XFA: Rename libpng to libpng16.

third_party/libpng/pngrutil.c

-
-/* pngrutil.c - utilities to read a PNG file
- *
- * Last changed in libpng 1.6.20 [December 3, 2015]
- * Copyright (c) 1998-2015 Glenn Randers-Pehrson
- * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
- * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
- *
- * This code is released under the libpng license.
- * For conditions of distribution and use, see the disclaimer
- * and license in png.h
- *
- * This file contains routines that are only called from within
- * libpng itself during the course of reading an image.
- */
-
-#include "pngpriv.h"
-
-#ifdef PNG_READ_SUPPORTED
-
-png_uint_32 PNGAPI
-png_get_uint_31(png_const_structrp png_ptr, png_const_bytep buf)
-{
-   png_uint_32 uval = png_get_uint_32(buf);
-
-   if (uval > PNG_UINT_31_MAX)
-      png_error(png_ptr, "PNG unsigned integer out of range");
-
-   return (uval);
-}
-
-#if defined(PNG_READ_gAMA_SUPPORTED) || defined(PNG_READ_cHRM_SUPPORTED)
-/* The following is a variation on the above for use with the fixed
- * point values used for gAMA and cHRM.  Instead of png_error it
- * issues a warning and returns (-1) - an invalid value because both
- * gAMA and cHRM use *unsigned* integers for fixed point values.
- */
-#define PNG_FIXED_ERROR (-1)
-
-static png_fixed_point /* PRIVATE */
-png_get_fixed_point(png_structrp png_ptr, png_const_bytep buf)
-{
-   png_uint_32 uval = png_get_uint_32(buf);
-
-   if (uval <= PNG_UINT_31_MAX)
-      return (png_fixed_point)uval; /* known to be in range */
-
-   /* The caller can turn off the warning by passing NULL. */
-   if (png_ptr != NULL)
-      png_warning(png_ptr, "PNG fixed point integer out of range");
-
-   return PNG_FIXED_ERROR;
-}
-#endif
-
-#ifdef PNG_READ_INT_FUNCTIONS_SUPPORTED
-/* NOTE: the read macros will obscure these definitions, so that if
- * PNG_USE_READ_MACROS is set the library will not use them internally,
- * but the APIs will still be available externally.
- *
- * The parentheses around "PNGAPI function_name" in the following three
- * functions are necessary because they allow the macros to co-exist with
- * these (unused but exported) functions.
- */
-
-/* Grab an unsigned 32-bit integer from a buffer in big-endian format. */
-png_uint_32 (PNGAPI
-png_get_uint_32)(png_const_bytep buf)
-{
-   png_uint_32 uval =
-       ((png_uint_32)(*(buf    )) << 24) +
-       ((png_uint_32)(*(buf + 1)) << 16) +
-       ((png_uint_32)(*(buf + 2)) <<  8) +
-       ((png_uint_32)(*(buf + 3))      ) ;
-
-   return uval;
-}
-
-/* Grab a signed 32-bit integer from a buffer in big-endian format.  The
- * data is stored in the PNG file in two's complement format and there
- * is no guarantee that a 'png_int_32' is exactly 32 bits, therefore
- * the following code does a two's complement to native conversion.
- */
-png_int_32 (PNGAPI
-png_get_int_32)(png_const_bytep buf)
-{
-   png_uint_32 uval = png_get_uint_32(buf);
-   if ((uval & 0x80000000) == 0) /* non-negative */
-      return uval;
-
-   uval = (uval ^ 0xffffffff) + 1;  /* 2's complement: -x = ~x+1 */
-   if ((uval & 0x80000000) == 0) /* no overflow */
-       return -(png_int_32)uval;
-   /* The following has to be safe; this function only gets called on PNG data
-    * and if we get here that data is invalid.  0 is the most safe value and
-    * if not then an attacker would surely just generate a PNG with 0 instead.
-    */
-   return 0;
-}
-
-/* Grab an unsigned 16-bit integer from a buffer in big-endian format. */
-png_uint_16 (PNGAPI
-png_get_uint_16)(png_const_bytep buf)
-{
-   /* ANSI-C requires an int value to accomodate at least 16 bits so this
-    * works and allows the compiler not to worry about possible narrowing
-    * on 32-bit systems.  (Pre-ANSI systems did not make integers smaller
-    * than 16 bits either.)
-    */
-   unsigned int val =
-       ((unsigned int)(*buf) << 8) +
-       ((unsigned int)(*(buf + 1)));
-
-   return (png_uint_16)val;
-}
-
-#endif /* READ_INT_FUNCTIONS */
-
-/* Read and check the PNG file signature */
-void /* PRIVATE */
-png_read_sig(png_structrp png_ptr, png_inforp info_ptr)
-{
-   png_size_t num_checked, num_to_check;
-
-   /* Exit if the user application does not expect a signature. */
-   if (png_ptr->sig_bytes >= 8)
-      return;
-
-   num_checked = png_ptr->sig_bytes;
-   num_to_check = 8 - num_checked;
-
-#ifdef PNG_IO_STATE_SUPPORTED
-   png_ptr->io_state = PNG_IO_READING | PNG_IO_SIGNATURE;
-#endif
-
-   /* The signature must be serialized in a single I/O call. */
-   png_read_data(png_ptr, &(info_ptr->signature[num_checked]), num_to_check);
-   png_ptr->sig_bytes = 8;
-
-   if (png_sig_cmp(info_ptr->signature, num_checked, num_to_check) != 0)
-   {
-      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");
-   }
-   if (num_checked < 3)
-      png_ptr->mode |= PNG_HAVE_PNG_SIGNATURE;
-}
-
-/* Read the chunk header (length + type name).
- * Put the type name into png_ptr->chunk_name, and return the length.
- */
-png_uint_32 /* PRIVATE */
-png_read_chunk_header(png_structrp png_ptr)
-{
-   png_byte buf[8];
-   png_uint_32 length;
-
-#ifdef PNG_IO_STATE_SUPPORTED
-   png_ptr->io_state = PNG_IO_READING | PNG_IO_CHUNK_HDR;
-#endif
-
-   /* Read the length and the chunk name.
-    * This must be performed in a single I/O call.
-    */
-   png_read_data(png_ptr, buf, 8);
-   length = png_get_uint_31(png_ptr, buf);
-
-   /* Put the chunk name into png_ptr->chunk_name. */
-   png_ptr->chunk_name = PNG_CHUNK_FROM_STRING(buf+4);
-
-   png_debug2(0, "Reading %lx chunk, length = %lu",
-       (unsigned long)png_ptr->chunk_name, (unsigned long)length);
-
-   /* Reset the crc and run it over the chunk name. */
-   png_reset_crc(png_ptr);
-   png_calculate_crc(png_ptr, buf + 4, 4);
-
-   /* Check to see if chunk name is valid. */
-   png_check_chunk_name(png_ptr, png_ptr->chunk_name);
-
-#ifdef PNG_IO_STATE_SUPPORTED
-   png_ptr->io_state = PNG_IO_READING | PNG_IO_CHUNK_DATA;
-#endif
-
-   return length;
-}
-
-/* Read data, and (optionally) run it through the CRC. */
-void /* PRIVATE */
-png_crc_read(png_structrp png_ptr, png_bytep buf, png_uint_32 length)
-{
-   if (png_ptr == NULL)
-      return;
-
-   png_read_data(png_ptr, buf, length);
-   png_calculate_crc(png_ptr, buf, length);
-}
-
-/* Optionally skip data and then check the CRC.  Depending on whether we
- * are reading an ancillary or critical chunk, and how the program has set
- * things up, we may calculate the CRC on the data and print a message.
- * Returns '1' if there was a CRC error, '0' otherwise.
- */
-int /* PRIVATE */
-png_crc_finish(png_structrp png_ptr, png_uint_32 skip)
-{
-   /* The size of the local buffer for inflate is a good guess as to a
-    * reasonable size to use for buffering reads from the application.
-    */
-   while (skip > 0)
-   {
-      png_uint_32 len;
-      png_byte tmpbuf[PNG_INFLATE_BUF_SIZE];
-
-      len = (sizeof tmpbuf);
-      if (len > skip)
-         len = skip;
-      skip -= len;
-
-      png_crc_read(png_ptr, tmpbuf, len);
-   }
-
-   if (png_crc_error(png_ptr) != 0)
-   {
-      if (PNG_CHUNK_ANCILLARY(png_ptr->chunk_name) != 0 ?
-          (png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_NOWARN) == 0 :
-          (png_ptr->flags & PNG_FLAG_CRC_CRITICAL_USE) != 0)
-      {
-         png_chunk_warning(png_ptr, "CRC error");
-      }
-
-      else
-         png_chunk_error(png_ptr, "CRC error");
-
-      return (1);
-   }
-
-   return (0);
-}
-
-/* Compare the CRC stored in the PNG file with that calculated by libpng from
- * the data it has read thus far.
- */
-int /* PRIVATE */
-png_crc_error(png_structrp png_ptr)
-{
-   png_byte crc_bytes[4];
-   png_uint_32 crc;
-   int need_crc = 1;
-
-   if (PNG_CHUNK_ANCILLARY(png_ptr->chunk_name) != 0)
-   {
-      if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_MASK) ==
-          (PNG_FLAG_CRC_ANCILLARY_USE | PNG_FLAG_CRC_ANCILLARY_NOWARN))
-         need_crc = 0;
-   }
-
-   else /* critical */
-   {
-      if ((png_ptr->flags & PNG_FLAG_CRC_CRITICAL_IGNORE) != 0)
-         need_crc = 0;
-   }
-
-#ifdef PNG_IO_STATE_SUPPORTED
-   png_ptr->io_state = PNG_IO_READING | PNG_IO_CHUNK_CRC;
-#endif
-
-   /* The chunk CRC must be serialized in a single I/O call. */
-   png_read_data(png_ptr, crc_bytes, 4);
-
-   if (need_crc != 0)
-   {
-      crc = png_get_uint_32(crc_bytes);
-      return ((int)(crc != png_ptr->crc));
-   }
-
-   else
-      return (0);
-}
-
-#if defined(PNG_READ_iCCP_SUPPORTED) || defined(PNG_READ_iTXt_SUPPORTED) ||\
-    defined(PNG_READ_pCAL_SUPPORTED) || defined(PNG_READ_sCAL_SUPPORTED) ||\
-    defined(PNG_READ_sPLT_SUPPORTED) || defined(PNG_READ_tEXt_SUPPORTED) ||\
-    defined(PNG_READ_zTXt_SUPPORTED) || defined(PNG_SEQUENTIAL_READ_SUPPORTED)
-/* Manage the read buffer; this simply reallocates the buffer if it is not small
- * enough (or if it is not allocated).  The routine returns a pointer to the
- * buffer; if an error occurs and 'warn' is set the routine returns NULL, else
- * it will call png_error (via png_malloc) on failure.  (warn == 2 means
- * 'silent').
- */
-static png_bytep
-png_read_buffer(png_structrp png_ptr, png_alloc_size_t new_size, int warn)
-{
-   png_bytep buffer = png_ptr->read_buffer;
-
-   if (buffer != NULL && new_size > png_ptr->read_buffer_size)
-   {
-      png_ptr->read_buffer = NULL;
-      png_ptr->read_buffer = NULL;
-      png_ptr->read_buffer_size = 0;
-      png_free(png_ptr, buffer);
-      buffer = NULL;
-   }
-
-   if (buffer == NULL)
-   {
-      buffer = png_voidcast(png_bytep, png_malloc_base(png_ptr, new_size));
-
-      if (buffer != NULL)
-      {
-         png_ptr->read_buffer = buffer;
-         png_ptr->read_buffer_size = new_size;
-      }
-
-      else if (warn < 2) /* else silent */
-      {
-         if (warn != 0)
-             png_chunk_warning(png_ptr, "insufficient memory to read chunk");
-
-         else
-             png_chunk_error(png_ptr, "insufficient memory to read chunk");
-      }
-   }
-
-   return buffer;
-}
-#endif /* READ_iCCP|iTXt|pCAL|sCAL|sPLT|tEXt|zTXt|SEQUENTIAL_READ */
-
-/* png_inflate_claim: claim the zstream for some nefarious purpose that involves
- * decompression.  Returns Z_OK on success, else a zlib error code.  It checks
- * the owner but, in final release builds, just issues a warning if some other
- * chunk apparently owns the stream.  Prior to release it does a png_error.
- */
-static int
-png_inflate_claim(png_structrp png_ptr, png_uint_32 owner)
-{
-   if (png_ptr->zowner != 0)
-   {
-      char msg[64];
-
-      PNG_STRING_FROM_CHUNK(msg, png_ptr->zowner);
-      /* So the message that results is "<chunk> using zstream"; this is an
-       * internal error, but is very useful for debugging.  i18n requirements
-       * are minimal.
-       */
-      (void)png_safecat(msg, (sizeof msg), 4, " using zstream");
-#if PNG_RELEASE_BUILD
-      png_chunk_warning(png_ptr, msg);
-      png_ptr->zowner = 0;
-#else
-      png_chunk_error(png_ptr, msg);
-#endif
-   }
-
-   /* Implementation note: unlike 'png_deflate_claim' this internal function
-    * does not take the size of the data as an argument.  Some efficiency could
-    * be gained by using this when it is known *if* the zlib stream itself does
-    * not record the number; however, this is an illusion: the original writer
-    * of the PNG may have selected a lower window size, and we really must
-    * follow that because, for systems with with limited capabilities, we
-    * would otherwise reject the application's attempts to use a smaller window
-    * size (zlib doesn't have an interface to say "this or lower"!).
-    *
-    * inflateReset2 was added to zlib 1.2.4; before this the window could not be
-    * reset, therefore it is necessary to always allocate the maximum window
-    * size with earlier zlibs just in case later compressed chunks need it.
-    */
-   {
-      int ret; /* zlib return code */
-#if PNG_ZLIB_VERNUM >= 0x1240
-
-# if defined(PNG_SET_OPTION_SUPPORTED) && defined(PNG_MAXIMUM_INFLATE_WINDOW)
-      int window_bits;
-
-      if (((png_ptr->options >> PNG_MAXIMUM_INFLATE_WINDOW) & 3) ==
-          PNG_OPTION_ON)
-      {
-         window_bits = 15;
-         png_ptr->zstream_start = 0; /* fixed window size */
-      }
-
-      else
-      {
-         window_bits = 0;
-         png_ptr->zstream_start = 1;
-      }
-# else
-#   define window_bits 0
-# endif
-#endif
-
-      /* Set this for safety, just in case the previous owner left pointers to
-       * memory allocations.
-       */
-      png_ptr->zstream.next_in = NULL;
-      png_ptr->zstream.avail_in = 0;
-      png_ptr->zstream.next_out = NULL;
-      png_ptr->zstream.avail_out = 0;
-
-      if ((png_ptr->flags & PNG_FLAG_ZSTREAM_INITIALIZED) != 0)
-      {
-#if PNG_ZLIB_VERNUM < 0x1240
-         ret = inflateReset(&png_ptr->zstream);
-#else
-         ret = inflateReset2(&png_ptr->zstream, window_bits);
-#endif
-      }
-
-      else
-      {
-#if PNG_ZLIB_VERNUM < 0x1240
-         ret = inflateInit(&png_ptr->zstream);
-#else
-         ret = inflateInit2(&png_ptr->zstream, window_bits);
-#endif
-
-         if (ret == Z_OK)
-            png_ptr->flags |= PNG_FLAG_ZSTREAM_INITIALIZED;
-      }
-
-      if (ret == Z_OK)
-         png_ptr->zowner = owner;
-
-      else
-         png_zstream_error(png_ptr, ret);
-
-      return ret;
-   }
-
-#ifdef window_bits
-# undef window_bits
-#endif
-}
-
-#if PNG_ZLIB_VERNUM >= 0x1240
-/* Handle the start of the inflate stream if we called inflateInit2(strm,0);
- * in this case some zlib versions skip validation of the CINFO field and, in
- * certain circumstances, libpng may end up displaying an invalid image, in
- * contrast to implementations that call zlib in the normal way (e.g. libpng
- * 1.5).
- */
-int /* PRIVATE */
-png_zlib_inflate(png_structrp png_ptr, int flush)
-{
-   if (png_ptr->zstream_start && png_ptr->zstream.avail_in > 0)
-   {
-      if ((*png_ptr->zstream.next_in >> 4) > 7)
-      {
-         png_ptr->zstream.msg = "invalid window size (libpng)";
-         return Z_DATA_ERROR;
-      }
-
-      png_ptr->zstream_start = 0;
-   }
-
-   return inflate(&png_ptr->zstream, flush);
-}
-#endif /* Zlib >= 1.2.4 */
-
-#ifdef PNG_READ_COMPRESSED_TEXT_SUPPORTED
-/* png_inflate now returns zlib error codes including Z_OK and Z_STREAM_END to
- * allow the caller to do multiple calls if required.  If the 'finish' flag is
- * set Z_FINISH will be passed to the final inflate() call and Z_STREAM_END must
- * be returned or there has been a problem, otherwise Z_SYNC_FLUSH is used and
- * Z_OK or Z_STREAM_END will be returned on success.
- *
- * The input and output sizes are updated to the actual amounts of data consumed
- * or written, not the amount available (as in a z_stream).  The data pointers
- * are not changed, so the next input is (data+input_size) and the next
- * available output is (output+output_size).
- */
-static int
-png_inflate(png_structrp png_ptr, png_uint_32 owner, int finish,
-    /* INPUT: */ png_const_bytep input, png_uint_32p input_size_ptr,
-    /* OUTPUT: */ png_bytep output, png_alloc_size_t *output_size_ptr)
-{
-   if (png_ptr->zowner == owner) /* Else not claimed */
-   {
-      int ret;
-      png_alloc_size_t avail_out = *output_size_ptr;
-      png_uint_32 avail_in = *input_size_ptr;
-
-      /* zlib can't necessarily handle more than 65535 bytes at once (i.e. it
-       * can't even necessarily handle 65536 bytes) because the type uInt is
-       * "16 bits or more".  Consequently it is necessary to chunk the input to
-       * zlib.  This code uses ZLIB_IO_MAX, from pngpriv.h, as the maximum (the
-       * maximum value that can be stored in a uInt.)  It is possible to set
-       * ZLIB_IO_MAX to a lower value in pngpriv.h and this may sometimes have
-       * a performance advantage, because it reduces the amount of data accessed
-       * at each step and that may give the OS more time to page it in.
-       */
-      png_ptr->zstream.next_in = PNGZ_INPUT_CAST(input);
-      /* avail_in and avail_out are set below from 'size' */
-      png_ptr->zstream.avail_in = 0;
-      png_ptr->zstream.avail_out = 0;
-
-      /* Read directly into the output if it is available (this is set to
-       * a local buffer below if output is NULL).
