    /* pngrutil.c - utilities to read a PNG file
     *
     * Last changed in libpng 1.6.7 [November 14, 2013]
     * Copyright (c) 1998-2013 Glenn Randers-Pehrson
     * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
     * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
     *
     * This code is released under the libpng license.
     * For conditions of distribution and use, see the disclaimer
     * and license in png.h
     *
     * 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 */
       return -(png_int_32)uval;
    }

    /* 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 /* PNG_READ_INT_FUNCTIONS_SUPPORTED */

    /* 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))
       {
          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))
       {
          if (PNG_CHUNK_ANCILLARY(png_ptr->chunk_name) ?
              !(png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_NOWARN) :
              (png_ptr->flags & PNG_FLAG_CRC_CRITICAL_USE))
          {
             png_chunk_warning(png_ptr, "CRC error");
          }

          else
          {
             png_chunk_benign_error(png_ptr, "CRC error");
             return (0);
          }

          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))
       {
          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)
             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)
       {
          crc = png_get_uint_32(crc_bytes);
          return ((int)(crc != png_ptr->crc));
       }

       else
          return (0);
    }

    /* 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 */
          {
    #ifdef PNG_WARNINGS_SUPPORTED
             if (warn)
                 png_chunk_warning(png_ptr, "insufficient memory to read chunk");
             else
    #endif
             {
    #ifdef PNG_ERROR_TEXT_SUPPORTED
                 png_chunk_error(png_ptr, "insufficient memory to read chunk");
    #endif
             }
          }
       }

       return buffer;
    }

    /* 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_LIBPNG_BUILD_BASE_TYPE >= PNG_LIBPNG_BUILD_RC
             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;

                else
                   window_bits = 0;
    #        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)
          {
    #        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
    }

    #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 = inflate(&png_ptr->zstream, 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_CHUNK_MALLOC_LIMIT_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)
                               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 /* PNG_READ_COMPRESSED_TEXT_SUPPORTED */

    #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 = inflate(&png_ptr->zstream,
                *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)
          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 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))
          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)
          png_chunk_error(png_ptr, "duplicate");

       else if (png_ptr->mode & PNG_HAVE_IDAT)
       {
          /* 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))
       {
          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;

    #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, 0);
       }

    #ifndef PNG_READ_OPT_PLTE_SUPPORTED
       else if (png_crc_error(png_ptr))  /* 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))
          {
             if (png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_NOWARN)
             {
                png_chunk_benign_error(png_ptr, "CRC error");
             }

             else
             {
                png_chunk_warning(png_ptr, "CRC error");
                return;
             }
          }

          /* Otherwise, we (optionally) emit a warning and use the chunk. */
          else if (!(png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_NOWARN))
          {
             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) || !(png_ptr->mode & PNG_HAVE_IDAT))
          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))
          png_chunk_error(png_ptr, "missing IHDR");

       else if (png_ptr->mode & (PNG_HAVE_IDAT|PNG_HAVE_PLTE))
       {
          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))
          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;
       png_byte buf[4];

       png_debug(1, "in png_handle_sBIT");

       buf[0] = buf[1] = buf[2] = buf[3] = 0;

       if (!(png_ptr->mode & PNG_HAVE_IHDR))
          png_chunk_error(png_ptr, "missing IHDR");

       else if (png_ptr->mode & (PNG_HAVE_IDAT|PNG_HAVE_PLTE))
       {
          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))
       {
          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;

       else
          truelen = png_ptr->channels;

       if (length != truelen || length > 4)
       {
          png_chunk_benign_error(png_ptr, "invalid");
          png_crc_finish(png_ptr, length);
          return;
       }

       png_crc_read(png_ptr, buf, truelen);

       if (png_crc_finish(png_ptr, 0))
          return;

       if (png_ptr->color_type & PNG_COLOR_MASK_COLOR)
       {
          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))
          png_chunk_error(png_ptr, "missing IHDR");

       else if (png_ptr->mode & (PNG_HAVE_IDAT|PNG_HAVE_PLTE))
       {
          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))
          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)
          return;

       if (png_ptr->colorspace.flags & PNG_COLORSPACE_FROM_cHRM)
       {
          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))
          png_chunk_error(png_ptr, "missing IHDR");

       else if (png_ptr->mode & (PNG_HAVE_IDAT|PNG_HAVE_PLTE))
       {
          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))
          return;

