    /* pngerror.c - stub functions for i/o and memory allocation
     *
     * Last changed in libpng 1.6.1 [March 28, 2013]
     * Copyright (c) 1998-2013 Glenn Randers-Pehrson
     * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
     * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
     *
     * This code is released under the libpng license.
     * For conditions of distribution and use, see the disclaimer
     * and license in png.h
     *
     * This file provides a location for all error handling.  Users who
     * need special error handling are expected to write replacement functions
     * and use png_set_error_fn() to use those functions.  See the instructions
     * at each function.
     */

    #include "pngpriv.h"

    #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)

    static PNG_FUNCTION(void, png_default_error,PNGARG((png_const_structrp png_ptr,
        png_const_charp error_message)),PNG_NORETURN);

    #ifdef PNG_WARNINGS_SUPPORTED
    static void /* PRIVATE */
    png_default_warning PNGARG((png_const_structrp png_ptr,
       png_const_charp warning_message));
    #endif /* PNG_WARNINGS_SUPPORTED */

    /* This function is called whenever there is a fatal error.  This function
     * should not be changed.  If there is a need to handle errors differently,
     * you should supply a replacement error function and use png_set_error_fn()
     * to replace the error function at run-time.
     */
    #ifdef PNG_ERROR_TEXT_SUPPORTED
    PNG_FUNCTION(void,PNGAPI
    png_error,(png_const_structrp png_ptr, png_const_charp error_message),
       PNG_NORETURN)
    {
    #ifdef PNG_ERROR_NUMBERS_SUPPORTED
       char msg[16];
       if (png_ptr != NULL)
       {
          if (png_ptr->flags&
             (PNG_FLAG_STRIP_ERROR_NUMBERS|PNG_FLAG_STRIP_ERROR_TEXT))
          {
             if (*error_message == PNG_LITERAL_SHARP)
             {
                /* Strip "#nnnn " from beginning of error message. */
                int offset;
                for (offset = 1; offset<15; offset++)
                   if (error_message[offset] == ' ')
                      break;

                if (png_ptr->flags&PNG_FLAG_STRIP_ERROR_TEXT)
                {
                   int i;
                   for (i = 0; i < offset - 1; i++)
                      msg[i] = error_message[i + 1];
                   msg[i - 1] = '\0';
                   error_message = msg;
                }

                else
                   error_message += offset;
          }

          else
          {
             if (png_ptr->flags&PNG_FLAG_STRIP_ERROR_TEXT)
             {
                msg[0] = '0';
                msg[1] = '\0';
                error_message = msg;
             }
           }
         }
       }
    #endif
       if (png_ptr != NULL && png_ptr->error_fn != NULL)
          (*(png_ptr->error_fn))(png_constcast(png_structrp,png_ptr),
              error_message);

       /* If the custom handler doesn't exist, or if it returns,
          use the default handler, which will not return. */
       png_default_error(png_ptr, error_message);
    }
    #else
    PNG_FUNCTION(void,PNGAPI
    png_err,(png_const_structrp png_ptr),PNG_NORETURN)
    {
       /* Prior to 1.5.2 the error_fn received a NULL pointer, expressed
        * erroneously as '\0', instead of the empty string "".  This was
        * apparently an error, introduced in libpng-1.2.20, and png_default_error
        * will crash in this case.
        */
       if (png_ptr != NULL && png_ptr->error_fn != NULL)
          (*(png_ptr->error_fn))(png_constcast(png_structrp,png_ptr), "");

       /* If the custom handler doesn't exist, or if it returns,
          use the default handler, which will not return. */
       png_default_error(png_ptr, "");
    }
    #endif /* PNG_ERROR_TEXT_SUPPORTED */