-       */
-      if (output != NULL)
-         png_ptr->zstream.next_out = output;
-
-      do
-      {
-         uInt avail;
-         Byte local_buffer[PNG_INFLATE_BUF_SIZE];
-
-         /* zlib INPUT BUFFER */
-         /* The setting of 'avail_in' used to be outside the loop; by setting it
-          * inside it is possible to chunk the input to zlib and simply rely on
-          * zlib to advance the 'next_in' pointer.  This allows arbitrary
-          * amounts of data to be passed through zlib at the unavoidable cost of
-          * requiring a window save (memcpy of up to 32768 output bytes)
-          * every ZLIB_IO_MAX input bytes.
-          */
-         avail_in += png_ptr->zstream.avail_in; /* not consumed last time */
-
-         avail = ZLIB_IO_MAX;
-
-         if (avail_in < avail)
-            avail = (uInt)avail_in; /* safe: < than ZLIB_IO_MAX */
-
-         avail_in -= avail;
-         png_ptr->zstream.avail_in = avail;
-
-         /* zlib OUTPUT BUFFER */
-         avail_out += png_ptr->zstream.avail_out; /* not written last time */
-
-         avail = ZLIB_IO_MAX; /* maximum zlib can process */
-
-         if (output == NULL)
-         {
-            /* Reset the output buffer each time round if output is NULL and
-             * make available the full buffer, up to 'remaining_space'
-             */
-            png_ptr->zstream.next_out = local_buffer;
-            if ((sizeof local_buffer) < avail)
-               avail = (sizeof local_buffer);
-         }
-
-         if (avail_out < avail)
-            avail = (uInt)avail_out; /* safe: < ZLIB_IO_MAX */
-
-         png_ptr->zstream.avail_out = avail;
-         avail_out -= avail;
-
-         /* zlib inflate call */
-         /* In fact 'avail_out' may be 0 at this point, that happens at the end
-          * of the read when the final LZ end code was not passed at the end of
-          * the previous chunk of input data.  Tell zlib if we have reached the
-          * end of the output buffer.
-          */
-         ret = PNG_INFLATE(png_ptr, avail_out > 0 ? Z_NO_FLUSH :
-             (finish ? Z_FINISH : Z_SYNC_FLUSH));
-      } while (ret == Z_OK);
-
-      /* For safety kill the local buffer pointer now */
-      if (output == NULL)
-         png_ptr->zstream.next_out = NULL;
-
-      /* Claw back the 'size' and 'remaining_space' byte counts. */
-      avail_in += png_ptr->zstream.avail_in;
-      avail_out += png_ptr->zstream.avail_out;
-
-      /* Update the input and output sizes; the updated values are the amount
-       * consumed or written, effectively the inverse of what zlib uses.
-       */
-      if (avail_out > 0)
-         *output_size_ptr -= avail_out;
-
-      if (avail_in > 0)
-         *input_size_ptr -= avail_in;
-
-      /* Ensure png_ptr->zstream.msg is set (even in the success case!) */
-      png_zstream_error(png_ptr, ret);
-      return ret;
-   }
-
-   else
-   {
-      /* This is a bad internal error.  The recovery assigns to the zstream msg
-       * pointer, which is not owned by the caller, but this is safe; it's only
-       * used on errors!
-       */
-      png_ptr->zstream.msg = PNGZ_MSG_CAST("zstream unclaimed");
-      return Z_STREAM_ERROR;
-   }
-}
-
-/*
- * Decompress trailing data in a chunk.  The assumption is that read_buffer
- * points at an allocated area holding the contents of a chunk with a
- * trailing compressed part.  What we get back is an allocated area
- * holding the original prefix part and an uncompressed version of the
- * trailing part (the malloc area passed in is freed).
- */
-static int
-png_decompress_chunk(png_structrp png_ptr,
-   png_uint_32 chunklength, png_uint_32 prefix_size,
-   png_alloc_size_t *newlength /* must be initialized to the maximum! */,
-   int terminate /*add a '\0' to the end of the uncompressed data*/)
-{
-   /* TODO: implement different limits for different types of chunk.
-    *
-    * The caller supplies *newlength set to the maximum length of the
-    * uncompressed data, but this routine allocates space for the prefix and
-    * maybe a '\0' terminator too.  We have to assume that 'prefix_size' is
-    * limited only by the maximum chunk size.
-    */
-   png_alloc_size_t limit = PNG_SIZE_MAX;
-
-# ifdef PNG_SET_USER_LIMITS_SUPPORTED
-   if (png_ptr->user_chunk_malloc_max > 0 &&
-       png_ptr->user_chunk_malloc_max < limit)
-      limit = png_ptr->user_chunk_malloc_max;
-# elif PNG_USER_CHUNK_MALLOC_MAX > 0
-   if (PNG_USER_CHUNK_MALLOC_MAX < limit)
-      limit = PNG_USER_CHUNK_MALLOC_MAX;
-# endif
-
-   if (limit >= prefix_size + (terminate != 0))
-   {
-      int ret;
-
-      limit -= prefix_size + (terminate != 0);
-
-      if (limit < *newlength)
-         *newlength = limit;
-
-      /* Now try to claim the stream. */
-      ret = png_inflate_claim(png_ptr, png_ptr->chunk_name);
-
-      if (ret == Z_OK)
-      {
-         png_uint_32 lzsize = chunklength - prefix_size;
-
-         ret = png_inflate(png_ptr, png_ptr->chunk_name, 1/*finish*/,
-            /* input: */ png_ptr->read_buffer + prefix_size, &lzsize,
-            /* output: */ NULL, newlength);
-
-         if (ret == Z_STREAM_END)
-         {
-            /* Use 'inflateReset' here, not 'inflateReset2' because this
-             * preserves the previously decided window size (otherwise it would
-             * be necessary to store the previous window size.)  In practice
-             * this doesn't matter anyway, because png_inflate will call inflate
-             * with Z_FINISH in almost all cases, so the window will not be
-             * maintained.
-             */
-            if (inflateReset(&png_ptr->zstream) == Z_OK)
-            {
-               /* Because of the limit checks above we know that the new,
-                * expanded, size will fit in a size_t (let alone an
-                * png_alloc_size_t).  Use png_malloc_base here to avoid an
-                * extra OOM message.
-                */
-               png_alloc_size_t new_size = *newlength;
-               png_alloc_size_t buffer_size = prefix_size + new_size +
-                  (terminate != 0);
-               png_bytep text = png_voidcast(png_bytep, png_malloc_base(png_ptr,
-                  buffer_size));
-
-               if (text != NULL)
-               {
-                  ret = png_inflate(png_ptr, png_ptr->chunk_name, 1/*finish*/,
-                     png_ptr->read_buffer + prefix_size, &lzsize,
-                     text + prefix_size, newlength);
-
-                  if (ret == Z_STREAM_END)
-                  {
-                     if (new_size == *newlength)
-                     {
-                        if (terminate != 0)
-                           text[prefix_size + *newlength] = 0;
-
-                        if (prefix_size > 0)
-                           memcpy(text, png_ptr->read_buffer, prefix_size);
-
-                        {
-                           png_bytep old_ptr = png_ptr->read_buffer;
-
-                           png_ptr->read_buffer = text;
-                           png_ptr->read_buffer_size = buffer_size;
-                           text = old_ptr; /* freed below */
-                        }
-                     }
-
-                     else
-                     {
-                        /* The size changed on the second read, there can be no
-                         * guarantee that anything is correct at this point.
-                         * The 'msg' pointer has been set to "unexpected end of
-                         * LZ stream", which is fine, but return an error code
-                         * that the caller won't accept.
-                         */
-                        ret = PNG_UNEXPECTED_ZLIB_RETURN;
-                     }
-                  }
-
-                  else if (ret == Z_OK)
-                     ret = PNG_UNEXPECTED_ZLIB_RETURN; /* for safety */
-
-                  /* Free the text pointer (this is the old read_buffer on
-                   * success)
-                   */
-                  png_free(png_ptr, text);
-
-                  /* This really is very benign, but it's still an error because
-                   * the extra space may otherwise be used as a Trojan Horse.
-                   */
-                  if (ret == Z_STREAM_END &&
-                     chunklength - prefix_size != lzsize)
-                     png_chunk_benign_error(png_ptr, "extra compressed data");
-               }
-
-               else
-               {
-                  /* Out of memory allocating the buffer */
-                  ret = Z_MEM_ERROR;
-                  png_zstream_error(png_ptr, Z_MEM_ERROR);
-               }
-            }
-
-            else
-            {
-               /* inflateReset failed, store the error message */
-               png_zstream_error(png_ptr, ret);
-
-               if (ret == Z_STREAM_END)
-                  ret = PNG_UNEXPECTED_ZLIB_RETURN;
-            }
-         }
-
-         else if (ret == Z_OK)
-            ret = PNG_UNEXPECTED_ZLIB_RETURN;
-
-         /* Release the claimed stream */
-         png_ptr->zowner = 0;
-      }
-
-      else /* the claim failed */ if (ret == Z_STREAM_END) /* impossible! */
-         ret = PNG_UNEXPECTED_ZLIB_RETURN;
-
-      return ret;
-   }
-
-   else
-   {
-      /* Application/configuration limits exceeded */
-      png_zstream_error(png_ptr, Z_MEM_ERROR);
-      return Z_MEM_ERROR;
-   }
-}
-#endif /* READ_COMPRESSED_TEXT */
-
-#ifdef PNG_READ_iCCP_SUPPORTED
-/* Perform a partial read and decompress, producing 'avail_out' bytes and
- * reading from the current chunk as required.
- */
-static int
-png_inflate_read(png_structrp png_ptr, png_bytep read_buffer, uInt read_size,
-   png_uint_32p chunk_bytes, png_bytep next_out, png_alloc_size_t *out_size,
-   int finish)
-{
-   if (png_ptr->zowner == png_ptr->chunk_name)
-   {
-      int ret;
-
-      /* next_in and avail_in must have been initialized by the caller. */
-      png_ptr->zstream.next_out = next_out;
-      png_ptr->zstream.avail_out = 0; /* set in the loop */
-
-      do
-      {
-         if (png_ptr->zstream.avail_in == 0)
-         {
-            if (read_size > *chunk_bytes)
-               read_size = (uInt)*chunk_bytes;
-            *chunk_bytes -= read_size;
-
-            if (read_size > 0)
-               png_crc_read(png_ptr, read_buffer, read_size);
-
-            png_ptr->zstream.next_in = read_buffer;
-            png_ptr->zstream.avail_in = read_size;
-         }
-
-         if (png_ptr->zstream.avail_out == 0)
-         {
-            uInt avail = ZLIB_IO_MAX;
-            if (avail > *out_size)
-               avail = (uInt)*out_size;
-            *out_size -= avail;
-
-            png_ptr->zstream.avail_out = avail;
-         }
-
-         /* Use Z_SYNC_FLUSH when there is no more chunk data to ensure that all
-          * the available output is produced; this allows reading of truncated
-          * streams.
-          */
-         ret = PNG_INFLATE(png_ptr,
-            *chunk_bytes > 0 ? Z_NO_FLUSH : (finish ? Z_FINISH : Z_SYNC_FLUSH));
-      }
-      while (ret == Z_OK && (*out_size > 0 || png_ptr->zstream.avail_out > 0));
-
-      *out_size += png_ptr->zstream.avail_out;
-      png_ptr->zstream.avail_out = 0; /* Should not be required, but is safe */
-
-      /* Ensure the error message pointer is always set: */
-      png_zstream_error(png_ptr, ret);
-      return ret;
-   }
-
-   else
-   {
-      png_ptr->zstream.msg = PNGZ_MSG_CAST("zstream unclaimed");
-      return Z_STREAM_ERROR;
-   }
-}
-#endif
-
-/* Read and check the IDHR chunk */
-
-void /* PRIVATE */
-png_handle_IHDR(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
-{
-   png_byte buf[13];
-   png_uint_32 width, height;
-   int bit_depth, color_type, compression_type, filter_type;
-   int interlace_type;
-
-   png_debug(1, "in png_handle_IHDR");
-
-   if ((png_ptr->mode & PNG_HAVE_IHDR) != 0)
-      png_chunk_error(png_ptr, "out of place");
-
-   /* Check the length */
-   if (length != 13)
-      png_chunk_error(png_ptr, "invalid");
-
-   png_ptr->mode |= PNG_HAVE_IHDR;
-
-   png_crc_read(png_ptr, buf, 13);
-   png_crc_finish(png_ptr, 0);
-
-   width = png_get_uint_31(png_ptr, buf);
-   height = png_get_uint_31(png_ptr, buf + 4);
-   bit_depth = buf[8];
-   color_type = buf[9];
-   compression_type = buf[10];
-   filter_type = buf[11];
-   interlace_type = buf[12];
-
-   /* Set internal variables */
-   png_ptr->width = width;
-   png_ptr->height = height;
-   png_ptr->bit_depth = (png_byte)bit_depth;
-   png_ptr->interlaced = (png_byte)interlace_type;
-   png_ptr->color_type = (png_byte)color_type;
-#ifdef PNG_MNG_FEATURES_SUPPORTED
-   png_ptr->filter_type = (png_byte)filter_type;
-#endif
-   png_ptr->compression_type = (png_byte)compression_type;
-
-   /* Find number of channels */
-   switch (png_ptr->color_type)
-   {
-      default: /* invalid, png_set_IHDR calls png_error */
-      case PNG_COLOR_TYPE_GRAY:
-      case PNG_COLOR_TYPE_PALETTE:
-         png_ptr->channels = 1;
-         break;
-
-      case PNG_COLOR_TYPE_RGB:
-         png_ptr->channels = 3;
-         break;
-
-      case PNG_COLOR_TYPE_GRAY_ALPHA:
-         png_ptr->channels = 2;
-         break;
-
-      case PNG_COLOR_TYPE_RGB_ALPHA:
-         png_ptr->channels = 4;
-         break;
-   }
-
-   /* Set up other useful info */
-   png_ptr->pixel_depth = (png_byte)(png_ptr->bit_depth * png_ptr->channels);
-   png_ptr->rowbytes = PNG_ROWBYTES(png_ptr->pixel_depth, png_ptr->width);
-   png_debug1(3, "bit_depth = %d", png_ptr->bit_depth);
-   png_debug1(3, "channels = %d", png_ptr->channels);
-   png_debug1(3, "rowbytes = %lu", (unsigned long)png_ptr->rowbytes);
-   png_set_IHDR(png_ptr, info_ptr, width, height, bit_depth,
-       color_type, interlace_type, compression_type, filter_type);
-}
-
-/* Read and check the palette */
-void /* PRIVATE */
-png_handle_PLTE(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
-{
-   png_color palette[PNG_MAX_PALETTE_LENGTH];
-   int max_palette_length, num, i;
-#ifdef PNG_POINTER_INDEXING_SUPPORTED
-   png_colorp pal_ptr;
-#endif
-
-   png_debug(1, "in png_handle_PLTE");
-
-   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
-      png_chunk_error(png_ptr, "missing IHDR");
-
-   /* Moved to before the 'after IDAT' check below because otherwise duplicate
-    * PLTE chunks are potentially ignored (the spec says there shall not be more
-    * than one PLTE, the error is not treated as benign, so this check trumps
-    * the requirement that PLTE appears before IDAT.)
-    */
-   else if ((png_ptr->mode & PNG_HAVE_PLTE) != 0)
-      png_chunk_error(png_ptr, "duplicate");
-
-   else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
-   {
-      /* This is benign because the non-benign error happened before, when an
-       * IDAT was encountered in a color-mapped image with no PLTE.
-       */
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "out of place");
-      return;
-   }
-
-   png_ptr->mode |= PNG_HAVE_PLTE;
-
-   if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) == 0)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "ignored in grayscale PNG");
-      return;
-   }
-
-#ifndef PNG_READ_OPT_PLTE_SUPPORTED
-   if (png_ptr->color_type != PNG_COLOR_TYPE_PALETTE)
-   {
-      png_crc_finish(png_ptr, length);
-      return;
-   }
-#endif
-
-   if (length > 3*PNG_MAX_PALETTE_LENGTH || length % 3)
-   {
-      png_crc_finish(png_ptr, length);
-
-      if (png_ptr->color_type != PNG_COLOR_TYPE_PALETTE)
-         png_chunk_benign_error(png_ptr, "invalid");
-
-      else
-         png_chunk_error(png_ptr, "invalid");
-
-      return;
-   }
-
-   /* The cast is safe because 'length' is less than 3*PNG_MAX_PALETTE_LENGTH */
-   num = (int)length / 3;
-
-   /* If the palette has 256 or fewer entries but is too large for the bit
-    * depth, we don't issue an error, to preserve the behavior of previous
-    * libpng versions. We silently truncate the unused extra palette entries
-    * here.
-    */
-   if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
-      max_palette_length = (1 << png_ptr->bit_depth);
-   else
-      max_palette_length = PNG_MAX_PALETTE_LENGTH;
-
-   if (num > max_palette_length)
-      num = max_palette_length;
-
-#ifdef PNG_POINTER_INDEXING_SUPPORTED
-   for (i = 0, pal_ptr = palette; i < num; i++, pal_ptr++)
-   {
-      png_byte buf[3];
-
-      png_crc_read(png_ptr, buf, 3);
-      pal_ptr->red = buf[0];
-      pal_ptr->green = buf[1];
-      pal_ptr->blue = buf[2];
-   }
-#else
-   for (i = 0; i < num; i++)
-   {
-      png_byte buf[3];
-
-      png_crc_read(png_ptr, buf, 3);
-      /* Don't depend upon png_color being any order */
-      palette[i].red = buf[0];
-      palette[i].green = buf[1];
-      palette[i].blue = buf[2];
-   }
-#endif
-
-   /* If we actually need the PLTE chunk (ie for a paletted image), we do
-    * whatever the normal CRC configuration tells us.  However, if we
-    * have an RGB image, the PLTE can be considered ancillary, so
-    * we will act as though it is.
-    */
-#ifndef PNG_READ_OPT_PLTE_SUPPORTED
-   if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
-#endif
-   {
-      png_crc_finish(png_ptr, (int) length - num * 3);
-   }
-
-#ifndef PNG_READ_OPT_PLTE_SUPPORTED
-   else if (png_crc_error(png_ptr) != 0)  /* Only if we have a CRC error */
-   {
-      /* If we don't want to use the data from an ancillary chunk,
-       * we have two options: an error abort, or a warning and we
-       * ignore the data in this chunk (which should be OK, since
-       * it's considered ancillary for a RGB or RGBA image).
-       *
-       * IMPLEMENTATION NOTE: this is only here because png_crc_finish uses the
-       * chunk type to determine whether to check the ancillary or the critical
-       * flags.
-       */
-      if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_USE) == 0)
-      {
-         if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_NOWARN) != 0)
-            return;
-
-         else
-            png_chunk_error(png_ptr, "CRC error");
-      }
-
-      /* Otherwise, we (optionally) emit a warning and use the chunk. */
-      else if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_NOWARN) == 0)
-         png_chunk_warning(png_ptr, "CRC error");
-   }
-#endif
-
-   /* TODO: png_set_PLTE has the side effect of setting png_ptr->palette to its
-    * own copy of the palette.  This has the side effect that when png_start_row
-    * is called (this happens after any call to png_read_update_info) the
-    * info_ptr palette gets changed.  This is extremely unexpected and
-    * confusing.
