/* png.c - location for general purpose libpng functions
 *
 * Last changed in libpng 1.5.4 [July 7, 2011]
 * Copyright (c) 1998-2011 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
 *
 * This code is released under the libpng license.
 * For conditions of distribution and use, see the disclaimer
 * and license in png.h
 */

#include "pngpriv.h"

/* Generate a compiler error if there is an old png.h in the search path. */
typedef png_libpng_version_1_5_4 Your_png_h_is_not_version_1_5_4;

/* Tells libpng that we have already handled the first "num_bytes" bytes
 * of the PNG file signature.  If the PNG data is embedded into another
 * stream we can set num_bytes = 8 so that libpng will not attempt to read
 * or write any of the magic bytes before it starts on the IHDR.
 */

#ifdef PNG_READ_SUPPORTED
void PNGAPI
png_set_sig_bytes(png_structp png_ptr, int num_bytes)
{
   png_debug(1, "in png_set_sig_bytes");

   if (png_ptr == NULL)
      return;

   if (num_bytes > 8)
      png_error(png_ptr, "Too many bytes for PNG signature");

   png_ptr->sig_bytes = (png_byte)(num_bytes < 0 ? 0 : num_bytes);
}

/* Checks whether the supplied bytes match the PNG signature.  We allow
 * checking less than the full 8-byte signature so that those apps that
 * already read the first few bytes of a file to determine the file type
 * can simply check the remaining bytes for extra assurance.  Returns
 * an integer less than, equal to, or greater than zero if sig is found,
 * respectively, to be less than, to match, or be greater than the correct
 * PNG signature (this is the same behaviour as strcmp, memcmp, etc).
 */
int PNGAPI
png_sig_cmp(png_const_bytep sig, png_size_t start, png_size_t num_to_check)
{
   png_byte png_signature[8] = {137, 80, 78, 71, 13, 10, 26, 10};

   if (num_to_check > 8)
      num_to_check = 8;

   else if (num_to_check < 1)
      return (-1);

   if (start > 7)
      return (-1);

   if (start + num_to_check > 8)
      num_to_check = 8 - start;

   return ((int)(png_memcmp(&sig[start], &png_signature[start], num_to_check)));
}

#endif /* PNG_READ_SUPPORTED */

#if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
/* Function to allocate memory for zlib */
PNG_FUNCTION(voidpf /* PRIVATE */,
png_zalloc,(voidpf png_ptr, uInt items, uInt size),PNG_ALLOCATED)
{
   png_voidp ptr;
   png_structp p=(png_structp)png_ptr;
   png_uint_32 save_flags=p->flags;
   png_alloc_size_t num_bytes;

   if (png_ptr == NULL)
      return (NULL);

   if (items > PNG_UINT_32_MAX/size)
   {
     png_warning (p, "Potential overflow in png_zalloc()");
     return (NULL);
   }
   num_bytes = (png_alloc_size_t)items * size;

   p->flags|=PNG_FLAG_MALLOC_NULL_MEM_OK;
   ptr = (png_voidp)png_malloc((png_structp)png_ptr, num_bytes);
   p->flags=save_flags;

   return ((voidpf)ptr);
}

/* Function to free memory for zlib */
void /* PRIVATE */
png_zfree(voidpf png_ptr, voidpf ptr)
{
   png_free((png_structp)png_ptr, (png_voidp)ptr);
}

/* Reset the CRC variable to 32 bits of 1's.  Care must be taken
 * in case CRC is > 32 bits to leave the top bits 0.
 */
void /* PRIVATE */
png_reset_crc(png_structp png_ptr)
{
   png_ptr->crc = crc32(0, Z_NULL, 0);
}

/* Calculate the CRC over a section of data.  We can only pass as
 * much data to this routine as the largest single buffer size.  We
 * also check that this data will actually be used before going to the
 * trouble of calculating it.
 */
void /* PRIVATE */
png_calculate_crc(png_structp png_ptr, png_const_bytep ptr, png_size_t length)
{
   int need_crc = 1;

   if (png_ptr->chunk_name[0] & 0x20)                     /* ancillary */
   {
      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;
   }

   if (need_crc)
      png_ptr->crc = crc32(png_ptr->crc, ptr, (uInt)length);
}

/* Check a user supplied version number, called from both read and write
 * functions that create a png_struct
 */
int
png_user_version_check(png_structp png_ptr, png_const_charp user_png_ver)
{
   if (user_png_ver)
   {
      int i = 0;

      do
      {
         if (user_png_ver[i] != png_libpng_ver[i])
            png_ptr->flags |= PNG_FLAG_LIBRARY_MISMATCH;
      } while (png_libpng_ver[i++]);
   }

   else
      png_ptr->flags |= PNG_FLAG_LIBRARY_MISMATCH;

   if (png_ptr->flags & PNG_FLAG_LIBRARY_MISMATCH)
   {
     /* Libpng 0.90 and later are binary incompatible with libpng 0.89, so
      * we must recompile any applications that use any older library version.
      * For versions after libpng 1.0, we will be compatible, so we need
      * only check the first digit.
      */
      if (user_png_ver == NULL || user_png_ver[0] != png_libpng_ver[0] ||
          (user_png_ver[0] == '1' && user_png_ver[2] != png_libpng_ver[2]) ||
          (user_png_ver[0] == '0' && user_png_ver[2] < '9'))
      {
#ifdef PNG_WARNINGS_SUPPORTED
         size_t pos = 0;
         char m[128];

         pos = png_safecat(m, sizeof m, pos, "Application built with libpng-");
         pos = png_safecat(m, sizeof m, pos, user_png_ver);
         pos = png_safecat(m, sizeof m, pos, " but running with ");
         pos = png_safecat(m, sizeof m, pos, png_libpng_ver);

         png_warning(png_ptr, m);
#endif

#ifdef PNG_ERROR_NUMBERS_SUPPORTED
         png_ptr->flags = 0;
#endif

         return 0;
      }
   }

   /* Success return. */
   return 1;
}

/* Allocate the memory for an info_struct for the application.  We don't
 * really need the png_ptr, but it could potentially be useful in the
 * future.  This should be used in favour of malloc(png_sizeof(png_info))
 * and png_info_init() so that applications that want to use a shared
 * libpng don't have to be recompiled if png_info changes size.
 */
PNG_FUNCTION(png_infop,PNGAPI
png_create_info_struct,(png_structp png_ptr),PNG_ALLOCATED)
{
   png_infop info_ptr;

   png_debug(1, "in png_create_info_struct");

   if (png_ptr == NULL)
      return (NULL);

