_out))
-      {
-         if ((
-#if defined(PNG_READ_INTERLACING_SUPPORTED)
-             png_ptr->interlaced && png_ptr->pass > 6) ||
-             (!png_ptr->interlaced &&
-#endif
-             png_ptr->row_number == png_ptr->num_rows))
-         {
-           if (png_ptr->zstream.avail_in)
-             png_warning(png_ptr, "Too much data in IDAT chunks");
-           png_ptr->flags |= PNG_FLAG_ZLIB_FINISHED;
-           break;
-         }
-         png_push_process_row(png_ptr);
-         png_ptr->zstream.avail_out = (uInt)png_ptr->irowbytes;
-         png_ptr->zstream.next_out = png_ptr->row_buf;
-      }
-      else
-         break;
-   }
+
+         /* 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_ZLIB_FINISHED;
+   }
+
+   /* 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_structp png_ptr)
 {
-   png_ptr->row_info.color_type = png_ptr->color_type;
-   png_ptr->row_info.width = png_ptr->iwidth;
-   png_ptr->row_info.channels = png_ptr->channels;
-   png_ptr->row_info.bit_depth = png_ptr->bit_depth;
-   png_ptr->row_info.pixel_depth = png_ptr->pixel_depth;
-
-   png_ptr->row_info.rowbytes = PNG_ROWBYTES(png_ptr->row_info.pixel_depth,
-       png_ptr->row_info.width);
-
-   png_read_filter_row(png_ptr, &(png_ptr->row_info),
-      png_ptr->row_buf + 1, png_ptr->prev_row + 1,
-      (int)(png_ptr->row_buf[0]));
-
-   png_memcpy_check(png_ptr, png_ptr->prev_row, png_ptr->row_buf,
-      png_ptr->rowbytes + 1);
-
-   if (png_ptr->transformations || (png_ptr->flags&PNG_FLAG_STRIP_ALPHA))
-      png_do_read_transformations(png_ptr);
-
-#if defined(PNG_READ_INTERLACING_SUPPORTED)
-   /* blow up interlaced rows to full size */
+   /* 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:
+    */
+   png_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)
-/*       old interface (pre-1.0.9):
-         png_do_read_interlace(&(png_ptr->row_info),
-            png_ptr->row_buf + 1, png_ptr->pass, png_ptr->transformations);
- */
-         png_do_read_interlace(png_ptr);
+         png_do_read_interlace(&row_info, png_ptr->row_buf + 1, png_ptr->pass,
+            png_ptr->transformations);
 
     switch (png_ptr->pass)
     {
@@ -837,31 +1016,36 @@
             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 */
+               png_read_push_finish_row(png_ptr); /* Updates png_ptr->pass */
+            }
+
+            if (png_ptr->pass == 2) /* Pass 1 might be empty */
             {
                for (i = 0; i < 4 && png_ptr->pass == 2; i++)
                {
-                  png_push_have_row(png_ptr, png_bytep_NULL);
+                  png_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, png_bytep_NULL);
+                  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, png_bytep_NULL);
+                png_push_have_row(png_ptr, NULL);
                 png_read_push_finish_row(png_ptr);
             }
+
             break;
          }
+
          case 1:
          {
             int i;
@@ -870,99 +1054,123 @@
                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 */
+
+            if (png_ptr->pass == 2) /* Skip top 4 generated rows */
             {
                for (i = 0; i < 4 && png_ptr->pass == 2; i++)
                {
-                  png_push_have_row(png_ptr, png_bytep_NULL);
+                  png_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, png_bytep_NULL);
+               png_push_have_row(png_ptr, NULL);
                png_read_push_finish_row(png_ptr);
             }