    /* Utility to safely appends strings to a buffer.  This never errors out so
     * error checking is not required in the caller.
     */
    size_t
    png_safecat(png_charp buffer, size_t bufsize, size_t pos,
       png_const_charp string)
    {
       if (buffer != NULL && pos < bufsize)
       {
          if (string != NULL)
             while (*string != '\0' && pos < bufsize-1)
               buffer[pos++] = *string++;

          buffer[pos] = '\0';
       }

       return pos;
    }

    #if defined(PNG_WARNINGS_SUPPORTED) || defined(PNG_TIME_RFC1123_SUPPORTED)
    /* Utility to dump an unsigned value into a buffer, given a start pointer and
     * and end pointer (which should point just *beyond* the end of the buffer!)
     * Returns the pointer to the start of the formatted string.
     */
    png_charp
    png_format_number(png_const_charp start, png_charp end, int format,
       png_alloc_size_t number)
    {
       int count = 0;    /* number of digits output */
       int mincount = 1; /* minimum number required */
       int output = 0;   /* digit output (for the fixed point format) */

       *--end = '\0';

       /* This is written so that the loop always runs at least once, even with
        * number zero.
        */
       while (end > start && (number != 0 || count < mincount))
       {

          static const char digits[] = "0123456789ABCDEF";

          switch (format)
          {
             case PNG_NUMBER_FORMAT_fixed:
                /* Needs five digits (the fraction) */
                mincount = 5;
                if (output || number % 10 != 0)
                {
                   *--end = digits[number % 10];
                   output = 1;
                }
                number /= 10;
                break;

             case PNG_NUMBER_FORMAT_02u:
                /* Expects at least 2 digits. */
                mincount = 2;
                /* FALL THROUGH */

             case PNG_NUMBER_FORMAT_u:
                *--end = digits[number % 10];
                number /= 10;
                break;

             case PNG_NUMBER_FORMAT_02x:
                /* This format expects at least two digits */
                mincount = 2;
                /* FALL THROUGH */

             case PNG_NUMBER_FORMAT_x:
                *--end = digits[number & 0xf];
                number >>= 4;
                break;

             default: /* an error */
                number = 0;
                break;
          }

          /* Keep track of the number of digits added */
          ++count;

          /* Float a fixed number here: */
          if (format == PNG_NUMBER_FORMAT_fixed) if (count == 5) if (end > start)
          {
             /* End of the fraction, but maybe nothing was output?  In that case
              * drop the decimal point.  If the number is a true zero handle that
              * here.
              */
             if (output)
                *--end = '.';
             else if (number == 0) /* and !output */
                *--end = '0';
          }
       }

       return end;
    }
    #endif

    #ifdef PNG_WARNINGS_SUPPORTED
    /* This function is called whenever there is a non-fatal error.  This function
     * should not be changed.  If there is a need to handle warnings differently,
     * you should supply a replacement warning function and use
     * png_set_error_fn() to replace the warning function at run-time.
     */
    void PNGAPI
    png_warning(png_const_structrp png_ptr, png_const_charp warning_message)
    {
       int offset = 0;
       if (png_ptr != NULL)
       {
    #ifdef PNG_ERROR_NUMBERS_SUPPORTED
       if (png_ptr->flags&
           (PNG_FLAG_STRIP_ERROR_NUMBERS|PNG_FLAG_STRIP_ERROR_TEXT))
    #endif
          {
             if (*warning_message == PNG_LITERAL_SHARP)
             {
                for (offset = 1; offset < 15; offset++)
                   if (warning_message[offset] == ' ')
                      break;
             }
          }
       }
       if (png_ptr != NULL && png_ptr->warning_fn != NULL)
          (*(png_ptr->warning_fn))(png_constcast(png_structrp,png_ptr),
             warning_message + offset);
       else
          png_default_warning(png_ptr, warning_message + offset);
    }

