text: 
  /* pngerror.c - stub functions for i/o and memory allocation
   *
   * Last changed in libpng 1.2.13 November 13, 2006
   * For conditions of distribution and use, see copyright notice in png.h
   * Copyright (c) 1998-2006 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 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.
   */
  
  #define PNG_INTERNAL
  #include "png.h"
  
  #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
  static void /* PRIVATE */
  png_default_error PNGARG((png_structp png_ptr,
    png_const_charp error_message));
  static void /* PRIVATE */
  png_default_warning PNGARG((png_structp png_ptr,
    png_const_charp warning_message));
  
  /* 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.
   */
  void PNGAPI
  png_error(png_structp png_ptr, png_const_charp error_message)
  {
  #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 == '#')
         {
             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]='\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);
  }
  
  /* 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 == '#')
         {
             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 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))
  const static 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)
  {
     int iout = 0, iin = 0;
  
     while (iin < 4)
     {
        int c = png_ptr->chunk_name[iin++];
        if (isnonalpha(c))
        {
           buffer[iout++] = '[';
           buffer[iout++] = png_digit[(c & 0xf0) >> 4];
           buffer[iout++] = png_digit[c & 0x0f];
           buffer[iout++] = ']';
        }
        else
        {
           buffer[iout++] = (png_byte)c;
        }
     }
  
     if (error_message == NULL)
        buffer[iout] = 0;
     else
     {
        buffer[iout++] = ':';
        buffer[iout++] = ' ';
        png_strncpy(buffer+iout, error_message, 63);
        buffer[iout+63] = 0;
     }
  }
  
  void PNGAPI
  png_chunk_error(png_structp png_ptr, png_const_charp error_message)
  {
     char msg[18+64];
     if (png_ptr == NULL)
       png_error(png_ptr, error_message);
     else
     {
       png_format_buffer(png_ptr, msg, error_message);
       png_error(png_ptr, msg);
     }
  }
  
  void PNGAPI
  png_chunk_warning(png_structp png_ptr, png_const_charp warning_message)
  {
     char msg[18+64];
     if (png_ptr == NULL)
       png_warning(png_ptr, warning_message);
     else
     {
       png_format_buffer(png_ptr, msg, warning_message);
       png_warning(png_ptr, msg);
     }
  }
  
  /* 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 void /* PRIVATE */
  png_default_error(png_structp png_ptr, png_const_charp error_message)
  {
  #ifndef PNG_NO_CONSOLE_IO
  #ifdef PNG_ERROR_NUMBERS_SUPPORTED
     if (*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\n", error_number,
            error_message+offset);
       }
       else
         fprintf(stderr, "libpng error: %s, offset=%d\n", error_message,offset);
     }
     else
  #endif
     fprintf(stderr, "libpng error: %s\n", error_message);
  #endif
  
  #ifdef PNG_SETJMP_SUPPORTED
     if (png_ptr)
     {
  #  ifdef USE_FAR_KEYWORD
     {
        jmp_buf jmpbuf;
        png_memcpy(jmpbuf,png_ptr->jmpbuf,png_sizeof(jmp_buf));
        longjmp(jmpbuf, 1);
     }
  #  else
     longjmp(png_ptr->jmpbuf, 1);
  #  endif
     }
  #else
     PNG_ABORT();
  #endif
  #ifdef PNG_NO_CONSOLE_IO
     /* make compiler happy */ ;
     if (&error_message != NULL)
        return;
  #endif
  }
  
  /* 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)
  {
  #ifndef PNG_NO_CONSOLE_IO
  #  ifdef PNG_ERROR_NUMBERS_SUPPORTED
     if (*warning_message == '#')
     {
       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\n", warning_number,
            warning_message+offset);
       }
       else
         fprintf(stderr, "libpng warning: %s\n", warning_message);
     }
     else
  #  endif
       fprintf(stderr, "libpng warning: %s\n", warning_message);
  #else
     /* make compiler happy */ ;
     if (warning_message)
       return;
  #endif
     /* make compiler happy */ ;
     if (png_ptr)
        return;
  }
  
  /* 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->jmpbuf, 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;
     png_ptr->warning_fn = warning_fn;
  }
  
  
  /* 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_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 */
  