-    *
-    * Fix this by not sharing the palette in this way.
-    */
-   png_set_PLTE(png_ptr, info_ptr, palette, num);
-
-   /* The three chunks, bKGD, hIST and tRNS *must* appear after PLTE and before
-    * IDAT.  Prior to 1.6.0 this was not checked; instead the code merely
-    * checked the apparent validity of a tRNS chunk inserted before PLTE on a
-    * palette PNG.  1.6.0 attempts to rigorously follow the standard and
-    * therefore does a benign error if the erroneous condition is detected *and*
-    * cancels the tRNS if the benign error returns.  The alternative is to
-    * amend the standard since it would be rather hypocritical of the standards
-    * maintainers to ignore it.
-    */
-#ifdef PNG_READ_tRNS_SUPPORTED
-   if (png_ptr->num_trans > 0 ||
-       (info_ptr != NULL && (info_ptr->valid & PNG_INFO_tRNS) != 0))
-   {
-      /* Cancel this because otherwise it would be used if the transforms
-       * require it.  Don't cancel the 'valid' flag because this would prevent
-       * detection of duplicate chunks.
-       */
-      png_ptr->num_trans = 0;
-
-      if (info_ptr != NULL)
-         info_ptr->num_trans = 0;
-
-      png_chunk_benign_error(png_ptr, "tRNS must be after");
-   }
-#endif
-
-#ifdef PNG_READ_hIST_SUPPORTED
-   if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_hIST) != 0)
-      png_chunk_benign_error(png_ptr, "hIST must be after");
-#endif
-
-#ifdef PNG_READ_bKGD_SUPPORTED
-   if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_bKGD) != 0)
-      png_chunk_benign_error(png_ptr, "bKGD must be after");
-#endif
-}
-
-void /* PRIVATE */
-png_handle_IEND(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
-{
-   png_debug(1, "in png_handle_IEND");
-
-   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0 ||
-       (png_ptr->mode & PNG_HAVE_IDAT) == 0)
-      png_chunk_error(png_ptr, "out of place");
-
-   png_ptr->mode |= (PNG_AFTER_IDAT | PNG_HAVE_IEND);
-
-   png_crc_finish(png_ptr, length);
-
-   if (length != 0)
-      png_chunk_benign_error(png_ptr, "invalid");
-
-   PNG_UNUSED(info_ptr)
-}
-
-#ifdef PNG_READ_gAMA_SUPPORTED
-void /* PRIVATE */
-png_handle_gAMA(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
-{
-   png_fixed_point igamma;
-   png_byte buf[4];
-
-   png_debug(1, "in png_handle_gAMA");
-
-   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
-      png_chunk_error(png_ptr, "missing IHDR");
-
-   else if ((png_ptr->mode & (PNG_HAVE_IDAT|PNG_HAVE_PLTE)) != 0)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "out of place");
-      return;
-   }
-
-   if (length != 4)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "invalid");
-      return;
-   }
-
-   png_crc_read(png_ptr, buf, 4);
-
-   if (png_crc_finish(png_ptr, 0) != 0)
-      return;
-
-   igamma = png_get_fixed_point(NULL, buf);
-
-   png_colorspace_set_gamma(png_ptr, &png_ptr->colorspace, igamma);
-   png_colorspace_sync(png_ptr, info_ptr);
-}
-#endif
-
-#ifdef PNG_READ_sBIT_SUPPORTED
-void /* PRIVATE */
-png_handle_sBIT(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
-{
-   unsigned int truelen, i;
-   png_byte sample_depth;
-   png_byte buf[4];
-
-   png_debug(1, "in png_handle_sBIT");
-
-   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
-      png_chunk_error(png_ptr, "missing IHDR");
-
-   else if ((png_ptr->mode & (PNG_HAVE_IDAT|PNG_HAVE_PLTE)) != 0)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "out of place");
-      return;
-   }
-
-   if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_sBIT) != 0)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "duplicate");
-      return;
-   }
-
-   if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
-   {
-      truelen = 3;
-      sample_depth = 8;
-   }
-
-   else
-   {
-      truelen = png_ptr->channels;
-      sample_depth = png_ptr->bit_depth;
-   }
-
-   if (length != truelen || length > 4)
-   {
-      png_chunk_benign_error(png_ptr, "invalid");
-      png_crc_finish(png_ptr, length);
-      return;
-   }
-
-   buf[0] = buf[1] = buf[2] = buf[3] = sample_depth;
-   png_crc_read(png_ptr, buf, truelen);
-
-   if (png_crc_finish(png_ptr, 0) != 0)
-      return;
-
-   for (i=0; i<truelen; ++i)
-   {
-      if (buf[i] == 0 || buf[i] > sample_depth)
-      {
-         png_chunk_benign_error(png_ptr, "invalid");
-         return;
-      }
-   }
-
-   if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
-   {
-      png_ptr->sig_bit.red = buf[0];
-      png_ptr->sig_bit.green = buf[1];
-      png_ptr->sig_bit.blue = buf[2];
-      png_ptr->sig_bit.alpha = buf[3];
-   }
-
-   else
-   {
-      png_ptr->sig_bit.gray = buf[0];
-      png_ptr->sig_bit.red = buf[0];
-      png_ptr->sig_bit.green = buf[0];
-      png_ptr->sig_bit.blue = buf[0];
-      png_ptr->sig_bit.alpha = buf[1];
-   }
-
-   png_set_sBIT(png_ptr, info_ptr, &(png_ptr->sig_bit));
-}
-#endif
-
-#ifdef PNG_READ_cHRM_SUPPORTED
-void /* PRIVATE */
-png_handle_cHRM(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
-{
-   png_byte buf[32];
-   png_xy xy;
-
-   png_debug(1, "in png_handle_cHRM");
-
-   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
-      png_chunk_error(png_ptr, "missing IHDR");
-
-   else if ((png_ptr->mode & (PNG_HAVE_IDAT|PNG_HAVE_PLTE)) != 0)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "out of place");
-      return;
-   }
-
-   if (length != 32)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "invalid");
-      return;
-   }
-
-   png_crc_read(png_ptr, buf, 32);
-
-   if (png_crc_finish(png_ptr, 0) != 0)
-      return;
-
-   xy.whitex = png_get_fixed_point(NULL, buf);
-   xy.whitey = png_get_fixed_point(NULL, buf + 4);
-   xy.redx   = png_get_fixed_point(NULL, buf + 8);
-   xy.redy   = png_get_fixed_point(NULL, buf + 12);
-   xy.greenx = png_get_fixed_point(NULL, buf + 16);
-   xy.greeny = png_get_fixed_point(NULL, buf + 20);
-   xy.bluex  = png_get_fixed_point(NULL, buf + 24);
-   xy.bluey  = png_get_fixed_point(NULL, buf + 28);
-
-   if (xy.whitex == PNG_FIXED_ERROR ||
-       xy.whitey == PNG_FIXED_ERROR ||
-       xy.redx   == PNG_FIXED_ERROR ||
-       xy.redy   == PNG_FIXED_ERROR ||
-       xy.greenx == PNG_FIXED_ERROR ||
-       xy.greeny == PNG_FIXED_ERROR ||
-       xy.bluex  == PNG_FIXED_ERROR ||
-       xy.bluey  == PNG_FIXED_ERROR)
-   {
-      png_chunk_benign_error(png_ptr, "invalid values");
-      return;
-   }
-
-   /* If a colorspace error has already been output skip this chunk */
-   if ((png_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) != 0)
-      return;
-
-   if ((png_ptr->colorspace.flags & PNG_COLORSPACE_FROM_cHRM) != 0)
-   {
-      png_ptr->colorspace.flags |= PNG_COLORSPACE_INVALID;
-      png_colorspace_sync(png_ptr, info_ptr);
-      png_chunk_benign_error(png_ptr, "duplicate");
-      return;
-   }
-
-   png_ptr->colorspace.flags |= PNG_COLORSPACE_FROM_cHRM;
-   (void)png_colorspace_set_chromaticities(png_ptr, &png_ptr->colorspace, &xy,
-      1/*prefer cHRM values*/);
-   png_colorspace_sync(png_ptr, info_ptr);
-}
-#endif
-
-#ifdef PNG_READ_sRGB_SUPPORTED
-void /* PRIVATE */
-png_handle_sRGB(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
-{
-   png_byte intent;
-
-   png_debug(1, "in png_handle_sRGB");
-
-   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
-      png_chunk_error(png_ptr, "missing IHDR");
-
-   else if ((png_ptr->mode & (PNG_HAVE_IDAT|PNG_HAVE_PLTE)) != 0)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "out of place");
-      return;
-   }
-
-   if (length != 1)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "invalid");
-      return;
-   }
-
-   png_crc_read(png_ptr, &intent, 1);
-
-   if (png_crc_finish(png_ptr, 0) != 0)
-      return;
-
-   /* If a colorspace error has already been output skip this chunk */
-   if ((png_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) != 0)
-      return;
-
-   /* Only one sRGB or iCCP chunk is allowed, use the HAVE_INTENT flag to detect
-    * this.
-    */
-   if ((png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_INTENT) != 0)
-   {
-      png_ptr->colorspace.flags |= PNG_COLORSPACE_INVALID;
-      png_colorspace_sync(png_ptr, info_ptr);
-      png_chunk_benign_error(png_ptr, "too many profiles");
-      return;
-   }
-
-   (void)png_colorspace_set_sRGB(png_ptr, &png_ptr->colorspace, intent);
-   png_colorspace_sync(png_ptr, info_ptr);
-}
-#endif /* READ_sRGB */
-
-#ifdef PNG_READ_iCCP_SUPPORTED
-void /* PRIVATE */
-png_handle_iCCP(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
-/* Note: this does not properly handle profiles that are > 64K under DOS */
-{
-   png_const_charp errmsg = NULL; /* error message output, or no error */
-   int finished = 0; /* crc checked */
-
-   png_debug(1, "in png_handle_iCCP");
-
-   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
-      png_chunk_error(png_ptr, "missing IHDR");
-
-   else if ((png_ptr->mode & (PNG_HAVE_IDAT|PNG_HAVE_PLTE)) != 0)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "out of place");
-      return;
-   }
-
-   /* Consistent with all the above colorspace handling an obviously *invalid*
-    * chunk is just ignored, so does not invalidate the color space.  An
-    * alternative is to set the 'invalid' flags at the start of this routine
-    * and only clear them in they were not set before and all the tests pass.
-    * The minimum 'deflate' stream is assumed to be just the 2 byte header and
-    * 4 byte checksum.  The keyword must be at least one character and there is
-    * a terminator (0) byte and the compression method.
-    */
-   if (length < 9)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "too short");
-      return;
-   }
-
-   /* If a colorspace error has already been output skip this chunk */
-   if ((png_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) != 0)
-   {
-      png_crc_finish(png_ptr, length);
-      return;
-   }
-
-   /* Only one sRGB or iCCP chunk is allowed, use the HAVE_INTENT flag to detect
-    * this.
-    */
-   if ((png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_INTENT) == 0)
-   {
-      uInt read_length, keyword_length;
-      char keyword[81];
-
-      /* Find the keyword; the keyword plus separator and compression method
-       * bytes can be at most 81 characters long.
-       */
-      read_length = 81; /* maximum */
-      if (read_length > length)
-         read_length = (uInt)length;
-
-      png_crc_read(png_ptr, (png_bytep)keyword, read_length);
-      length -= read_length;
-
-      keyword_length = 0;
-      while (keyword_length < 80 && keyword_length < read_length &&
-         keyword[keyword_length] != 0)
-         ++keyword_length;
-
-      /* TODO: make the keyword checking common */
-      if (keyword_length >= 1 && keyword_length <= 79)
-      {
-         /* We only understand '0' compression - deflate - so if we get a
-          * different value we can't safely decode the chunk.
-          */
-         if (keyword_length+1 < read_length &&
-            keyword[keyword_length+1] == PNG_COMPRESSION_TYPE_BASE)
-         {
-            read_length -= keyword_length+2;
-
-            if (png_inflate_claim(png_ptr, png_iCCP) == Z_OK)
-            {
-               Byte profile_header[132];
-               Byte local_buffer[PNG_INFLATE_BUF_SIZE];
-               png_alloc_size_t size = (sizeof profile_header);
-
-               png_ptr->zstream.next_in = (Bytef*)keyword + (keyword_length+2);
-               png_ptr->zstream.avail_in = read_length;
-               (void)png_inflate_read(png_ptr, local_buffer,
-                  (sizeof local_buffer), &length, profile_header, &size,
-                  0/*finish: don't, because the output is too small*/);
-
-               if (size == 0)
-               {
-                  /* We have the ICC profile header; do the basic header checks.
-                   */
-                  const png_uint_32 profile_length =
-                     png_get_uint_32(profile_header);
-
-                  if (png_icc_check_length(png_ptr, &png_ptr->colorspace,
-                     keyword, profile_length) != 0)
-                  {
-                     /* The length is apparently ok, so we can check the 132
-                      * byte header.
-                      */
-                     if (png_icc_check_header(png_ptr, &png_ptr->colorspace,
-                        keyword, profile_length, profile_header,
-                        png_ptr->color_type) != 0)
-                     {
-                        /* Now read the tag table; a variable size buffer is
-                         * needed at this point, allocate one for the whole
-                         * profile.  The header check has already validated
-                         * that none of these stuff will overflow.
-                         */
-                        const png_uint_32 tag_count = png_get_uint_32(
-                           profile_header+128);
-                        png_bytep profile = png_read_buffer(png_ptr,
-                           profile_length, 2/*silent*/);
-
-                        if (profile != NULL)
-                        {
-                           memcpy(profile, profile_header,
-                              (sizeof profile_header));
-
-                           size = 12 * tag_count;
-
-                           (void)png_inflate_read(png_ptr, local_buffer,
-                              (sizeof local_buffer), &length,
-                              profile + (sizeof profile_header), &size, 0);
-
-                           /* Still expect a buffer error because we expect
-                            * there to be some tag data!
-                            */
-                           if (size == 0)
-                           {
-                              if (png_icc_check_tag_table(png_ptr,
-                                 &png_ptr->colorspace, keyword, profile_length,
-                                 profile) != 0)
-                              {
-                                 /* The profile has been validated for basic
-                                  * security issues, so read the whole thing in.
-                                  */
-                                 size = profile_length - (sizeof profile_header)
-                                    - 12 * tag_count;
-
-                                 (void)png_inflate_read(png_ptr, local_buffer,
-                                    (sizeof local_buffer), &length,
-                                    profile + (sizeof profile_header) +
-                                    12 * tag_count, &size, 1/*finish*/);
-
-                                 if (length > 0 && !(png_ptr->flags &
-                                       PNG_FLAG_BENIGN_ERRORS_WARN))
-                                    errmsg = "extra compressed data";
-
-                                 /* But otherwise allow extra data: */
-                                 else if (size == 0)
-                                 {
-                                    if (length > 0)
-                                    {
-                                       /* This can be handled completely, so
-                                        * keep going.
-                                        */
-                                       png_chunk_warning(png_ptr,
-                                          "extra compressed data");
-                                    }
-
-                                    png_crc_finish(png_ptr, length);
-                                    finished = 1;
-
-#                                   ifdef PNG_sRGB_SUPPORTED
-                                    /* Check for a match against sRGB */
-                                    png_icc_set_sRGB(png_ptr,
-                                       &png_ptr->colorspace, profile,
-                                       png_ptr->zstream.adler);
-#                                   endif
-
-                                    /* Steal the profile for info_ptr. */
-                                    if (info_ptr != NULL)
-                                    {
-                                       png_free_data(png_ptr, info_ptr,
-                                          PNG_FREE_ICCP, 0);
-
-                                       info_ptr->iccp_name = png_voidcast(char*,
-                                          png_malloc_base(png_ptr,
-                                          keyword_length+1));
-                                       if (info_ptr->iccp_name != NULL)
-                                       {
-                                          memcpy(info_ptr->iccp_name, keyword,
-                                             keyword_length+1);
-                                          info_ptr->iccp_proflen =
-                                             profile_length;
-                                          info_ptr->iccp_profile = profile;
-                                          png_ptr->read_buffer = NULL; /*steal*/
-                                          info_ptr->free_me |= PNG_FREE_ICCP;
-                                          info_ptr->valid |= PNG_INFO_iCCP;
-                                       }
-
-                                       else
-                                       {
-                                          png_ptr->colorspace.flags |=
-                                             PNG_COLORSPACE_INVALID;
-                                          errmsg = "out of memory";
-                                       }
-                                    }
-
-                                    /* else the profile remains in the read
-                                     * buffer which gets reused for subsequent
-                                     * chunks.
-                                     */
-
-                                    if (info_ptr != NULL)
-                                       png_colorspace_sync(png_ptr, info_ptr);
-
-                                    if (errmsg == NULL)
-                                    {
-                                       png_ptr->zowner = 0;
-                                       return;
-                                    }
-                                 }
-
-                                 else if (size > 0)
-                                    errmsg = "truncated";
-
-#ifndef __COVERITY__
-                                 else
-                                    errmsg = png_ptr->zstream.msg;
-#endif
-                              }
-
-                              /* else png_icc_check_tag_table output an error */
-                           }
-
-                           else /* profile truncated */
-                              errmsg = png_ptr->zstream.msg;
-                        }
-
-                        else
-                           errmsg = "out of memory";
-                     }
-
-                     /* else png_icc_check_header output an error */
-                  }
-
-                  /* else png_icc_check_length output an error */
-               }
-
-               else /* profile truncated */
-                  errmsg = png_ptr->zstream.msg;
-
-               /* Release the stream */
-               png_ptr->zowner = 0;
-            }
-
-            else /* png_inflate_claim failed */
-               errmsg = png_ptr->zstream.msg;
-         }
-
-         else
-            errmsg = "bad compression method"; /* or missing */
-      }
-
-      else
-         errmsg = "bad keyword";
-   }
-
-   else
-      errmsg = "too many profiles";
-
-   /* Failure: the reason is in 'errmsg' */
-   if (finished == 0)
-      png_crc_finish(png_ptr, length);
-
-   png_ptr->colorspace.flags |= PNG_COLORSPACE_INVALID;
-   png_colorspace_sync(png_ptr, info_ptr);
-   if (errmsg != NULL) /* else already output */
-      png_chunk_benign_error(png_ptr, errmsg);
-}
-#endif /* READ_iCCP */
-
-#ifdef PNG_READ_sPLT_SUPPORTED
-void /* PRIVATE */
-png_handle_sPLT(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
-/* Note: this does not properly handle chunks that are > 64K under DOS */
-{
-   png_bytep entry_start, buffer;
-   png_sPLT_t new_palette;
-   png_sPLT_entryp pp;
-   png_uint_32 data_length;
-   int entry_size, i;
-   png_uint_32 skip = 0;
-   png_uint_32 dl;
-   png_size_t max_dl;
-
-   png_debug(1, "in png_handle_sPLT");
-
-#ifdef PNG_USER_LIMITS_SUPPORTED
-   if (png_ptr->user_chunk_cache_max != 0)
-   {
-      if (png_ptr->user_chunk_cache_max == 1)
-      {
-         png_crc_finish(png_ptr, length);
-         return;
-      }
-
-      if (--png_ptr->user_chunk_cache_max == 1)
-      {
-         png_warning(png_ptr, "No space in chunk cache for sPLT");
-         png_crc_finish(png_ptr, length);
-         return;
-      }
-   }
-#endif
-
-   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
-      png_chunk_error(png_ptr, "missing IHDR");
-
-   else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "out of place");
-      return;
-   }
-
-#ifdef PNG_MAX_MALLOC_64K
-   if (length > 65535U)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "too large to fit in memory");
-      return;
-   }
-#endif
-
-   buffer = png_read_buffer(png_ptr, length+1, 2/*silent*/);
-   if (buffer == NULL)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "out of memory");
-      return;
-   }
-
-
-   /* WARNING: this may break if size_t is less than 32 bits; it is assumed
-    * that the PNG_MAX_MALLOC_64K test is enabled in this case, but this is a
-    * potential breakage point if the types in pngconf.h aren't exactly right.
