src/png/pngrio.c


/* pngrio.c - functions for data input
 *
 * Last changed in libpng 1.6.0 [February 14, 2013]
 * Copyright (c) 1998-2013 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 input.  Users who need
 * special handling are expected to write a function that has the same
 * arguments as this and performs a similar function, but that possibly
 * has a different input method.  Note that you shouldn't change this
 * function, but rather write a replacement function and then make
 * libpng use it at run time with png_set_read_fn(...).
 */

#include "pngpriv.h"

#ifdef PNG_READ_SUPPORTED

/* Read the data from whatever input you are using.  The default routine
 * reads from 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 reads.  This should never be asked
 * to read more then 64K on a 16 bit machine.
 */
void /* PRIVATE */
png_read_data(png_structrp png_ptr, png_bytep data, png_size_t length)
{
   png_debug1(4, "reading %d bytes", (int)length);

   if (png_ptr->read_data_fn != NULL)
      (*(png_ptr->read_data_fn))(png_ptr, data, length);

   else
      png_error(png_ptr, "Call to NULL read function");
}

#ifdef PNG_STDIO_SUPPORTED
/* This is the function that does the actual reading of data.  If you are
 * not reading from a standard C stream, you should create a replacement
 * read_data function and use it at run time with png_set_read_fn(), rather
 * than changing the library.
 */
void PNGCBAPI
png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
{
   png_size_t check;

   if (png_ptr == NULL)
      return;

   /* fread() returns 0 on error, so it is OK to store this in a png_size_t
    * instead of an int, which is what fread() actually returns.
    */
   check = fread(data, 1, length, png_voidcast(png_FILE_p, png_ptr->io_ptr));

   if (check != length)
      png_error(png_ptr, "Read Error");
}
#endif

/* This function allows the application to supply a new input function
 * for libpng if standard C streams aren't being used.
 *
 * This function takes as its arguments:
 *
 * png_ptr      - pointer to a png input data structure
 *
 * io_ptr       - pointer to user supplied structure containing info about
 *                the input functions.  May be NULL.
 *
 * read_data_fn - pointer to a new input function that takes as its
 *                arguments a pointer to a png_struct, a pointer to
 *                a location where input data can be stored, and a 32-bit
 *                unsigned int that is the number of bytes to be read.
 *                To exit and output any fatal error messages the new write
 *                function should call png_error(png_ptr, "Error msg").
 *                May be NULL, in which case libpng's default function will
 *                be used.
 */
void PNGAPI
png_set_read_fn(png_structrp png_ptr, png_voidp io_ptr,
   png_rw_ptr read_data_fn)
{
   if (png_ptr == NULL)
      return;

   png_ptr->io_ptr = io_ptr;

#ifdef PNG_STDIO_SUPPORTED
   if (read_data_fn != NULL)
      png_ptr->read_data_fn = read_data_fn;

   else
      png_ptr->read_data_fn = png_default_read_data;
#else
   png_ptr->read_data_fn = read_data_fn;
#endif

   /* It is an error to write to a read device */
   if (png_ptr->write_data_fn != NULL)
   {
      png_ptr->write_data_fn = NULL;
      png_warning(png_ptr,
          "Can't set both read_data_fn and write_data_fn in the"
          " same structure");
   }