-            if (png_ptr->pass == 4) /* pass 3 might be empty */
+
+            if (png_ptr->pass == 4) /* Pass 3 might be empty */
             {
                for (i = 0; i < 2 && png_ptr->pass == 4; i++)
                {
-                  png_push_have_row(png_ptr, png_bytep_NULL);
+                  png_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 */
+
+            if (png_ptr->pass == 4) /* Skip top two generated rows */
             {
                for (i = 0; i < 2 && png_ptr->pass == 4; i++)
                {
-                  png_push_have_row(png_ptr, png_bytep_NULL);
+                  png_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, png_bytep_NULL);
+               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, png_bytep_NULL);
+
+            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, png_bytep_NULL);
+
+            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, png_bytep_NULL);
+
+            png_push_have_row(png_ptr, NULL);
             png_read_push_finish_row(png_ptr);
          }
       }
@@ -978,29 +1186,24 @@
 void /* PRIVATE */
 png_read_push_finish_row(png_structp png_ptr)
 {
-#ifdef PNG_USE_LOCAL_ARRAYS
-   /* arrays to facilitate easy interlacing - use pass (0 - 6) as index */
-
-   /* start of interlace block */
-   const int FARDATA png_pass_start[] = {0, 4, 0, 2, 0, 1, 0};
-
-   /* offset to next interlace block */
-   const int FARDATA png_pass_inc[] = {8, 8, 4, 4, 2, 2, 1};
-
-   /* start of interlace block in the y direction */
-   const int FARDATA png_pass_ystart[] = {0, 0, 4, 0, 2, 0, 1};
-
-   /* offset to next interlace block in the y direction */
-   const int FARDATA png_pass_yinc[] = {8, 8, 8, 4, 4, 2, 2};
-
-   /* Width of interlace block.  This is not currently used - if you need
-    * it, uncomment it here and in png.h
-   const int FARDATA png_pass_width[] = {8, 4, 4, 2, 2, 1, 1};
-   */
+#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 FARDATA png_pass_start[] = {0, 4, 0, 2, 0, 1, 0};
+
+   /* Offset to next interlace block */
+   static PNG_CONST png_byte FARDATA png_pass_inc[] = {8, 8, 4, 4, 2, 2, 1};
+
+   /* Start of interlace block in the y direction */
+   static PNG_CONST png_byte FARDATA png_pass_ystart[] = {0, 0, 4, 0, 2, 0, 1};
+
+   /* Offset to next interlace block in the y direction */
+   static PNG_CONST png_byte FARDATA 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
-   const int FARDATA png_pass_height[] = {8, 8, 4, 4, 2, 2, 1};
+   static PNG_CONST png_byte FARDATA png_pass_height[] = {8, 8, 4, 4, 2, 2, 1};
    */
 #endif
 
@@ -1008,515 +1211,42 @@
    if (png_ptr->row_number < png_ptr->num_rows)
       return;
 
+#ifdef PNG_READ_INTERLACING_SUPPORTED
    if (png_ptr->interlaced)
    {
       png_ptr->row_number = 0;
-      png_memset_check(png_ptr, png_ptr->prev_row, 0,
-         png_ptr->rowbytes + 1);
+      png_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++;
+            png_ptr->pass++;
 
          if (png_ptr->pass > 7)
             png_ptr->pass--;
+
          if (png_ptr->pass >= 7)
             break;
 
          png_ptr->iwidth = (png_ptr->width +
-            png_pass_inc[png_ptr->pass] - 1 -
-            png_pass_start[png_ptr->pass]) /
-            png_pass_inc[png_ptr->pass];
-
-         png_ptr->irowbytes = PNG_ROWBYTES(png_ptr->pixel_depth,
-            png_ptr->iwidth) + 1;
+             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];
+             png_pass_yinc[png_ptr->pass] - 1 -
+             png_pass_ystart[png_ptr->pass]) /