-    */
-   png_crc_read(png_ptr, buffer, length);
-
-   if (png_crc_finish(png_ptr, skip) != 0)
-      return;
-
-   buffer[length] = 0;
-
-   for (entry_start = buffer; *entry_start; entry_start++)
-      /* Empty loop to find end of name */ ;
-
-   ++entry_start;
-
-   /* A sample depth should follow the separator, and we should be on it  */
-   if (length < 2U || entry_start > buffer + (length - 2U))
-   {
-      png_warning(png_ptr, "malformed sPLT chunk");
-      return;
-   }
-
-   new_palette.depth = *entry_start++;
-   entry_size = (new_palette.depth == 8 ? 6 : 10);
-   /* This must fit in a png_uint_32 because it is derived from the original
-    * chunk data length.
-    */
-   data_length = length - (png_uint_32)(entry_start - buffer);
-
-   /* Integrity-check the data length */
-   if ((data_length % entry_size) != 0)
-   {
-      png_warning(png_ptr, "sPLT chunk has bad length");
-      return;
-   }
-
-   dl = (png_int_32)(data_length / entry_size);
-   max_dl = PNG_SIZE_MAX / (sizeof (png_sPLT_entry));
-
-   if (dl > max_dl)
-   {
-      png_warning(png_ptr, "sPLT chunk too long");
-      return;
-   }
-
-   new_palette.nentries = (png_int_32)(data_length / entry_size);
-
-   new_palette.entries = (png_sPLT_entryp)png_malloc_warn(
-       png_ptr, new_palette.nentries * (sizeof (png_sPLT_entry)));
-
-   if (new_palette.entries == NULL)
-   {
-      png_warning(png_ptr, "sPLT chunk requires too much memory");
-      return;
-   }
-
-#ifdef PNG_POINTER_INDEXING_SUPPORTED
-   for (i = 0; i < new_palette.nentries; i++)
-   {
-      pp = new_palette.entries + i;
-
-      if (new_palette.depth == 8)
-      {
-         pp->red = *entry_start++;
-         pp->green = *entry_start++;
-         pp->blue = *entry_start++;
-         pp->alpha = *entry_start++;
-      }
-
-      else
-      {
-         pp->red   = png_get_uint_16(entry_start); entry_start += 2;
-         pp->green = png_get_uint_16(entry_start); entry_start += 2;
-         pp->blue  = png_get_uint_16(entry_start); entry_start += 2;
-         pp->alpha = png_get_uint_16(entry_start); entry_start += 2;
-      }
-
-      pp->frequency = png_get_uint_16(entry_start); entry_start += 2;
-   }
-#else
-   pp = new_palette.entries;
-
-   for (i = 0; i < new_palette.nentries; i++)
-   {
-
-      if (new_palette.depth == 8)
-      {
-         pp[i].red   = *entry_start++;
-         pp[i].green = *entry_start++;
-         pp[i].blue  = *entry_start++;
-         pp[i].alpha = *entry_start++;
-      }
-
-      else
-      {
-         pp[i].red   = png_get_uint_16(entry_start); entry_start += 2;
-         pp[i].green = png_get_uint_16(entry_start); entry_start += 2;
-         pp[i].blue  = png_get_uint_16(entry_start); entry_start += 2;
-         pp[i].alpha = png_get_uint_16(entry_start); entry_start += 2;
-      }
-
-      pp[i].frequency = png_get_uint_16(entry_start); entry_start += 2;
-   }
-#endif
-
-   /* Discard all chunk data except the name and stash that */
-   new_palette.name = (png_charp)buffer;
-
-   png_set_sPLT(png_ptr, info_ptr, &new_palette, 1);
-
-   png_free(png_ptr, new_palette.entries);
-}
-#endif /* READ_sPLT */
-
-#ifdef PNG_READ_tRNS_SUPPORTED
-void /* PRIVATE */
-png_handle_tRNS(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
-{
-   png_byte readbuf[PNG_MAX_PALETTE_LENGTH];
-
-   png_debug(1, "in png_handle_tRNS");
-
-   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
-      png_chunk_error(png_ptr, "missing IHDR");
-
-   else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "out of place");
-      return;
-   }
-
-   else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_tRNS) != 0)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "duplicate");
-      return;
-   }
-
-   if (png_ptr->color_type == PNG_COLOR_TYPE_GRAY)
-   {
-      png_byte buf[2];
-
-      if (length != 2)
-      {
-         png_crc_finish(png_ptr, length);
-         png_chunk_benign_error(png_ptr, "invalid");
-         return;
-      }
-
-      png_crc_read(png_ptr, buf, 2);
-      png_ptr->num_trans = 1;
-      png_ptr->trans_color.gray = png_get_uint_16(buf);
-   }
-
-   else if (png_ptr->color_type == PNG_COLOR_TYPE_RGB)
-   {
-      png_byte buf[6];
-
-      if (length != 6)
-      {
-         png_crc_finish(png_ptr, length);
-         png_chunk_benign_error(png_ptr, "invalid");
-         return;
-      }
-
-      png_crc_read(png_ptr, buf, length);
-      png_ptr->num_trans = 1;
-      png_ptr->trans_color.red = png_get_uint_16(buf);
-      png_ptr->trans_color.green = png_get_uint_16(buf + 2);
-      png_ptr->trans_color.blue = png_get_uint_16(buf + 4);
-   }
-
-   else if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
-   {
-      if ((png_ptr->mode & PNG_HAVE_PLTE) == 0)
-      {
-         /* TODO: is this actually an error in the ISO spec? */
-         png_crc_finish(png_ptr, length);
-         png_chunk_benign_error(png_ptr, "out of place");
-         return;
-      }
-
-      if (length > (unsigned int) png_ptr->num_palette ||
-         length > (unsigned int) PNG_MAX_PALETTE_LENGTH ||
-         length == 0)
-      {
-         png_crc_finish(png_ptr, length);
-         png_chunk_benign_error(png_ptr, "invalid");
-         return;
-      }
-
-      png_crc_read(png_ptr, readbuf, length);
-      png_ptr->num_trans = (png_uint_16)length;
-   }
-
-   else
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "invalid with alpha channel");
-      return;
-   }
-
-   if (png_crc_finish(png_ptr, 0) != 0)
-   {
-      png_ptr->num_trans = 0;
-      return;
-   }
-
-   /* TODO: this is a horrible side effect in the palette case because the
-    * png_struct ends up with a pointer to the tRNS buffer owned by the
-    * png_info.  Fix this.
-    */
-   png_set_tRNS(png_ptr, info_ptr, readbuf, png_ptr->num_trans,
-       &(png_ptr->trans_color));
-}
-#endif
-
-#ifdef PNG_READ_bKGD_SUPPORTED
-void /* PRIVATE */
-png_handle_bKGD(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
-{
-   unsigned int truelen;
-   png_byte buf[6];
-   png_color_16 background;
-
-   png_debug(1, "in png_handle_bKGD");
-
-   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
-      png_chunk_error(png_ptr, "missing IHDR");
-
-   else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0 ||
-       (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
-       (png_ptr->mode & PNG_HAVE_PLTE) == 0))
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "out of place");
-      return;
-   }
-
-   else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_bKGD) != 0)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "duplicate");
-      return;
-   }
-
-   if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
-      truelen = 1;
-
-   else if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
-      truelen = 6;
-
-   else
-      truelen = 2;
-
-   if (length != truelen)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "invalid");
-      return;
-   }
-
-   png_crc_read(png_ptr, buf, truelen);
-
-   if (png_crc_finish(png_ptr, 0) != 0)
-      return;
-
-   /* We convert the index value into RGB components so that we can allow
-    * arbitrary RGB values for background when we have transparency, and
-    * so it is easy to determine the RGB values of the background color
-    * from the info_ptr struct.
-    */
-   if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
-   {
-      background.index = buf[0];
-
-      if (info_ptr != NULL && info_ptr->num_palette != 0)
-      {
-         if (buf[0] >= info_ptr->num_palette)
-         {
-            png_chunk_benign_error(png_ptr, "invalid index");
-            return;
-         }
-
-         background.red = (png_uint_16)png_ptr->palette[buf[0]].red;
-         background.green = (png_uint_16)png_ptr->palette[buf[0]].green;
-         background.blue = (png_uint_16)png_ptr->palette[buf[0]].blue;
-      }
-
-      else
-         background.red = background.green = background.blue = 0;
-
-      background.gray = 0;
-   }
-
-   else if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) == 0) /* GRAY */
-   {
-      background.index = 0;
-      background.red =
-      background.green =
-      background.blue =
-      background.gray = png_get_uint_16(buf);
-   }
-
-   else
-   {
-      background.index = 0;
-      background.red = png_get_uint_16(buf);
-      background.green = png_get_uint_16(buf + 2);
-      background.blue = png_get_uint_16(buf + 4);
-      background.gray = 0;
-   }
-
-   png_set_bKGD(png_ptr, info_ptr, &background);
-}
-#endif
-
-#ifdef PNG_READ_hIST_SUPPORTED
-void /* PRIVATE */
-png_handle_hIST(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
-{
-   unsigned int num, i;
-   png_uint_16 readbuf[PNG_MAX_PALETTE_LENGTH];
-
-   png_debug(1, "in png_handle_hIST");
-
-   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
-      png_chunk_error(png_ptr, "missing IHDR");
-
-   else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0 ||
-       (png_ptr->mode & PNG_HAVE_PLTE) == 0)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "out of place");
-      return;
-   }
-
-   else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_hIST) != 0)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "duplicate");
-      return;
-   }
-
-   num = length / 2 ;
-
-   if (num != (unsigned int) png_ptr->num_palette ||
-       num > (unsigned int) PNG_MAX_PALETTE_LENGTH)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "invalid");
-      return;
-   }
-
-   for (i = 0; i < num; i++)
-   {
-      png_byte buf[2];
-
-      png_crc_read(png_ptr, buf, 2);
-      readbuf[i] = png_get_uint_16(buf);
-   }
-
-   if (png_crc_finish(png_ptr, 0) != 0)
-      return;
-
-   png_set_hIST(png_ptr, info_ptr, readbuf);
-}
-#endif
-
-#ifdef PNG_READ_pHYs_SUPPORTED
-void /* PRIVATE */
-png_handle_pHYs(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
-{
-   png_byte buf[9];
-   png_uint_32 res_x, res_y;
-   int unit_type;
-
-   png_debug(1, "in png_handle_pHYs");
-
-   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
-      png_chunk_error(png_ptr, "missing IHDR");
-
-   else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "out of place");
-      return;
-   }
-
-   else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_pHYs) != 0)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "duplicate");
-      return;
-   }
-
-   if (length != 9)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "invalid");
-      return;
-   }
-
-   png_crc_read(png_ptr, buf, 9);
-
-   if (png_crc_finish(png_ptr, 0) != 0)
-      return;
-
-   res_x = png_get_uint_32(buf);
-   res_y = png_get_uint_32(buf + 4);
-   unit_type = buf[8];
-   png_set_pHYs(png_ptr, info_ptr, res_x, res_y, unit_type);
-}
-#endif
-
-#ifdef PNG_READ_oFFs_SUPPORTED
-void /* PRIVATE */
-png_handle_oFFs(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
-{
-   png_byte buf[9];
-   png_int_32 offset_x, offset_y;
-   int unit_type;
-
-   png_debug(1, "in png_handle_oFFs");
-
-   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
-      png_chunk_error(png_ptr, "missing IHDR");
-
-   else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "out of place");
-      return;
-   }
-
-   else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_oFFs) != 0)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "duplicate");
-      return;
-   }
-
-   if (length != 9)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "invalid");
-      return;
-   }
-
-   png_crc_read(png_ptr, buf, 9);
-
-   if (png_crc_finish(png_ptr, 0) != 0)
-      return;
-
-   offset_x = png_get_int_32(buf);
-   offset_y = png_get_int_32(buf + 4);
-   unit_type = buf[8];
-   png_set_oFFs(png_ptr, info_ptr, offset_x, offset_y, unit_type);
-}
-#endif
-
-#ifdef PNG_READ_pCAL_SUPPORTED
-/* Read the pCAL chunk (described in the PNG Extensions document) */
-void /* PRIVATE */
-png_handle_pCAL(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
-{
-   png_int_32 X0, X1;
-   png_byte type, nparams;
-   png_bytep buffer, buf, units, endptr;
-   png_charpp params;
-   int i;
-
-   png_debug(1, "in png_handle_pCAL");
-
-   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
-      png_chunk_error(png_ptr, "missing IHDR");
-
-   else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "out of place");
-      return;
-   }
-
-   else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_pCAL) != 0)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "duplicate");
-      return;
-   }
-
-   png_debug1(2, "Allocating and reading pCAL chunk data (%u bytes)",
-       length + 1);
-
-   buffer = png_read_buffer(png_ptr, length+1, 2/*silent*/);
-
-   if (buffer == NULL)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "out of memory");
-      return;
-   }
-
-   png_crc_read(png_ptr, buffer, length);
-
-   if (png_crc_finish(png_ptr, 0) != 0)
-      return;
-
-   buffer[length] = 0; /* Null terminate the last string */
-
-   png_debug(3, "Finding end of pCAL purpose string");
-   for (buf = buffer; *buf; buf++)
-      /* Empty loop */ ;
-
-   endptr = buffer + length;
-
-   /* We need to have at least 12 bytes after the purpose string
-    * in order to get the parameter information.
-    */
-   if (endptr - buf <= 12)
-   {
-      png_chunk_benign_error(png_ptr, "invalid");
-      return;
-   }
-
-   png_debug(3, "Reading pCAL X0, X1, type, nparams, and units");
-   X0 = png_get_int_32((png_bytep)buf+1);
-   X1 = png_get_int_32((png_bytep)buf+5);
-   type = buf[9];
-   nparams = buf[10];
-   units = buf + 11;
-
-   png_debug(3, "Checking pCAL equation type and number of parameters");
-   /* Check that we have the right number of parameters for known
-    * equation types.
-    */
-   if ((type == PNG_EQUATION_LINEAR && nparams != 2) ||
-       (type == PNG_EQUATION_BASE_E && nparams != 3) ||
-       (type == PNG_EQUATION_ARBITRARY && nparams != 3) ||
-       (type == PNG_EQUATION_HYPERBOLIC && nparams != 4))
-   {
-      png_chunk_benign_error(png_ptr, "invalid parameter count");
-      return;
-   }
-
-   else if (type >= PNG_EQUATION_LAST)
-   {
-      png_chunk_benign_error(png_ptr, "unrecognized equation type");
-   }
-
-   for (buf = units; *buf; buf++)
-      /* Empty loop to move past the units string. */ ;
-
-   png_debug(3, "Allocating pCAL parameters array");
-
-   params = png_voidcast(png_charpp, png_malloc_warn(png_ptr,
-       nparams * (sizeof (png_charp))));
-
-   if (params == NULL)
-   {
-      png_chunk_benign_error(png_ptr, "out of memory");
-      return;
-   }
-
-   /* Get pointers to the start of each parameter string. */
-   for (i = 0; i < nparams; i++)
-   {
-      buf++; /* Skip the null string terminator from previous parameter. */
-
-      png_debug1(3, "Reading pCAL parameter %d", i);
-
-      for (params[i] = (png_charp)buf; buf <= endptr && *buf != 0; buf++)
-         /* Empty loop to move past each parameter string */ ;
-
-      /* Make sure we haven't run out of data yet */
-      if (buf > endptr)
-      {
-         png_free(png_ptr, params);
-         png_chunk_benign_error(png_ptr, "invalid data");
-         return;
-      }
-   }
-
-   png_set_pCAL(png_ptr, info_ptr, (png_charp)buffer, X0, X1, type, nparams,
-      (png_charp)units, params);
-
-   png_free(png_ptr, params);
-}
-#endif
-
-#ifdef PNG_READ_sCAL_SUPPORTED
-/* Read the sCAL chunk */
-void /* PRIVATE */
-png_handle_sCAL(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
-{
-   png_bytep buffer;
-   png_size_t i;
-   int state;
-
-   png_debug(1, "in png_handle_sCAL");
-
-   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
-      png_chunk_error(png_ptr, "missing IHDR");
-
-   else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "out of place");
-      return;
-   }
-
-   else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_sCAL) != 0)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "duplicate");
-      return;
-   }
-
-   /* Need unit type, width, \0, height: minimum 4 bytes */
-   else if (length < 4)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "invalid");
-      return;
-   }
-
-   png_debug1(2, "Allocating and reading sCAL chunk data (%u bytes)",
-      length + 1);
-
-   buffer = png_read_buffer(png_ptr, length+1, 2/*silent*/);
-
-   if (buffer == NULL)
-   {
-      png_chunk_benign_error(png_ptr, "out of memory");
-      png_crc_finish(png_ptr, length);
-      return;
-   }
-
-   png_crc_read(png_ptr, buffer, length);
-   buffer[length] = 0; /* Null terminate the last string */
-
-   if (png_crc_finish(png_ptr, 0) != 0)
-      return;
-
-   /* Validate the unit. */
-   if (buffer[0] != 1 && buffer[0] != 2)
-   {
-      png_chunk_benign_error(png_ptr, "invalid unit");
-      return;
-   }
-
-   /* Validate the ASCII numbers, need two ASCII numbers separated by
-    * a '\0' and they need to fit exactly in the chunk data.