    /* These functions support 'formatted' warning messages with up to
     * PNG_WARNING_PARAMETER_COUNT parameters.  In the format string the parameter
     * is introduced by @<number>, where 'number' starts at 1.  This follows the
     * standard established by X/Open for internationalizable error messages.
     */
    void
    png_warning_parameter(png_warning_parameters p, int number,
       png_const_charp string)
    {
       if (number > 0 && number <= PNG_WARNING_PARAMETER_COUNT)
          (void)png_safecat(p[number-1], (sizeof p[number-1]), 0, string);
    }

    void
    png_warning_parameter_unsigned(png_warning_parameters p, int number, int format,
       png_alloc_size_t value)
    {
       char buffer[PNG_NUMBER_BUFFER_SIZE];
       png_warning_parameter(p, number, PNG_FORMAT_NUMBER(buffer, format, value));
    }

    void
    png_warning_parameter_signed(png_warning_parameters p, int number, int format,
       png_int_32 value)
    {
       png_alloc_size_t u;
       png_charp str;
       char buffer[PNG_NUMBER_BUFFER_SIZE];

       /* Avoid overflow by doing the negate in a png_alloc_size_t: */
       u = (png_alloc_size_t)value;
       if (value < 0)
          u = ~u + 1;

       str = PNG_FORMAT_NUMBER(buffer, format, u);

       if (value < 0 && str > buffer)
          *--str = '-';

       png_warning_parameter(p, number, str);
    }

    void
    png_formatted_warning(png_const_structrp png_ptr, png_warning_parameters p,
       png_const_charp message)
    {
       /* The internal buffer is just 192 bytes - enough for all our messages,
        * overflow doesn't happen because this code checks!  If someone figures
        * out how to send us a message longer than 192 bytes, all that will
        * happen is that the message will be truncated appropriately.
        */
       size_t i = 0; /* Index in the msg[] buffer: */
       char msg[192];

       /* Each iteration through the following loop writes at most one character
        * to msg[i++] then returns here to validate that there is still space for
        * the trailing '\0'.  It may (in the case of a parameter) read more than
        * one character from message[]; it must check for '\0' and continue to the
        * test if it finds the end of string.
        */
       while (i<(sizeof msg)-1 && *message != '\0')
       {
          /* '@' at end of string is now just printed (previously it was skipped);
           * it is an error in the calling code to terminate the string with @.
           */
          if (p != NULL && *message == '@' && message[1] != '\0')
          {
             int parameter_char = *++message; /* Consume the '@' */
             static const char valid_parameters[] = "123456789";
             int parameter = 0;

             /* Search for the parameter digit, the index in the string is the
              * parameter to use.
              */
             while (valid_parameters[parameter] != parameter_char &&
                valid_parameters[parameter] != '\0')
                ++parameter;

             /* If the parameter digit is out of range it will just get printed. */
             if (parameter < PNG_WARNING_PARAMETER_COUNT)
             {
                /* Append this parameter */
                png_const_charp parm = p[parameter];
                png_const_charp pend = p[parameter] + (sizeof p[parameter]);

                /* No need to copy the trailing '\0' here, but there is no guarantee
                 * that parm[] has been initialized, so there is no guarantee of a
                 * trailing '\0':
                 */
                while (i<(sizeof msg)-1 && *parm != '\0' && parm < pend)
                   msg[i++] = *parm++;

                /* Consume the parameter digit too: */
                ++message;
                continue;
             }

             /* else not a parameter and there is a character after the @ sign; just
              * copy that.  This is known not to be '\0' because of the test above.
              */
          }

          /* At this point *message can't be '\0', even in the bad parameter case
           * above where there is a lone '@' at the end of the message string.
           */
          msg[i++] = *message++;
       }

       /* i is always less than (sizeof msg), so: */
       msg[i] = '\0';

       /* And this is the formatted message. It may be larger than
        * PNG_MAX_ERROR_TEXT, but that is only used for 'chunk' errors and these
        * are not (currently) formatted.
        */
       png_warning(png_ptr, msg);
    }
    #endif /* PNG_WARNINGS_SUPPORTED */