+             png_pass_yinc[png_ptr->pass];
 
       } while (png_ptr->iwidth == 0 || png_ptr->num_rows == 0);
    }
-}
-
-#if defined(PNG_READ_tEXt_SUPPORTED)
-void /* PRIVATE */
-png_push_handle_tEXt(png_structp png_ptr, png_infop info_ptr, png_uint_32
-   length)
-{
-   if (!(png_ptr->mode & PNG_HAVE_IHDR) || (png_ptr->mode & PNG_HAVE_IEND))
-      {
-         png_error(png_ptr, "Out of place tEXt");
-         /* to quiet some compiler warnings */
-         if(info_ptr == NULL) return;
-      }
-
-#ifdef PNG_MAX_MALLOC_64K
-   png_ptr->skip_length = 0;  /* This may not be necessary */
-
-   if (length > (png_uint_32)65535L) /* Can't hold entire string in memory */
-   {
-      png_warning(png_ptr, "tEXt chunk too large to fit in memory");
-      png_ptr->skip_length = length - (png_uint_32)65535L;
-      length = (png_uint_32)65535L;
-   }
-#endif
-
-   png_ptr->current_text = (png_charp)png_malloc(png_ptr,
-         (png_uint_32)(length+1));
-   png_ptr->current_text[length] = '\0';
-   png_ptr->current_text_ptr = png_ptr->current_text;
-   png_ptr->current_text_size = (png_size_t)length;
-   png_ptr->current_text_left = (png_size_t)length;
-   png_ptr->process_mode = PNG_READ_tEXt_MODE;
-}
-
-void /* PRIVATE */
-png_push_read_tEXt(png_structp png_ptr, png_infop info_ptr)
-{
-   if (png_ptr->buffer_size && png_ptr->current_text_left)
-   {
-      png_size_t text_size;
-
-      if (png_ptr->buffer_size < png_ptr->current_text_left)
-         text_size = png_ptr->buffer_size;
-      else
-         text_size = png_ptr->current_text_left;
-      png_crc_read(png_ptr, (png_bytep)png_ptr->current_text_ptr, text_size);
-      png_ptr->current_text_left -= text_size;
-      png_ptr->current_text_ptr += text_size;
-   }
-   if (!(png_ptr->current_text_left))
-   {
-      png_textp text_ptr;
-      png_charp text;
-      png_charp key;
-      int ret;
-
-      if (png_ptr->buffer_size < 4)
-      {
-         png_push_save_buffer(png_ptr);
-         return;
-      }
-
-      png_push_crc_finish(png_ptr);
-
-#if defined(PNG_MAX_MALLOC_64K)
-      if (png_ptr->skip_length)
-         return;
-#endif
-
-      key = png_ptr->current_text;
-
-      for (text = key; *text; text++)
-         /* empty loop */ ;
-
-      if (text != key + png_ptr->current_text_size)
-         text++;
-
-      text_ptr = (png_textp)png_malloc(png_ptr,
-         (png_uint_32)png_sizeof(png_text));
-      text_ptr->compression = PNG_TEXT_COMPRESSION_NONE;
-      text_ptr->key = key;
-#ifdef PNG_iTXt_SUPPORTED
-      text_ptr->lang = NULL;
-      text_ptr->lang_key = NULL;
-#endif
-      text_ptr->text = text;
-
-      ret = png_set_text_2(png_ptr, info_ptr, text_ptr, 1);
-
-      png_free(png_ptr, key);
-      png_free(png_ptr, text_ptr);
-      png_ptr->current_text = NULL;
-
-      if (ret)
-        png_warning(png_ptr, "Insufficient memory to store text chunk.");
-   }
-}
-#endif
-
-#if defined(PNG_READ_zTXt_SUPPORTED)
-void /* PRIVATE */
-png_push_handle_zTXt(png_structp png_ptr, png_infop info_ptr, png_uint_32
-   length)
-{
-   if (!(png_ptr->mode & PNG_HAVE_IHDR) || (png_ptr->mode & PNG_HAVE_IEND))
-      {
-         png_error(png_ptr, "Out of place zTXt");
-         /* to quiet some compiler warnings */
-         if(info_ptr == NULL) return;
-      }
-
-#ifdef PNG_MAX_MALLOC_64K
-   /* We can't handle zTXt chunks > 64K, since we don't have enough space
-    * to be able to store the uncompressed data.  Actually, the threshold
-    * is probably around 32K, but it isn't as definite as 64K is.