-    */
-   i = 1;
-   state = 0;
-
-   if (png_check_fp_number((png_const_charp)buffer, length, &state, &i) == 0 ||
-       i >= length || buffer[i++] != 0)
-      png_chunk_benign_error(png_ptr, "bad width format");
-
-   else if (PNG_FP_IS_POSITIVE(state) == 0)
-      png_chunk_benign_error(png_ptr, "non-positive width");
-
-   else
-   {
-      png_size_t heighti = i;
-
-      state = 0;
-      if (png_check_fp_number((png_const_charp)buffer, length,
-          &state, &i) == 0 || i != length)
-         png_chunk_benign_error(png_ptr, "bad height format");
-
-      else if (PNG_FP_IS_POSITIVE(state) == 0)
-         png_chunk_benign_error(png_ptr, "non-positive height");
-
-      else
-         /* This is the (only) success case. */
-         png_set_sCAL_s(png_ptr, info_ptr, buffer[0],
-            (png_charp)buffer+1, (png_charp)buffer+heighti);
-   }
-}
-#endif
-
-#ifdef PNG_READ_tIME_SUPPORTED
-void /* PRIVATE */
-png_handle_tIME(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
-{
-   png_byte buf[7];
-   png_time mod_time;
-
-   png_debug(1, "in png_handle_tIME");
-
-   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
-      png_chunk_error(png_ptr, "missing IHDR");
-
-   else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_tIME) != 0)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "duplicate");
-      return;
-   }
-
-   if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
-      png_ptr->mode |= PNG_AFTER_IDAT;
-
-   if (length != 7)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "invalid");
-      return;
-   }
-
-   png_crc_read(png_ptr, buf, 7);
-
-   if (png_crc_finish(png_ptr, 0) != 0)
-      return;
-
-   mod_time.second = buf[6];
-   mod_time.minute = buf[5];
-   mod_time.hour = buf[4];
-   mod_time.day = buf[3];
-   mod_time.month = buf[2];
-   mod_time.year = png_get_uint_16(buf);
-
-   png_set_tIME(png_ptr, info_ptr, &mod_time);
-}
-#endif
-
-#ifdef PNG_READ_tEXt_SUPPORTED
-/* Note: this does not properly handle chunks that are > 64K under DOS */
-void /* PRIVATE */
-png_handle_tEXt(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
-{
-   png_text  text_info;
-   png_bytep buffer;
-   png_charp key;
-   png_charp text;
-   png_uint_32 skip = 0;
-
-   png_debug(1, "in png_handle_tEXt");
-
-#ifdef PNG_USER_LIMITS_SUPPORTED
-   if (png_ptr->user_chunk_cache_max != 0)
-   {
-      if (png_ptr->user_chunk_cache_max == 1)
-      {
-         png_crc_finish(png_ptr, length);
-         return;
-      }
-
-      if (--png_ptr->user_chunk_cache_max == 1)
-      {
-         png_crc_finish(png_ptr, length);
-         png_chunk_benign_error(png_ptr, "no space in chunk cache");
-         return;
-      }
-   }
-#endif
-
-   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
-      png_chunk_error(png_ptr, "missing IHDR");
-
-   if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
-      png_ptr->mode |= PNG_AFTER_IDAT;
-
-#ifdef PNG_MAX_MALLOC_64K
-   if (length > 65535U)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "too large to fit in memory");
-      return;
-   }
-#endif
-
-   buffer = png_read_buffer(png_ptr, length+1, 1/*warn*/);
-
-   if (buffer == NULL)
-   {
-     png_chunk_benign_error(png_ptr, "out of memory");
-     return;
-   }
-
-   png_crc_read(png_ptr, buffer, length);
-
-   if (png_crc_finish(png_ptr, skip) != 0)
-      return;
-
-   key = (png_charp)buffer;
-   key[length] = 0;
-
-   for (text = key; *text; text++)
-      /* Empty loop to find end of key */ ;
-
-   if (text != key + length)
-      text++;
-
-   text_info.compression = PNG_TEXT_COMPRESSION_NONE;
-   text_info.key = key;
-   text_info.lang = NULL;
-   text_info.lang_key = NULL;
-   text_info.itxt_length = 0;
-   text_info.text = text;
-   text_info.text_length = strlen(text);
-
-   if (png_set_text_2(png_ptr, info_ptr, &text_info, 1) != 0)
-      png_warning(png_ptr, "Insufficient memory to process text chunk");
-}
-#endif
-
-#ifdef PNG_READ_zTXt_SUPPORTED
-/* Note: this does not correctly handle chunks that are > 64K under DOS */
-void /* PRIVATE */
-png_handle_zTXt(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
-{
-   png_const_charp errmsg = NULL;
-   png_bytep       buffer;
-   png_uint_32     keyword_length;
-
-   png_debug(1, "in png_handle_zTXt");
-
-#ifdef PNG_USER_LIMITS_SUPPORTED
-   if (png_ptr->user_chunk_cache_max != 0)
-   {
-      if (png_ptr->user_chunk_cache_max == 1)
-      {
-         png_crc_finish(png_ptr, length);
-         return;
-      }
-
-      if (--png_ptr->user_chunk_cache_max == 1)
-      {
-         png_crc_finish(png_ptr, length);
-         png_chunk_benign_error(png_ptr, "no space in chunk cache");
-         return;
-      }
-   }
-#endif
-
-   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
-      png_chunk_error(png_ptr, "missing IHDR");
-
-   if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
-      png_ptr->mode |= PNG_AFTER_IDAT;
-
-   buffer = png_read_buffer(png_ptr, length, 2/*silent*/);
-
-   if (buffer == NULL)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "out of memory");
-      return;
-   }
-
-   png_crc_read(png_ptr, buffer, length);
-
-   if (png_crc_finish(png_ptr, 0) != 0)
-      return;
-
-   /* TODO: also check that the keyword contents match the spec! */
-   for (keyword_length = 0;
-      keyword_length < length && buffer[keyword_length] != 0;
-      ++keyword_length)
-      /* Empty loop to find end of name */ ;
-
-   if (keyword_length > 79 || keyword_length < 1)
-      errmsg = "bad keyword";
-
-   /* zTXt must have some LZ data after the keyword, although it may expand to
-    * zero bytes; we need a '\0' at the end of the keyword, the compression type
-    * then the LZ data:
-    */
-   else if (keyword_length + 3 > length)
-      errmsg = "truncated";
-
-   else if (buffer[keyword_length+1] != PNG_COMPRESSION_TYPE_BASE)
-      errmsg = "unknown compression type";
-
-   else
-   {
-      png_alloc_size_t uncompressed_length = PNG_SIZE_MAX;
-
-      /* TODO: at present png_decompress_chunk imposes a single application
-       * level memory limit, this should be split to different values for iCCP
-       * and text chunks.
-       */
-      if (png_decompress_chunk(png_ptr, length, keyword_length+2,
-         &uncompressed_length, 1/*terminate*/) == Z_STREAM_END)
-      {
-         png_text text;
-
-         /* It worked; png_ptr->read_buffer now looks like a tEXt chunk except
-          * for the extra compression type byte and the fact that it isn't
-          * necessarily '\0' terminated.
-          */
-         buffer = png_ptr->read_buffer;
-         buffer[uncompressed_length+(keyword_length+2)] = 0;
-
-         text.compression = PNG_TEXT_COMPRESSION_zTXt;
-         text.key = (png_charp)buffer;
-         text.text = (png_charp)(buffer + keyword_length+2);
-         text.text_length = uncompressed_length;
-         text.itxt_length = 0;
-         text.lang = NULL;
-         text.lang_key = NULL;
-
-         if (png_set_text_2(png_ptr, info_ptr, &text, 1) != 0)
-            errmsg = "insufficient memory";
-      }
-
-      else
-         errmsg = png_ptr->zstream.msg;
-   }
-
-   if (errmsg != NULL)
-      png_chunk_benign_error(png_ptr, errmsg);
-}
-#endif
-
-#ifdef PNG_READ_iTXt_SUPPORTED
-/* Note: this does not correctly handle chunks that are > 64K under DOS */
-void /* PRIVATE */
-png_handle_iTXt(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
-{
-   png_const_charp errmsg = NULL;
-   png_bytep buffer;
-   png_uint_32 prefix_length;
-
-   png_debug(1, "in png_handle_iTXt");
-
-#ifdef PNG_USER_LIMITS_SUPPORTED
-   if (png_ptr->user_chunk_cache_max != 0)
-   {
-      if (png_ptr->user_chunk_cache_max == 1)
-      {
-         png_crc_finish(png_ptr, length);
-         return;
-      }
-
-      if (--png_ptr->user_chunk_cache_max == 1)
-      {
-         png_crc_finish(png_ptr, length);
-         png_chunk_benign_error(png_ptr, "no space in chunk cache");
-         return;
-      }
-   }
-#endif
-
-   if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
-      png_chunk_error(png_ptr, "missing IHDR");
-
-   if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
-      png_ptr->mode |= PNG_AFTER_IDAT;
-
-   buffer = png_read_buffer(png_ptr, length+1, 1/*warn*/);
-
-   if (buffer == NULL)
-   {
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "out of memory");
-      return;
-   }
-
-   png_crc_read(png_ptr, buffer, length);
-
-   if (png_crc_finish(png_ptr, 0) != 0)
-      return;
-
-   /* First the keyword. */
-   for (prefix_length=0;
-      prefix_length < length && buffer[prefix_length] != 0;
-      ++prefix_length)
-      /* Empty loop */ ;
-
-   /* Perform a basic check on the keyword length here. */
-   if (prefix_length > 79 || prefix_length < 1)
-      errmsg = "bad keyword";
-
-   /* Expect keyword, compression flag, compression type, language, translated
-    * keyword (both may be empty but are 0 terminated) then the text, which may
-    * be empty.
-    */
-   else if (prefix_length + 5 > length)
-      errmsg = "truncated";
-
-   else if (buffer[prefix_length+1] == 0 ||
-      (buffer[prefix_length+1] == 1 &&
-      buffer[prefix_length+2] == PNG_COMPRESSION_TYPE_BASE))
-   {
-      int compressed = buffer[prefix_length+1] != 0;
-      png_uint_32 language_offset, translated_keyword_offset;
-      png_alloc_size_t uncompressed_length = 0;
-
-      /* Now the language tag */
-      prefix_length += 3;
-      language_offset = prefix_length;
-
-      for (; prefix_length < length && buffer[prefix_length] != 0;
-         ++prefix_length)
-         /* Empty loop */ ;
-
-      /* WARNING: the length may be invalid here, this is checked below. */
-      translated_keyword_offset = ++prefix_length;
-
-      for (; prefix_length < length && buffer[prefix_length] != 0;
-         ++prefix_length)
-         /* Empty loop */ ;
-
-      /* prefix_length should now be at the trailing '\0' of the translated
-       * keyword, but it may already be over the end.  None of this arithmetic
-       * can overflow because chunks are at most 2^31 bytes long, but on 16-bit
-       * systems the available allocation may overflow.
-       */
-      ++prefix_length;
-
-      if (compressed == 0 && prefix_length <= length)
-         uncompressed_length = length - prefix_length;
-
-      else if (compressed != 0 && prefix_length < length)
-      {
-         uncompressed_length = PNG_SIZE_MAX;
-
-         /* TODO: at present png_decompress_chunk imposes a single application
-          * level memory limit, this should be split to different values for
-          * iCCP and text chunks.
-          */
-         if (png_decompress_chunk(png_ptr, length, prefix_length,
-            &uncompressed_length, 1/*terminate*/) == Z_STREAM_END)
-            buffer = png_ptr->read_buffer;
-
-         else
-            errmsg = png_ptr->zstream.msg;
-      }
-
-      else
-         errmsg = "truncated";
-
-      if (errmsg == NULL)
-      {
-         png_text text;
-
-         buffer[uncompressed_length+prefix_length] = 0;
-
-         if (compressed == 0)
-            text.compression = PNG_ITXT_COMPRESSION_NONE;
-
-         else
-            text.compression = PNG_ITXT_COMPRESSION_zTXt;
-
-         text.key = (png_charp)buffer;
-         text.lang = (png_charp)buffer + language_offset;
-         text.lang_key = (png_charp)buffer + translated_keyword_offset;
-         text.text = (png_charp)buffer + prefix_length;
-         text.text_length = 0;
-         text.itxt_length = uncompressed_length;
-
-         if (png_set_text_2(png_ptr, info_ptr, &text, 1) != 0)
-            errmsg = "insufficient memory";
-      }
-   }
-
-   else
-      errmsg = "bad compression info";
-
-   if (errmsg != NULL)
-      png_chunk_benign_error(png_ptr, errmsg);
-}
-#endif
-
-#ifdef PNG_READ_UNKNOWN_CHUNKS_SUPPORTED
-/* Utility function for png_handle_unknown; set up png_ptr::unknown_chunk */
-static int
-png_cache_unknown_chunk(png_structrp png_ptr, png_uint_32 length)
-{
-   png_alloc_size_t limit = PNG_SIZE_MAX;
-
-   if (png_ptr->unknown_chunk.data != NULL)
-   {
-      png_free(png_ptr, png_ptr->unknown_chunk.data);
-      png_ptr->unknown_chunk.data = NULL;
-   }
-
-#  ifdef PNG_SET_USER_LIMITS_SUPPORTED
-   if (png_ptr->user_chunk_malloc_max > 0 &&
-       png_ptr->user_chunk_malloc_max < limit)
-      limit = png_ptr->user_chunk_malloc_max;
-
-#  elif PNG_USER_CHUNK_MALLOC_MAX > 0
-   if (PNG_USER_CHUNK_MALLOC_MAX < limit)
-      limit = PNG_USER_CHUNK_MALLOC_MAX;
-#  endif
-
-   if (length <= limit)
-   {
-      PNG_CSTRING_FROM_CHUNK(png_ptr->unknown_chunk.name, png_ptr->chunk_name);
-      /* The following is safe because of the PNG_SIZE_MAX init above */
-      png_ptr->unknown_chunk.size = (png_size_t)length/*SAFE*/;
-      /* 'mode' is a flag array, only the bottom four bits matter here */
-      png_ptr->unknown_chunk.location = (png_byte)png_ptr->mode/*SAFE*/;
-
-      if (length == 0)
-         png_ptr->unknown_chunk.data = NULL;
-
-      else
-      {
-         /* Do a 'warn' here - it is handled below. */
-         png_ptr->unknown_chunk.data = png_voidcast(png_bytep,
-            png_malloc_warn(png_ptr, length));
-      }
-   }
-
-   if (png_ptr->unknown_chunk.data == NULL && length > 0)
-   {
-      /* This is benign because we clean up correctly */
-      png_crc_finish(png_ptr, length);
-      png_chunk_benign_error(png_ptr, "unknown chunk exceeds memory limits");
-      return 0;
-   }
-
-   else
-   {
-      if (length > 0)
-         png_crc_read(png_ptr, png_ptr->unknown_chunk.data, length);
-      png_crc_finish(png_ptr, 0);
-      return 1;
-   }
-}
-#endif /* READ_UNKNOWN_CHUNKS */
-
-/* Handle an unknown, or known but disabled, chunk */
-void /* PRIVATE */
-png_handle_unknown(png_structrp png_ptr, png_inforp info_ptr,
-   png_uint_32 length, int keep)
-{
-   int handled = 0; /* the chunk was handled */
-
-   png_debug(1, "in png_handle_unknown");
-
-#ifdef PNG_READ_UNKNOWN_CHUNKS_SUPPORTED
-   /* NOTE: this code is based on the code in libpng-1.4.12 except for fixing
-    * the bug which meant that setting a non-default behavior for a specific
-    * chunk would be ignored (the default was always used unless a user
-    * callback was installed).
-    *
-    * 'keep' is the value from the png_chunk_unknown_handling, the setting for
-    * this specific chunk_name, if PNG_HANDLE_AS_UNKNOWN_SUPPORTED, if not it
-    * will always be PNG_HANDLE_CHUNK_AS_DEFAULT and it needs to be set here.
-    * This is just an optimization to avoid multiple calls to the lookup
-    * function.
-    */
-#  ifndef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
-#     ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
-   keep = png_chunk_unknown_handling(png_ptr, png_ptr->chunk_name);
-#     endif
-#  endif
-
-   /* One of the following methods will read the chunk or skip it (at least one
-    * of these is always defined because this is the only way to switch on
-    * PNG_READ_UNKNOWN_CHUNKS_SUPPORTED)
-    */
-#  ifdef PNG_READ_USER_CHUNKS_SUPPORTED
-   /* The user callback takes precedence over the chunk keep value, but the
-    * keep value is still required to validate a save of a critical chunk.
-    */
-   if (png_ptr->read_user_chunk_fn != NULL)
-   {
-      if (png_cache_unknown_chunk(png_ptr, length) != 0)
-      {
-         /* Callback to user unknown chunk handler */
-         int ret = (*(png_ptr->read_user_chunk_fn))(png_ptr,
-            &png_ptr->unknown_chunk);
-
-         /* ret is:
-          * negative: An error occurred; png_chunk_error will be called.
-          *     zero: The chunk was not handled, the chunk will be discarded
-          *           unless png_set_keep_unknown_chunks has been used to set
-          *           a 'keep' behavior for this particular chunk, in which
-          *           case that will be used.  A critical chunk will cause an
-          *           error at this point unless it is to be saved.
-          * positive: The chunk was handled, libpng will ignore/discard it.
-          */
-         if (ret < 0)
-            png_chunk_error(png_ptr, "error in user chunk");
-
-         else if (ret == 0)
-         {
-            /* If the keep value is 'default' or 'never' override it, but
-             * still error out on critical chunks unless the keep value is
-             * 'always'  While this is weird it is the behavior in 1.4.12.
-             * A possible improvement would be to obey the value set for the
-             * chunk, but this would be an API change that would probably
-             * damage some applications.
-             *
-             * The png_app_warning below catches the case that matters, where
-             * the application has not set specific save or ignore for this
-             * chunk or global save or ignore.
-             */
-            if (keep < PNG_HANDLE_CHUNK_IF_SAFE)
-            {
-#              ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
-               if (png_ptr->unknown_default < PNG_HANDLE_CHUNK_IF_SAFE)
-               {
-                  png_chunk_warning(png_ptr, "Saving unknown chunk:");
-                  png_app_warning(png_ptr,
-                     "forcing save of an unhandled chunk;"
-                     " please call png_set_keep_unknown_chunks");
-                     /* with keep = PNG_HANDLE_CHUNK_IF_SAFE */
-               }
-#              endif
-               keep = PNG_HANDLE_CHUNK_IF_SAFE;
-            }
-         }
-
-         else /* chunk was handled */
-         {
-            handled = 1;
-            /* Critical chunks can be safely discarded at this point. */
-            keep = PNG_HANDLE_CHUNK_NEVER;
-         }
-      }
-
-      else
-         keep = PNG_HANDLE_CHUNK_NEVER; /* insufficient memory */
-   }
-
-   else
-   /* Use the SAVE_UNKNOWN_CHUNKS code or skip the chunk */
-#  endif /* READ_USER_CHUNKS */
-
-#  ifdef PNG_SAVE_UNKNOWN_CHUNKS_SUPPORTED
-   {
-      /* keep is currently just the per-chunk setting, if there was no
-       * setting change it to the global default now (not that this may
-       * still be AS_DEFAULT) then obtain the cache of the chunk if required,
-       * if not simply skip the chunk.
