/* pngwio.c - functions for data output

 *

 * (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(...).

 */

#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");

}

/* 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;

   check = fwrite(data, 1, length, (png_FILE_p)(png_ptr->io_ptr));

   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)

   {

      check = fwrite(near_data, 1, length, io_ptr);

   }

   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 */

         err = fwrite(buf, 1, written, io_ptr);

         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.

 */

void /* PRIVATE */

png_flush(png_structp png_ptr)

{

   if (png_ptr->output_flush_fn != NULL)

      (*(png_ptr->output_flush_fn))(png_ptr);

}

void PNGAPI

png_default_flush(png_structp png_ptr)

{

   png_FILE_p io_ptr;

   if (png_ptr == NULL)

      return;

   io_ptr = (png_FILE_p)CVT_PTR((png_ptr->io_ptr));

   fflush(io_ptr);

}

#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 ouput, 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;

   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

   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,

   }

}

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 */