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1 :
2 : /* pngwio.c - functions for data output
3 : *
4 : * Last changed in libpng 1.6.24 [August 4, 2016]
5 : * Copyright (c) 1998-2002,2004,2006-2014,2016 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 output. Users who need
14 : * special handling are expected to write functions that have the same
15 : * arguments as these and perform similar functions, but that possibly
16 : * use different output methods. Note that you shouldn't change these
17 : * functions, but rather write replacement functions and then change
18 : * them at run time with png_set_write_fn(...).
19 : */
20 :
21 : #include "pngpriv.h"
22 :
23 : #ifdef PNG_WRITE_SUPPORTED
24 :
25 : /* Write the data to whatever output you are using. The default routine
26 : * writes to 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 writes. This should never be asked
29 : * to write more than 64K on a 16-bit machine.
30 : */
31 :
32 : void /* PRIVATE */
33 0 : png_write_data(png_structrp png_ptr, png_const_bytep data, png_size_t length)
34 : {
35 : /* NOTE: write_data_fn must not change the buffer! */
36 0 : if (png_ptr->write_data_fn != NULL )
37 0 : (*(png_ptr->write_data_fn))(png_ptr, png_constcast(png_bytep,data),
38 : length);
39 :
40 : else
41 0 : png_error(png_ptr, "Call to NULL write function");
42 0 : }
43 :
44 : #ifdef PNG_STDIO_SUPPORTED
45 : /* This is the function that does the actual writing of data. If you are
46 : * not writing to a standard C stream, you should create a replacement
47 : * write_data function and use it at run time with png_set_write_fn(), rather
48 : * than changing the library.
49 : */
50 : void PNGCBAPI
51 0 : png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
52 : {
53 : png_size_t check;
54 :
55 0 : if (png_ptr == NULL)
56 0 : return;
57 :
58 0 : check = fwrite(data, 1, length, (png_FILE_p)(png_ptr->io_ptr));
59 :
60 0 : if (check != length)
61 0 : png_error(png_ptr, "Write Error");
62 : }
63 : #endif
64 :
65 : /* This function is called to output any data pending writing (normally
66 : * to disk). After png_flush is called, there should be no data pending
67 : * writing in any buffers.
68 : */
69 : #ifdef PNG_WRITE_FLUSH_SUPPORTED
70 : void /* PRIVATE */
71 0 : png_flush(png_structrp png_ptr)
72 : {
73 0 : if (png_ptr->output_flush_fn != NULL)
74 0 : (*(png_ptr->output_flush_fn))(png_ptr);
75 0 : }
76 :
77 : # ifdef PNG_STDIO_SUPPORTED
78 : void PNGCBAPI
79 0 : png_default_flush(png_structp png_ptr)
80 : {
81 : png_FILE_p io_ptr;
82 :
83 0 : if (png_ptr == NULL)
84 0 : return;
85 :
86 0 : io_ptr = png_voidcast(png_FILE_p, (png_ptr->io_ptr));
87 0 : fflush(io_ptr);
88 : }
89 : # endif
90 : #endif
91 :
92 : /* This function allows the application to supply new output functions for
93 : * libpng if standard C streams aren't being used.
94 : *
95 : * This function takes as its arguments:
96 : * png_ptr - pointer to a png output data structure
97 : * io_ptr - pointer to user supplied structure containing info about
98 : * the output functions. May be NULL.
99 : * write_data_fn - pointer to a new output function that takes as its
100 : * arguments a pointer to a png_struct, a pointer to
101 : * data to be written, and a 32-bit unsigned int that is
102 : * the number of bytes to be written. The new write
103 : * function should call png_error(png_ptr, "Error msg")
104 : * to exit and output any fatal error messages. May be
105 : * NULL, in which case libpng's default function will
106 : * be used.
107 : * flush_data_fn - pointer to a new flush function that takes as its
108 : * arguments a pointer to a png_struct. After a call to
109 : * the flush function, there should be no data in any buffers
110 : * or pending transmission. If the output method doesn't do
111 : * any buffering of output, a function prototype must still be
112 : * supplied although it doesn't have to do anything. If
113 : * PNG_WRITE_FLUSH_SUPPORTED is not defined at libpng compile
114 : * time, output_flush_fn will be ignored, although it must be
115 : * supplied for compatibility. May be NULL, in which case
116 : * libpng's default function will be used, if
117 : * PNG_WRITE_FLUSH_SUPPORTED is defined. This is not
118 : * a good idea if io_ptr does not point to a standard
119 : * *FILE structure.
120 : */
121 : void PNGAPI
122 0 : png_set_write_fn(png_structrp png_ptr, png_voidp io_ptr,
123 : png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn)
124 : {
125 0 : if (png_ptr == NULL)
126 0 : return;
127 :
128 0 : png_ptr->io_ptr = io_ptr;
129 :
130 : #ifdef PNG_STDIO_SUPPORTED
131 0 : if (write_data_fn != NULL)
132 0 : png_ptr->write_data_fn = write_data_fn;
133 :
134 : else
135 0 : png_ptr->write_data_fn = png_default_write_data;
136 : #else
137 : png_ptr->write_data_fn = write_data_fn;
138 : #endif
139 :
140 : #ifdef PNG_WRITE_FLUSH_SUPPORTED
141 : # ifdef PNG_STDIO_SUPPORTED
142 :
143 0 : if (output_flush_fn != NULL)
144 0 : png_ptr->output_flush_fn = output_flush_fn;
145 :
146 : else
147 0 : png_ptr->output_flush_fn = png_default_flush;
148 :
149 : # else
150 : png_ptr->output_flush_fn = output_flush_fn;
151 : # endif
152 : #else
153 : PNG_UNUSED(output_flush_fn)
154 : #endif /* WRITE_FLUSH */
155 :
156 : #ifdef PNG_READ_SUPPORTED
157 : /* It is an error to read while writing a png file */
158 0 : if (png_ptr->read_data_fn != NULL)
159 : {
160 0 : png_ptr->read_data_fn = NULL;
161 :
162 0 : png_warning(png_ptr,
163 : "Can't set both read_data_fn and write_data_fn in the"
164 : " same structure");
165 : }
166 : #endif
167 : }
168 : #endif /* WRITE */
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