1
2 /* pngrio.c - functions for data input
3 *
4 * Last changed in libpng 1.2.43 [February 25, 2010]
5 * Copyright (c) 1998-2010 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 input. Users who need
14 * special handling are expected to write a function that has the same
15 * arguments as this and performs a similar function, but that possibly
16 * has a different input method. Note that you shouldn't change this
17 * function, but rather write a replacement function and then make
18 * libpng use it at run time with png_set_read_fn(...).
19 */
20
21 #define PNG_INTERNAL
22 #define PNG_NO_PEDANTIC_WARNINGS
23 #include "png.h"
24 #ifdef PNG_READ_SUPPORTED
25
26 /* Read the data from whatever input you are using. The default routine
27 * reads from a file pointer. Note that this routine sometimes gets called
28 * with very small lengths, so you should implement some kind of simple
29 * buffering if you are using unbuffered reads. This should never be asked
30 * to read more then 64K on a 16 bit machine.
31 */
32 void /* PRIVATE */
png_read_data(png_structp png_ptr,png_bytep data,png_size_t length)33 png_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
34 {
35 png_debug1(4, "reading %d bytes", (int)length);
36
37 if (png_ptr->read_data_fn != NULL)
38 (*(png_ptr->read_data_fn))(png_ptr, data, length);
39 else
40 png_error(png_ptr, "Call to NULL read function");
41
42 #ifdef PNG_INDEX_SUPPORTED
43 png_ptr->total_data_read += length;
44 #endif
45 }
46
47 #ifdef PNG_INDEX_SUPPORTED
48 void /* PRIVATE */
png_seek_data(png_structp png_ptr,png_uint_32 offset)49 png_seek_data(png_structp png_ptr, png_uint_32 offset)
50 {
51 if (png_ptr->seek_data_fn != NULL)
52 (*(png_ptr->seek_data_fn))(png_ptr, offset);
53 else
54 png_error(png_ptr, "Call to NULL seek function");
55 }
56 #endif
57
58 #ifdef PNG_STDIO_SUPPORTED
59 /* This is the function that does the actual reading of data. If you are
60 * not reading from a standard C stream, you should create a replacement
61 * read_data function and use it at run time with png_set_read_fn(), rather
62 * than changing the library.
63 */
64 #ifndef USE_FAR_KEYWORD
65 void PNGAPI
png_default_read_data(png_structp png_ptr,png_bytep data,png_size_t length)66 png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
67 {
68 png_size_t check;
69
70 if (png_ptr == NULL)
71 return;
72 /* fread() returns 0 on error, so it is OK to store this in a png_size_t
73 * instead of an int, which is what fread() actually returns.
74 */
75 #ifdef _WIN32_WCE
76 if ( !ReadFile((HANDLE)(png_ptr->io_ptr), data, length, &check, NULL) )
77 check = 0;
78 #else
79 check = (png_size_t)fread(data, (png_size_t)1, length,
80 (png_FILE_p)png_ptr->io_ptr);
81 #endif
82
83 if (check != length)
84 png_error(png_ptr, "Read Error");
85 }
86 #else
87 /* This is the model-independent version. Since the standard I/O library
88 can't handle far buffers in the medium and small models, we have to copy
89 the data.
90 */
91
92 #define NEAR_BUF_SIZE 1024
93 #define MIN(a,b) (a <= b ? a : b)
94
95 static void PNGAPI
png_default_read_data(png_structp png_ptr,png_bytep data,png_size_t length)96 png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
97 {
98 int check;
99 png_byte *n_data;
100 png_FILE_p io_ptr;
101
102 if (png_ptr == NULL)
103 return;
104 /* Check if data really is near. If so, use usual code. */
105 n_data = (png_byte *)CVT_PTR_NOCHECK(data);
106 io_ptr = (png_FILE_p)CVT_PTR(png_ptr->io_ptr);
107 if ((png_bytep)n_data == data)
108 {
109 #ifdef _WIN32_WCE
110 if ( !ReadFile((HANDLE)(png_ptr->io_ptr), data, length, &check,
111 NULL) )
112 check = 0;
113 #else
114 check = fread(n_data, 1, length, io_ptr);
115 #endif
116 }
117 else
118 {
119 png_byte buf[NEAR_BUF_SIZE];
120 png_size_t read, remaining, err;
121 check = 0;
122 remaining = length;
123 do
124 {
125 read = MIN(NEAR_BUF_SIZE, remaining);
126 #ifdef _WIN32_WCE
127 if ( !ReadFile((HANDLE)(io_ptr), buf, read, &err, NULL) )
128 err = 0;
129 #else
130 err = fread(buf, (png_size_t)1, read, io_ptr);
131 #endif
132 png_memcpy(data, buf, read); /* copy far buffer to near buffer */
133 if (err != read)
134 break;
135 else
136 check += err;
137 data += read;
138 remaining -= read;
139 }
140 while (remaining != 0);
141 }
142 if ((png_uint_32)check != (png_uint_32)length)
143 png_error(png_ptr, "read Error");
144 }
145 #endif
146 #endif
147
148 /* This function allows the application to supply a new input function
149 * for libpng if standard C streams aren't being used.
150 *
151 * This function takes as its arguments:
152 * png_ptr - pointer to a png input data structure
153 * io_ptr - pointer to user supplied structure containing info about
154 * the input functions. May be NULL.
155 * read_data_fn - pointer to a new input function that takes as its
156 * arguments a pointer to a png_struct, a pointer to
157 * a location where input data can be stored, and a 32-bit
158 * unsigned int that is the number of bytes to be read.
159 * To exit and output any fatal error messages the new write
160 * function should call png_error(png_ptr, "Error msg").
161 * May be NULL, in which case libpng's default function will
162 * be used.
163 */
164 void PNGAPI
png_set_read_fn(png_structp png_ptr,png_voidp io_ptr,png_rw_ptr read_data_fn)165 png_set_read_fn(png_structp png_ptr, png_voidp io_ptr,
166 png_rw_ptr read_data_fn)
167 {
168 if (png_ptr == NULL)
169 return;
170 png_ptr->io_ptr = io_ptr;
171
172 #ifdef PNG_STDIO_SUPPORTED
173 if (read_data_fn != NULL)
174 png_ptr->read_data_fn = read_data_fn;
175 else
176 png_ptr->read_data_fn = png_default_read_data;
177 #else
178 png_ptr->read_data_fn = read_data_fn;
179 #endif
180
181 /* It is an error to write to a read device */
182 if (png_ptr->write_data_fn != NULL)
183 {
184 png_ptr->write_data_fn = NULL;
185 png_warning(png_ptr,
186 "It's an error to set both read_data_fn and write_data_fn in the ");
187 png_warning(png_ptr,
188 "same structure. Resetting write_data_fn to NULL.");
189 }
190
191 #ifdef PNG_WRITE_FLUSH_SUPPORTED
192 png_ptr->output_flush_fn = NULL;
193 #endif
194 }
195
196 #ifdef PNG_INDEX_SUPPORTED
197 void PNGAPI
png_set_seek_fn(png_structp png_ptr,png_seek_ptr seek_data_fn)198 png_set_seek_fn(png_structp png_ptr, png_seek_ptr seek_data_fn)
199 {
200 if (png_ptr == NULL)
201 return;
202 png_ptr->seek_data_fn = seek_data_fn;
203 }
204 #endif
205 #endif /* PNG_READ_SUPPORTED */
206