    #ifdef PNG_BENIGN_ERRORS_SUPPORTED
    void PNGAPI
    png_benign_error(png_const_structrp png_ptr, png_const_charp error_message)
    {
       if (png_ptr->flags & PNG_FLAG_BENIGN_ERRORS_WARN)
       {
    #     ifdef PNG_READ_SUPPORTED
             if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0 &&
                png_ptr->chunk_name != 0)
                png_chunk_warning(png_ptr, error_message);
             else
    #     endif
          png_warning(png_ptr, error_message);
       }

       else
       {
    #     ifdef PNG_READ_SUPPORTED
             if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0 &&
                png_ptr->chunk_name != 0)
                png_chunk_error(png_ptr, error_message);
             else
    #     endif
          png_error(png_ptr, error_message);
       }
    }

    void /* PRIVATE */
    png_app_warning(png_const_structrp png_ptr, png_const_charp error_message)
    {
      if (png_ptr->flags & PNG_FLAG_APP_WARNINGS_WARN)
         png_warning(png_ptr, error_message);
      else
         png_error(png_ptr, error_message);
    }

    void /* PRIVATE */
    png_app_error(png_const_structrp png_ptr, png_const_charp error_message)
    {
      if (png_ptr->flags & PNG_FLAG_APP_ERRORS_WARN)
         png_warning(png_ptr, error_message);
      else
         png_error(png_ptr, error_message);
    }
    #endif /* BENIGN_ERRORS */

    /* These utilities are used internally to build an error message that relates
     * to the current chunk.  The chunk name comes from png_ptr->chunk_name,
     * this is used to prefix the message.  The message is limited in length
     * to 63 bytes, the name characters are output as hex digits wrapped in []
     * if the character is invalid.
     */
    #define isnonalpha(c) ((c) < 65 || (c) > 122 || ((c) > 90 && (c) < 97))
    static PNG_CONST char png_digit[16] = {
       '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
       'A', 'B', 'C', 'D', 'E', 'F'
    };

    #define PNG_MAX_ERROR_TEXT 196 /* Currently limited be profile_error in png.c */
    #if defined(PNG_WARNINGS_SUPPORTED) || defined(PNG_ERROR_TEXT_SUPPORTED)
    static void /* PRIVATE */
    png_format_buffer(png_const_structrp png_ptr, png_charp buffer, png_const_charp
        error_message)
    {
       png_uint_32 chunk_name = png_ptr->chunk_name;
       int iout = 0, ishift = 24;

       while (ishift >= 0)
       {
          int c = (int)(chunk_name >> ishift) & 0xff;

          ishift -= 8;
          if (isnonalpha(c))
          {
             buffer[iout++] = PNG_LITERAL_LEFT_SQUARE_BRACKET;
             buffer[iout++] = png_digit[(c & 0xf0) >> 4];
             buffer[iout++] = png_digit[c & 0x0f];
             buffer[iout++] = PNG_LITERAL_RIGHT_SQUARE_BRACKET;
          }

          else
          {
             buffer[iout++] = (char)c;
          }
       }

       if (error_message == NULL)
          buffer[iout] = '\0';

       else
       {
          int iin = 0;

          buffer[iout++] = ':';
          buffer[iout++] = ' ';

          while (iin < PNG_MAX_ERROR_TEXT-1 && error_message[iin] != '\0')
             buffer[iout++] = error_message[iin++];

          /* iin < PNG_MAX_ERROR_TEXT, so the following is safe: */
          buffer[iout] = '\0';
       }
    }
    #endif /* PNG_WARNINGS_SUPPORTED || PNG_ERROR_TEXT_SUPPORTED */

    #if defined(PNG_READ_SUPPORTED) && defined(PNG_ERROR_TEXT_SUPPORTED)
    PNG_FUNCTION(void,PNGAPI
    png_chunk_error,(png_const_structrp png_ptr, png_const_charp error_message),
       PNG_NORETURN)
    {
       char msg[18+PNG_MAX_ERROR_TEXT];
       if (png_ptr == NULL)
          png_error(png_ptr, error_message);

       else
       {
          png_format_buffer(png_ptr, msg, error_message);
          png_error(png_ptr, msg);
       }
    }
    #endif /* PNG_READ_SUPPORTED && PNG_ERROR_TEXT_SUPPORTED */