-       */
-      if (keep == PNG_HANDLE_CHUNK_AS_DEFAULT)
-         keep = png_ptr->unknown_default;
-
-      if (keep == PNG_HANDLE_CHUNK_ALWAYS ||
-         (keep == PNG_HANDLE_CHUNK_IF_SAFE &&
-          PNG_CHUNK_ANCILLARY(png_ptr->chunk_name)))
-      {
-         if (png_cache_unknown_chunk(png_ptr, length) == 0)
-            keep = PNG_HANDLE_CHUNK_NEVER;
-      }
-
-      else
-         png_crc_finish(png_ptr, length);
-   }
-#  else
-#     ifndef PNG_READ_USER_CHUNKS_SUPPORTED
-#        error no method to support READ_UNKNOWN_CHUNKS
-#     endif
-
-   {
-      /* If here there is no read callback pointer set and no support is
-       * compiled in to just save the unknown chunks, so simply skip this
-       * chunk.  If 'keep' is something other than AS_DEFAULT or NEVER then
-       * the app has erroneously asked for unknown chunk saving when there
-       * is no support.
-       */
-      if (keep > PNG_HANDLE_CHUNK_NEVER)
-         png_app_error(png_ptr, "no unknown chunk support available");
-
-      png_crc_finish(png_ptr, length);
-   }
-#  endif
-
-#  ifdef PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED
-   /* Now store the chunk in the chunk list if appropriate, and if the limits
-    * permit it.
-    */
-   if (keep == PNG_HANDLE_CHUNK_ALWAYS ||
-      (keep == PNG_HANDLE_CHUNK_IF_SAFE &&
-       PNG_CHUNK_ANCILLARY(png_ptr->chunk_name)))
-   {
-#     ifdef PNG_USER_LIMITS_SUPPORTED
-      switch (png_ptr->user_chunk_cache_max)
-      {
-         case 2:
-            png_ptr->user_chunk_cache_max = 1;
-            png_chunk_benign_error(png_ptr, "no space in chunk cache");
-            /* FALL THROUGH */
-         case 1:
-            /* NOTE: prior to 1.6.0 this case resulted in an unknown critical
-             * chunk being skipped, now there will be a hard error below.
-             */
-            break;
-
-         default: /* not at limit */
-            --(png_ptr->user_chunk_cache_max);
-            /* FALL THROUGH */
-         case 0: /* no limit */
-#  endif /* USER_LIMITS */
-            /* Here when the limit isn't reached or when limits are compiled
-             * out; store the chunk.
-             */
-            png_set_unknown_chunks(png_ptr, info_ptr,
-               &png_ptr->unknown_chunk, 1);
-            handled = 1;
-#  ifdef PNG_USER_LIMITS_SUPPORTED
-            break;
-      }
-#  endif
-   }
-#  else /* no store support: the chunk must be handled by the user callback */
-   PNG_UNUSED(info_ptr)
-#  endif
-
-   /* Regardless of the error handling below the cached data (if any) can be
-    * freed now.  Notice that the data is not freed if there is a png_error, but
-    * it will be freed by destroy_read_struct.
-    */
-   if (png_ptr->unknown_chunk.data != NULL)
-      png_free(png_ptr, png_ptr->unknown_chunk.data);
-   png_ptr->unknown_chunk.data = NULL;
-
-#else /* !PNG_READ_UNKNOWN_CHUNKS_SUPPORTED */
-   /* There is no support to read an unknown chunk, so just skip it. */
-   png_crc_finish(png_ptr, length);
-   PNG_UNUSED(info_ptr)
-   PNG_UNUSED(keep)
-#endif /* !READ_UNKNOWN_CHUNKS */
-
-   /* Check for unhandled critical chunks */
-   if (handled == 0 && PNG_CHUNK_CRITICAL(png_ptr->chunk_name))
-      png_chunk_error(png_ptr, "unhandled critical chunk");
-}
-
-/* This function is called to verify that a chunk name is valid.
- * This function can't have the "critical chunk check" incorporated
- * into it, since in the future we will need to be able to call user
- * functions to handle unknown critical chunks after we check that
- * the chunk name itself is valid.
- */
-
-/* Bit hacking: the test for an invalid byte in the 4 byte chunk name is:
- *
- * ((c) < 65 || (c) > 122 || ((c) > 90 && (c) < 97))
- */
-
-void /* PRIVATE */
-png_check_chunk_name(png_structrp png_ptr, png_uint_32 chunk_name)
-{
-   int i;
-
-   png_debug(1, "in png_check_chunk_name");
-
-   for (i=1; i<=4; ++i)
-   {
-      int c = chunk_name & 0xff;
-
-      if (c < 65 || c > 122 || (c > 90 && c < 97))
-         png_chunk_error(png_ptr, "invalid chunk type");
-
-      chunk_name >>= 8;
-   }
-}
-
-/* Combines the row recently read in with the existing pixels in the row.  This
- * routine takes care of alpha and transparency if requested.  This routine also
- * handles the two methods of progressive display of interlaced images,
- * depending on the 'display' value; if 'display' is true then the whole row
- * (dp) is filled from the start by replicating the available pixels.  If
- * 'display' is false only those pixels present in the pass are filled in.
- */
-void /* PRIVATE */
-png_combine_row(png_const_structrp png_ptr, png_bytep dp, int display)
-{
-   unsigned int pixel_depth = png_ptr->transformed_pixel_depth;
-   png_const_bytep sp = png_ptr->row_buf + 1;
-   png_alloc_size_t row_width = png_ptr->width;
-   unsigned int pass = png_ptr->pass;
-   png_bytep end_ptr = 0;
-   png_byte end_byte = 0;
-   unsigned int end_mask;
-
-   png_debug(1, "in png_combine_row");
-
-   /* Added in 1.5.6: it should not be possible to enter this routine until at
-    * least one row has been read from the PNG data and transformed.
-    */
-   if (pixel_depth == 0)
-      png_error(png_ptr, "internal row logic error");
-
-   /* Added in 1.5.4: the pixel depth should match the information returned by
-    * any call to png_read_update_info at this point.  Do not continue if we got
-    * this wrong.
-    */
-   if (png_ptr->info_rowbytes != 0 && png_ptr->info_rowbytes !=
-          PNG_ROWBYTES(pixel_depth, row_width))
-      png_error(png_ptr, "internal row size calculation error");
-
-   /* Don't expect this to ever happen: */
-   if (row_width == 0)
-      png_error(png_ptr, "internal row width error");
-
-   /* Preserve the last byte in cases where only part of it will be overwritten,
-    * the multiply below may overflow, we don't care because ANSI-C guarantees
-    * we get the low bits.
-    */
-   end_mask = (pixel_depth * row_width) & 7;
-   if (end_mask != 0)
-   {
-      /* end_ptr == NULL is a flag to say do nothing */
-      end_ptr = dp + PNG_ROWBYTES(pixel_depth, row_width) - 1;
-      end_byte = *end_ptr;
-#     ifdef PNG_READ_PACKSWAP_SUPPORTED
-      if ((png_ptr->transformations & PNG_PACKSWAP) != 0)
-         /* little-endian byte */
-         end_mask = 0xff << end_mask;
-
-      else /* big-endian byte */
-#     endif
-      end_mask = 0xff >> end_mask;
-      /* end_mask is now the bits to *keep* from the destination row */
-   }
-
-   /* For non-interlaced images this reduces to a memcpy(). A memcpy()
-    * will also happen if interlacing isn't supported or if the application
-    * does not call png_set_interlace_handling().  In the latter cases the
-    * caller just gets a sequence of the unexpanded rows from each interlace
-    * pass.
-    */
-#ifdef PNG_READ_INTERLACING_SUPPORTED
-   if (png_ptr->interlaced != 0 &&
-       (png_ptr->transformations & PNG_INTERLACE) != 0 &&
-       pass < 6 && (display == 0 ||
-       /* The following copies everything for 'display' on passes 0, 2 and 4. */
-       (display == 1 && (pass & 1) != 0)))
-   {
-      /* Narrow images may have no bits in a pass; the caller should handle
-       * this, but this test is cheap:
-       */
-      if (row_width <= PNG_PASS_START_COL(pass))
-         return;
-
-      if (pixel_depth < 8)
-      {
-         /* For pixel depths up to 4 bpp the 8-pixel mask can be expanded to fit
-          * into 32 bits, then a single loop over the bytes using the four byte
-          * values in the 32-bit mask can be used.  For the 'display' option the
-          * expanded mask may also not require any masking within a byte.  To
-          * make this work the PACKSWAP option must be taken into account - it
-          * simply requires the pixels to be reversed in each byte.
-          *
-          * The 'regular' case requires a mask for each of the first 6 passes,
-          * the 'display' case does a copy for the even passes in the range
-          * 0..6.  This has already been handled in the test above.
-          *
-          * The masks are arranged as four bytes with the first byte to use in
-          * the lowest bits (little-endian) regardless of the order (PACKSWAP or
-          * not) of the pixels in each byte.
-          *
-          * NOTE: the whole of this logic depends on the caller of this function
-          * only calling it on rows appropriate to the pass.  This function only
-          * understands the 'x' logic; the 'y' logic is handled by the caller.
-          *
-          * The following defines allow generation of compile time constant bit
-          * masks for each pixel depth and each possibility of swapped or not
-          * swapped bytes.  Pass 'p' is in the range 0..6; 'x', a pixel index,
-          * is in the range 0..7; and the result is 1 if the pixel is to be
-          * copied in the pass, 0 if not.  'S' is for the sparkle method, 'B'
-          * for the block method.
-          *
-          * With some compilers a compile time expression of the general form:
-          *
-          *    (shift >= 32) ? (a >> (shift-32)) : (b >> shift)
-          *
-          * Produces warnings with values of 'shift' in the range 33 to 63
-          * because the right hand side of the ?: expression is evaluated by
-          * the compiler even though it isn't used.  Microsoft Visual C (various
-          * versions) and the Intel C compiler are known to do this.  To avoid
-          * this the following macros are used in 1.5.6.  This is a temporary
-          * solution to avoid destabilizing the code during the release process.
-          */
-#        if PNG_USE_COMPILE_TIME_MASKS
-#           define PNG_LSR(x,s) ((x)>>((s) & 0x1f))
-#           define PNG_LSL(x,s) ((x)<<((s) & 0x1f))
-#        else
-#           define PNG_LSR(x,s) ((x)>>(s))
-#           define PNG_LSL(x,s) ((x)<<(s))
-#        endif
-#        define S_COPY(p,x) (((p)<4 ? PNG_LSR(0x80088822,(3-(p))*8+(7-(x))) :\
-           PNG_LSR(0xaa55ff00,(7-(p))*8+(7-(x)))) & 1)
-#        define B_COPY(p,x) (((p)<4 ? PNG_LSR(0xff0fff33,(3-(p))*8+(7-(x))) :\
-           PNG_LSR(0xff55ff00,(7-(p))*8+(7-(x)))) & 1)
-
-         /* Return a mask for pass 'p' pixel 'x' at depth 'd'.  The mask is
-          * little endian - the first pixel is at bit 0 - however the extra
-          * parameter 's' can be set to cause the mask position to be swapped
-          * within each byte, to match the PNG format.  This is done by XOR of
-          * the shift with 7, 6 or 4 for bit depths 1, 2 and 4.
-          */
-#        define PIXEL_MASK(p,x,d,s) \
-            (PNG_LSL(((PNG_LSL(1U,(d)))-1),(((x)*(d))^((s)?8-(d):0))))
-
-         /* Hence generate the appropriate 'block' or 'sparkle' pixel copy mask.
-          */
-#        define S_MASKx(p,x,d,s) (S_COPY(p,x)?PIXEL_MASK(p,x,d,s):0)
-#        define B_MASKx(p,x,d,s) (B_COPY(p,x)?PIXEL_MASK(p,x,d,s):0)
-
-         /* Combine 8 of these to get the full mask.  For the 1-bpp and 2-bpp
-          * cases the result needs replicating, for the 4-bpp case the above
-          * generates a full 32 bits.
-          */
-#        define MASK_EXPAND(m,d) ((m)*((d)==1?0x01010101:((d)==2?0x00010001:1)))
-
-#        define S_MASK(p,d,s) MASK_EXPAND(S_MASKx(p,0,d,s) + S_MASKx(p,1,d,s) +\
-            S_MASKx(p,2,d,s) + S_MASKx(p,3,d,s) + S_MASKx(p,4,d,s) +\
-            S_MASKx(p,5,d,s) + S_MASKx(p,6,d,s) + S_MASKx(p,7,d,s), d)
-
-#        define B_MASK(p,d,s) MASK_EXPAND(B_MASKx(p,0,d,s) + B_MASKx(p,1,d,s) +\
-            B_MASKx(p,2,d,s) + B_MASKx(p,3,d,s) + B_MASKx(p,4,d,s) +\
-            B_MASKx(p,5,d,s) + B_MASKx(p,6,d,s) + B_MASKx(p,7,d,s), d)
-
-#if PNG_USE_COMPILE_TIME_MASKS
-         /* Utility macros to construct all the masks for a depth/swap
-          * combination.  The 's' parameter says whether the format is PNG
-          * (big endian bytes) or not.  Only the three odd-numbered passes are
-          * required for the display/block algorithm.
-          */
-#        define S_MASKS(d,s) { S_MASK(0,d,s), S_MASK(1,d,s), S_MASK(2,d,s),\
-            S_MASK(3,d,s), S_MASK(4,d,s), S_MASK(5,d,s) }
-
-#        define B_MASKS(d,s) { B_MASK(1,d,s), B_MASK(3,d,s), B_MASK(5,d,s) }
-
-#        define DEPTH_INDEX(d) ((d)==1?0:((d)==2?1:2))
-
-         /* Hence the pre-compiled masks indexed by PACKSWAP (or not), depth and
-          * then pass:
-          */
-         static PNG_CONST png_uint_32 row_mask[2/*PACKSWAP*/][3/*depth*/][6] =
-         {
-            /* Little-endian byte masks for PACKSWAP */
-            { S_MASKS(1,0), S_MASKS(2,0), S_MASKS(4,0) },
-            /* Normal (big-endian byte) masks - PNG format */
-            { S_MASKS(1,1), S_MASKS(2,1), S_MASKS(4,1) }
-         };
-
-         /* display_mask has only three entries for the odd passes, so index by
-          * pass>>1.
-          */
-         static PNG_CONST png_uint_32 display_mask[2][3][3] =
-         {
-            /* Little-endian byte masks for PACKSWAP */
-            { B_MASKS(1,0), B_MASKS(2,0), B_MASKS(4,0) },
-            /* Normal (big-endian byte) masks - PNG format */
-            { B_MASKS(1,1), B_MASKS(2,1), B_MASKS(4,1) }
-         };
-
-#        define MASK(pass,depth,display,png)\
-            ((display)?display_mask[png][DEPTH_INDEX(depth)][pass>>1]:\
-               row_mask[png][DEPTH_INDEX(depth)][pass])
-
-#else /* !PNG_USE_COMPILE_TIME_MASKS */
-         /* This is the runtime alternative: it seems unlikely that this will
-          * ever be either smaller or faster than the compile time approach.
-          */
-#        define MASK(pass,depth,display,png)\
-            ((display)?B_MASK(pass,depth,png):S_MASK(pass,depth,png))
-#endif /* !USE_COMPILE_TIME_MASKS */
-
-         /* Use the appropriate mask to copy the required bits.  In some cases
-          * the byte mask will be 0 or 0xff; optimize these cases.  row_width is
-          * the number of pixels, but the code copies bytes, so it is necessary
-          * to special case the end.
-          */
-         png_uint_32 pixels_per_byte = 8 / pixel_depth;
-         png_uint_32 mask;
-
-#        ifdef PNG_READ_PACKSWAP_SUPPORTED
-         if ((png_ptr->transformations & PNG_PACKSWAP) != 0)
-            mask = MASK(pass, pixel_depth, display, 0);
-
-         else
-#        endif
-         mask = MASK(pass, pixel_depth, display, 1);
-
-         for (;;)
-         {
-            png_uint_32 m;
-
-            /* It doesn't matter in the following if png_uint_32 has more than
-             * 32 bits because the high bits always match those in m<<24; it is,
-             * however, essential to use OR here, not +, because of this.
-             */
-            m = mask;
-            mask = (m >> 8) | (m << 24); /* rotate right to good compilers */
-            m &= 0xff;
-
-            if (m != 0) /* something to copy */
-            {
-               if (m != 0xff)
-                  *dp = (png_byte)((*dp & ~m) | (*sp & m));
-               else
-                  *dp = *sp;
-            }
-
-            /* NOTE: this may overwrite the last byte with garbage if the image
-             * is not an exact number of bytes wide; libpng has always done
-             * this.
-             */
-            if (row_width <= pixels_per_byte)
-               break; /* May need to restore part of the last byte */
-
-            row_width -= pixels_per_byte;
-            ++dp;
-            ++sp;
-         }
-      }
-
-      else /* pixel_depth >= 8 */
-      {
-         unsigned int bytes_to_copy, bytes_to_jump;
-
-         /* Validate the depth - it must be a multiple of 8 */
-         if (pixel_depth & 7)
-            png_error(png_ptr, "invalid user transform pixel depth");
-
-         pixel_depth >>= 3; /* now in bytes */
-         row_width *= pixel_depth;
-
-         /* Regardless of pass number the Adam 7 interlace always results in a
-          * fixed number of pixels to copy then to skip.  There may be a
-          * different number of pixels to skip at the start though.
-          */
-         {
-            unsigned int offset = PNG_PASS_START_COL(pass) * pixel_depth;
-
-            row_width -= offset;
-            dp += offset;
-            sp += offset;
-         }
-
-         /* Work out the bytes to copy. */
-         if (display != 0)
-         {
-            /* When doing the 'block' algorithm the pixel in the pass gets
-             * replicated to adjacent pixels.  This is why the even (0,2,4,6)
-             * passes are skipped above - the entire expanded row is copied.
-             */
-            bytes_to_copy = (1<<((6-pass)>>1)) * pixel_depth;
-
-            /* But don't allow this number to exceed the actual row width. */
-            if (bytes_to_copy > row_width)
-               bytes_to_copy = (unsigned int)/*SAFE*/row_width;
-         }
-
-         else /* normal row; Adam7 only ever gives us one pixel to copy. */
-            bytes_to_copy = pixel_depth;
-
-         /* In Adam7 there is a constant offset between where the pixels go. */
-         bytes_to_jump = PNG_PASS_COL_OFFSET(pass) * pixel_depth;
-
-         /* And simply copy these bytes.  Some optimization is possible here,
-          * depending on the value of 'bytes_to_copy'.  Special case the low
-          * byte counts, which we know to be frequent.
-          *
-          * Notice that these cases all 'return' rather than 'break' - this
-          * avoids an unnecessary test on whether to restore the last byte
-          * below.
-          */
-         switch (bytes_to_copy)
-         {
-            case 1:
-               for (;;)
-               {
-                  *dp = *sp;
-
-                  if (row_width <= bytes_to_jump)
-                     return;
-
-                  dp += bytes_to_jump;
-                  sp += bytes_to_jump;
-                  row_width -= bytes_to_jump;
-               }
-
-            case 2:
-               /* There is a possibility of a partial copy at the end here; this
-                * slows the code down somewhat.