#ifdef PNG_WRITE_FLUSH_SUPPORTED
   png_ptr->output_flush_fn = NULL;
#endif
}
#endif /* PNG_READ_SUPPORTED */
Commit	Line	Data
	1
	2	/* pngrio.c - functions for data input
	3	*
	4	* Last changed in libpng 1.6.0 [February 14, 2013]
	5	* Copyright (c) 1998-2013 Glenn Randers-Pehrson
	6	* (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
	7	* (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
	8	*
	9	* This code is released under the libpng license.
	10	* For conditions of distribution and use, see the disclaimer
	11	* and license in png.h
	12	*
	13	* This file provides a location for all input. Users who need
	14	* special handling are expected to write a function that has the same
	15	* arguments as this and performs a similar function, but that possibly
	16	* has a different input method. Note that you shouldn't change this
	17	* function, but rather write a replacement function and then make
	18	* libpng use it at run time with png_set_read_fn(...).
	19	*/
	20
	21	#include "pngpriv.h"
	22
	23	#ifdef PNG_READ_SUPPORTED
	24
	25	/* Read the data from whatever input you are using. The default routine
	26	* reads from a file pointer. Note that this routine sometimes gets called
	27	* with very small lengths, so you should implement some kind of simple
	28	* buffering if you are using unbuffered reads. This should never be asked
	29	* to read more then 64K on a 16 bit machine.
	30	*/
	31	void /* PRIVATE */
	32	png_read_data(png_structrp png_ptr, png_bytep data, png_size_t length)
	33	{
	34	png_debug1(4, "reading %d bytes", (int)length);
	35
	36	if (png_ptr->read_data_fn != NULL)
	37	(*(png_ptr->read_data_fn))(png_ptr, data, length);
	38
	39	else
	40	png_error(png_ptr, "Call to NULL read function");
	41	}
	42
	43	#ifdef PNG_STDIO_SUPPORTED
	44	/* This is the function that does the actual reading of data. If you are
	45	* not reading from a standard C stream, you should create a replacement
	46	* read_data function and use it at run time with png_set_read_fn(), rather
	47	* than changing the library.
	48	*/
	49	void PNGCBAPI
	50	png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
	51	{
	52	png_size_t check;
	53
	54	if (png_ptr == NULL)
	55	return;
	56
	57	/* fread() returns 0 on error, so it is OK to store this in a png_size_t
	58	* instead of an int, which is what fread() actually returns.
	59	*/
	60	check = fread(data, 1, length, png_voidcast(png_FILE_p, png_ptr->io_ptr));
	61
	62	if (check != length)
	63	png_error(png_ptr, "Read Error");
	64	}
	65	#endif
	66
	67	/* This function allows the application to supply a new input function
	68	* for libpng if standard C streams aren't being used.
	69	*
	70	* This function takes as its arguments:
	71	*
	72	* png_ptr - pointer to a png input data structure
	73	*
	74	* io_ptr - pointer to user supplied structure containing info about
	75	* the input functions. May be NULL.
	76	*
	77	* read_data_fn - pointer to a new input function that takes as its
	78	* arguments a pointer to a png_struct, a pointer to
	79	* a location where input data can be stored, and a 32-bit
	80	* unsigned int that is the number of bytes to be read.
	81	* To exit and output any fatal error messages the new write
	82	* function should call png_error(png_ptr, "Error msg").
	83	* May be NULL, in which case libpng's default function will
	84	* be used.
	85	*/
	86	void PNGAPI
	87	png_set_read_fn(png_structrp png_ptr, png_voidp io_ptr,
	88	png_rw_ptr read_data_fn)
	89	{
	90	if (png_ptr == NULL)
	91	return;
	92
	93	png_ptr->io_ptr = io_ptr;
	94
	95	#ifdef PNG_STDIO_SUPPORTED
	96	if (read_data_fn != NULL)
	97	png_ptr->read_data_fn = read_data_fn;
	98
	99	else
	100	png_ptr->read_data_fn = png_default_read_data;
	101	#else
	102	png_ptr->read_data_fn = read_data_fn;
	103	#endif
	104
	105	/* It is an error to write to a read device */
	106	if (png_ptr->write_data_fn != NULL)
	107	{
	108	png_ptr->write_data_fn = NULL;
	109	png_warning(png_ptr,
	110	"Can't set both read_data_fn and write_data_fn in the"
	111	" same structure");
	112	}
	113
	114	#ifdef PNG_WRITE_FLUSH_SUPPORTED
	115	png_ptr->output_flush_fn = NULL;
	116	#endif
	117	}
	118	#endif /* PNG_READ_SUPPORTED */