    #ifdef PNG_WARNINGS_SUPPORTED
    void PNGAPI
    png_chunk_warning(png_const_structrp png_ptr, png_const_charp warning_message)
    {
       char msg[18+PNG_MAX_ERROR_TEXT];
       if (png_ptr == NULL)
          png_warning(png_ptr, warning_message);

       else
       {
          png_format_buffer(png_ptr, msg, warning_message);
          png_warning(png_ptr, msg);
       }
    }
    #endif /* PNG_WARNINGS_SUPPORTED */

    #ifdef PNG_READ_SUPPORTED
    #ifdef PNG_BENIGN_ERRORS_SUPPORTED
    void PNGAPI
    png_chunk_benign_error(png_const_structrp png_ptr, png_const_charp
        error_message)
    {
       if (png_ptr->flags & PNG_FLAG_BENIGN_ERRORS_WARN)
          png_chunk_warning(png_ptr, error_message);

       else
          png_chunk_error(png_ptr, error_message);
    }
    #endif
    #endif /* PNG_READ_SUPPORTED */

    void /* PRIVATE */
    png_chunk_report(png_const_structrp png_ptr, png_const_charp message, int error)
    {
       /* This is always supported, but for just read or just write it
        * unconditionally does the right thing.
        */
    #  if defined(PNG_READ_SUPPORTED) && defined(PNG_WRITE_SUPPORTED)
          if (png_ptr->mode & PNG_IS_READ_STRUCT)
    #  endif

    #  ifdef PNG_READ_SUPPORTED
          {
             if (error < PNG_CHUNK_ERROR)
                png_chunk_warning(png_ptr, message);

             else
                png_chunk_benign_error(png_ptr, message);
          }
    #  endif

    #  if defined(PNG_READ_SUPPORTED) && defined(PNG_WRITE_SUPPORTED)
          else if (!(png_ptr->mode & PNG_IS_READ_STRUCT))
    #  endif

    #  ifdef PNG_WRITE_SUPPORTED
          {
             if (error < PNG_CHUNK_WRITE_ERROR)
                png_app_warning(png_ptr, message);

             else
                png_app_error(png_ptr, message);
          }
    #  endif
    }

    #ifdef PNG_ERROR_TEXT_SUPPORTED
    #ifdef PNG_FLOATING_POINT_SUPPORTED
    PNG_FUNCTION(void,
    png_fixed_error,(png_const_structrp png_ptr, png_const_charp name),PNG_NORETURN)
    {
    #  define fixed_message "fixed point overflow in "
    #  define fixed_message_ln ((sizeof fixed_message)-1)
       int  iin;
       char msg[fixed_message_ln+PNG_MAX_ERROR_TEXT];
       memcpy(msg, fixed_message, fixed_message_ln);
       iin = 0;
       if (name != NULL) while (iin < (PNG_MAX_ERROR_TEXT-1) && name[iin] != 0)
       {
          msg[fixed_message_ln + iin] = name[iin];
          ++iin;
       }
       msg[fixed_message_ln + iin] = 0;
       png_error(png_ptr, msg);
    }
    #endif
    #endif

    #ifdef PNG_SETJMP_SUPPORTED
    /* This API only exists if ANSI-C style error handling is used,
     * otherwise it is necessary for png_default_error to be overridden.
     */
    jmp_buf* PNGAPI
    png_set_longjmp_fn(png_structrp png_ptr, png_longjmp_ptr longjmp_fn,
        size_t jmp_buf_size)
    {
       /* From libpng 1.6.0 the app gets one chance to set a 'jmpbuf_size' value
        * and it must not change after that.  Libpng doesn't care how big the
        * buffer is, just that it doesn't change.
        *
        * If the buffer size is no *larger* than the size of jmp_buf when libpng is
        * compiled a built in jmp_buf is returned; this preserves the pre-1.6.0
        * semantics that this call will not fail.  If the size is larger, however,
        * the buffer is allocated and this may fail, causing the function to return
        * NULL.
        */
       if (png_ptr == NULL)
          return NULL;

