text: 
  /* pngwio.c - functions for data output
   *
   * Last changed in libpng 1.2.41 [December 3, 2009]
   * Copyright (c) 1998-2009 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 output.  Users who need
   * special handling are expected to write functions that have the same
   * arguments as these and perform similar functions, but that possibly
   * use different output methods.  Note that you shouldn't change these
   * functions, but rather write replacement functions and then change
   * them at run time with png_set_write_fn(...).
   */
  
  #define PNG_INTERNAL
  #define PNG_NO_PEDANTIC_WARNINGS
  #include "png.h"
  #ifdef PNG_WRITE_SUPPORTED
  
  /* Write the data to whatever output you are using.  The default routine
   * writes to a file pointer.  Note that this routine sometimes gets called
   * with very small lengths, so you should implement some kind of simple
   * buffering if you are using unbuffered writes.  This should never be asked
   * to write more than 64K on a 16 bit machine.
   */
  
  void /* PRIVATE */
  png_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
  {
     if (png_ptr->write_data_fn != NULL )
        (*(png_ptr->write_data_fn))(png_ptr, data, length);
     else
        png_error(png_ptr, "Call to NULL write function");
  }
  
  #ifdef PNG_STDIO_SUPPORTED
  /* This is the function that does the actual writing of data.  If you are
   * not writing to a standard C stream, you should create a replacement
   * write_data function and use it at run time with png_set_write_fn(), rather
   * than changing the library.
   */
  #ifndef USE_FAR_KEYWORD
  void PNGAPI
  png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
  {
     png_uint_32 check;
  
     if (png_ptr == NULL)
        return;
  #ifdef _WIN32_WCE
     if ( !WriteFile((HANDLE)(png_ptr->io_ptr), data, length, &check, NULL) )
        check = 0;
  #else
     check = fwrite(data, 1, length, (png_FILE_p)(png_ptr->io_ptr));
  #endif
     if (check != length)
        png_error(png_ptr, "Write Error");
  }
  #else
  /* This is the model-independent version. Since the standard I/O library
   * can't handle far buffers in the medium and small models, we have to copy
   * the data.
   */
  
  #define NEAR_BUF_SIZE 1024
  #define MIN(a,b) (a <= b ? a : b)
  
  void PNGAPI
  png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
  {
     png_uint_32 check;
     png_byte *near_data;  /* Needs to be "png_byte *" instead of "png_bytep" */
     png_FILE_p io_ptr;
  
     if (png_ptr == NULL)
        return;
     /* Check if data really is near. If so, use usual code. */
     near_data = (png_byte *)CVT_PTR_NOCHECK(data);
     io_ptr = (png_FILE_p)CVT_PTR(png_ptr->io_ptr);
     if ((png_bytep)near_data == data)
     {
  #ifdef _WIN32_WCE
        if ( !WriteFile(io_ptr, near_data, length, &check, NULL) )
           check = 0;
  #else
        check = fwrite(near_data, 1, length, io_ptr);
  #endif
     }
     else
     {
        png_byte buf[NEAR_BUF_SIZE];
        png_size_t written, remaining, err;
        check = 0;
        remaining = length;
        do
        {
           written = MIN(NEAR_BUF_SIZE, remaining);
           png_memcpy(buf, data, written); /* Copy far buffer to near buffer */
  #ifdef _WIN32_WCE
           if ( !WriteFile(io_ptr, buf, written, &err, NULL) )
              err = 0;
  #else
           err = fwrite(buf, 1, written, io_ptr);
  #endif
           if (err != written)
              break;
  
           else
              check += err;
  
           data += written;
           remaining -= written;
        }
        while (remaining != 0);
     }
     if (check != length)
        png_error(png_ptr, "Write Error");
  }
  
  #endif
  #endif
  
  /* This function is called to output any data pending writing (normally
   * to disk).  After png_flush is called, there should be no data pending
   * writing in any buffers.
   */
  #ifdef PNG_WRITE_FLUSH_SUPPORTED
  void /* PRIVATE */
  png_flush(png_structp png_ptr)
  {
     if (png_ptr->output_flush_fn != NULL)
        (*(png_ptr->output_flush_fn))(png_ptr);
  }
  