#ifdef PNG_USER_MEM_SUPPORTED
   info_ptr = (png_infop)png_create_struct_2(PNG_STRUCT_INFO,
      png_ptr->malloc_fn, png_ptr->mem_ptr);
#else
   info_ptr = (png_infop)png_create_struct(PNG_STRUCT_INFO);
#endif
   if (info_ptr != NULL)
      png_info_init_3(&info_ptr, png_sizeof(png_info));

   return (info_ptr);
}

/* This function frees the memory associated with a single info struct.
 * Normally, one would use either png_destroy_read_struct() or
 * png_destroy_write_struct() to free an info struct, but this may be
 * useful for some applications.
 */
void PNGAPI
png_destroy_info_struct(png_structp png_ptr, png_infopp info_ptr_ptr)
{
   png_infop info_ptr = NULL;

   png_debug(1, "in png_destroy_info_struct");

   if (png_ptr == NULL)
      return;

   if (info_ptr_ptr != NULL)
      info_ptr = *info_ptr_ptr;

   if (info_ptr != NULL)
   {
      png_info_destroy(png_ptr, info_ptr);

#ifdef PNG_USER_MEM_SUPPORTED
      png_destroy_struct_2((png_voidp)info_ptr, png_ptr->free_fn,
          png_ptr->mem_ptr);
#else
      png_destroy_struct((png_voidp)info_ptr);
#endif
      *info_ptr_ptr = NULL;
   }
}

/* Initialize the info structure.  This is now an internal function (0.89)
 * and applications using it are urged to use png_create_info_struct()
 * instead.
 */

void PNGAPI
png_info_init_3(png_infopp ptr_ptr, png_size_t png_info_struct_size)
{
   png_infop info_ptr = *ptr_ptr;

   png_debug(1, "in png_info_init_3");

   if (info_ptr == NULL)
      return;

   if (png_sizeof(png_info) > png_info_struct_size)
   {
      png_destroy_struct(info_ptr);
      info_ptr = (png_infop)png_create_struct(PNG_STRUCT_INFO);
      *ptr_ptr = info_ptr;
   }

   /* Set everything to 0 */
   png_memset(info_ptr, 0, png_sizeof(png_info));
}

void PNGAPI
png_data_freer(png_structp png_ptr, png_infop info_ptr,
   int freer, png_uint_32 mask)
{
   png_debug(1, "in png_data_freer");

   if (png_ptr == NULL || info_ptr == NULL)
      return;

   if (freer == PNG_DESTROY_WILL_FREE_DATA)
      info_ptr->free_me |= mask;

   else if (freer == PNG_USER_WILL_FREE_DATA)
      info_ptr->free_me &= ~mask;

   else
      png_warning(png_ptr,
         "Unknown freer parameter in png_data_freer");
}

void PNGAPI
png_free_data(png_structp png_ptr, png_infop info_ptr, png_uint_32 mask,
   int num)
{
   png_debug(1, "in png_free_data");

   if (png_ptr == NULL || info_ptr == NULL)
      return;

#ifdef PNG_TEXT_SUPPORTED
   /* Free text item num or (if num == -1) all text items */
   if ((mask & PNG_FREE_TEXT) & info_ptr->free_me)
   {
      if (num != -1)
      {
         if (info_ptr->text && info_ptr->text[num].key)
         {
            png_free(png_ptr, info_ptr->text[num].key);
            info_ptr->text[num].key = NULL;
         }
      }

      else
      {
         int i;
         for (i = 0; i < info_ptr->num_text; i++)
             png_free_data(png_ptr, info_ptr, PNG_FREE_TEXT, i);
         png_free(png_ptr, info_ptr->text);
         info_ptr->text = NULL;
         info_ptr->num_text=0;
      }
   }
#endif

#ifdef PNG_tRNS_SUPPORTED
   /* Free any tRNS entry */
   if ((mask & PNG_FREE_TRNS) & info_ptr->free_me)
   {
      png_free(png_ptr, info_ptr->trans_alpha);
      info_ptr->trans_alpha = NULL;
      info_ptr->valid &= ~PNG_INFO_tRNS;
   }
#endif

#ifdef PNG_sCAL_SUPPORTED
   /* Free any sCAL entry */
   if ((mask & PNG_FREE_SCAL) & info_ptr->free_me)
   {
      png_free(png_ptr, info_ptr->scal_s_width);
      png_free(png_ptr, info_ptr->scal_s_height);
      info_ptr->scal_s_width = NULL;
      info_ptr->scal_s_height = NULL;
      info_ptr->valid &= ~PNG_INFO_sCAL;
   }
#endif

#ifdef PNG_pCAL_SUPPORTED
   /* Free any pCAL entry */
   if ((mask & PNG_FREE_PCAL) & info_ptr->free_me)
   {
      png_free(png_ptr, info_ptr->pcal_purpose);
      png_free(png_ptr, info_ptr->pcal_units);
      info_ptr->pcal_purpose = NULL;
      info_ptr->pcal_units = NULL;
      if (info_ptr->pcal_params != NULL)
         {
            int i;
            for (i = 0; i < (int)info_ptr->pcal_nparams; i++)
            {
               png_free(png_ptr, info_ptr->pcal_params[i]);
               info_ptr->pcal_params[i] = NULL;
            }
            png_free(png_ptr, info_ptr->pcal_params);
            info_ptr->pcal_params = NULL;
         }
      info_ptr->valid &= ~PNG_INFO_pCAL;
   }
#endif

#ifdef PNG_iCCP_SUPPORTED
   /* Free any iCCP entry */
   if ((mask & PNG_FREE_ICCP) & info_ptr->free_me)
   {
      png_free(png_ptr, info_ptr->iccp_name);
      png_free(png_ptr, info_ptr->iccp_profile);
      info_ptr->iccp_name = NULL;
      info_ptr->iccp_profile = NULL;
      info_ptr->valid &= ~PNG_INFO_iCCP;
   }
#endif

#ifdef PNG_sPLT_SUPPORTED
   /* Free a given sPLT entry, or (if num == -1) all sPLT entries */
   if ((mask & PNG_FREE_SPLT) & info_ptr->free_me)
   {
      if (num != -1)
      {
         if (info_ptr->splt_palettes)
         {
            png_free(png_ptr, info_ptr->splt_palettes[num].name);
            png_free(png_ptr, info_ptr->splt_palettes[num].entries);
            info_ptr->splt_palettes[num].name = NULL;
            info_ptr->splt_palettes[num].entries = NULL;
         }
      }

      else
      {
         if (info_ptr->splt_palettes_num)
         {
            int i;
            for (i = 0; i < (int)info_ptr->splt_palettes_num; i++)
               png_free_data(png_ptr, info_ptr, PNG_FREE_SPLT, i);

            png_free(png_ptr, info_ptr->splt_palettes);
            info_ptr->splt_palettes = NULL;
            info_ptr->splt_palettes_num = 0;
         }
         info_ptr->valid &= ~PNG_INFO_sPLT;
      }
   }
#endif