-    */
-   if (length > (png_uint_32)65535L)
-   {
-      png_warning(png_ptr, "zTXt chunk too large to fit in memory");
-      png_push_crc_skip(png_ptr, length);
-      return;
-   }
-#endif
-
-   png_ptr->current_text = (png_charp)png_malloc(png_ptr,
-       (png_uint_32)(length+1));
-   png_ptr->current_text[length] = '\0';
-   png_ptr->current_text_ptr = png_ptr->current_text;
-   png_ptr->current_text_size = (png_size_t)length;
-   png_ptr->current_text_left = (png_size_t)length;
-   png_ptr->process_mode = PNG_READ_zTXt_MODE;
-}
-
-void /* PRIVATE */
-png_push_read_zTXt(png_structp png_ptr, png_infop info_ptr)
-{
-   if (png_ptr->buffer_size && png_ptr->current_text_left)
-   {
-      png_size_t text_size;
-
-      if (png_ptr->buffer_size < (png_uint_32)png_ptr->current_text_left)
-         text_size = png_ptr->buffer_size;
-      else
-         text_size = png_ptr->current_text_left;
-      png_crc_read(png_ptr, (png_bytep)png_ptr->current_text_ptr, text_size);
-      png_ptr->current_text_left -= text_size;
-      png_ptr->current_text_ptr += text_size;
-   }
-   if (!(png_ptr->current_text_left))
-   {
-      png_textp text_ptr;
-      png_charp text;
-      png_charp key;
-      int ret;
-      png_size_t text_size, key_size;
-
-      if (png_ptr->buffer_size < 4)
-      {
-         png_push_save_buffer(png_ptr);
-         return;
-      }
-
-      png_push_crc_finish(png_ptr);
-
-      key = png_ptr->current_text;
-
-      for (text = key; *text; text++)
-         /* empty loop */ ;
-
-      /* zTXt can't have zero text */
-      if (text == key + png_ptr->current_text_size)
-      {
-         png_ptr->current_text = NULL;
-         png_free(png_ptr, key);
-         return;
-      }
-
-      text++;
-
-      if (*text != PNG_TEXT_COMPRESSION_zTXt) /* check compression byte */
-      {
-         png_ptr->current_text = NULL;
-         png_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 = (uInt)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_ptr->current_text = NULL;
-            png_free(png_ptr, key);
-            png_free(png_ptr, text);
-            return;
-         }
-         if (!(png_ptr->zstream.avail_out) || ret == Z_STREAM_END)
-         {
-            if (text == NULL)
-            {
-               text = (png_charp)png_malloc(png_ptr,
-                  (png_uint_32)(png_ptr->zbuf_size - png_ptr->zstream.avail_out
-                     + key_size + 1));
-               png_memcpy(text + key_size, png_ptr->zbuf,
-                  png_ptr->zbuf_size - png_ptr->zstream.avail_out);
-               png_memcpy(text, key, key_size);
-               text_size = key_size + png_ptr->zbuf_size -
-                  png_ptr->zstream.avail_out;
-               *(text + text_size) = '\0';
-            }
-            else
-            {
-               png_charp tmp;
-
-               tmp = text;
-               text = (png_charp)png_malloc(png_ptr, text_size +
-                  (png_uint_32)(png_ptr->zbuf_size - png_ptr->zstream.avail_out
-                   + 1));
-               png_memcpy(text, tmp, text_size);
-               png_free(png_ptr, tmp);
-               png_memcpy(text + text_size, png_ptr->zbuf,
-                  png_ptr->zbuf_size - png_ptr->zstream.avail_out);
-               text_size += png_ptr->zbuf_size - png_ptr->zstream.avail_out;
-               *(text + 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_ptr->current_text = NULL;
-         png_free(png_ptr, key);
-         png_free(png_ptr, text);
-         return;
-      }
-
-      png_ptr->current_text = NULL;
-      png_free(png_ptr, key);
-      key = text;
-      text += key_size;
-
-      text_ptr = (png_textp)png_malloc(png_ptr,
-          (png_uint_32)png_sizeof(png_text));
-      text_ptr->compression = PNG_TEXT_COMPRESSION_zTXt;
-      text_ptr->key = key;
