1
2 /* pngwio.c - functions for data output
3 *
4 * Last changed in libpng 1.6.0 [February 14, 2013]
5 * Copyright (c) 1998-2013 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 #include "pngpriv.h"
21
22 #ifdef PNG_WRITE_SUPPORTED
23
24 /* Write the data to whatever output you are using. The default routine
25 * writes to 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 writes. This should never be asked
28 * to write more than 64K on a 16 bit machine.
29 */
30
31 void /* PRIVATE */
png_write_data(png_structrp png_ptr,png_const_bytep data,png_size_t length)32 png_write_data(png_structrp png_ptr, png_const_bytep data, png_size_t length)
33 {
34 /* NOTE: write_data_fn must not change the buffer! */
35 if (png_ptr->write_data_fn != NULL )
36 (*(png_ptr->write_data_fn))(png_ptr, png_constcast(png_bytep,data),
37 length);
38
39 else
40 png_error(png_ptr, "Call to NULL write function");
41 }
42
43 #ifdef PNG_STDIO_SUPPORTED
44 /* This is the function that does the actual writing of data. If you are
45 * not writing to a standard C stream, you should create a replacement
46 * write_data function and use it at run time with png_set_write_fn(), rather
47 * than changing the library.
48 */
49 void PNGCBAPI
png_default_write_data(png_structp png_ptr,png_bytep data,png_size_t length)50 png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
51 {
52 png_size_t check;
53
54 if (png_ptr == NULL)
55 return;
56
57 check = fwrite(data, 1, length, (png_FILE_p)(png_ptr->io_ptr));
58
59 if (check != length)
60 png_error(png_ptr, "Write Error");
61 }
62 #endif
63
64 /* This function is called to output any data pending writing (normally
65 * to disk). After png_flush is called, there should be no data pending
66 * writing in any buffers.
67 */
68 #ifdef PNG_WRITE_FLUSH_SUPPORTED
69 void /* PRIVATE */
png_flush(png_structrp png_ptr)70 png_flush(png_structrp png_ptr)
71 {
72 if (png_ptr->output_flush_fn != NULL)
73 (*(png_ptr->output_flush_fn))(png_ptr);
74 }
75
76 # ifdef PNG_STDIO_SUPPORTED
77 void PNGCBAPI
png_default_flush(png_structp png_ptr)78 png_default_flush(png_structp png_ptr)
79 {
80 png_FILE_p io_ptr;
81
82 if (png_ptr == NULL)
83 return;
84
85 io_ptr = png_voidcast(png_FILE_p, (png_ptr->io_ptr));
86 fflush(io_ptr);
87 }
88 # endif
89 #endif
90
91 /* This function allows the application to supply new output functions for
92 * libpng if standard C streams aren't being used.
93 *
94 * This function takes as its arguments:
95 * png_ptr - pointer to a png output data structure
96 * io_ptr - pointer to user supplied structure containing info about
97 * the output functions. May be NULL.
98 * write_data_fn - pointer to a new output function that takes as its
99 * arguments a pointer to a png_struct, a pointer to
100 * data to be written, and a 32-bit unsigned int that is
101 * the number of bytes to be written. The new write
102 * function should call png_error(png_ptr, "Error msg")
103 * to exit and output any fatal error messages. May be
104 * NULL, in which case libpng's default function will
105 * be used.
106 * flush_data_fn - pointer to a new flush function that takes as its
107 * arguments a pointer to a png_struct. After a call to
108 * the flush function, there should be no data in any buffers
109 * or pending transmission. If the output method doesn't do
110 * any buffering of output, a function prototype must still be
111 * supplied although it doesn't have to do anything. If
112 * PNG_WRITE_FLUSH_SUPPORTED is not defined at libpng compile
113 * time, output_flush_fn will be ignored, although it must be
114 * supplied for compatibility. May be NULL, in which case
115 * libpng's default function will be used, if
116 * PNG_WRITE_FLUSH_SUPPORTED is defined. This is not
117 * a good idea if io_ptr does not point to a standard
118 * *FILE structure.
119 */
120 void PNGAPI
png_set_write_fn(png_structrp png_ptr,png_voidp io_ptr,png_rw_ptr write_data_fn,png_flush_ptr output_flush_fn)121 png_set_write_fn(png_structrp png_ptr, png_voidp io_ptr,
122 png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn)
123 {
124 if (png_ptr == NULL)
125 return;
126
127 png_ptr->io_ptr = io_ptr;
128
129 #ifdef PNG_STDIO_SUPPORTED
130 if (write_data_fn != NULL)
131 png_ptr->write_data_fn = write_data_fn;
132
133 else
134 png_ptr->write_data_fn = png_default_write_data;
135 #else
136 png_ptr->write_data_fn = write_data_fn;
137 #endif
138
139 #ifdef PNG_WRITE_FLUSH_SUPPORTED
140 # ifdef PNG_STDIO_SUPPORTED
141
142 if (output_flush_fn != NULL)
143 png_ptr->output_flush_fn = output_flush_fn;
144
145 else
146 png_ptr->output_flush_fn = png_default_flush;
147
148 # else
149 png_ptr->output_flush_fn = output_flush_fn;
150 # endif
151 #endif /* PNG_WRITE_FLUSH_SUPPORTED */
152
153 /* It is an error to read while writing a png file */
154 if (png_ptr->read_data_fn != NULL)
155 {
156 png_ptr->read_data_fn = NULL;
157
158 png_warning(png_ptr,
159 "Can't set both read_data_fn and write_data_fn in the"
160 " same structure");
161 }
162 }
163 #endif /* PNG_WRITE_SUPPORTED */
164