src/png/pngrio.c


/* pngrio.c - functions for data input
 *
 * Last changed in libpng 1.2.37 [June 4, 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 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(...).
 */

#define PNG_INTERNAL
#include "png.h"
#if defined(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_structp 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");
}

#if !defined(PNG_NO_STDIO)
/* 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.
 */
#ifndef USE_FAR_KEYWORD
void PNGAPI
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.
    */
#if defined(_WIN32_WCE)
   if ( !ReadFile((HANDLE)(png_ptr->io_ptr), data, length, &check, NULL) )
      check = 0;
#else
   check = (png_size_t)fread(data, (png_size_t)1, length,
      (png_FILE_p)png_ptr->io_ptr);
#endif

   if (check != length)
      png_error(png_ptr, "Read 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)

static void PNGAPI
png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
{
   int check;
   png_byte *n_data;
   png_FILE_p io_ptr;

   if (png_ptr == NULL)
      return;
   /* Check if data really is near. If so, use usual code. */
   n_data = (png_byte *)CVT_PTR_NOCHECK(data);
   io_ptr = (png_FILE_p)CVT_PTR(png_ptr->io_ptr);
   if ((png_bytep)n_data == data)
   {
#if defined(_WIN32_WCE)
      if ( !ReadFile((HANDLE)(png_ptr->io_ptr), data, length, &check, NULL) )
         check = 0;
#else
      check = fread(n_data, 1, length, io_ptr);
#endif
   }
   else
   {
      png_byte buf[NEAR_BUF_SIZE];
      png_size_t read, remaining, err;
      check = 0;
      remaining = length;
      do
      {
         read = MIN(NEAR_BUF_SIZE, remaining);
#if defined(_WIN32_WCE)
         if ( !ReadFile((HANDLE)(io_ptr), buf, read, &err, NULL) )
            err = 0;
#else
         err = fread(buf, (png_size_t)1, read, io_ptr);
#endif
         png_memcpy(data, buf, read); /* copy far buffer to near buffer */
         if (err != read)
            break;
         else
            check += err;
         data += read;
         remaining -= read;
      }
      while (remaining != 0);
   }
   if ((png_uint_32)check != (png_uint_32)length)
      png_error(png_ptr, "read Error");
}
#endif
#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_structp png_ptr, png_voidp io_ptr,
   png_rw_ptr read_data_fn)
{
   if (png_ptr == NULL)
      return;
   png_ptr->io_ptr = io_ptr;

#if !defined(PNG_NO_STDIO)
   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,
         "It's an error to set both read_data_fn and write_data_fn in the ");
      png_warning(png_ptr,
         "same structure.  Resetting write_data_fn to NULL.");
   }