       if (png_ptr->jmp_buf_ptr == NULL)
       {
          png_ptr->jmp_buf_size = 0; /* not allocated */

          if (jmp_buf_size <= (sizeof png_ptr->jmp_buf_local))
             png_ptr->jmp_buf_ptr = &png_ptr->jmp_buf_local;

          else
          {
             png_ptr->jmp_buf_ptr = png_voidcast(jmp_buf *,
                png_malloc_warn(png_ptr, jmp_buf_size));

             if (png_ptr->jmp_buf_ptr == NULL)
                return NULL; /* new NULL return on OOM */

             png_ptr->jmp_buf_size = jmp_buf_size;
          }
       }

       else /* Already allocated: check the size */
       {
          size_t size = png_ptr->jmp_buf_size;

          if (size == 0)
          {
             size = (sizeof png_ptr->jmp_buf_local);
             if (png_ptr->jmp_buf_ptr != &png_ptr->jmp_buf_local)
             {
                /* This is an internal error in libpng: somehow we have been left
                 * with a stack allocated jmp_buf when the application regained
                 * control.  It's always possible to fix this up, but for the moment
                 * this is a png_error because that makes it easy to detect.
                 */
                png_error(png_ptr, "Libpng jmp_buf still allocated");
                /* png_ptr->jmp_buf_ptr = &png_ptr->jmp_buf_local; */
             }
          }

          if (size != jmp_buf_size)
          {
             png_warning(png_ptr, "Application jmp_buf size changed");
             return NULL; /* caller will probably crash: no choice here */
          }
       }

       /* Finally fill in the function, now we have a satisfactory buffer. It is
        * valid to change the function on every call.
        */
       png_ptr->longjmp_fn = longjmp_fn;
       return png_ptr->jmp_buf_ptr;
    }

    void /* PRIVATE */
    png_free_jmpbuf(png_structrp png_ptr)
    {
       if (png_ptr != NULL)
       {
          jmp_buf *jb = png_ptr->jmp_buf_ptr;

          /* A size of 0 is used to indicate a local, stack, allocation of the
           * pointer; used here and in png.c
           */
          if (jb != NULL && png_ptr->jmp_buf_size > 0)
          {

             /* This stuff is so that a failure to free the error control structure
              * does not leave libpng in a state with no valid error handling: the
              * free always succeeds, if there is an error it gets ignored.
              */
             if (jb != &png_ptr->jmp_buf_local)
             {
                /* Make an internal, libpng, jmp_buf to return here */
                jmp_buf free_jmp_buf;

                if (!setjmp(free_jmp_buf))
                {
                   png_ptr->jmp_buf_ptr = &free_jmp_buf; /* come back here */
                   png_ptr->jmp_buf_size = 0; /* stack allocation */
                   png_ptr->longjmp_fn = longjmp;
                   png_free(png_ptr, jb); /* Return to setjmp on error */
                }
             }
          }

          /* *Always* cancel everything out: */
          png_ptr->jmp_buf_size = 0;
          png_ptr->jmp_buf_ptr = NULL;
          png_ptr->longjmp_fn = 0;
       }
    }
    #endif