-                */
-               do
-               {
-                  dp[0] = sp[0], dp[1] = sp[1];
-
-                  if (row_width <= bytes_to_jump)
-                     return;
-
-                  sp += bytes_to_jump;
-                  dp += bytes_to_jump;
-                  row_width -= bytes_to_jump;
-               }
-               while (row_width > 1);
-
-               /* And there can only be one byte left at this point: */
-               *dp = *sp;
-               return;
-
-            case 3:
-               /* This can only be the RGB case, so each copy is exactly one
-                * pixel and it is not necessary to check for a partial copy.
-                */
-               for (;;)
-               {
-                  dp[0] = sp[0], dp[1] = sp[1], dp[2] = sp[2];
-
-                  if (row_width <= bytes_to_jump)
-                     return;
-
-                  sp += bytes_to_jump;
-                  dp += bytes_to_jump;
-                  row_width -= bytes_to_jump;
-               }
-
-            default:
-#if PNG_ALIGN_TYPE != PNG_ALIGN_NONE
-               /* Check for double byte alignment and, if possible, use a
-                * 16-bit copy.  Don't attempt this for narrow images - ones that
-                * are less than an interlace panel wide.  Don't attempt it for
-                * wide bytes_to_copy either - use the memcpy there.
-                */
-               if (bytes_to_copy < 16 /*else use memcpy*/ &&
-                   png_isaligned(dp, png_uint_16) &&
-                   png_isaligned(sp, png_uint_16) &&
-                   bytes_to_copy % (sizeof (png_uint_16)) == 0 &&
-                   bytes_to_jump % (sizeof (png_uint_16)) == 0)
-               {
-                  /* Everything is aligned for png_uint_16 copies, but try for
-                   * png_uint_32 first.
-                   */
-                  if (png_isaligned(dp, png_uint_32) != 0 &&
-                      png_isaligned(sp, png_uint_32) != 0 &&
-                      bytes_to_copy % (sizeof (png_uint_32)) == 0 &&
-                      bytes_to_jump % (sizeof (png_uint_32)) == 0)
-                  {
-                     png_uint_32p dp32 = png_aligncast(png_uint_32p,dp);
-                     png_const_uint_32p sp32 = png_aligncastconst(
-                         png_const_uint_32p, sp);
-                     size_t skip = (bytes_to_jump-bytes_to_copy) /
-                         (sizeof (png_uint_32));
-
-                     do
-                     {
-                        size_t c = bytes_to_copy;
-                        do
-                        {
-                           *dp32++ = *sp32++;
-                           c -= (sizeof (png_uint_32));
-                        }
-                        while (c > 0);
-
-                        if (row_width <= bytes_to_jump)
-                           return;
-
-                        dp32 += skip;
-                        sp32 += skip;
-                        row_width -= bytes_to_jump;
-                     }
-                     while (bytes_to_copy <= row_width);
-
-                     /* Get to here when the row_width truncates the final copy.
-                      * There will be 1-3 bytes left to copy, so don't try the
-                      * 16-bit loop below.
-                      */
-                     dp = (png_bytep)dp32;
-                     sp = (png_const_bytep)sp32;
-                     do
-                        *dp++ = *sp++;
-                     while (--row_width > 0);
-                     return;
-                  }
-
-                  /* Else do it in 16-bit quantities, but only if the size is
-                   * not too large.
-                   */
-                  else
-                  {
-                     png_uint_16p dp16 = png_aligncast(png_uint_16p, dp);
-                     png_const_uint_16p sp16 = png_aligncastconst(
-                        png_const_uint_16p, sp);
-                     size_t skip = (bytes_to_jump-bytes_to_copy) /
-                        (sizeof (png_uint_16));
-
-                     do
-                     {
-                        size_t c = bytes_to_copy;
-                        do
-                        {
-                           *dp16++ = *sp16++;
-                           c -= (sizeof (png_uint_16));
-                        }
-                        while (c > 0);
-
-                        if (row_width <= bytes_to_jump)
-                           return;
-
-                        dp16 += skip;
-                        sp16 += skip;
-                        row_width -= bytes_to_jump;
-                     }
-                     while (bytes_to_copy <= row_width);
-
-                     /* End of row - 1 byte left, bytes_to_copy > row_width: */
-                     dp = (png_bytep)dp16;
-                     sp = (png_const_bytep)sp16;
-                     do
-                        *dp++ = *sp++;
-                     while (--row_width > 0);
-                     return;
-                  }
-               }
-#endif /* ALIGN_TYPE code */
-
-               /* The true default - use a memcpy: */
-               for (;;)
-               {
-                  memcpy(dp, sp, bytes_to_copy);
-
-                  if (row_width <= bytes_to_jump)
-                     return;
-
-                  sp += bytes_to_jump;
-                  dp += bytes_to_jump;
-                  row_width -= bytes_to_jump;
-                  if (bytes_to_copy > row_width)
-                     bytes_to_copy = (unsigned int)/*SAFE*/row_width;
-               }
-         }
-
-         /* NOT REACHED*/
-      } /* pixel_depth >= 8 */
-
-      /* Here if pixel_depth < 8 to check 'end_ptr' below. */
-   }
-   else
-#endif /* READ_INTERLACING */
-
-   /* If here then the switch above wasn't used so just memcpy the whole row
-    * from the temporary row buffer (notice that this overwrites the end of the
-    * destination row if it is a partial byte.)
-    */
-   memcpy(dp, sp, PNG_ROWBYTES(pixel_depth, row_width));
-
-   /* Restore the overwritten bits from the last byte if necessary. */
-   if (end_ptr != NULL)
-      *end_ptr = (png_byte)((end_byte & end_mask) | (*end_ptr & ~end_mask));
-}
-
-#ifdef PNG_READ_INTERLACING_SUPPORTED
-void /* PRIVATE */
-png_do_read_interlace(png_row_infop row_info, png_bytep row, int pass,
-   png_uint_32 transformations /* Because these may affect the byte layout */)
-{
-   /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
-   /* Offset to next interlace block */
-   static PNG_CONST int png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
-
-   png_debug(1, "in png_do_read_interlace");
-   if (row != NULL && row_info != NULL)
-   {
-      png_uint_32 final_width;
-
-      final_width = row_info->width * png_pass_inc[pass];
-
-      switch (row_info->pixel_depth)
-      {
-         case 1:
-         {
-            png_bytep sp = row + (png_size_t)((row_info->width - 1) >> 3);
-            png_bytep dp = row + (png_size_t)((final_width - 1) >> 3);
-            int sshift, dshift;
-            int s_start, s_end, s_inc;
-            int jstop = png_pass_inc[pass];
-            png_byte v;
-            png_uint_32 i;
-            int j;
-
-#ifdef PNG_READ_PACKSWAP_SUPPORTED
-            if ((transformations & PNG_PACKSWAP) != 0)
-            {
-                sshift = (int)((row_info->width + 7) & 0x07);
-                dshift = (int)((final_width + 7) & 0x07);
-                s_start = 7;
-                s_end = 0;
-                s_inc = -1;
-            }
-
-            else
-#endif
-            {
-                sshift = 7 - (int)((row_info->width + 7) & 0x07);
-                dshift = 7 - (int)((final_width + 7) & 0x07);
-                s_start = 0;
-                s_end = 7;
-                s_inc = 1;
-            }
-
-            for (i = 0; i < row_info->width; i++)
-            {
-               v = (png_byte)((*sp >> sshift) & 0x01);
-               for (j = 0; j < jstop; j++)
-               {
-                  unsigned int tmp = *dp & (0x7f7f >> (7 - dshift));
-                  tmp |= v << dshift;
-                  *dp = (png_byte)(tmp & 0xff);
-
-                  if (dshift == s_end)
-                  {
-                     dshift = s_start;
-                     dp--;
-                  }
-
-                  else
-                     dshift += s_inc;
-               }
-
-               if (sshift == s_end)
-               {
-                  sshift = s_start;
-                  sp--;
-               }
-
-               else
-                  sshift += s_inc;
-            }
-            break;
-         }
-
-         case 2:
-         {
-            png_bytep sp = row + (png_uint_32)((row_info->width - 1) >> 2);
-            png_bytep dp = row + (png_uint_32)((final_width - 1) >> 2);
-            int sshift, dshift;
-            int s_start, s_end, s_inc;
-            int jstop = png_pass_inc[pass];
-            png_uint_32 i;
-
-#ifdef PNG_READ_PACKSWAP_SUPPORTED
-            if ((transformations & PNG_PACKSWAP) != 0)
-            {
-               sshift = (int)(((row_info->width + 3) & 0x03) << 1);
-               dshift = (int)(((final_width + 3) & 0x03) << 1);
-               s_start = 6;
-               s_end = 0;
-               s_inc = -2;
-            }
-
-            else
-#endif
-            {
-               sshift = (int)((3 - ((row_info->width + 3) & 0x03)) << 1);
-               dshift = (int)((3 - ((final_width + 3) & 0x03)) << 1);
-               s_start = 0;
-               s_end = 6;
-               s_inc = 2;
-            }
-
-            for (i = 0; i < row_info->width; i++)
-            {
-               png_byte v;
-               int j;
-
-               v = (png_byte)((*sp >> sshift) & 0x03);
-               for (j = 0; j < jstop; j++)
-               {
-                  unsigned int tmp = *dp & (0x3f3f >> (6 - dshift));
-                  tmp |= v << dshift;
-                  *dp = (png_byte)(tmp & 0xff);
-
-                  if (dshift == s_end)
-                  {
-                     dshift = s_start;
-                     dp--;
-                  }
-
-                  else
-                     dshift += s_inc;
-               }
-
-               if (sshift == s_end)
-               {
-                  sshift = s_start;
-                  sp--;
-               }
-
-               else
-                  sshift += s_inc;
-            }
-            break;
-         }
-
-         case 4:
-         {
-            png_bytep sp = row + (png_size_t)((row_info->width - 1) >> 1);
-            png_bytep dp = row + (png_size_t)((final_width - 1) >> 1);
-            int sshift, dshift;
-            int s_start, s_end, s_inc;
-            png_uint_32 i;
-            int jstop = png_pass_inc[pass];
-
-#ifdef PNG_READ_PACKSWAP_SUPPORTED
-            if ((transformations & PNG_PACKSWAP) != 0)
-            {
-               sshift = (int)(((row_info->width + 1) & 0x01) << 2);
-               dshift = (int)(((final_width + 1) & 0x01) << 2);
-               s_start = 4;
-               s_end = 0;
-               s_inc = -4;
-            }
-
-            else
-#endif
-            {
-               sshift = (int)((1 - ((row_info->width + 1) & 0x01)) << 2);
-               dshift = (int)((1 - ((final_width + 1) & 0x01)) << 2);
-               s_start = 0;
-               s_end = 4;
-               s_inc = 4;
-            }
-
-            for (i = 0; i < row_info->width; i++)
-            {
-               png_byte v = (png_byte)((*sp >> sshift) & 0x0f);
-               int j;
-
-               for (j = 0; j < jstop; j++)
-               {
-                  unsigned int tmp = *dp & (0xf0f >> (4 - dshift));
-                  tmp |= v << dshift;
-                  *dp = (png_byte)(tmp & 0xff);
-
-                  if (dshift == s_end)
-                  {
-                     dshift = s_start;
-                     dp--;
-                  }
-
-                  else
-                     dshift += s_inc;
-               }
-
-               if (sshift == s_end)
-               {
-                  sshift = s_start;
-                  sp--;
-               }
-
-               else
-                  sshift += s_inc;
-            }
-            break;
-         }
-
-         default:
-         {
-            png_size_t pixel_bytes = (row_info->pixel_depth >> 3);
-
-            png_bytep sp = row + (png_size_t)(row_info->width - 1)
-                * pixel_bytes;
-
-            png_bytep dp = row + (png_size_t)(final_width - 1) * pixel_bytes;
-
-            int jstop = png_pass_inc[pass];
-            png_uint_32 i;
-
-            for (i = 0; i < row_info->width; i++)
-            {
-               png_byte v[8]; /* SAFE; pixel_depth does not exceed 64 */
-               int j;
-
-               memcpy(v, sp, pixel_bytes);
-
-               for (j = 0; j < jstop; j++)
-               {
-                  memcpy(dp, v, pixel_bytes);
-                  dp -= pixel_bytes;
-               }
-
-               sp -= pixel_bytes;
-            }
-            break;
-         }
-      }
-
-      row_info->width = final_width;
-      row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, final_width);
-   }
-#ifndef PNG_READ_PACKSWAP_SUPPORTED
-   PNG_UNUSED(transformations)  /* Silence compiler warning */
-#endif
-}
-#endif /* READ_INTERLACING */
-
-static void
-png_read_filter_row_sub(png_row_infop row_info, png_bytep row,
-   png_const_bytep prev_row)
-{
-   png_size_t i;
-   png_size_t istop = row_info->rowbytes;
-   unsigned int bpp = (row_info->pixel_depth + 7) >> 3;
-   png_bytep rp = row + bpp;
-
-   PNG_UNUSED(prev_row)
-
-   for (i = bpp; i < istop; i++)
-   {
-      *rp = (png_byte)(((int)(*rp) + (int)(*(rp-bpp))) & 0xff);
-      rp++;
-   }
-}
-
-static void
-png_read_filter_row_up(png_row_infop row_info, png_bytep row,
-   png_const_bytep prev_row)
-{
-   png_size_t i;
-   png_size_t istop = row_info->rowbytes;
-   png_bytep rp = row;
-   png_const_bytep pp = prev_row;
-
-   for (i = 0; i < istop; i++)
-   {
-      *rp = (png_byte)(((int)(*rp) + (int)(*pp++)) & 0xff);
-      rp++;
-   }
-}
-
-static void
-png_read_filter_row_avg(png_row_infop row_info, png_bytep row,
-   png_const_bytep prev_row)
-{
-   png_size_t i;
-   png_bytep rp = row;
-   png_const_bytep pp = prev_row;
-   unsigned int bpp = (row_info->pixel_depth + 7) >> 3;
-   png_size_t istop = row_info->rowbytes - bpp;
-
-   for (i = 0; i < bpp; i++)
-   {
-      *rp = (png_byte)(((int)(*rp) +
-         ((int)(*pp++) / 2 )) & 0xff);
-
-      rp++;
-   }
-
-   for (i = 0; i < istop; i++)
-   {
-      *rp = (png_byte)(((int)(*rp) +
-         (int)(*pp++ + *(rp-bpp)) / 2 ) & 0xff);
-
-      rp++;
-   }
-}
-
-static void
-png_read_filter_row_paeth_1byte_pixel(png_row_infop row_info, png_bytep row,
-   png_const_bytep prev_row)
-{
-   png_bytep rp_end = row + row_info->rowbytes;
-   int a, c;
-
-   /* First pixel/byte */
-   c = *prev_row++;
-   a = *row + c;
-   *row++ = (png_byte)a;
-
-   /* Remainder */
-   while (row < rp_end)
-   {
-      int b, pa, pb, pc, p;
-
-      a &= 0xff; /* From previous iteration or start */
-      b = *prev_row++;
-
-      p = b - c;
-      pc = a - c;
-
-#ifdef PNG_USE_ABS
-      pa = abs(p);
-      pb = abs(pc);
-      pc = abs(p + pc);
-#else
-      pa = p < 0 ? -p : p;
-      pb = pc < 0 ? -pc : pc;
-      pc = (p + pc) < 0 ? -(p + pc) : p + pc;
-#endif
-
-      /* Find the best predictor, the least of pa, pb, pc favoring the earlier
-       * ones in the case of a tie.
-       */
-      if (pb < pa) pa = pb, a = b;
-      if (pc < pa) a = c;
-
-      /* Calculate the current pixel in a, and move the previous row pixel to c
-       * for the next time round the loop
-       */
-      c = b;
-      a += *row;
-      *row++ = (png_byte)a;
-   }
-}
-
-static void
-png_read_filter_row_paeth_multibyte_pixel(png_row_infop row_info, png_bytep row,
-   png_const_bytep prev_row)
-{
-   int bpp = (row_info->pixel_depth + 7) >> 3;
-   png_bytep rp_end = row + bpp;
-
-   /* Process the first pixel in the row completely (this is the same as 'up'
-    * because there is only one candidate predictor for the first row).
-    */
-   while (row < rp_end)
-   {
-      int a = *row + *prev_row++;
-      *row++ = (png_byte)a;
-   }
-
-   /* Remainder */
-   rp_end += row_info->rowbytes - bpp;
-
-   while (row < rp_end)
-   {
-      int a, b, c, pa, pb, pc, p;
-
-      c = *(prev_row - bpp);
-      a = *(row - bpp);
-      b = *prev_row++;
-
-      p = b - c;
-      pc = a - c;
-
-#ifdef PNG_USE_ABS
-      pa = abs(p);
-      pb = abs(pc);
-      pc = abs(p + pc);
-#else
-      pa = p < 0 ? -p : p;
-      pb = pc < 0 ? -pc : pc;
-      pc = (p + pc) < 0 ? -(p + pc) : p + pc;
-#endif
-
-      if (pb < pa) pa = pb, a = b;
-      if (pc < pa) a = c;
-
-      a += *row;
-      *row++ = (png_byte)a;
-   }
-}
-
-static void
-png_init_filter_functions(png_structrp pp)
-   /* This function is called once for every PNG image (except for PNG images
-    * that only use PNG_FILTER_VALUE_NONE for all rows) to set the
-    * implementations required to reverse the filtering of PNG rows.  Reversing
-    * the filter is the first transformation performed on the row data.  It is
-    * performed in place, therefore an implementation can be selected based on
-    * the image pixel format.  If the implementation depends on image width then
-    * take care to ensure that it works correctly if the image is interlaced -
-    * interlacing causes the actual row width to vary.
-    */
-{
-   unsigned int bpp = (pp->pixel_depth + 7) >> 3;
-
-   pp->read_filter[PNG_FILTER_VALUE_SUB-1] = png_read_filter_row_sub;
-   pp->read_filter[PNG_FILTER_VALUE_UP-1] = png_read_filter_row_up;
-   pp->read_filter[PNG_FILTER_VALUE_AVG-1] = png_read_filter_row_avg;
-   if (bpp == 1)
-      pp->read_filter[PNG_FILTER_VALUE_PAETH-1] =
-         png_read_filter_row_paeth_1byte_pixel;
-   else
-      pp->read_filter[PNG_FILTER_VALUE_PAETH-1] =
-         png_read_filter_row_paeth_multibyte_pixel;
-
-#ifdef PNG_FILTER_OPTIMIZATIONS
-   /* To use this define PNG_FILTER_OPTIMIZATIONS as the name of a function to
-    * call to install hardware optimizations for the above functions; simply
-    * replace whatever elements of the pp->read_filter[] array with a hardware
-    * specific (or, for that matter, generic) optimization.
-    *
-    * To see an example of this examine what configure.ac does when
-    * --enable-arm-neon is specified on the command line.