#ifdef PNG_UNKNOWN_CHUNKS_SUPPORTED
   if (png_ptr->unknown_chunk.data)
   {
      png_free(png_ptr, png_ptr->unknown_chunk.data);
      png_ptr->unknown_chunk.data = NULL;
   }

   if ((mask & PNG_FREE_UNKN) & info_ptr->free_me)
   {
      if (num != -1)
      {
          if (info_ptr->unknown_chunks)
          {
             png_free(png_ptr, info_ptr->unknown_chunks[num].data);
             info_ptr->unknown_chunks[num].data = NULL;
          }
      }

      else
      {
         int i;

         if (info_ptr->unknown_chunks_num)
         {
            for (i = 0; i < info_ptr->unknown_chunks_num; i++)
               png_free_data(png_ptr, info_ptr, PNG_FREE_UNKN, i);

            png_free(png_ptr, info_ptr->unknown_chunks);
            info_ptr->unknown_chunks = NULL;
            info_ptr->unknown_chunks_num = 0;
         }
      }
   }
#endif

#ifdef PNG_hIST_SUPPORTED
   /* Free any hIST entry */
   if ((mask & PNG_FREE_HIST)  & info_ptr->free_me)
   {
      png_free(png_ptr, info_ptr->hist);
      info_ptr->hist = NULL;
      info_ptr->valid &= ~PNG_INFO_hIST;
   }
#endif

   /* Free any PLTE entry that was internally allocated */
   if ((mask & PNG_FREE_PLTE) & info_ptr->free_me)
   {
      png_zfree(png_ptr, info_ptr->palette);
      info_ptr->palette = NULL;
      info_ptr->valid &= ~PNG_INFO_PLTE;
      info_ptr->num_palette = 0;
   }

#ifdef PNG_INFO_IMAGE_SUPPORTED
   /* Free any image bits attached to the info structure */
   if ((mask & PNG_FREE_ROWS) & info_ptr->free_me)
   {
      if (info_ptr->row_pointers)
      {
         int row;
         for (row = 0; row < (int)info_ptr->height; row++)
         {
            png_free(png_ptr, info_ptr->row_pointers[row]);
            info_ptr->row_pointers[row] = NULL;
         }
         png_free(png_ptr, info_ptr->row_pointers);
         info_ptr->row_pointers = NULL;
      }
      info_ptr->valid &= ~PNG_INFO_IDAT;
   }
#endif

   if (num != -1)
      mask &= ~PNG_FREE_MUL;

   info_ptr->free_me &= ~mask;
}

/* This is an internal routine to free any memory that the info struct is
 * pointing to before re-using it or freeing the struct itself.  Recall
 * that png_free() checks for NULL pointers for us.
 */
void /* PRIVATE */
png_info_destroy(png_structp png_ptr, png_infop info_ptr)
{
   png_debug(1, "in png_info_destroy");

   png_free_data(png_ptr, info_ptr, PNG_FREE_ALL, -1);

#ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
   if (png_ptr->num_chunk_list)
   {
      png_free(png_ptr, png_ptr->chunk_list);
      png_ptr->chunk_list = NULL;
      png_ptr->num_chunk_list = 0;
   }
#endif

   png_info_init_3(&info_ptr, png_sizeof(png_info));
}
#endif /* defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) */

/* This function returns a pointer to the io_ptr associated with the user
 * functions.  The application should free any memory associated with this
 * pointer before png_write_destroy() or png_read_destroy() are called.
 */
png_voidp PNGAPI
png_get_io_ptr(png_structp png_ptr)
{
   if (png_ptr == NULL)
      return (NULL);

   return (png_ptr->io_ptr);
}

#if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
#  ifdef PNG_STDIO_SUPPORTED
/* Initialize the default input/output functions for the PNG file.  If you
 * use your own read or write routines, you can call either png_set_read_fn()
 * or png_set_write_fn() instead of png_init_io().  If you have defined
 * PNG_NO_STDIO, you must use a function of your own because "FILE *" isn't
 * necessarily available.
 */
void PNGAPI
png_init_io(png_structp png_ptr, png_FILE_p fp)
{
   png_debug(1, "in png_init_io");

   if (png_ptr == NULL)
      return;

   png_ptr->io_ptr = (png_voidp)fp;
}
#  endif

#  ifdef PNG_TIME_RFC1123_SUPPORTED
/* Convert the supplied time into an RFC 1123 string suitable for use in
 * a "Creation Time" or other text-based time string.
 */
png_const_charp PNGAPI
png_convert_to_rfc1123(png_structp png_ptr, png_const_timep ptime)
{
   static PNG_CONST char short_months[12][4] =
        {"Jan", "Feb", "Mar", "Apr", "May", "Jun",
         "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};

   if (png_ptr == NULL)
      return (NULL);

   {
      size_t pos = 0;
      char number_buf[5]; /* enough for a four digit year */

#     define APPEND_STRING(string)\
         pos = png_safecat(png_ptr->time_buffer, sizeof png_ptr->time_buffer,\
            pos, (string))
#     define APPEND_NUMBER(format, value)\
         APPEND_STRING(PNG_FORMAT_NUMBER(number_buf, format, (value)))
#     define APPEND(ch)\
         if (pos < (sizeof png_ptr->time_buffer)-1)\
            png_ptr->time_buffer[pos++] = (ch)

      APPEND_NUMBER(PNG_NUMBER_FORMAT_u, (unsigned)ptime->day % 32);
      APPEND(' ');
      APPEND_STRING(short_months[(ptime->month - 1) % 12]);
      APPEND(' ');
      APPEND_NUMBER(PNG_NUMBER_FORMAT_u, ptime->year);
      APPEND(' ');
      APPEND_NUMBER(PNG_NUMBER_FORMAT_02u, (unsigned)ptime->hour % 24);
      APPEND(':');
      APPEND_NUMBER(PNG_NUMBER_FORMAT_02u, (unsigned)ptime->minute % 60);
      APPEND(':');
      APPEND_NUMBER(PNG_NUMBER_FORMAT_02u, (unsigned)ptime->second % 61);
      APPEND_STRING(" +0000"); /* This reliably terminates the buffer */