    /* This is the default error handling function.  Note that replacements for
     * this function MUST NOT RETURN, or the program will likely crash.  This
     * function is used by default, or if the program supplies NULL for the
     * error function pointer in png_set_error_fn().
     */
    static PNG_FUNCTION(void /* PRIVATE */,
    png_default_error,(png_const_structrp png_ptr, png_const_charp error_message),
       PNG_NORETURN)
    {
    #ifdef PNG_CONSOLE_IO_SUPPORTED
    #ifdef PNG_ERROR_NUMBERS_SUPPORTED
       /* Check on NULL only added in 1.5.4 */
       if (error_message != NULL && *error_message == PNG_LITERAL_SHARP)
       {
          /* Strip "#nnnn " from beginning of error message. */
          int offset;
          char error_number[16];
          for (offset = 0; offset<15; offset++)
          {
             error_number[offset] = error_message[offset + 1];
             if (error_message[offset] == ' ')
                break;
          }

          if ((offset > 1) && (offset < 15))
          {
             error_number[offset - 1] = '\0';
             fprintf(stderr, "libpng error no. %s: %s",
                 error_number, error_message + offset + 1);
             fprintf(stderr, PNG_STRING_NEWLINE);
          }

          else
          {
             fprintf(stderr, "libpng error: %s, offset=%d",
                 error_message, offset);
             fprintf(stderr, PNG_STRING_NEWLINE);
          }
       }
       else
    #endif
       {
          fprintf(stderr, "libpng error: %s", error_message ? error_message :
             "undefined");
          fprintf(stderr, PNG_STRING_NEWLINE);
       }
    #else
       PNG_UNUSED(error_message) /* Make compiler happy */
    #endif
       png_longjmp(png_ptr, 1);
    }

    PNG_FUNCTION(void,PNGAPI
    png_longjmp,(png_const_structrp png_ptr, int val),PNG_NORETURN)
    {
    #ifdef PNG_SETJMP_SUPPORTED
       if (png_ptr && png_ptr->longjmp_fn && png_ptr->jmp_buf_ptr)
          png_ptr->longjmp_fn(*png_ptr->jmp_buf_ptr, val);
    #endif

       /* Here if not setjmp support or if png_ptr is null. */
       PNG_ABORT();
    }

    #ifdef PNG_WARNINGS_SUPPORTED
    /* This function is called when there is a warning, but the library thinks
     * it can continue anyway.  Replacement functions don't have to do anything
     * here if you don't want them to.  In the default configuration, png_ptr is
     * not used, but it is passed in case it may be useful.
     */
    static void /* PRIVATE */
    png_default_warning(png_const_structrp png_ptr, png_const_charp warning_message)
    {
    #ifdef PNG_CONSOLE_IO_SUPPORTED
    #  ifdef PNG_ERROR_NUMBERS_SUPPORTED
       if (*warning_message == PNG_LITERAL_SHARP)
       {
          int offset;
          char warning_number[16];
          for (offset = 0; offset < 15; offset++)
          {
             warning_number[offset] = warning_message[offset + 1];
             if (warning_message[offset] == ' ')
                break;
          }

          if ((offset > 1) && (offset < 15))
          {
             warning_number[offset + 1] = '\0';
             fprintf(stderr, "libpng warning no. %s: %s",
                 warning_number, warning_message + offset);
             fprintf(stderr, PNG_STRING_NEWLINE);
          }

          else
          {
             fprintf(stderr, "libpng warning: %s",
                 warning_message);
             fprintf(stderr, PNG_STRING_NEWLINE);
          }
       }
       else
    #  endif

       {
          fprintf(stderr, "libpng warning: %s", warning_message);
          fprintf(stderr, PNG_STRING_NEWLINE);
       }
    #else
       PNG_UNUSED(warning_message) /* Make compiler happy */
    #endif
       PNG_UNUSED(png_ptr) /* Make compiler happy */
    }
    #endif /* PNG_WARNINGS_SUPPORTED */

    /* This function is called when the application wants to use another method
     * of handling errors and warnings.  Note that the error function MUST NOT
     * return to the calling routine or serious problems will occur.  The return
     * method used in the default routine calls longjmp(png_ptr->jmp_buf_ptr, 1)
     */
    void PNGAPI
    png_set_error_fn(png_structrp png_ptr, png_voidp error_ptr,
        png_error_ptr error_fn, png_error_ptr warning_fn)
    {
       if (png_ptr == NULL)
          return;

       png_ptr->error_ptr = error_ptr;
       png_ptr->error_fn = error_fn;
    #ifdef PNG_WARNINGS_SUPPORTED
       png_ptr->warning_fn = warning_fn;
    #else
       PNG_UNUSED(warning_fn)
    #endif
    }