       /* If a colorspace error has already been output skip this chunk */
       if (png_ptr->colorspace.flags & PNG_COLORSPACE_INVALID)
          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)
       {
          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 /* PNG_READ_sRGB_SUPPORTED */

    #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))
          png_chunk_error(png_ptr, "missing IHDR");

       else if (png_ptr->mode & (PNG_HAVE_IDAT|PNG_HAVE_PLTE))
       {
          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 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)
       {
          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))
                      {
                         /* 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))
                         {
                            /* 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 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))
                                  {
                                     /* 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";

                                     else
                                        errmsg = png_ptr->zstream.msg;
                                  }

                                  /* 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)
          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 /* PNG_READ_iCCP_SUPPORTED */

    #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))
          png_chunk_error(png_ptr, "missing IHDR");

       else if (png_ptr->mode & PNG_HAVE_IDAT)
       {
          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))
          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 (entry_start > buffer + length - 2)
       {
          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)
       {
          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 /* PNG_READ_sPLT_SUPPORTED */

    #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))
          png_chunk_error(png_ptr, "missing IHDR");

       else if (png_ptr->mode & PNG_HAVE_IDAT)
       {
          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))
       {
          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))
          {
             /* 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 > png_ptr->num_palette || length > 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))
       {
          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))
          png_chunk_error(png_ptr, "missing IHDR");

       else if ((png_ptr->mode & PNG_HAVE_IDAT) ||
          (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
           !(png_ptr->mode & PNG_HAVE_PLTE)))
       {
          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))
       {
          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)
          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))
          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 && info_ptr->num_palette)
          {
             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)) /* 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))
          png_chunk_error(png_ptr, "missing IHDR");

       else if ((png_ptr->mode & PNG_HAVE_IDAT) || !(png_ptr->mode & PNG_HAVE_PLTE))
       {
          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))
       {
          png_crc_finish(png_ptr, length);
          png_chunk_benign_error(png_ptr, "duplicate");
          return;
       }

       num = length / 2 ;

       if (num != png_ptr->num_palette || num > 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))
          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))
          png_chunk_error(png_ptr, "missing IHDR");

       else if (png_ptr->mode & PNG_HAVE_IDAT)
       {
          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))
       {
          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))
          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))
          png_chunk_error(png_ptr, "missing IHDR");

       else if (png_ptr->mode & PNG_HAVE_IDAT)
       {
          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))
       {
          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))
          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))
          png_chunk_error(png_ptr, "missing IHDR");

       else if (png_ptr->mode & PNG_HAVE_IDAT)
       {
          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))
       {
          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))
          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))
          png_chunk_error(png_ptr, "missing IHDR");

       else if (png_ptr->mode & PNG_HAVE_IDAT)
       {
          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))
       {
          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))
          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) ||
           i >= length || buffer[i++] != 0)
          png_chunk_benign_error(png_ptr, "bad width format");

       else if (!PNG_FP_IS_POSITIVE(state))
          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) ||
             i != length)
             png_chunk_benign_error(png_ptr, "bad height format");

          else if (!PNG_FP_IS_POSITIVE(state))
             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))
          png_chunk_error(png_ptr, "missing IHDR");

       else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_tIME))
       {
          png_crc_finish(png_ptr, length);
          png_chunk_benign_error(png_ptr, "duplicate");
          return;
       }

       if (png_ptr->mode & PNG_HAVE_IDAT)
          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))
          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))
          png_chunk_error(png_ptr, "missing IHDR");

       if (png_ptr->mode & PNG_HAVE_IDAT)
          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))
          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))
          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))
          png_chunk_error(png_ptr, "missing IHDR");

       if (png_ptr->mode & PNG_HAVE_IDAT)
          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))
          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))
                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))
          png_chunk_error(png_ptr, "missing IHDR");

       if (png_ptr->mode & PNG_HAVE_IDAT)
          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))
          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 allocaton may overflow.
           */
          ++prefix_length;

          if (!compressed && prefix_length <= length)
             uncompressed_length = length - prefix_length;

          else if (compressed && 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)
                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))
                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_CHUNK_MALLOC_LIMIT_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 /* PNG_READ_UNKNOWN_CHUNKS_SUPPORTED */