#     undef APPEND
#     undef APPEND_NUMBER
#     undef APPEND_STRING
   }

   return png_ptr->time_buffer;
}
#  endif /* PNG_TIME_RFC1123_SUPPORTED */

#endif /* defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) */

png_const_charp PNGAPI
png_get_copyright(png_const_structp png_ptr)
{
   PNG_UNUSED(png_ptr)  /* Silence compiler warning about unused png_ptr */
#ifdef PNG_STRING_COPYRIGHT
   return PNG_STRING_COPYRIGHT
#else
#  ifdef __STDC__
   return PNG_STRING_NEWLINE \
     "libpng version 1.5.4 - July 7, 2011" PNG_STRING_NEWLINE \
     "Copyright (c) 1998-2011 Glenn Randers-Pehrson" PNG_STRING_NEWLINE \
     "Copyright (c) 1996-1997 Andreas Dilger" PNG_STRING_NEWLINE \
     "Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc." \
     PNG_STRING_NEWLINE;
#  else
      return "libpng version 1.5.4 - July 7, 2011\
      Copyright (c) 1998-2011 Glenn Randers-Pehrson\
      Copyright (c) 1996-1997 Andreas Dilger\
      Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.";
#  endif
#endif
}

/* The following return the library version as a short string in the
 * format 1.0.0 through 99.99.99zz.  To get the version of *.h files
 * used with your application, print out PNG_LIBPNG_VER_STRING, which
 * is defined in png.h.
 * Note: now there is no difference between png_get_libpng_ver() and
 * png_get_header_ver().  Due to the version_nn_nn_nn typedef guard,
 * it is guaranteed that png.c uses the correct version of png.h.
 */
png_const_charp PNGAPI
png_get_libpng_ver(png_const_structp png_ptr)
{
   /* Version of *.c files used when building libpng */
   return png_get_header_ver(png_ptr);
}

png_const_charp PNGAPI
png_get_header_ver(png_const_structp png_ptr)
{
   /* Version of *.h files used when building libpng */
   PNG_UNUSED(png_ptr)  /* Silence compiler warning about unused png_ptr */
   return PNG_LIBPNG_VER_STRING;
}

png_const_charp PNGAPI
png_get_header_version(png_const_structp png_ptr)
{
   /* Returns longer string containing both version and date */
   PNG_UNUSED(png_ptr)  /* Silence compiler warning about unused png_ptr */
#ifdef __STDC__
   return PNG_HEADER_VERSION_STRING
#  ifndef PNG_READ_SUPPORTED
   "     (NO READ SUPPORT)"
#  endif
   PNG_STRING_NEWLINE;
#else
   return PNG_HEADER_VERSION_STRING;
#endif
}

#if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
#  ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
int PNGAPI
png_handle_as_unknown(png_structp png_ptr, png_const_bytep chunk_name)
{
   /* Check chunk_name and return "keep" value if it's on the list, else 0 */
   int i;
   png_bytep p;
   if (png_ptr == NULL || chunk_name == NULL || png_ptr->num_chunk_list<=0)
      return 0;

   p = png_ptr->chunk_list + png_ptr->num_chunk_list*5 - 5;
   for (i = png_ptr->num_chunk_list; i; i--, p -= 5)
      if (!png_memcmp(chunk_name, p, 4))
        return ((int)*(p + 4));
   return 0;
}
#  endif
#endif /* defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) */

#ifdef PNG_READ_SUPPORTED
/* This function, added to libpng-1.0.6g, is untested. */
int PNGAPI
png_reset_zstream(png_structp png_ptr)
{
   if (png_ptr == NULL)
      return Z_STREAM_ERROR;

   return (inflateReset(&png_ptr->zstream));
}
#endif /* PNG_READ_SUPPORTED */

/* This function was added to libpng-1.0.7 */
png_uint_32 PNGAPI
png_access_version_number(void)
{
   /* Version of *.c files used when building libpng */
   return((png_uint_32)PNG_LIBPNG_VER);
}



#if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
#  ifdef PNG_SIZE_T
/* Added at libpng version 1.2.6 */
   PNG_EXTERN png_size_t PNGAPI png_convert_size PNGARG((size_t size));
png_size_t PNGAPI
png_convert_size(size_t size)
{
   if (size > (png_size_t)-1)
      PNG_ABORT();  /* We haven't got access to png_ptr, so no png_error() */

   return ((png_size_t)size);
}
#  endif /* PNG_SIZE_T */

/* Added at libpng version 1.2.34 and 1.4.0 (moved from pngset.c) */
#  ifdef PNG_CHECK_cHRM_SUPPORTED

int /* PRIVATE */
png_check_cHRM_fixed(png_structp png_ptr,
   png_fixed_point white_x, png_fixed_point white_y, png_fixed_point red_x,
   png_fixed_point red_y, png_fixed_point green_x, png_fixed_point green_y,
   png_fixed_point blue_x, png_fixed_point blue_y)
{
   int ret = 1;
   unsigned long xy_hi,xy_lo,yx_hi,yx_lo;

   png_debug(1, "in function png_check_cHRM_fixed");

   if (png_ptr == NULL)
      return 0;

   /* (x,y,z) values are first limited to 0..100000 (PNG_FP_1), the white
    * y must also be greater than 0.  To test for the upper limit calculate
    * (PNG_FP_1-y) - x must be <= to this for z to be >= 0 (and the expression
    * cannot overflow.)  At this point we know x and y are >= 0 and (x+y) is
    * <= PNG_FP_1.  The previous test on PNG_MAX_UINT_31 is removed because it
    * pointless (and it produces compiler warnings!)
    */
   if (white_x < 0 || white_y <= 0 ||
         red_x < 0 ||   red_y <  0 ||
       green_x < 0 || green_y <  0 ||
        blue_x < 0 ||  blue_y <  0)
   {
      png_warning(png_ptr,
        "Ignoring attempt to set negative chromaticity value");
      ret = 0;
   }
   /* And (x+y) must be <= PNG_FP_1 (so z is >= 0) */
   if (white_x > PNG_FP_1 - white_y)
   {
      png_warning(png_ptr, "Invalid cHRM white point");
      ret = 0;
   }

   if (red_x > PNG_FP_1 - red_y)
   {
      png_warning(png_ptr, "Invalid cHRM red point");
      ret = 0;
   }

   if (green_x > PNG_FP_1 - green_y)
   {
      png_warning(png_ptr, "Invalid cHRM green point");
      ret = 0;
   }

   if (blue_x > PNG_FP_1 - blue_y)
   {
      png_warning(png_ptr, "Invalid cHRM blue point");
      ret = 0;
   }

   png_64bit_product(green_x - red_x, blue_y - red_y, &xy_hi, &xy_lo);
   png_64bit_product(green_y - red_y, blue_x - red_x, &yx_hi, &yx_lo);

   if (xy_hi == yx_hi && xy_lo == yx_lo)
   {
      png_warning(png_ptr,
         "Ignoring attempt to set cHRM RGB triangle with zero area");
      ret = 0;
   }

   return ret;
}
#  endif /* PNG_CHECK_cHRM_SUPPORTED */

void /* PRIVATE */
png_check_IHDR(png_structp png_ptr,
   png_uint_32 width, png_uint_32 height, int bit_depth,
   int color_type, int interlace_type, int compression_type,
   int filter_type)
{
   int error = 0;

