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1 /* pngrio.c - functions for data input | |
2 * | |
3 * Last changed in libpng 1.6.0 [February 14, 2013] | |
4 * Copyright (c) 1998-2013 Glenn Randers-Pehrson | |
5 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger) | |
6 * (Version 0.88 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 then 64K on a 16 bit machine. | |
29 */ | |
30 void /* PRIVATE */ | |
31 png_read_data(png_structrp png_ptr, png_bytep data, png_size_t length) | |
32 { | |
33 png_debug1(4, "reading %d bytes", (int)length); | |
34 | |
35 if (png_ptr->read_data_fn != NULL) | |
36 (*(png_ptr->read_data_fn))(png_ptr, data, length); | |
37 | |
38 else | |
39 png_error(png_ptr, "Call to NULL read function"); | |
40 } | |
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, png_size_t length) | |
50 { | |
51 png_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 png_size_t | |
57 * instead of an int, which is what fread() actually returns. | |
58 */ | |
59 check = fread(data, 1, length, png_voidcast(png_FILE_p, 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 { | |
89 if (png_ptr == NULL) | |
90 return; | |
91 | |
92 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 png_ptr->read_data_fn = read_data_fn; | |
102 #endif | |
103 | |
104 /* It is an error to write to a read device */ | |
105 if (png_ptr->write_data_fn != NULL) | |
106 { | |
107 png_ptr->write_data_fn = NULL; | |
108 png_warning(png_ptr, | |
109 "Can't set both read_data_fn and write_data_fn in the" | |
110 " same structure"); | |
111 } | |
112 | |
113 #ifdef PNG_WRITE_FLUSH_SUPPORTED | |
114 png_ptr->output_flush_fn = NULL; | |
115 #endif | |
116 } | |
117 #endif /* PNG_READ_SUPPORTED */ | |
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