The Tor Browser: media/libpng/pngrutil.c@97036ab72558 (annotated)

media/libpng/pngrutil.c@97036ab72558 (annotated)

media/libpng/pngrutil.c

Tue, 06 Jan 2015 21:39:09 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Tue, 06 Jan 2015 21:39:09 +0100
branch: TOR_BUG_9701
changeset 8: 97036ab72558
permissions: -rw-r--r--

Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.

 /* pngrutil.c - utilities to read a PNG file
  *
  * Last changed in libpng 1.6.10 [March 6, 2014]
  * Copyright (c) 1998-2014 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_error(png_ptr, "CRC error");
       return (1);
    }
    return (0);
 }
 /* Compare the CRC stored in the PNG file with that calculated by libpng from
  * the data it has read thus far.
  */
 int /* PRIVATE */
 png_crc_error(png_structrp png_ptr)
 {
    png_byte crc_bytes[4];
    png_uint_32 crc;
    int need_crc = 1;
    if (PNG_CHUNK_ANCILLARY(png_ptr->chunk_name))
    {
       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);
 }
 #if defined(PNG_READ_iCCP_SUPPORTED) || defined(PNG_READ_iTXt_SUPPORTED) ||\
     defined(PNG_READ_pCAL_SUPPORTED) || defined(PNG_READ_sCAL_SUPPORTED) ||\
     defined(PNG_READ_sPLT_SUPPORTED) || defined(PNG_READ_tEXt_SUPPORTED) ||\
     defined(PNG_READ_zTXt_SUPPORTED) || defined(PNG_SEQUENTIAL_READ_SUPPORTED)
 /* Manage the read buffer; this simply reallocates the buffer if it is not small
  * enough (or if it is not allocated).  The routine returns a pointer to the
  * buffer; if an error occurs and 'warn' is set the routine returns NULL, else
  * it will call png_error (via png_malloc) on failure.  (warn == 2 means
  * 'silent').
  */
 static png_bytep
 png_read_buffer(png_structrp png_ptr, png_alloc_size_t new_size, int warn)
 {
    png_bytep buffer = png_ptr->read_buffer;
    if (buffer != NULL && new_size > png_ptr->read_buffer_size)
    {
       png_ptr->read_buffer = NULL;
       png_ptr->read_buffer = NULL;
       png_ptr->read_buffer_size = 0;
       png_free(png_ptr, buffer);
       buffer = NULL;
    }
    if (buffer == NULL)
    {
       buffer = png_voidcast(png_bytep, png_malloc_base(png_ptr, new_size));
       if (buffer != NULL)
       {
          png_ptr->read_buffer = buffer;
          png_ptr->read_buffer_size = new_size;
       }
       else if (warn < 2) /* else silent */
       {
          if (warn)
              png_chunk_warning(png_ptr, "insufficient memory to read chunk");
          else
              png_chunk_error(png_ptr, "insufficient memory to read chunk");
       }
    }
    return buffer;
 }
 #endif /* PNG_READ_iCCP|iTXt|pCAL|sCAL|sPLT|tEXt|zTXt|SEQUENTIAL_READ */
 /* png_inflate_claim: claim the zstream for some nefarious purpose that involves
  * decompression.  Returns Z_OK on success, else a zlib error code.  It checks
  * the owner but, in final release builds, just issues a warning if some other
  * chunk apparently owns the stream.  Prior to release it does a png_error.
  */
 static int
 png_inflate_claim(png_structrp png_ptr, png_uint_32 owner)
 {
    if (png_ptr->zowner != 0)
    {
       char msg[64];
       PNG_STRING_FROM_CHUNK(msg, png_ptr->zowner);
       /* So the message that results is "<chunk> using zstream"; this is an
        * internal error, but is very useful for debugging.  i18n requirements
        * are minimal.
        */
       (void)png_safecat(msg, (sizeof msg), 4, " using zstream");
 #     if PNG_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];
 #ifdef PNG_READ_APNG_SUPPORTED
    png_ptr->first_frame_width = width;
    png_ptr->first_frame_height = height;
 #endif
    /* 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)
             return;
          else
             png_chunk_error(png_ptr, "CRC error");
       }
       /* Otherwise, we (optionally) emit a warning and use the chunk. */
       else if (!(png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_NOWARN))
          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, i;
    png_byte sample_depth;
    png_byte buf[4];
    png_debug(1, "in png_handle_sBIT");
    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;
       sample_depth = 8;
    }
    else
    {
       truelen = png_ptr->channels;
       sample_depth = png_ptr->bit_depth;
    }
    if (length != truelen || length > 4)
    {
       png_chunk_benign_error(png_ptr, "invalid");
       png_crc_finish(png_ptr, length);
       return;
    }
    buf[0] = buf[1] = buf[2] = buf[3] = sample_depth;
    png_crc_read(png_ptr, buf, truelen);
    if (png_crc_finish(png_ptr, 0))
       return;
    for (i=0; i<truelen; ++i)
       if (buf[i] == 0 || buf[i] > sample_depth)
       {
          png_chunk_benign_error(png_ptr, "invalid");
          return;
       }