    /* 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))
             {
                /* 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 occured, 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 /* PNG_READ_USER_CHUNKS_SUPPORTED */

    #  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))
                   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 /* PNG_USER_LIMITS_SUPPORTED */
                   /* 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 /* !PNG_READ_UNKNOWN_CHUNKS_SUPPORTED */

       /* Check for unhandled critical chunks */
       if (!handled && 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_uint_32 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) /* 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 && (png_ptr->transformations & PNG_INTERLACE) &&
          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), S_MASK(3,d,s), S_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 /* !PNG_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)
                   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)
             {
                /* 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 = 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) &&
                         png_isaligned(sp, png_uint_32) &&
                         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 /* PNG_ALIGN_ 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 = row_width;
                   }
             }

             /* NOT REACHED*/
          } /* pixel_depth >= 8 */

          /* Here if pixel_depth < 8 to check 'end_ptr' below. */
       }
       else
    #endif

       /* 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)
                {
                    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)
                {
                   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)
                {
                   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 /* PNG_READ_INTERLACING_SUPPORTED */

    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;

          c = b;
          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 = inflate(&png_ptr->zstream, 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))
       {
          /* 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))
          {
             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)
    {
    #ifdef PNG_READ_INTERLACING_SUPPORTED
       /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */

       /* Start of interlace block */
       static PNG_CONST png_byte png_pass_start[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};
    #endif /* PNG_READ_INTERLACING_SUPPORTED */

       png_debug(1, "in png_read_finish_row");
       png_ptr->row_number++;
       if (png_ptr->row_number < png_ptr->num_rows)
          return;

    #ifdef PNG_READ_INTERLACING_SUPPORTED
       if (png_ptr->interlaced)
       {
          png_ptr->row_number = 0;

          /* 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))
             {
                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;
       }
    #endif /* PNG_READ_INTERLACING_SUPPORTED */

       /* Here after at the end of the last row of the last pass. */
       png_read_finish_IDAT(png_ptr);
    }
    #endif /* PNG_SEQUENTIAL_READ_SUPPORTED */

    void /* PRIVATE */
    png_read_start_row(png_structrp png_ptr)
    {
    #ifdef PNG_READ_INTERLACING_SUPPORTED
       /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */

       /* Start of interlace block */
       static PNG_CONST png_byte png_pass_start[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};
    #endif

       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
    #ifdef PNG_READ_INTERLACING_SUPPORTED
       if (png_ptr->interlaced)
       {
          if (!(png_ptr->transformations & PNG_INTERLACE))
             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
    #endif /* PNG_READ_INTERLACING_SUPPORTED */
       {
          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 simpliar 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) && png_ptr->bit_depth < 8)
          max_pixel_depth = 8;
    #endif

    #ifdef PNG_READ_EXPAND_SUPPORTED
       if (png_ptr->transformations & PNG_EXPAND)
       {
          if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
          {
             if (png_ptr->num_trans)
                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)
                max_pixel_depth *= 2;
          }

          else if (png_ptr->color_type == PNG_COLOR_TYPE_RGB)
          {
             if (png_ptr->num_trans)
             {
                max_pixel_depth *= 4;
                max_pixel_depth /= 3;
             }
          }
       }
    #endif

    #ifdef PNG_READ_EXPAND_16_SUPPORTED
       if (png_ptr->transformations & PNG_EXPAND_16)
       {
    #     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)
             {
                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))
       {
          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)
       {
          if (
    #ifdef PNG_READ_EXPAND_SUPPORTED
              (png_ptr->num_trans && (png_ptr->transformations & PNG_EXPAND)) ||
    #endif
    #ifdef PNG_READ_FILLER_SUPPORTED
              (png_ptr->transformations & (PNG_FILLER)) ||
    #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)
       {
          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)
            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)
       {
          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 /* PNG_READ_SUPPORTED */