  #ifdef PNG_STDIO_SUPPORTED
  void PNGAPI
  png_default_flush(png_structp png_ptr)
  {
  #ifndef _WIN32_WCE
     png_FILE_p io_ptr;
  #endif
     if (png_ptr == NULL)
        return;
  #ifndef _WIN32_WCE
     io_ptr = (png_FILE_p)CVT_PTR((png_ptr->io_ptr));
     fflush(io_ptr);
  #endif
  }
  #endif
  #endif
  
  /* This function allows the application to supply new output functions for
   * libpng if standard C streams aren't being used.
   *
   * This function takes as its arguments:
   * png_ptr       - pointer to a png output data structure
   * io_ptr        - pointer to user supplied structure containing info about
   *                 the output functions.  May be NULL.
   * write_data_fn - pointer to a new output function that takes as its
   *                 arguments a pointer to a png_struct, a pointer to
   *                 data to be written, and a 32-bit unsigned int that is
   *                 the number of bytes to be written.  The new write
   *                 function should call png_error(png_ptr, "Error msg")
   *                 to exit and output any fatal error messages.  May be
   *                 NULL, in which case libpng's default function will
   *                 be used.
   * flush_data_fn - pointer to a new flush function that takes as its
   *                 arguments a pointer to a png_struct.  After a call to
   *                 the flush function, there should be no data in any buffers
   *                 or pending transmission.  If the output method doesn't do
   *                 any buffering of output, a function prototype must still be
   *                 supplied although it doesn't have to do anything.  If
   *                 PNG_WRITE_FLUSH_SUPPORTED is not defined at libpng compile
   *                 time, output_flush_fn will be ignored, although it must be
   *                 supplied for compatibility.  May be NULL, in which case
   *                 libpng's default function will be used, if
   *                 PNG_WRITE_FLUSH_SUPPORTED is defined.  This is not
   *                 a good idea if io_ptr does not point to a standard
   *                 *FILE structure.
   */
  void PNGAPI
  png_set_write_fn(png_structp png_ptr, png_voidp io_ptr,
     png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn)
  {
     if (png_ptr == NULL)
        return;
  
     png_ptr->io_ptr = io_ptr;
  
  #ifdef PNG_STDIO_SUPPORTED
     if (write_data_fn != NULL)
        png_ptr->write_data_fn = write_data_fn;
  
     else
        png_ptr->write_data_fn = png_default_write_data;
  #else
     png_ptr->write_data_fn = write_data_fn;
  #endif
  
  #ifdef PNG_WRITE_FLUSH_SUPPORTED
  #ifdef PNG_STDIO_SUPPORTED
     if (output_flush_fn != NULL)
        png_ptr->output_flush_fn = output_flush_fn;
  
     else
        png_ptr->output_flush_fn = png_default_flush;
  #else
     png_ptr->output_flush_fn = output_flush_fn;
  #endif
  #endif /* PNG_WRITE_FLUSH_SUPPORTED */
  
     /* It is an error to read while writing a png file */
     if (png_ptr->read_data_fn != NULL)
     {
        png_ptr->read_data_fn = NULL;
        png_warning(png_ptr,
           "Attempted to set both read_data_fn and write_data_fn in");
        png_warning(png_ptr,
           "the same structure.  Resetting read_data_fn to NULL.");
     }
  }
  
  #ifdef USE_FAR_KEYWORD
  #ifdef _MSC_VER
  void *png_far_to_near(png_structp png_ptr, png_voidp ptr, int check)
  {
     void *near_ptr;
     void FAR *far_ptr;
     FP_OFF(near_ptr) = FP_OFF(ptr);
     far_ptr = (void FAR *)near_ptr;
  
     if (check != 0)
        if (FP_SEG(ptr) != FP_SEG(far_ptr))
           png_error(png_ptr, "segment lost in conversion");
  
     return(near_ptr);
  }
  #  else
  void *png_far_to_near(png_structp png_ptr, png_voidp ptr, int check)
  {
     void *near_ptr;
     void FAR *far_ptr;
     near_ptr = (void FAR *)ptr;
     far_ptr = (void FAR *)near_ptr;
  
     if (check != 0)
        if (far_ptr != ptr)
           png_error(png_ptr, "segment lost in conversion");
  
     return(near_ptr);
  }
  #   endif
  #   endif
  #endif /* PNG_WRITE_SUPPORTED */
  