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

       return ((png_voidp)png_ptr->error_ptr);
    }

    #ifdef PNG_ERROR_NUMBERS_SUPPORTED
    void PNGAPI
    png_set_strip_error_numbers(png_structrp png_ptr, png_uint_32 strip_mode)
    {
       if (png_ptr != NULL)
       {
          png_ptr->flags &=
             ((~(PNG_FLAG_STRIP_ERROR_NUMBERS |
             PNG_FLAG_STRIP_ERROR_TEXT))&strip_mode);
       }
    }
    #endif

    #if defined(PNG_SIMPLIFIED_READ_SUPPORTED) ||\
       defined(PNG_SIMPLIFIED_WRITE_SUPPORTED)
       /* Currently the above both depend on SETJMP_SUPPORTED, however it would be
        * possible to implement without setjmp support just so long as there is some
        * way to handle the error return here:
        */
    PNG_FUNCTION(void /* PRIVATE */,
    png_safe_error,(png_structp png_nonconst_ptr, png_const_charp error_message),
       PNG_NORETURN)
    {
       const png_const_structrp png_ptr = png_nonconst_ptr;
       png_imagep image = png_voidcast(png_imagep, png_ptr->error_ptr);

       /* An error is always logged here, overwriting anything (typically a warning)
        * that is already there:
        */
       if (image != NULL)
       {
          png_safecat(image->message, (sizeof image->message), 0, error_message);
          image->warning_or_error |= PNG_IMAGE_ERROR;

          /* Retrieve the jmp_buf from within the png_control, making this work for
           * C++ compilation too is pretty tricky: C++ wants a pointer to the first
           * element of a jmp_buf, but C doesn't tell us the type of that.
           */
          if (image->opaque != NULL && image->opaque->error_buf != NULL)
             longjmp(png_control_jmp_buf(image->opaque), 1);

          /* Missing longjmp buffer, the following is to help debugging: */
          {
             size_t pos = png_safecat(image->message, (sizeof image->message), 0,
                "bad longjmp: ");
             png_safecat(image->message, (sizeof image->message), pos,
                 error_message);
          }
       }

       /* Here on an internal programming error. */
       abort();
    }

    #ifdef PNG_WARNINGS_SUPPORTED
    void /* PRIVATE */
    png_safe_warning(png_structp png_nonconst_ptr, png_const_charp warning_message)
    {
       const png_const_structrp png_ptr = png_nonconst_ptr;
       png_imagep image = png_voidcast(png_imagep, png_ptr->error_ptr);

       /* A warning is only logged if there is no prior warning or error. */
       if (image->warning_or_error == 0)
       {
          png_safecat(image->message, (sizeof image->message), 0, warning_message);
          image->warning_or_error |= PNG_IMAGE_WARNING;
       }
    }
    #endif

    int /* PRIVATE */
    png_safe_execute(png_imagep image_in, int (*function)(png_voidp), png_voidp arg)
    {
       volatile png_imagep image = image_in;
       volatile int result;
       volatile png_voidp saved_error_buf;
       jmp_buf safe_jmpbuf;

       /* Safely execute function(arg) with png_error returning to this function. */
       saved_error_buf = image->opaque->error_buf;
       result = setjmp(safe_jmpbuf) == 0;

       if (result)
       {

          image->opaque->error_buf = safe_jmpbuf;
          result = function(arg);
       }

       image->opaque->error_buf = saved_error_buf;

       /* And do the cleanup prior to any failure return. */
       if (!result)
          png_image_free(image);

       return result;
    }
    #endif /* SIMPLIFIED READ/WRITE */
    #endif /* PNG_READ_SUPPORTED || PNG_WRITE_SUPPORTED */