    if (png_ptr->color_type & PNG_COLOR_MASK_COLOR)
    {
       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,
 /*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,
 /*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 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) +
 * 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_APNG_SUPPORTED
 void /* PRIVATE */
 png_handle_acTL(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 {
     png_byte data[8];
     png_uint_32 num_frames;
     png_uint_32 num_plays;
     png_uint_32 didSet;
     png_debug(1, "in png_handle_acTL");
     if (!(png_ptr->mode & PNG_HAVE_IHDR))
     {
         png_error(png_ptr, "Missing IHDR before acTL");
     }
     else if (png_ptr->mode & PNG_HAVE_IDAT)
     {
         png_warning(png_ptr, "Invalid acTL after IDAT skipped");
         png_crc_finish(png_ptr, length);
         return;
     }
     else if (png_ptr->mode & PNG_HAVE_acTL)
     {
         png_warning(png_ptr, "Duplicate acTL skipped");
         png_crc_finish(png_ptr, length);
         return;
     }
     else if (length != 8)
     {
         png_warning(png_ptr, "acTL with invalid length skipped");
         png_crc_finish(png_ptr, length);
         return;
     }
     png_crc_read(png_ptr, data, 8);
     png_crc_finish(png_ptr, 0);
     num_frames = png_get_uint_31(png_ptr, data);
     num_plays = png_get_uint_31(png_ptr, data + 4);
     /* the set function will do error checking on num_frames */
     didSet = png_set_acTL(png_ptr, info_ptr, num_frames, num_plays);
     if(didSet)
         png_ptr->mode |= PNG_HAVE_acTL;
 }
 void /* PRIVATE */
 png_handle_fcTL(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 {
     png_byte data[22];
     png_uint_32 width;
     png_uint_32 height;
     png_uint_32 x_offset;
     png_uint_32 y_offset;
     png_uint_16 delay_num;
     png_uint_16 delay_den;
     png_byte dispose_op;
     png_byte blend_op;
     png_debug(1, "in png_handle_fcTL");
     png_ensure_sequence_number(png_ptr, length);
     if (!(png_ptr->mode & PNG_HAVE_IHDR))
     {
         png_error(png_ptr, "Missing IHDR before fcTL");
     }
     else if (png_ptr->mode & PNG_HAVE_IDAT)
     {
         /* for any frames other then the first this message may be misleading,
         * but correct. PNG_HAVE_IDAT is unset before the frame head is read
         * i can't think of a better message */
         png_warning(png_ptr, "Invalid fcTL after IDAT skipped");
         png_crc_finish(png_ptr, length-4);
         return;
     }
     else if (png_ptr->mode & PNG_HAVE_fcTL)
     {
         png_warning(png_ptr, "Duplicate fcTL within one frame skipped");
         png_crc_finish(png_ptr, length-4);
         return;
     }
     else if (length != 26)
     {
         png_warning(png_ptr, "fcTL with invalid length skipped");
         png_crc_finish(png_ptr, length-4);
         return;
     }
     png_crc_read(png_ptr, data, 22);
     png_crc_finish(png_ptr, 0);
     width = png_get_uint_31(png_ptr, data);
     height = png_get_uint_31(png_ptr, data + 4);
     x_offset = png_get_uint_31(png_ptr, data + 8);
     y_offset = png_get_uint_31(png_ptr, data + 12);
     delay_num = png_get_uint_16(data + 16);
     delay_den = png_get_uint_16(data + 18);
     dispose_op = data[20];
     blend_op = data[21];
     if (png_ptr->num_frames_read == 0 && (x_offset != 0 || y_offset != 0))
     {
         png_warning(png_ptr, "fcTL for the first frame must have zero offset");
         return;
     }
     if (info_ptr != NULL)
     {
         if (png_ptr->num_frames_read == 0 &&
             (width != info_ptr->width || height != info_ptr->height))
         {
             png_warning(png_ptr, "size in first frame's fcTL must match "
                                "the size in IHDR");
             return;
         }
         /* The set function will do more error checking */
         png_set_next_frame_fcTL(png_ptr, info_ptr, width, height,
                                 x_offset, y_offset, delay_num, delay_den,
                                 dispose_op, blend_op);
         png_read_reinit(png_ptr, info_ptr);
         png_ptr->mode |= PNG_HAVE_fcTL;
     }
 }
 void /* PRIVATE */
 png_have_info(png_structp png_ptr, png_infop info_ptr)
 {
     if((info_ptr->valid & PNG_INFO_acTL) && !(info_ptr->valid & PNG_INFO_fcTL))
     {
         png_ptr->apng_flags |= PNG_FIRST_FRAME_HIDDEN;
         info_ptr->num_frames++;
     }
 }
 void /* PRIVATE */
 png_handle_fdAT(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 {
     png_ensure_sequence_number(png_ptr, length);
     /* This function is only called from png_read_end(), png_read_info(),
     * and png_push_read_chunk() which means that:
     * - the user doesn't want to read this frame
     * - or this is an out-of-place fdAT
     * in either case it is safe to ignore the chunk with a warning */
     png_warning(png_ptr, "ignoring fdAT chunk");
     png_crc_finish(png_ptr, length - 4);
     PNG_UNUSED(info_ptr)
 }
 void /* PRIVATE */
 png_ensure_sequence_number(png_structp png_ptr, png_uint_32 length)
 {
     png_byte data[4];
     png_uint_32 sequence_number;
     if (length < 4)
         png_error(png_ptr, "invalid fcTL or fdAT chunk found");
     png_crc_read(png_ptr, data, 4);
     sequence_number = png_get_uint_31(png_ptr, data);
     if (sequence_number != png_ptr->next_seq_num)
         png_error(png_ptr, "fcTL or fdAT chunk with out-of-order sequence "
                            "number found");
     png_ptr->next_seq_num++;
 }
 #endif /* PNG_READ_APNG_SUPPORTED */
 #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;
       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;
 #ifdef PNG_READ_APNG_SUPPORTED
          png_uint_32 bytes_to_skip = 0;
          while (png_ptr->idat_size == 0 || bytes_to_skip != 0)
          {
             png_crc_finish(png_ptr, bytes_to_skip);
             bytes_to_skip = 0;
             png_ptr->idat_size = png_read_chunk_header(png_ptr);
             if (png_ptr->num_frames_read == 0)
             {
                if (png_ptr->chunk_name != png_IDAT)
                   png_error(png_ptr, "Not enough image data");
             }
             else
             {
                if (png_ptr->chunk_name == png_IEND)
                   png_error(png_ptr, "Not enough image data");
                if (png_ptr->chunk_name != png_fdAT)
                {
                   png_warning(png_ptr, "Skipped (ignored) a chunk "
                                        "between APNG chunks");
                   bytes_to_skip = png_ptr->idat_size;
                   continue;
                }
                png_ensure_sequence_number(png_ptr, png_ptr->idat_size);
                png_ptr->idat_size -= 4;
             }
          }
 #else
          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");
          }
 #endif /* PNG_READ_APNG_SUPPORTED */
          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;
 #ifdef PNG_READ_APNG_SUPPORTED
          png_ptr->num_frames_read++;
 #endif
          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) +
 + ((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;
 }
 #ifdef PNG_READ_APNG_SUPPORTED
 /* This function is to be called after the main IDAT set has been read and
  * before a new IDAT is read. It resets some parts of png_ptr
  * to make them usable by the read functions again */
 void /* PRIVATE */
 png_read_reset(png_structp png_ptr)
 {
     png_ptr->mode &= ~PNG_HAVE_IDAT;
     png_ptr->mode &= ~PNG_AFTER_IDAT;
     png_ptr->row_number = 0;
     png_ptr->pass = 0;
 }
 void /* PRIVATE */
 png_read_reinit(png_structp png_ptr, png_infop info_ptr)
 {
     png_ptr->width = info_ptr->next_frame_width;
     png_ptr->height = info_ptr->next_frame_height;
     png_ptr->rowbytes = PNG_ROWBYTES(png_ptr->pixel_depth,png_ptr->width);
     png_ptr->info_rowbytes = PNG_ROWBYTES(info_ptr->pixel_depth,
         png_ptr->width);
     if (png_ptr->prev_row)
         memset(png_ptr->prev_row, 0, png_ptr->rowbytes + 1);
 }
 #ifdef PNG_PROGRESSIVE_READ_SUPPORTED
 /* same as png_read_reset() but for the progressive reader */
 void /* PRIVATE */
 png_progressive_read_reset(png_structp png_ptr)
 {
 #ifdef PNG_READ_INTERLACING_SUPPORTED
     /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
     /* Start of interlace block */
     static PNG_CONST png_byte png_pass_start[] = {0, 4, 0, 2, 0, 1, 0};
     /* Offset to next interlace block */
     static PNG_CONST png_byte png_pass_inc[] = {8, 8, 4, 4, 2, 2, 1};
     /* Start of interlace block in the y direction */
     static PNG_CONST png_byte png_pass_ystart[] = {0, 0, 4, 0, 2, 0, 1};
     /* Offset to next interlace block in the y direction */
     static PNG_CONST png_byte png_pass_yinc[] = {8, 8, 8, 4, 4, 2, 2};
     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;
     }
     png_ptr->flags &= ~PNG_FLAG_ZSTREAM_ENDED;
     if (inflateReset(&(png_ptr->zstream)) != Z_OK)
         png_error(png_ptr, "inflateReset failed");
     png_ptr->zstream.avail_in = 0;
     png_ptr->zstream.next_in = 0;
     png_ptr->zstream.next_out = png_ptr->row_buf;
     png_ptr->zstream.avail_out = (uInt)PNG_ROWBYTES(png_ptr->pixel_depth,
         png_ptr->iwidth) + 1;
 }
 #endif /* PNG_PROGRESSIVE_READ_SUPPORTED */
 #endif /* PNG_READ_APNG_SUPPORTED */
 #endif /* PNG_READ_SUPPORTED */

The Tor Browser / annotate

media/libpng/pngrutil.c@97036ab72558 (annotated)

media/libpng/pngrutil.c