-    */
-   PNG_FILTER_OPTIMIZATIONS(pp, bpp);
-#endif
-}
-
-void /* PRIVATE */
-png_read_filter_row(png_structrp pp, png_row_infop row_info, png_bytep row,
-   png_const_bytep prev_row, int filter)
-{
-   /* OPTIMIZATION: DO NOT MODIFY THIS FUNCTION, instead #define
-    * PNG_FILTER_OPTIMIZATIONS to a function that overrides the generic
-    * implementations.  See png_init_filter_functions above.
-    */
-   if (filter > PNG_FILTER_VALUE_NONE && filter < PNG_FILTER_VALUE_LAST)
-   {
-      if (pp->read_filter[0] == NULL)
-         png_init_filter_functions(pp);
-
-      pp->read_filter[filter-1](row_info, row, prev_row);
-   }
-}
-
-#ifdef PNG_SEQUENTIAL_READ_SUPPORTED
-void /* PRIVATE */
-png_read_IDAT_data(png_structrp png_ptr, png_bytep output,
-   png_alloc_size_t avail_out)
-{
-   /* Loop reading IDATs and decompressing the result into output[avail_out] */
-   png_ptr->zstream.next_out = output;
-   png_ptr->zstream.avail_out = 0; /* safety: set below */
-
-   if (output == NULL)
-      avail_out = 0;
-
-   do
-   {
-      int ret;
-      png_byte tmpbuf[PNG_INFLATE_BUF_SIZE];
-
-      if (png_ptr->zstream.avail_in == 0)
-      {
-         uInt avail_in;
-         png_bytep buffer;
-
-         while (png_ptr->idat_size == 0)
-         {
-            png_crc_finish(png_ptr, 0);
-
-            png_ptr->idat_size = png_read_chunk_header(png_ptr);
-            /* This is an error even in the 'check' case because the code just
-             * consumed a non-IDAT header.
-             */
-            if (png_ptr->chunk_name != png_IDAT)
-               png_error(png_ptr, "Not enough image data");
-         }
-
-         avail_in = png_ptr->IDAT_read_size;
-
-         if (avail_in > png_ptr->idat_size)
-            avail_in = (uInt)png_ptr->idat_size;
-
-         /* A PNG with a gradually increasing IDAT size will defeat this attempt
-          * to minimize memory usage by causing lots of re-allocs, but
-          * realistically doing IDAT_read_size re-allocs is not likely to be a
-          * big problem.
-          */
-         buffer = png_read_buffer(png_ptr, avail_in, 0/*error*/);
-
-         png_crc_read(png_ptr, buffer, avail_in);
-         png_ptr->idat_size -= avail_in;
-
-         png_ptr->zstream.next_in = buffer;
-         png_ptr->zstream.avail_in = avail_in;
-      }
-
-      /* And set up the output side. */
-      if (output != NULL) /* standard read */
-      {
-         uInt out = ZLIB_IO_MAX;
-
-         if (out > avail_out)
-            out = (uInt)avail_out;
-
-         avail_out -= out;
-         png_ptr->zstream.avail_out = out;
-      }
-
-      else /* after last row, checking for end */
-      {
-         png_ptr->zstream.next_out = tmpbuf;
-         png_ptr->zstream.avail_out = (sizeof tmpbuf);
-      }
-
-      /* Use NO_FLUSH; this gives zlib the maximum opportunity to optimize the
-       * process.  If the LZ stream is truncated the sequential reader will
-       * terminally damage the stream, above, by reading the chunk header of the
-       * following chunk (it then exits with png_error).
-       *
-       * TODO: deal more elegantly with truncated IDAT lists.
-       */
-      ret = PNG_INFLATE(png_ptr, Z_NO_FLUSH);
-
-      /* Take the unconsumed output back. */
-      if (output != NULL)
-         avail_out += png_ptr->zstream.avail_out;
-
-      else /* avail_out counts the extra bytes */
-         avail_out += (sizeof tmpbuf) - png_ptr->zstream.avail_out;
-
-      png_ptr->zstream.avail_out = 0;
-
-      if (ret == Z_STREAM_END)
-      {
-         /* Do this for safety; we won't read any more into this row. */
-         png_ptr->zstream.next_out = NULL;
-
-         png_ptr->mode |= PNG_AFTER_IDAT;
-         png_ptr->flags |= PNG_FLAG_ZSTREAM_ENDED;
-
-         if (png_ptr->zstream.avail_in > 0 || png_ptr->idat_size > 0)
-            png_chunk_benign_error(png_ptr, "Extra compressed data");
-         break;
-      }
-
-      if (ret != Z_OK)
-      {
-         png_zstream_error(png_ptr, ret);
-
-         if (output != NULL)
-            png_chunk_error(png_ptr, png_ptr->zstream.msg);
-
-         else /* checking */
-         {
-            png_chunk_benign_error(png_ptr, png_ptr->zstream.msg);
-            return;
-         }
-      }
-   } while (avail_out > 0);
-
-   if (avail_out > 0)
-   {
-      /* The stream ended before the image; this is the same as too few IDATs so
-       * should be handled the same way.
-       */
-      if (output != NULL)
-         png_error(png_ptr, "Not enough image data");
-
-      else /* the deflate stream contained extra data */
-         png_chunk_benign_error(png_ptr, "Too much image data");
-   }
-}
-
-void /* PRIVATE */
-png_read_finish_IDAT(png_structrp png_ptr)
-{
-   /* We don't need any more data and the stream should have ended, however the
-    * LZ end code may actually not have been processed.  In this case we must
-    * read it otherwise stray unread IDAT data or, more likely, an IDAT chunk
-    * may still remain to be consumed.
-    */
-   if ((png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED) == 0)
-   {
-      /* The NULL causes png_read_IDAT_data to swallow any remaining bytes in
-       * the compressed stream, but the stream may be damaged too, so even after
-       * this call we may need to terminate the zstream ownership.
-       */
-      png_read_IDAT_data(png_ptr, NULL, 0);
-      png_ptr->zstream.next_out = NULL; /* safety */
-
-      /* Now clear everything out for safety; the following may not have been
-       * done.
-       */
-      if ((png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED) == 0)
-      {
-         png_ptr->mode |= PNG_AFTER_IDAT;
-         png_ptr->flags |= PNG_FLAG_ZSTREAM_ENDED;
-      }
-   }
-
-   /* If the zstream has not been released do it now *and* terminate the reading
-    * of the final IDAT chunk.
-    */
-   if (png_ptr->zowner == png_IDAT)
-   {
-      /* Always do this; the pointers otherwise point into the read buffer. */
-      png_ptr->zstream.next_in = NULL;
-      png_ptr->zstream.avail_in = 0;
-
-      /* Now we no longer own the zstream. */
-      png_ptr->zowner = 0;
-
-      /* The slightly weird semantics of the sequential IDAT reading is that we
-       * are always in or at the end of an IDAT chunk, so we always need to do a
-       * crc_finish here.  If idat_size is non-zero we also need to read the
-       * spurious bytes at the end of the chunk now.
-       */
-      (void)png_crc_finish(png_ptr, png_ptr->idat_size);
-   }
-}
-
-void /* PRIVATE */
-png_read_finish_row(png_structrp png_ptr)
-{
-   /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
-
-   /* Start of interlace block */
-   static PNG_CONST png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
-
-   /* Offset to next interlace block */
-   static PNG_CONST png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
-
-   /* Start of interlace block in the y direction */
-   static PNG_CONST png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
-
-   /* Offset to next interlace block in the y direction */
-   static PNG_CONST png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
-
-   png_debug(1, "in png_read_finish_row");
-   png_ptr->row_number++;
-   if (png_ptr->row_number < png_ptr->num_rows)
-      return;
-
-   if (png_ptr->interlaced != 0)
-   {
-      png_ptr->row_number = 0;
-
-      /* TO DO: don't do this if prev_row isn't needed (requires
-       * read-ahead of the next row's filter byte.
-       */
-      memset(png_ptr->prev_row, 0, png_ptr->rowbytes + 1);
-
-      do
-      {
-         png_ptr->pass++;
-
-         if (png_ptr->pass >= 7)
-            break;
-
-         png_ptr->iwidth = (png_ptr->width +
-            png_pass_inc[png_ptr->pass] - 1 -
-            png_pass_start[png_ptr->pass]) /
-            png_pass_inc[png_ptr->pass];
-
-         if ((png_ptr->transformations & PNG_INTERLACE) == 0)
-         {
-            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];
-         }
-
-         else  /* if (png_ptr->transformations & PNG_INTERLACE) */
-            break; /* libpng deinterlacing sees every row */
-
-      } while (png_ptr->num_rows == 0 || png_ptr->iwidth == 0);
-
-      if (png_ptr->pass < 7)
-         return;
-   }
-
-   /* Here after at the end of the last row of the last pass. */
-   png_read_finish_IDAT(png_ptr);
-}
-#endif /* SEQUENTIAL_READ */
-
-void /* PRIVATE */
-png_read_start_row(png_structrp png_ptr)
-{
-   /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
-
-   /* Start of interlace block */
-   static PNG_CONST png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
-
-   /* Offset to next interlace block */
-   static PNG_CONST png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
-
-   /* Start of interlace block in the y direction */
-   static PNG_CONST png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
-
-   /* Offset to next interlace block in the y direction */
-   static PNG_CONST png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
-
-   int max_pixel_depth;
-   png_size_t row_bytes;
-
-   png_debug(1, "in png_read_start_row");
-
-#ifdef PNG_READ_TRANSFORMS_SUPPORTED
-   png_init_read_transformations(png_ptr);
-#endif
-   if (png_ptr->interlaced != 0)
-   {
-      if ((png_ptr->transformations & PNG_INTERLACE) == 0)
-         png_ptr->num_rows = (png_ptr->height + png_pass_yinc[0] - 1 -
-             png_pass_ystart[0]) / png_pass_yinc[0];
-
-      else
-         png_ptr->num_rows = png_ptr->height;
-
-      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];
-   }
-
-   else
-   {
-      png_ptr->num_rows = png_ptr->height;
-      png_ptr->iwidth = png_ptr->width;
-   }
-
-   max_pixel_depth = png_ptr->pixel_depth;
-
-   /* WARNING: * png_read_transform_info (pngrtran.c) performs a simpler set of
-    * calculations to calculate the final pixel depth, then
-    * png_do_read_transforms actually does the transforms.  This means that the
-    * code which effectively calculates this value is actually repeated in three
-    * separate places.  They must all match.  Innocent changes to the order of
-    * transformations can and will break libpng in a way that causes memory
-    * overwrites.
-    *
-    * TODO: fix this.
-    */
-#ifdef PNG_READ_PACK_SUPPORTED
-   if ((png_ptr->transformations & PNG_PACK) != 0 && png_ptr->bit_depth < 8)
-      max_pixel_depth = 8;
-#endif
-
-#ifdef PNG_READ_EXPAND_SUPPORTED
-   if ((png_ptr->transformations & PNG_EXPAND) != 0)
-   {
-      if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
-      {
-         if (png_ptr->num_trans != 0)
-            max_pixel_depth = 32;
-
-         else
-            max_pixel_depth = 24;
-      }
-
-      else if (png_ptr->color_type == PNG_COLOR_TYPE_GRAY)
-      {
-         if (max_pixel_depth < 8)
-            max_pixel_depth = 8;
-
-         if (png_ptr->num_trans != 0)
-            max_pixel_depth *= 2;
-      }
-
-      else if (png_ptr->color_type == PNG_COLOR_TYPE_RGB)
-      {
-         if (png_ptr->num_trans != 0)
-         {
-            max_pixel_depth *= 4;
-            max_pixel_depth /= 3;
-         }
-      }
-   }
-#endif
-
-#ifdef PNG_READ_EXPAND_16_SUPPORTED
-   if ((png_ptr->transformations & PNG_EXPAND_16) != 0)
-   {
-#  ifdef PNG_READ_EXPAND_SUPPORTED
-      /* In fact it is an error if it isn't supported, but checking is
-       * the safe way.
-       */
-      if ((png_ptr->transformations & PNG_EXPAND) != 0)
-      {
-         if (png_ptr->bit_depth < 16)
-            max_pixel_depth *= 2;
-      }
-      else
-#  endif
-      png_ptr->transformations &= ~PNG_EXPAND_16;
-   }
-#endif
-
-#ifdef PNG_READ_FILLER_SUPPORTED
-   if ((png_ptr->transformations & (PNG_FILLER)) != 0)
-   {
-      if (png_ptr->color_type == PNG_COLOR_TYPE_GRAY)
-      {
-         if (max_pixel_depth <= 8)
-            max_pixel_depth = 16;
-
-         else
-            max_pixel_depth = 32;
-      }
-
-      else if (png_ptr->color_type == PNG_COLOR_TYPE_RGB ||
-         png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
-      {
-         if (max_pixel_depth <= 32)
-            max_pixel_depth = 32;
-
-         else
-            max_pixel_depth = 64;
-      }
-   }
-#endif
-
-#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
-   if ((png_ptr->transformations & PNG_GRAY_TO_RGB) != 0)
-   {
-      if (
-#ifdef PNG_READ_EXPAND_SUPPORTED
-          (png_ptr->num_trans != 0 &&
-          (png_ptr->transformations & PNG_EXPAND) != 0) ||
-#endif
-#ifdef PNG_READ_FILLER_SUPPORTED
-          (png_ptr->transformations & (PNG_FILLER)) != 0 ||
-#endif
-          png_ptr->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
-      {
-         if (max_pixel_depth <= 16)
-            max_pixel_depth = 32;
-
-         else
-            max_pixel_depth = 64;
-      }
-
-      else
-      {
-         if (max_pixel_depth <= 8)
-         {
-            if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
-               max_pixel_depth = 32;
-
-            else
-               max_pixel_depth = 24;
-         }
-
-         else if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
-            max_pixel_depth = 64;
-
-         else
-            max_pixel_depth = 48;
-      }
-   }
-#endif
-
-#if defined(PNG_READ_USER_TRANSFORM_SUPPORTED) && \
-defined(PNG_USER_TRANSFORM_PTR_SUPPORTED)
-   if ((png_ptr->transformations & PNG_USER_TRANSFORM) != 0)
-   {
-      int user_pixel_depth = png_ptr->user_transform_depth *
-         png_ptr->user_transform_channels;
-
-      if (user_pixel_depth > max_pixel_depth)
-         max_pixel_depth = user_pixel_depth;
-   }
-#endif
-
-   /* This value is stored in png_struct and double checked in the row read
-    * code.
-    */
-   png_ptr->maximum_pixel_depth = (png_byte)max_pixel_depth;
-   png_ptr->transformed_pixel_depth = 0; /* calculated on demand */
-
-   /* Align the width on the next larger 8 pixels.  Mainly used
-    * for interlacing
-    */
-   row_bytes = ((png_ptr->width + 7) & ~((png_uint_32)7));
-   /* Calculate the maximum bytes needed, adding a byte and a pixel
-    * for safety's sake
-    */
-   row_bytes = PNG_ROWBYTES(max_pixel_depth, row_bytes) +
-       1 + ((max_pixel_depth + 7) >> 3);
-
-#ifdef PNG_MAX_MALLOC_64K
-   if (row_bytes > (png_uint_32)65536L)
-      png_error(png_ptr, "This image requires a row greater than 64KB");
-#endif
-
-   if (row_bytes + 48 > png_ptr->old_big_row_buf_size)
-   {
-     png_free(png_ptr, png_ptr->big_row_buf);
-     png_free(png_ptr, png_ptr->big_prev_row);
-
-     if (png_ptr->interlaced != 0)
-        png_ptr->big_row_buf = (png_bytep)png_calloc(png_ptr,
-            row_bytes + 48);
-
-     else
-        png_ptr->big_row_buf = (png_bytep)png_malloc(png_ptr, row_bytes + 48);
-
-     png_ptr->big_prev_row = (png_bytep)png_malloc(png_ptr, row_bytes + 48);
-
-#ifdef PNG_ALIGNED_MEMORY_SUPPORTED
-     /* Use 16-byte aligned memory for row_buf with at least 16 bytes
-      * of padding before and after row_buf; treat prev_row similarly.
-      * NOTE: the alignment is to the start of the pixels, one beyond the start
-      * of the buffer, because of the filter byte.  Prior to libpng 1.5.6 this
-      * was incorrect; the filter byte was aligned, which had the exact
-      * opposite effect of that intended.
-      */
-     {
-        png_bytep temp = png_ptr->big_row_buf + 32;
-        int extra = (int)((temp - (png_bytep)0) & 0x0f);
-        png_ptr->row_buf = temp - extra - 1/*filter byte*/;
-
-        temp = png_ptr->big_prev_row + 32;
-        extra = (int)((temp - (png_bytep)0) & 0x0f);
-        png_ptr->prev_row = temp - extra - 1/*filter byte*/;
-     }
-
-#else
-     /* Use 31 bytes of padding before and 17 bytes after row_buf. */
-     png_ptr->row_buf = png_ptr->big_row_buf + 31;
-     png_ptr->prev_row = png_ptr->big_prev_row + 31;
-#endif
-     png_ptr->old_big_row_buf_size = row_bytes + 48;
-   }
-
-#ifdef PNG_MAX_MALLOC_64K
-   if (png_ptr->rowbytes > 65535)
-      png_error(png_ptr, "This image requires a row greater than 64KB");
-
-#endif
-   if (png_ptr->rowbytes > (PNG_SIZE_MAX - 1))
-      png_error(png_ptr, "Row has too many bytes to allocate in memory");
-
-   memset(png_ptr->prev_row, 0, png_ptr->rowbytes + 1);
-
-   png_debug1(3, "width = %u,", png_ptr->width);
-   png_debug1(3, "height = %u,", png_ptr->height);
-   png_debug1(3, "iwidth = %u,", png_ptr->iwidth);
-   png_debug1(3, "num_rows = %u,", png_ptr->num_rows);
-   png_debug1(3, "rowbytes = %lu,", (unsigned long)png_ptr->rowbytes);
-   png_debug1(3, "irowbytes = %lu",
-       (unsigned long)PNG_ROWBYTES(png_ptr->pixel_depth, png_ptr->iwidth) + 1);
-
-   /* The sequential reader needs a buffer for IDAT, but the progressive reader
-    * does not, so free the read buffer now regardless; the sequential reader
-    * reallocates it on demand.
-    */
-   if (png_ptr->read_buffer != 0)
-   {
-      png_bytep buffer = png_ptr->read_buffer;
-
-      png_ptr->read_buffer_size = 0;
-      png_ptr->read_buffer = NULL;
-      png_free(png_ptr, buffer);
-   }
-
-   /* Finally claim the zstream for the inflate of the IDAT data, use the bits
-    * value from the stream (note that this will result in a fatal error if the
-    * IDAT stream has a bogus deflate header window_bits value, but this should
-    * not be happening any longer!)
-    */
-   if (png_inflate_claim(png_ptr, png_IDAT) != Z_OK)
-      png_error(png_ptr, png_ptr->zstream.msg);
-
-   png_ptr->flags |= PNG_FLAG_ROW_INIT;
-}
-#endif /* READ */