-#ifdef PNG_iTXt_SUPPORTED
-      text_ptr->lang = NULL;
-      text_ptr->lang_key = NULL;
-#endif
-      text_ptr->text = text;
-
-      ret = png_set_text_2(png_ptr, info_ptr, text_ptr, 1);
-
-      png_free(png_ptr, key);
-      png_free(png_ptr, text_ptr);
-
-      if (ret)
-        png_warning(png_ptr, "Insufficient memory to store text chunk.");
-   }
-}
-#endif
-
-#if defined(PNG_READ_iTXt_SUPPORTED)
-void /* PRIVATE */
-png_push_handle_iTXt(png_structp png_ptr, png_infop info_ptr, png_uint_32
-   length)
-{
-   if (!(png_ptr->mode & PNG_HAVE_IHDR) || (png_ptr->mode & PNG_HAVE_IEND))
-      {
-         png_error(png_ptr, "Out of place iTXt");
-         /* to quiet some compiler warnings */
-         if(info_ptr == NULL) return;
-      }
-
-#ifdef PNG_MAX_MALLOC_64K
-   png_ptr->skip_length = 0;  /* This may not be necessary */
-
-   if (length > (png_uint_32)65535L) /* Can't hold entire string in memory */
-   {
-      png_warning(png_ptr, "iTXt chunk too large to fit in memory");
-      png_ptr->skip_length = length - (png_uint_32)65535L;
-      length = (png_uint_32)65535L;
-   }
-#endif
-
-   png_ptr->current_text = (png_charp)png_malloc(png_ptr,
-         (png_uint_32)(length+1));
-   png_ptr->current_text[length] = '\0';
-   png_ptr->current_text_ptr = png_ptr->current_text;
-   png_ptr->current_text_size = (png_size_t)length;
-   png_ptr->current_text_left = (png_size_t)length;
-   png_ptr->process_mode = PNG_READ_iTXt_MODE;
-}
-
-void /* PRIVATE */
-png_push_read_iTXt(png_structp png_ptr, png_infop info_ptr)
-{
-
-   if (png_ptr->buffer_size && png_ptr->current_text_left)
-   {
-      png_size_t text_size;
-
-      if (png_ptr->buffer_size < png_ptr->current_text_left)
-         text_size = png_ptr->buffer_size;
-      else
-         text_size = png_ptr->current_text_left;
-      png_crc_read(png_ptr, (png_bytep)png_ptr->current_text_ptr, text_size);
-      png_ptr->current_text_left -= text_size;
-      png_ptr->current_text_ptr += text_size;
-   }
-   if (!(png_ptr->current_text_left))
-   {
-      png_textp text_ptr;
-      png_charp key;
-      int comp_flag;
-      png_charp lang;
-      png_charp lang_key;
-      png_charp text;
-      int ret;
-
-      if (png_ptr->buffer_size < 4)
-      {
-         png_push_save_buffer(png_ptr);
-         return;
-      }
-
-      png_push_crc_finish(png_ptr);
-
-#if defined(PNG_MAX_MALLOC_64K)
-      if (png_ptr->skip_length)
-         return;
-#endif
-
-      key = png_ptr->current_text;
-
-      for (lang = key; *lang; lang++)
-         /* empty loop */ ;
-
-      if (lang != key + png_ptr->current_text_size)
-         lang++;
-
-      comp_flag = *lang++;
-      lang++;     /* skip comp_type, always zero */
-
-      for (lang_key = lang; *lang_key; lang_key++)
-         /* empty loop */ ;
-      lang_key++;        /* skip NUL separator */
-
-      for (text = lang_key; *text; text++)
-         /* empty loop */ ;
-
-      if (text != key + png_ptr->current_text_size)
-         text++;
-
-      text_ptr = (png_textp)png_malloc(png_ptr,
-         (png_uint_32)png_sizeof(png_text));
-      text_ptr->compression = comp_flag + 2;
-      text_ptr->key = key;
-      text_ptr->lang = lang;
-      text_ptr->lang_key = lang_key;
-      text_ptr->text = text;
-      text_ptr->text_length = 0;
-      text_ptr->itxt_length = png_strlen(text);
-
-      ret = png_set_text_2(png_ptr, info_ptr, text_ptr, 1);
-
-      png_ptr->current_text = NULL;
-
-      png_free(png_ptr, text_ptr);
-      if (ret)
-        png_warning(png_ptr, "Insufficient memory to store iTXt chunk.");
-   }
-}
-#endif
-
-/* This function is called when we haven't found a handler for this
- * chunk.  If there isn't a problem with the chunk itself (ie a bad chunk
- * name or a critical chunk), the chunk is (currently) silently ignored.