   /* Check for width and height valid values */
   if (width == 0)
   {
      png_warning(png_ptr, "Image width is zero in IHDR");
      error = 1;
   }

   if (height == 0)
   {
      png_warning(png_ptr, "Image height is zero in IHDR");
      error = 1;
   }

#  ifdef PNG_SET_USER_LIMITS_SUPPORTED
   if (width > png_ptr->user_width_max)

#  else
   if (width > PNG_USER_WIDTH_MAX)
#  endif
   {
      png_warning(png_ptr, "Image width exceeds user limit in IHDR");
      error = 1;
   }

#  ifdef PNG_SET_USER_LIMITS_SUPPORTED
   if (height > png_ptr->user_height_max)
#  else
   if (height > PNG_USER_HEIGHT_MAX)
#  endif
   {
      png_warning(png_ptr, "Image height exceeds user limit in IHDR");
      error = 1;
   }

   if (width > PNG_UINT_31_MAX)
   {
      png_warning(png_ptr, "Invalid image width in IHDR");
      error = 1;
   }

   if (height > PNG_UINT_31_MAX)
   {
      png_warning(png_ptr, "Invalid image height in IHDR");
      error = 1;
   }

   if (width > (PNG_UINT_32_MAX
                 >> 3)      /* 8-byte RGBA pixels */
                 - 48       /* bigrowbuf hack */
                 - 1        /* filter byte */
                 - 7*8      /* rounding of width to multiple of 8 pixels */
                 - 8)       /* extra max_pixel_depth pad */
      png_warning(png_ptr, "Width is too large for libpng to process pixels");

   /* Check other values */
   if (bit_depth != 1 && bit_depth != 2 && bit_depth != 4 &&
       bit_depth != 8 && bit_depth != 16)
   {
      png_warning(png_ptr, "Invalid bit depth in IHDR");
      error = 1;
   }

   if (color_type < 0 || color_type == 1 ||
       color_type == 5 || color_type > 6)
   {
      png_warning(png_ptr, "Invalid color type in IHDR");
      error = 1;
   }

   if (((color_type == PNG_COLOR_TYPE_PALETTE) && bit_depth > 8) ||
       ((color_type == PNG_COLOR_TYPE_RGB ||
         color_type == PNG_COLOR_TYPE_GRAY_ALPHA ||
         color_type == PNG_COLOR_TYPE_RGB_ALPHA) && bit_depth < 8))
   {
      png_warning(png_ptr, "Invalid color type/bit depth combination in IHDR");
      error = 1;
   }

   if (interlace_type >= PNG_INTERLACE_LAST)
   {
      png_warning(png_ptr, "Unknown interlace method in IHDR");
      error = 1;
   }

   if (compression_type != PNG_COMPRESSION_TYPE_BASE)
   {
      png_warning(png_ptr, "Unknown compression method in IHDR");
      error = 1;
   }

#  ifdef PNG_MNG_FEATURES_SUPPORTED
   /* Accept filter_method 64 (intrapixel differencing) only if
    * 1. Libpng was compiled with PNG_MNG_FEATURES_SUPPORTED and
    * 2. Libpng did not read a PNG signature (this filter_method is only
    *    used in PNG datastreams that are embedded in MNG datastreams) and
    * 3. The application called png_permit_mng_features with a mask that
    *    included PNG_FLAG_MNG_FILTER_64 and
    * 4. The filter_method is 64 and
    * 5. The color_type is RGB or RGBA
    */
   if ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) &&
       png_ptr->mng_features_permitted)
      png_warning(png_ptr, "MNG features are not allowed in a PNG datastream");

   if (filter_type != PNG_FILTER_TYPE_BASE)
   {
      if (!((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) &&
          (filter_type == PNG_INTRAPIXEL_DIFFERENCING) &&
          ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) == 0) &&
          (color_type == PNG_COLOR_TYPE_RGB ||
          color_type == PNG_COLOR_TYPE_RGB_ALPHA)))
      {
         png_warning(png_ptr, "Unknown filter method in IHDR");
         error = 1;
      }

      if (png_ptr->mode & PNG_HAVE_PNG_SIGNATURE)
      {
         png_warning(png_ptr, "Invalid filter method in IHDR");
         error = 1;
      }
   }

#  else
   if (filter_type != PNG_FILTER_TYPE_BASE)
   {
      png_warning(png_ptr, "Unknown filter method in IHDR");
      error = 1;
   }
#  endif

   if (error == 1)
      png_error(png_ptr, "Invalid IHDR data");
}

#if defined(PNG_sCAL_SUPPORTED) || defined(PNG_pCAL_SUPPORTED)
/* ASCII to fp functions */
/* Check an ASCII formated floating point value, see the more detailed
 * comments in pngpriv.h
 */
/* The following is used internally to preserve the sticky flags */
#define png_fp_add(state, flags) ((state) |= (flags))
#define png_fp_set(state, value) ((state) = (value) | ((state) & PNG_FP_STICKY))

int /* PRIVATE */
png_check_fp_number(png_const_charp string, png_size_t size, int *statep,
   png_size_tp whereami)
{
   int state = *statep;
   png_size_t i = *whereami;

   while (i < size)
   {
      int type;
      /* First find the type of the next character */
      switch (string[i])
      {
      case 43:  type = PNG_FP_SAW_SIGN;                   break;
      case 45:  type = PNG_FP_SAW_SIGN + PNG_FP_NEGATIVE; break;
      case 46:  type = PNG_FP_SAW_DOT;                    break;
      case 48:  type = PNG_FP_SAW_DIGIT;                  break;
      case 49: case 50: case 51: case 52:
      case 53: case 54: case 55: case 56:
      case 57:  type = PNG_FP_SAW_DIGIT + PNG_FP_NONZERO; break;
      case 69:
      case 101: type = PNG_FP_SAW_E;                      break;
      default:  goto PNG_FP_End;
      }