#if defined(PNG_WRITE_FLUSH_SUPPORTED)
   png_ptr->output_flush_fn = NULL;
#endif
}
#endif /* PNG_READ_SUPPORTED */
1
2	/* pngrio.c - functions for data input
3	*
4	* Last changed in libpng 1.2.37 [June 4, 2009]
5	* Copyright (c) 1998-2009 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	#define PNG_INTERNAL
22	#include "png.h"
23	#if defined(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_structp png_ptr, png_bytep data, png_size_t length)
33	{
34	png_debug1(4, "reading %d bytes", (int)length);
35	if (png_ptr->read_data_fn != NULL)
36	(*(png_ptr->read_data_fn))(png_ptr, data, length);
37	else
38	png_error(png_ptr, "Call to NULL read function");
39	}
40
41	#if !defined(PNG_NO_STDIO)
42	/* This is the function that does the actual reading of data. If you are
43	* not reading from a standard C stream, you should create a replacement
44	* read_data function and use it at run time with png_set_read_fn(), rather
45	* than changing the library.
46	*/
47	#ifndef USE_FAR_KEYWORD
48	void PNGAPI
49	png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
50	{
51	png_size_t check;
52
53	if (png_ptr == NULL)
54	return;
55	/* fread() returns 0 on error, so it is OK to store this in a png_size_t
56	* instead of an int, which is what fread() actually returns.
57	*/
58	#if defined(_WIN32_WCE)
59	if ( !ReadFile((HANDLE)(png_ptr->io_ptr), data, length, &check, NULL) )
60	check = 0;
61	#else
62	check = (png_size_t)fread(data, (png_size_t)1, length,
63	(png_FILE_p)png_ptr->io_ptr);
64	#endif
65
66	if (check != length)
67	png_error(png_ptr, "Read Error");
68	}
69	#else
70	/* This is the model-independent version. Since the standard I/O library
71	can't handle far buffers in the medium and small models, we have to copy
72	the data.
73	*/
74
75	#define NEAR_BUF_SIZE 1024
76	#define MIN(a,b) (a <= b ? a : b)
77
78	static void PNGAPI
79	png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
80	{
81	int check;
82	png_byte *n_data;
83	png_FILE_p io_ptr;
84
85	if (png_ptr == NULL)
86	return;
87	/* Check if data really is near. If so, use usual code. */
88	n_data = (png_byte *)CVT_PTR_NOCHECK(data);
89	io_ptr = (png_FILE_p)CVT_PTR(png_ptr->io_ptr);
90	if ((png_bytep)n_data == data)
91	{
92	#if defined(_WIN32_WCE)
93	if ( !ReadFile((HANDLE)(png_ptr->io_ptr), data, length, &check, NULL) )
94	check = 0;
95	#else
96	check = fread(n_data, 1, length, io_ptr);
97	#endif
98	}
99	else
100	{
101	png_byte buf[NEAR_BUF_SIZE];
102	png_size_t read, remaining, err;
103	check = 0;
104	remaining = length;
105	do
106	{
107	read = MIN(NEAR_BUF_SIZE, remaining);
108	#if defined(_WIN32_WCE)
109	if ( !ReadFile((HANDLE)(io_ptr), buf, read, &err, NULL) )
110	err = 0;
111	#else
112	err = fread(buf, (png_size_t)1, read, io_ptr);
113	#endif
114	png_memcpy(data, buf, read); /* copy far buffer to near buffer */
115	if (err != read)
116	break;
117	else
118	check += err;
119	data += read;
120	remaining -= read;
121	}
122	while (remaining != 0);
123	}
124	if ((png_uint_32)check != (png_uint_32)length)
125	png_error(png_ptr, "read Error");
126	}
127	#endif
128	#endif
129
130	/* This function allows the application to supply a new input function
131	* for libpng if standard C streams aren't being used.
132	*
133	* This function takes as its arguments:
134	* png_ptr - pointer to a png input data structure
135	* io_ptr - pointer to user supplied structure containing info about
136	* the input functions. May be NULL.
137	* read_data_fn - pointer to a new input function that takes as its
138	* arguments a pointer to a png_struct, a pointer to
139	* a location where input data can be stored, and a 32-bit
140	* unsigned int that is the number of bytes to be read.
141	* To exit and output any fatal error messages the new write
142	* function should call png_error(png_ptr, "Error msg").
143	* May be NULL, in which case libpng's default function will
144	* be used.
145	*/
146	void PNGAPI
147	png_set_read_fn(png_structp png_ptr, png_voidp io_ptr,
148	png_rw_ptr read_data_fn)
149	{
150	if (png_ptr == NULL)
151	return;
152	png_ptr->io_ptr = io_ptr;
153
154	#if !defined(PNG_NO_STDIO)
155	if (read_data_fn != NULL)
156	png_ptr->read_data_fn = read_data_fn;
157	else
158	png_ptr->read_data_fn = png_default_read_data;
159	#else
160	png_ptr->read_data_fn = read_data_fn;
161	#endif
162
163	/* It is an error to write to a read device */
164	if (png_ptr->write_data_fn != NULL)
165	{
166	png_ptr->write_data_fn = NULL;
167	png_warning(png_ptr,
168	"It's an error to set both read_data_fn and write_data_fn in the ");
169	png_warning(png_ptr,
170	"same structure. Resetting write_data_fn to NULL.");
171	}
172
173	#if defined(PNG_WRITE_FLUSH_SUPPORTED)
174	png_ptr->output_flush_fn = NULL;
175	#endif
176	}
177	#endif /* PNG_READ_SUPPORTED */