/src/libpng/pngrio.c

Source (jump to first uncovered line)
/* pngrio.c - functions for data input
 *
 * Copyright (c) 2018-2025 Cosmin Truta
 * Copyright (c) 1998-2002,2004,2006-2016,2018 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 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 than 64K on a 16-bit machine.
 */
void /* PRIVATE */
png_read_data(png_structrp png_ptr, png_bytep data, 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, size_t length)
{
   size_t check;

   if (png_ptr == NULL)
      return;

   /* fread() returns 0 on error, so it is OK to store this in a size_t
    * instead of an int, which is what fread() actually returns.
    */
   check = fread(data, 1, length, png_voidcast(FILE *, 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

#ifdef PNG_WRITE_SUPPORTED
   /* 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");
   }
#endif

#ifdef PNG_WRITE_FLUSH_SUPPORTED
   png_ptr->output_flush_fn = NULL;
#endif
}
#endif /* READ */

Line	Count	Source (jump to first uncovered line)
1		/* pngrio.c - functions for data input
2		*
3		* Copyright (c) 2018-2025 Cosmin Truta
4		* Copyright (c) 1998-2002,2004,2006-2016,2018 Glenn Randers-Pehrson
5		* Copyright (c) 1996-1997 Andreas Dilger
6		* Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
7		*
8		* This code is released under the libpng license.
9		* For conditions of distribution and use, see the disclaimer
10		* and license in png.h
11		*
12		* This file provides a location for all input. Users who need
13		* special handling are expected to write a function that has the same
14		* arguments as this and performs a similar function, but that possibly
15		* has a different input method. Note that you shouldn't change this
16		* function, but rather write a replacement function and then make
17		* libpng use it at run time with png_set_read_fn(...).
18		*/
19
20		#include "pngpriv.h"
21
22		#ifdef PNG_READ_SUPPORTED
23
24		/* Read the data from whatever input you are using. The default routine
25		* reads from a file pointer. Note that this routine sometimes gets called
26		* with very small lengths, so you should implement some kind of simple
27		* buffering if you are using unbuffered reads. This should never be asked
28		* to read more than 64K on a 16-bit machine.
29		*/
30		void /* PRIVATE */
31		png_read_data(png_structrp png_ptr, png_bytep data, size_t length)
32	148M	{
33	148M	png_debug1(4, "reading %d bytes", (int)length);
34
35	148M	if (png_ptr->read_data_fn != NULL)
36	148M	(*(png_ptr->read_data_fn))(png_ptr, data, length);
37
38	0	else
39	0	png_error(png_ptr, "Call to NULL read function");
40	148M	}
41
42		#ifdef PNG_STDIO_SUPPORTED
43		/* This is the function that does the actual reading of data. If you are
44		* not reading from a standard C stream, you should create a replacement
45		* read_data function and use it at run time with png_set_read_fn(), rather
46		* than changing the library.
47		*/
48		void PNGCBAPI
49		png_default_read_data(png_structp png_ptr, png_bytep data, size_t length)
50		{
51		size_t check;
52
53		if (png_ptr == NULL)
54		return;
55
56		/* fread() returns 0 on error, so it is OK to store this in a size_t
57		* instead of an int, which is what fread() actually returns.
58		*/
59		check = fread(data, 1, length, png_voidcast(FILE *, png_ptr->io_ptr));
60
61		if (check != length)
62		png_error(png_ptr, "Read Error");
63		}
64		#endif
65
66		/* This function allows the application to supply a new input function
67		* for libpng if standard C streams aren't being used.
68		*
69		* This function takes as its arguments:
70		*
71		* png_ptr - pointer to a png input data structure
72		*
73		* io_ptr - pointer to user supplied structure containing info about
74		* the input functions. May be NULL.
75		*
76		* read_data_fn - pointer to a new input function that takes as its
77		* arguments a pointer to a png_struct, a pointer to
78		* a location where input data can be stored, and a 32-bit
79		* unsigned int that is the number of bytes to be read.
80		* To exit and output any fatal error messages the new write
81		* function should call png_error(png_ptr, "Error msg").
82		* May be NULL, in which case libpng's default function will
83		* be used.
84		*/
85		void PNGAPI
86		png_set_read_fn(png_structrp png_ptr, png_voidp io_ptr,
87		png_rw_ptr read_data_fn)
88	90.5k	{
89	90.5k	if (png_ptr == NULL)
90	0	return;
91
92	90.5k	png_ptr->io_ptr = io_ptr;
93
94		#ifdef PNG_STDIO_SUPPORTED
95		if (read_data_fn != NULL)
96		png_ptr->read_data_fn = read_data_fn;
97
98		else
99		png_ptr->read_data_fn = png_default_read_data;
100		#else
101	90.5k	png_ptr->read_data_fn = read_data_fn;
102	90.5k	#endif
103
104		#ifdef PNG_WRITE_SUPPORTED
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		#endif
114
115		#ifdef PNG_WRITE_FLUSH_SUPPORTED
116		png_ptr->output_flush_fn = NULL;
117		#endif
118	90.5k	}
119		#endif /* READ */

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Created: 2025-06-13 06:34