      /* Now deal with this type according to the current
       * state, the type is arranged to not overlap the
       * bits of the PNG_FP_STATE.
       */
      switch ((state & PNG_FP_STATE) + (type & PNG_FP_SAW_ANY))
      {
      case PNG_FP_INTEGER + PNG_FP_SAW_SIGN:
         if (state & PNG_FP_SAW_ANY)
            goto PNG_FP_End; /* not a part of the number */

         png_fp_add(state, type);
         break;

      case PNG_FP_INTEGER + PNG_FP_SAW_DOT:
         /* Ok as trailer, ok as lead of fraction. */
         if (state & PNG_FP_SAW_DOT) /* two dots */
            goto PNG_FP_End;

         else if (state & PNG_FP_SAW_DIGIT) /* trailing dot? */
            png_fp_add(state, type);

         else
            png_fp_set(state, PNG_FP_FRACTION | type);

         break;

      case PNG_FP_INTEGER + PNG_FP_SAW_DIGIT:
         if (state & PNG_FP_SAW_DOT) /* delayed fraction */
            png_fp_set(state, PNG_FP_FRACTION | PNG_FP_SAW_DOT);

         png_fp_add(state, type | PNG_FP_WAS_VALID);

         break;

      case PNG_FP_INTEGER + PNG_FP_SAW_E:
         if ((state & PNG_FP_SAW_DIGIT) == 0)
            goto PNG_FP_End;

         png_fp_set(state, PNG_FP_EXPONENT);

         break;

   /* case PNG_FP_FRACTION + PNG_FP_SAW_SIGN:
         goto PNG_FP_End; ** no sign in fraction */

   /* case PNG_FP_FRACTION + PNG_FP_SAW_DOT:
         goto PNG_FP_End; ** Because SAW_DOT is always set */

      case PNG_FP_FRACTION + PNG_FP_SAW_DIGIT:
         png_fp_add(state, type | PNG_FP_WAS_VALID);
         break;

      case PNG_FP_FRACTION + PNG_FP_SAW_E:
         /* This is correct because the trailing '.' on an
          * integer is handled above - so we can only get here
          * with the sequence ".E" (with no preceding digits).
          */
         if ((state & PNG_FP_SAW_DIGIT) == 0)
            goto PNG_FP_End;

         png_fp_set(state, PNG_FP_EXPONENT);

         break;

      case PNG_FP_EXPONENT + PNG_FP_SAW_SIGN:
         if (state & PNG_FP_SAW_ANY)
            goto PNG_FP_End; /* not a part of the number */

         png_fp_add(state, PNG_FP_SAW_SIGN);

         break;

   /* case PNG_FP_EXPONENT + PNG_FP_SAW_DOT:
         goto PNG_FP_End; */

      case PNG_FP_EXPONENT + PNG_FP_SAW_DIGIT:
         png_fp_add(state, PNG_FP_SAW_DIGIT | PNG_FP_WAS_VALID);

         break;

   /* case PNG_FP_EXPONEXT + PNG_FP_SAW_E:
         goto PNG_FP_End; */

      default: goto PNG_FP_End; /* I.e. break 2 */
      }

      /* The character seems ok, continue. */
      ++i;
   }

PNG_FP_End:
   /* Here at the end, update the state and return the correct
    * return code.
    */
   *statep = state;
   *whereami = i;

   return (state & PNG_FP_SAW_DIGIT) != 0;
}


/* The same but for a complete string. */
int
png_check_fp_string(png_const_charp string, png_size_t size)
{
   int        state=0;
   png_size_t char_index=0;

   if (png_check_fp_number(string, size, &state, &char_index) &&
      (char_index == size || string[char_index] == 0))
      return state /* must be non-zero - see above */;

   return 0; /* i.e. fail */
}
#endif /* pCAL or sCAL */

#ifdef PNG_READ_sCAL_SUPPORTED
#  ifdef PNG_FLOATING_POINT_SUPPORTED
/* Utility used below - a simple accurate power of ten from an integral
 * exponent.
 */
static double
png_pow10(int power)
{
   int recip = 0;
   double d = 1;

   /* Handle negative exponent with a reciprocal at the end because
    * 10 is exact whereas .1 is inexact in base 2
    */
   if (power < 0)
   {
      if (power < DBL_MIN_10_EXP) return 0;
      recip = 1, power = -power;
   }

   if (power > 0)
   {
      /* Decompose power bitwise. */
      double mult = 10;
      do
      {
         if (power & 1) d *= mult;
         mult *= mult;
         power >>= 1;
      }
      while (power > 0);

      if (recip) d = 1/d;
   }
   /* else power is 0 and d is 1 */

   return d;
}

/* Function to format a floating point value in ASCII with a given
 * precision.
 */
void /* PRIVATE */
png_ascii_from_fp(png_structp png_ptr, png_charp ascii, png_size_t size,
    double fp, unsigned int precision)
{
   /* We use standard functions from math.h, but not printf because
    * that would require stdio.  The caller must supply a buffer of
    * sufficient size or we will png_error.  The tests on size and
    * the space in ascii[] consumed are indicated below.
    */
   if (precision < 1)
      precision = DBL_DIG;

   /* Enforce the limit of the implementation precision too. */
   if (precision > DBL_DIG+1)
      precision = DBL_DIG+1;

   /* Basic sanity checks */
   if (size >= precision+5) /* See the requirements below. */
   {
      if (fp < 0)
      {
         fp = -fp;
         *ascii++ = 45; /* '-'  PLUS 1 TOTAL 1 */
         --size;
      }

      if (fp >= DBL_MIN && fp <= DBL_MAX)
      {
         int exp_b10;       /* A base 10 exponent */
         double base;   /* 10^exp_b10 */

         /* First extract a base 10 exponent of the number,
          * the calculation below rounds down when converting
          * from base 2 to base 10 (multiply by log10(2) -
          * 0.3010, but 77/256 is 0.3008, so exp_b10 needs to
          * be increased.  Note that the arithmetic shift
          * performs a floor() unlike C arithmetic - using a
          * C multiply would break the following for negative
          * exponents.
          */
         (void)frexp(fp, &exp_b10); /* exponent to base 2 */

         exp_b10 = (exp_b10 * 77) >> 8; /* <= exponent to base 10 */

         /* Avoid underflow here. */
         base = png_pow10(exp_b10); /* May underflow */

         while (base < DBL_MIN || base < fp)
         {
            /* And this may overflow. */
            double test = png_pow10(exp_b10+1);

            if (test <= DBL_MAX)
               ++exp_b10, base = test;

            else
               break;
         }

         /* Normalize fp and correct exp_b10, after this fp is in the
          * range [.1,1) and exp_b10 is both the exponent and the digit
          * *before* which the decimal point should be inserted
          * (starting with 0 for the first digit).  Note that this
          * works even if 10^exp_b10 is out of range because of the
          * test on DBL_MAX above.
          */
         fp /= base;
         while (fp >= 1) fp /= 10, ++exp_b10;

         /* Because of the code above fp may, at this point, be
          * less than .1, this is ok because the code below can
          * handle the leading zeros this generates, so no attempt
          * is made to correct that here.
          */