- */
-void /* PRIVATE */
-png_push_handle_unknown(png_structp png_ptr, png_infop info_ptr, png_uint_32
-   length)
-{
-   png_uint_32 skip=0;
-   png_check_chunk_name(png_ptr, png_ptr->chunk_name);
-
-   if (!(png_ptr->chunk_name[0] & 0x20))
-   {
-#if defined(PNG_READ_UNKNOWN_CHUNKS_SUPPORTED)
-      if(png_handle_as_unknown(png_ptr, png_ptr->chunk_name) !=
-           PNG_HANDLE_CHUNK_ALWAYS
-#if defined(PNG_READ_USER_CHUNKS_SUPPORTED)
-           && png_ptr->read_user_chunk_fn == NULL
-#endif
-         )
-#endif
-         png_chunk_error(png_ptr, "unknown critical chunk");
-
-      /* to quiet compiler warnings about unused info_ptr */
-      if (info_ptr == NULL)
-         return;
-   }
-
-#if defined(PNG_READ_UNKNOWN_CHUNKS_SUPPORTED)
-   if (png_ptr->flags & PNG_FLAG_KEEP_UNKNOWN_CHUNKS)
-   {
-       png_unknown_chunk chunk;
-
-#ifdef PNG_MAX_MALLOC_64K
-       if (length > (png_uint_32)65535L)
-       {
-           png_warning(png_ptr, "unknown chunk too large to fit in memory");
-           skip = length - (png_uint_32)65535L;
-           length = (png_uint_32)65535L;
-       }
-#endif
-
-       png_strcpy((png_charp)chunk.name, (png_charp)png_ptr->chunk_name);
-       chunk.data = (png_bytep)png_malloc(png_ptr, length);
-       png_crc_read(png_ptr, chunk.data, length);
-       chunk.size = length;
-#if defined(PNG_READ_USER_CHUNKS_SUPPORTED)
-       if(png_ptr->read_user_chunk_fn != NULL)
-       {
-          /* callback to user unknown chunk handler */
-          if ((*(png_ptr->read_user_chunk_fn)) (png_ptr, &chunk) <= 0)
-          {
-             if (!(png_ptr->chunk_name[0] & 0x20))
-                if(png_handle_as_unknown(png_ptr, png_ptr->chunk_name) !=
-                     PNG_HANDLE_CHUNK_ALWAYS)
-                   png_chunk_error(png_ptr, "unknown critical chunk");
-          }
-             png_set_unknown_chunks(png_ptr, info_ptr, &chunk, 1);
-       }
-       else
-#endif
-          png_set_unknown_chunks(png_ptr, info_ptr, &chunk, 1);
-       png_free(png_ptr, chunk.data);
-   }
-   else
-#endif
-      skip=length;
-   png_push_crc_skip(png_ptr, skip);
+#endif /* PNG_READ_INTERLACING_SUPPORTED */
 }
 
 void /* PRIVATE */
@@ -1541,23 +1271,31 @@
          (int)png_ptr->pass);
 }
 
+#ifdef PNG_READ_INTERLACING_SUPPORTED
 void PNGAPI
-png_progressive_combine_row (png_structp png_ptr,
-   png_bytep old_row, png_bytep new_row)
-{
-#ifdef PNG_USE_LOCAL_ARRAYS
-   const int FARDATA png_pass_dsp_mask[7] =
-      {0xff, 0x0f, 0xff, 0x33, 0xff, 0x55, 0xff};
-#endif
-   if (new_row != NULL)    /* new_row must == png_ptr->row_buf here. */
-      png_combine_row(png_ptr, old_row, png_pass_dsp_mask[png_ptr->pass]);
-}
+png_progressive_combine_row (png_structp 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_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_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;
@@ -1566,8 +1304,11 @@
 }
 
 png_voidp PNGAPI
-png_get_progressive_ptr(png_structp png_ptr)
-{
+png_get_progressive_ptr(png_const_structp png_ptr)
+{
+   if (png_ptr == NULL)
+      return (NULL);
+
    return png_ptr->io_ptr;
 }
 #endif /* PNG_PROGRESSIVE_READ_SUPPORTED */