pngerror.c - third_party/libpng - Git at Google


 /* pngerror.c - stub functions for i/o and memory allocation
  *
  * Last changed in libpng 1.5.28 [December 29, 2016]
  * Copyright (c) 1998-2002,2004,2006-2014,2016 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_structp png_ptr,
     png_const_charp error_message)),PNG_NORETURN);

 #ifdef PNG_WARNINGS_SUPPORTED
 static void /* PRIVATE */
 png_default_warning PNGARG((png_structp 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_structp 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_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_structp 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_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 != 0)
             *--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_structp 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_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_structp 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_structp png_ptr, png_const_charp error_message)
 {
   if (png_ptr->flags & PNG_FLAG_BENIGN_ERRORS_WARN)
      png_warning(png_ptr, error_message);
   else
      png_error(png_ptr, error_message);
 }
 #endif

 /* 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 PNG_MAX_ERROR_TEXT 64
 #if defined(PNG_WARNINGS_SUPPORTED) || defined(PNG_ERROR_TEXT_SUPPORTED)
 #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'
 };

 static void /* PRIVATE */
 png_format_buffer(png_structp 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_structp 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_structp 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_structp 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 */

 #ifdef PNG_ERROR_TEXT_SUPPORTED
 #ifdef PNG_FLOATING_POINT_SUPPORTED
 PNG_FUNCTION(void,
 png_fixed_error,(png_structp 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];
    png_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_structp png_ptr, png_longjmp_ptr longjmp_fn,
     size_t jmp_buf_size)
 {
    if (png_ptr == NULL || jmp_buf_size != png_sizeof(jmp_buf))
       return NULL;

    png_ptr->longjmp_fn = longjmp_fn;
    return &png_ptr->longjmp_buffer;
 }
 #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_structp 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_structp png_ptr, int val),PNG_NORETURN)
 {
 #ifdef PNG_SETJMP_SUPPORTED
    if (png_ptr && png_ptr->longjmp_fn)
    {
 #  ifdef USE_FAR_KEYWORD
       {
          jmp_buf tmp_jmpbuf;
          png_memcpy(tmp_jmpbuf, png_ptr->longjmp_buffer, png_sizeof(jmp_buf));
          png_ptr->longjmp_fn(tmp_jmpbuf, val);
       }

 #  else
    png_ptr->longjmp_fn(png_ptr->longjmp_buffer, val);
 #  endif
    }
 #else
    PNG_UNUSED(png_ptr);
    PNG_UNUSED(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_structp 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->longjmp_buffer, 1)
  */
 void PNGAPI
 png_set_error_fn(png_structp 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_structp 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_structp 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
 #endif /* PNG_READ_SUPPORTED || PNG_WRITE_SUPPORTED */

	/* pngerror.c - stub functions for i/o and memory allocation
	*
	* Last changed in libpng 1.5.28 [December 29, 2016]
	* Copyright (c) 1998-2002,2004,2006-2014,2016 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_structp png_ptr,
	png_const_charp error_message)),PNG_NORETURN);

	#ifdef PNG_WARNINGS_SUPPORTED
	static void /* PRIVATE */
	png_default_warning PNGARG((png_structp 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_structp 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_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_structp 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_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 != 0)
	*--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_structp 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_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_structp 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_structp png_ptr, png_const_charp error_message)
	{
	if (png_ptr->flags & PNG_FLAG_BENIGN_ERRORS_WARN)
	png_warning(png_ptr, error_message);
	else
	png_error(png_ptr, error_message);
	}
	#endif

	/* 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 PNG_MAX_ERROR_TEXT 64
	#if defined(PNG_WARNINGS_SUPPORTED) \|\| defined(PNG_ERROR_TEXT_SUPPORTED)
	#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'
	};

	static void /* PRIVATE */
	png_format_buffer(png_structp 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_structp 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_structp 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_structp 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 */

	#ifdef PNG_ERROR_TEXT_SUPPORTED
	#ifdef PNG_FLOATING_POINT_SUPPORTED
	PNG_FUNCTION(void,
	png_fixed_error,(png_structp 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];
	png_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_structp png_ptr, png_longjmp_ptr longjmp_fn,
	size_t jmp_buf_size)
	{
	if (png_ptr == NULL \|\| jmp_buf_size != png_sizeof(jmp_buf))
	return NULL;

	png_ptr->longjmp_fn = longjmp_fn;
	return &png_ptr->longjmp_buffer;
	}
	#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_structp 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_structp png_ptr, int val),PNG_NORETURN)
	{
	#ifdef PNG_SETJMP_SUPPORTED
	if (png_ptr && png_ptr->longjmp_fn)
	{
	# ifdef USE_FAR_KEYWORD
	{
	jmp_buf tmp_jmpbuf;
	png_memcpy(tmp_jmpbuf, png_ptr->longjmp_buffer, png_sizeof(jmp_buf));
	png_ptr->longjmp_fn(tmp_jmpbuf, val);
	}

	# else
	png_ptr->longjmp_fn(png_ptr->longjmp_buffer, val);
	# endif
	}
	#else
	PNG_UNUSED(png_ptr);
	PNG_UNUSED(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_structp 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->longjmp_buffer, 1)
	*/
	void PNGAPI
	png_set_error_fn(png_structp 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_structp 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_structp 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
	#endif /* PNG_READ_SUPPORTED \|\| PNG_WRITE_SUPPORTED */