/* pngwio.c - functions for data output

 *

 * Copyright (c) 2018-2025 Cosmin Truta

 * Copyright (c) 1998-2002,2004,2006-2014,2016,2018 Glenn Randers-Pehrson

 * Copyright (c) 1996-1997 Andreas Dilger

 * 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 "pngpriv.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_structrp png_ptr, png_const_bytep data, size_t length)

{

   /* NOTE: write_data_fn must not change the buffer! */

   if (png_ptr->write_data_fn != NULL )

      (*(png_ptr->write_data_fn))(png_ptr, png_constcast(png_bytep,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.

 */

void PNGCBAPI

png_default_write_data(png_structp png_ptr, png_bytep data, size_t length)

{

   size_t check;

   if (png_ptr == NULL)

      return;

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

   if (check != length)

      png_error(png_ptr, "Write Error");

}

#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_structrp png_ptr)

{

   if (png_ptr->output_flush_fn != NULL)

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

}

#  ifdef PNG_STDIO_SUPPORTED

void PNGCBAPI

png_default_flush(png_structp png_ptr)

{

   FILE *io_ptr;

   if (png_ptr == NULL)

      return;

   io_ptr = png_voidcast(FILE *, 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 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_structrp 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

#else

   PNG_UNUSED(output_flush_fn)

#endif /* WRITE_FLUSH */

#ifdef PNG_READ_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,

          "Can't set both read_data_fn and write_data_fn in the"

          " same structure");

   }

#endif

}

#endif /* WRITE */