         {
            int czero, clead, cdigits;
            char exponent[10];

            /* Allow up to two leading zeros - this will not lengthen
             * the number compared to using E-n.
             */
            if (exp_b10 < 0 && exp_b10 > -3) /* PLUS 3 TOTAL 4 */
            {
               czero = -exp_b10; /* PLUS 2 digits: TOTAL 3 */
               exp_b10 = 0;      /* Dot added below before first output. */
            }
            else
               czero = 0;    /* No zeros to add */

            /* Generate the digit list, stripping trailing zeros and
             * inserting a '.' before a digit if the exponent is 0.
             */
            clead = czero; /* Count of leading zeros */
            cdigits = 0;   /* Count of digits in list. */

            do
            {
               double d;

               fp *= 10;
               /* Use modf here, not floor and subtract, so that
                * the separation is done in one step.  At the end
                * of the loop don't break the number into parts so
                * that the final digit is rounded.
                */
               if (cdigits+czero-clead+1 < (int)precision)
                  fp = modf(fp, &d);

               else
               {
                  d = floor(fp + .5);

                  if (d > 9)
                  {
                     /* Rounding up to 10, handle that here. */
                     if (czero > 0)
                     {
                        --czero, d = 1;
                        if (cdigits == 0) --clead;
                     }
                     else
                     {
                        while (cdigits > 0 && d > 9)
                        {
                           int ch = *--ascii;

                           if (exp_b10 != (-1))
                              ++exp_b10;

                           else if (ch == 46)
                           {
                              ch = *--ascii, ++size;
                              /* Advance exp_b10 to '1', so that the
                               * decimal point happens after the
                               * previous digit.
                               */
                              exp_b10 = 1;
                           }

                           --cdigits;
                           d = ch - 47;  /* I.e. 1+(ch-48) */
                        }

                        /* Did we reach the beginning? If so adjust the
                         * exponent but take into account the leading
                         * decimal point.
                         */
                        if (d > 9)  /* cdigits == 0 */
                        {
                           if (exp_b10 == (-1))
                           {
                              /* Leading decimal point (plus zeros?), if
                               * we lose the decimal point here it must
                               * be reentered below.
                               */
                              int ch = *--ascii;

                              if (ch == 46)
                                 ++size, exp_b10 = 1;

                              /* Else lost a leading zero, so 'exp_b10' is
                               * still ok at (-1)
                               */
                           }
                           else
                              ++exp_b10;

                           /* In all cases we output a '1' */
                           d = 1;
                        }
                     }
                  }
                  fp = 0; /* Guarantees termination below. */
               }

               if (d == 0)
               {
                  ++czero;
                  if (cdigits == 0) ++clead;
               }
               else
               {
                  /* Included embedded zeros in the digit count. */
                  cdigits += czero - clead;
                  clead = 0;

                  while (czero > 0)
                  {
                     /* exp_b10 == (-1) means we just output the decimal
                      * place - after the DP don't adjust 'exp_b10' any
                      * more!
                      */
                     if (exp_b10 != (-1))
                     {
                        if (exp_b10 == 0) *ascii++ = 46, --size;
                        /* PLUS 1: TOTAL 4 */
                        --exp_b10;
                     }
                     *ascii++ = 48, --czero;
                  }

                  if (exp_b10 != (-1))
                  {
                     if (exp_b10 == 0) *ascii++ = 46, --size; /* counted
                                                                 above */
                     --exp_b10;
                  }
                  *ascii++ = (char)(48 + (int)d), ++cdigits;
               }
            }
            while (cdigits+czero-clead < (int)precision && fp > DBL_MIN);

            /* The total output count (max) is now 4+precision */

            /* Check for an exponent, if we don't need one we are
             * done and just need to terminate the string.  At
             * this point exp_b10==(-1) is effectively if flag - it got
             * to '-1' because of the decrement after outputing
             * the decimal point above (the exponent required is
             * *not* -1!)
             */
            if (exp_b10 >= (-1) && exp_b10 <= 2)
            {
               /* The following only happens if we didn't output the
                * leading zeros above for negative exponent, so this
                * doest add to the digit requirement.  Note that the
                * two zeros here can only be output if the two leading
                * zeros were *not* output, so this doesn't increase
                * the output count.
                */
               while (--exp_b10 >= 0) *ascii++ = 48;

               *ascii = 0;

               /* Total buffer requirement (including the '\0') is
                * 5+precision - see check at the start.
                */
               return;
            }

            /* Here if an exponent is required, adjust size for
             * the digits we output but did not count.  The total
             * digit output here so far is at most 1+precision - no
             * decimal point and no leading or trailing zeros have
             * been output.
             */
            size -= cdigits;

            *ascii++ = 69, --size;    /* 'E': PLUS 1 TOTAL 2+precision */
            if (exp_b10 < 0)
            {
               *ascii++ = 45, --size; /* '-': PLUS 1 TOTAL 3+precision */
               exp_b10 = -exp_b10;
            }

            cdigits = 0;

            while (exp_b10 > 0)
            {
               exponent[cdigits++] = (char)(48 + exp_b10 % 10);
               exp_b10 /= 10;
            }

            /* Need another size check here for the exponent digits, so
             * this need not be considered above.
             */
            if ((int)size > cdigits)
            {
               while (cdigits > 0) *ascii++ = exponent[--cdigits];

               *ascii = 0;

               return;
            }
         }
      }
      else if (!(fp >= DBL_MIN))
      {
         *ascii++ = 48; /* '0' */
         *ascii = 0;
         return;
      }
      else
      {
         *ascii++ = 105; /* 'i' */
         *ascii++ = 110; /* 'n' */
         *ascii++ = 102; /* 'f' */
         *ascii = 0;
         return;
      }
   }

   /* Here on buffer too small. */
   png_error(png_ptr, "ASCII conversion buffer too small");
}

#  endif /* FLOATING_POINT */

#  ifdef PNG_FIXED_POINT_SUPPORTED
/* Function to format a fixed point value in ASCII.
 */
void /* PRIVATE */
png_ascii_from_fixed(png_structp png_ptr, png_charp ascii, png_size_t size,
    png_fixed_point fp)
{
   /* Require space for 10 decimal digits, a decimal point, a minus sign and a
    * trailing \0, 13 characters:
    */
   if (size > 12)
   {
      png_uint_32 num;

