1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
|
/* pngrio.c - functions for data input
*
* Last changed in libpng 1.4.1 [February 19, 2010]
* Copyright (c) 1998-2010 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_NO_PEDANTIC_WARNINGS
#include "png.h"
#ifdef PNG_READ_SUPPORTED
#include "pngpriv.h"
/* 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");
}
#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.
*/
#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.
*/
check = fread(data, 1, length, (png_FILE_p)png_ptr->io_ptr);
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)
{
png_size_t 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)
{
check = fread(n_data, 1, length, io_ptr);
}
else
{
png_byte buf[NEAR_BUF_SIZE];
png_size_t read, remaining, err;
check = 0;
remaining = length;
do
{
read = MIN(NEAR_BUF_SIZE, remaining);
err = fread(buf, 1, read, io_ptr);
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;
#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,
"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");
}
#ifdef PNG_WRITE_FLUSH_SUPPORTED
png_ptr->output_flush_fn = NULL;
#endif
}
#endif /* PNG_READ_SUPPORTED */
|
