1 /*
2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation. Oracle designates this
7 * particular file as subject to the "Classpath" exception as provided
8 * by Oracle in the LICENSE file that accompanied this code.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 */
24
25 /* pngrio.c - functions for data input
26 *
27 * This file is available under and governed by the GNU General Public
28 * License version 2 only, as published by the Free Software Foundation.
29 * However, the following notice accompanied the original version of this
30 * file and, per its terms, should not be removed:
31 *
32 * Last changed in libpng 1.6.17 [March 26, 2015]
33 * Copyright (c) 1998-2015 Glenn Randers-Pehrson
34 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
35 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
36 *
37 * This code is released under the libpng license.
38 * For conditions of distribution and use, see the disclaimer
39 * and license in png.h
40 *
41 * This file provides a location for all input. Users who need
42 * special handling are expected to write a function that has the same
43 * arguments as this and performs a similar function, but that possibly
44 * has a different input method. Note that you shouldn't change this
45 * function, but rather write a replacement function and then make
46 * libpng use it at run time with png_set_read_fn(...).
47 */
48
49 #include "pngpriv.h"
50
51 #ifdef PNG_READ_SUPPORTED
52
53 /* Read the data from whatever input you are using. The default routine
54 * reads from a file pointer. Note that this routine sometimes gets called
55 * with very small lengths, so you should implement some kind of simple
56 * buffering if you are using unbuffered reads. This should never be asked
57 * to read more than 64K on a 16-bit machine.
58 */
59 void /* PRIVATE */
60 png_read_data(png_structrp png_ptr, png_bytep data, png_size_t length)
61 {
62 png_debug1(4, "reading %d bytes", (int)length);
63
64 if (png_ptr->read_data_fn != NULL)
65 (*(png_ptr->read_data_fn))(png_ptr, data, length);
66
67 else
68 png_error(png_ptr, "Call to NULL read function");
69 }
70
71 #ifdef PNG_STDIO_SUPPORTED
72 /* This is the function that does the actual reading of data. If you are
73 * not reading from a standard C stream, you should create a replacement
74 * read_data function and use it at run time with png_set_read_fn(), rather
75 * than changing the library.
76 */
77 void PNGCBAPI
78 png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
79 {
80 png_size_t check;
81
82 if (png_ptr == NULL)
83 return;
84
85 /* fread() returns 0 on error, so it is OK to store this in a png_size_t
86 * instead of an int, which is what fread() actually returns.
87 */
88 check = fread(data, 1, length, png_voidcast(png_FILE_p, png_ptr->io_ptr));
89
90 if (check != length)
91 png_error(png_ptr, "Read Error");
92 }
93 #endif
94
95 /* This function allows the application to supply a new input function
96 * for libpng if standard C streams aren't being used.
97 *
98 * This function takes as its arguments:
99 *
100 * png_ptr - pointer to a png input data structure
101 *
102 * io_ptr - pointer to user supplied structure containing info about
103 * the input functions. May be NULL.
104 *
105 * read_data_fn - pointer to a new input function that takes as its
106 * arguments a pointer to a png_struct, a pointer to
107 * a location where input data can be stored, and a 32-bit
108 * unsigned int that is the number of bytes to be read.
109 * To exit and output any fatal error messages the new write
110 * function should call png_error(png_ptr, "Error msg").
111 * May be NULL, in which case libpng's default function will
112 * be used.
113 */
114 void PNGAPI
115 png_set_read_fn(png_structrp png_ptr, png_voidp io_ptr,
116 png_rw_ptr read_data_fn)
117 {
118 if (png_ptr == NULL)
119 return;
120
121 png_ptr->io_ptr = io_ptr;
122
123 #ifdef PNG_STDIO_SUPPORTED
124 if (read_data_fn != NULL)
125 png_ptr->read_data_fn = read_data_fn;
126
127 else
128 png_ptr->read_data_fn = png_default_read_data;
129 #else
130 png_ptr->read_data_fn = read_data_fn;
131 #endif
132
133 #ifdef PNG_WRITE_SUPPORTED
134 /* It is an error to write to a read device */
135 if (png_ptr->write_data_fn != NULL)
136 {
137 png_ptr->write_data_fn = NULL;
138 png_warning(png_ptr,
139 "Can't set both read_data_fn and write_data_fn in the"
140 " same structure");
141 }
142 #endif
143
144 #ifdef PNG_WRITE_FLUSH_SUPPORTED
145 png_ptr->output_flush_fn = NULL;
146 #endif
147 }
148 #endif /* READ */