      /* Avoid overflow here on the minimum integer. */
      if (fp < 0)
         *ascii++ = 45, --size, num = -fp;
      else
         num = fp;

      if (num <= 0x80000000U) /* else overflowed */
      {
         unsigned int ndigits = 0, first = 16 /* flag value */;
         char digits[10];

         while (num)
         {
            /* Split the low digit off num: */
            unsigned int tmp = num/10;
            num -= tmp*10;
            digits[ndigits++] = (char)(48 + num);
            /* Record the first non-zero digit, note that this is a number
             * starting at 1, it's not actually the array index.
             */
            if (first == 16 && num > 0)
               first = ndigits;
            num = tmp;
         }

         if (ndigits > 0)
         {
            while (ndigits > 5) *ascii++ = digits[--ndigits];
            /* The remaining digits are fractional digits, ndigits is '5' or
             * smaller at this point.  It is certainly not zero.  Check for a
             * non-zero fractional digit:
             */
            if (first <= 5)
            {
               unsigned int i;
               *ascii++ = 46; /* decimal point */
               /* ndigits may be <5 for small numbers, output leading zeros
                * then ndigits digits to first:
                */
               i = 5;
               while (ndigits < i) *ascii++ = 48, --i;
               while (ndigits >= first) *ascii++ = digits[--ndigits];
               /* Don't output the trailing zeros! */
            }
         }
         else
            *ascii++ = 48;

         /* And null terminate the string: */
         *ascii = 0;
         return;
      }
   }

   /* Here on buffer too small. */
   png_error(png_ptr, "ASCII conversion buffer too small");
}
#   endif /* FIXED_POINT */
#endif /* READ_SCAL */

#if defined(PNG_FLOATING_POINT_SUPPORTED) && \
   !defined(PNG_FIXED_POINT_MACRO_SUPPORTED)
png_fixed_point
png_fixed(png_structp png_ptr, double fp, png_const_charp text)
{
   double r = floor(100000 * fp + .5);

   if (r > 2147483647. || r < -2147483648.)
      png_fixed_error(png_ptr, text);

   return (png_fixed_point)r;
}
#endif

#if defined(PNG_READ_GAMMA_SUPPORTED) || \
    defined(PNG_INCH_CONVERSIONS_SUPPORTED) || defined(PNG__READ_pHYs_SUPPORTED)
/* muldiv functions */
/* This API takes signed arguments and rounds the result to the nearest
 * integer (or, for a fixed point number - the standard argument - to
 * the nearest .00001).  Overflow and divide by zero are signalled in
 * the result, a boolean - true on success, false on overflow.
 */
int
png_muldiv(png_fixed_point_p res, png_fixed_point a, png_int_32 times,
    png_int_32 divisor)
{
   /* Return a * times / divisor, rounded. */
   if (divisor != 0)
   {
      if (a == 0 || times == 0)
      {
         *res = 0;
         return 1;
      }
      else
      {
#ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
         double r = a;
         r *= times;
         r /= divisor;
         r = floor(r+.5);

         /* A png_fixed_point is a 32-bit integer. */
         if (r <= 2147483647. && r >= -2147483648.)
         {
            *res = (png_fixed_point)r;
            return 1;
         }
#else
         int negative = 0;
         png_uint_32 A, T, D;
         png_uint_32 s16, s32, s00;

         if (a < 0)
            negative = 1, A = -a;
         else
            A = a;

         if (times < 0)
            negative = !negative, T = -times;
         else
            T = times;

         if (divisor < 0)
            negative = !negative, D = -divisor;
         else
            D = divisor;

         /* Following can't overflow because the arguments only
          * have 31 bits each, however the result may be 32 bits.
          */
         s16 = (A >> 16) * (T & 0xffff) +
                           (A & 0xffff) * (T >> 16);
         /* Can't overflow because the a*times bit is only 30
          * bits at most.
          */
         s32 = (A >> 16) * (T >> 16) + (s16 >> 16);
         s00 = (A & 0xffff) * (T & 0xffff);

         s16 = (s16 & 0xffff) << 16;
         s00 += s16;

         if (s00 < s16)
            ++s32; /* carry */

         if (s32 < D) /* else overflow */
         {
            /* s32.s00 is now the 64-bit product, do a standard
             * division, we know that s32 < D, so the maximum
             * required shift is 31.
             */
            int bitshift = 32;
            png_fixed_point result = 0; /* NOTE: signed */

            while (--bitshift >= 0)
            {
               png_uint_32 d32, d00;

               if (bitshift > 0)
                  d32 = D >> (32-bitshift), d00 = D << bitshift;

               else
                  d32 = 0, d00 = D;

               if (s32 > d32)
               {
                  if (s00 < d00) --s32; /* carry */
                  s32 -= d32, s00 -= d00, result += 1<<bitshift;
               }

               else
                  if (s32 == d32 && s00 >= d00)
                     s32 = 0, s00 -= d00, result += 1<<bitshift;
            }

            /* Handle the rounding. */
            if (s00 >= (D >> 1))
               ++result;

            if (negative)
               result = -result;

            /* Check for overflow. */
            if ((negative && result <= 0) || (!negative && result >= 0))
            {
               *res = result;
               return 1;
            }
         }
#endif
      }
   }

   return 0;
}
#endif /* READ_GAMMA || INCH_CONVERSIONS */

#if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_INCH_CONVERSIONS_SUPPORTED)
/* The following is for when the caller doesn't much care about the
 * result.
 */
png_fixed_point
png_muldiv_warn(png_structp png_ptr, png_fixed_point a, png_int_32 times,
    png_int_32 divisor)
{
   png_fixed_point result;

   if (png_muldiv(&result, a, times, divisor))
      return result;

   png_warning(png_ptr, "fixed point overflow ignored");
   return 0;
}
#endif

#ifdef PNG_READ_GAMMA_SUPPORTED /* more fixed point functions for gammma */
/* Calculate a reciprocal, return 0 on div-by-zero or overflow. */
png_fixed_point
png_reciprocal(png_fixed_point a)
{
#ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
   double r = floor(1E10/a+.5);

   if (r <= 2147483647. && r >= -2147483648.)
      return (png_fixed_point)r;
#else
   png_fixed_point res;

   if (png_muldiv(&res, 100000, 100000, a))
      return res;
#endif

   return 0; /* error/overflow */
}

/* A local convenience routine. */
static png_fixed_point
png_product2(png_fixed_point a, png_fixed_point b)
{
   /* The required result is 1/a * 1/b; the following preserves accuracy. */
#ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
   double r = a * 1E-5;
   r *= b;
   r = floor(r+.5);

   if (r <= 2147483647. && r >= -2147483648.)
      return (png_fixed_point)r;
#else
   png_fixed_point res;

   if (png_muldiv(&res, a, b, 100000))
      return res;
#endif

   return 0; /* overflow */
}

/* The inverse of the above. */
png_fixed_point
png_reciprocal2(png_fixed_point a, png_fixed_point b)
{
   /* The required result is 1/a * 1/…