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0272a10d VZ |
1 | |
2 | /* pngrio.c - functions for data input | |
3 | * | |
b61cc19c PC |
4 | * Last changed in libpng 1.4.1 [February 25, 2010] |
5 | * Copyright (c) 1998-2010 Glenn Randers-Pehrson | |
0272a10d VZ |
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 | * | |
b61cc19c PC |
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 | * | |
0272a10d VZ |
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 | ||
b61cc19c | 21 | #define PNG_NO_PEDANTIC_WARNINGS |
0272a10d | 22 | #include "png.h" |
b61cc19c PC |
23 | #ifdef PNG_READ_SUPPORTED |
24 | #include "pngpriv.h" | |
0272a10d VZ |
25 | |
26 | /* Read the data from whatever input you are using. The default routine | |
b61cc19c PC |
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 | */ | |
0272a10d VZ |
32 | void /* PRIVATE */ |
33 | png_read_data(png_structp png_ptr, png_bytep data, png_size_t length) | |
34 | { | |
970f6abe | 35 | png_debug1(4, "reading %d bytes", (int)length); |
b61cc19c | 36 | |
0272a10d VZ |
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 | ||
b61cc19c | 43 | #ifdef PNG_STDIO_SUPPORTED |
0272a10d | 44 | /* This is the function that does the actual reading of data. If you are |
b61cc19c PC |
45 | * not reading from a standard C stream, you should create a replacement |
46 | * read_data function and use it at run time with png_set_read_fn(), rather | |
47 | * than changing the library. | |
48 | */ | |
0272a10d VZ |
49 | #ifndef USE_FAR_KEYWORD |
50 | void PNGAPI | |
51 | png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length) | |
52 | { | |
53 | png_size_t check; | |
54 | ||
b61cc19c PC |
55 | if (png_ptr == NULL) |
56 | return; | |
0272a10d VZ |
57 | /* fread() returns 0 on error, so it is OK to store this in a png_size_t |
58 | * instead of an int, which is what fread() actually returns. | |
59 | */ | |
b61cc19c | 60 | check = fread(data, 1, length, (png_FILE_p)png_ptr->io_ptr); |
0272a10d VZ |
61 | |
62 | if (check != length) | |
63 | png_error(png_ptr, "Read Error"); | |
64 | } | |
65 | #else | |
b61cc19c | 66 | /* This is the model-independent version. Since the standard I/O library |
0272a10d VZ |
67 | can't handle far buffers in the medium and small models, we have to copy |
68 | the data. | |
69 | */ | |
70 | ||
71 | #define NEAR_BUF_SIZE 1024 | |
72 | #define MIN(a,b) (a <= b ? a : b) | |
73 | ||
74 | static void PNGAPI | |
75 | png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length) | |
76 | { | |
b61cc19c | 77 | png_size_t check; |
0272a10d VZ |
78 | png_byte *n_data; |
79 | png_FILE_p io_ptr; | |
80 | ||
b61cc19c PC |
81 | if (png_ptr == NULL) |
82 | return; | |
0272a10d VZ |
83 | /* Check if data really is near. If so, use usual code. */ |
84 | n_data = (png_byte *)CVT_PTR_NOCHECK(data); | |
85 | io_ptr = (png_FILE_p)CVT_PTR(png_ptr->io_ptr); | |
86 | if ((png_bytep)n_data == data) | |
87 | { | |
0272a10d | 88 | check = fread(n_data, 1, length, io_ptr); |
0272a10d VZ |
89 | } |
90 | else | |
91 | { | |
92 | png_byte buf[NEAR_BUF_SIZE]; | |
93 | png_size_t read, remaining, err; | |
94 | check = 0; | |
95 | remaining = length; | |
96 | do | |
97 | { | |
98 | read = MIN(NEAR_BUF_SIZE, remaining); | |
b61cc19c | 99 | err = fread(buf, 1, read, io_ptr); |
0272a10d | 100 | png_memcpy(data, buf, read); /* copy far buffer to near buffer */ |
970f6abe | 101 | if (err != read) |
0272a10d VZ |
102 | break; |
103 | else | |
104 | check += err; | |
105 | data += read; | |
106 | remaining -= read; | |
107 | } | |
108 | while (remaining != 0); | |
109 | } | |
110 | if ((png_uint_32)check != (png_uint_32)length) | |
111 | png_error(png_ptr, "read Error"); | |
112 | } | |
113 | #endif | |
114 | #endif | |
115 | ||
116 | /* This function allows the application to supply a new input function | |
b61cc19c PC |
117 | * for libpng if standard C streams aren't being used. |
118 | * | |
119 | * This function takes as its arguments: | |
120 | * png_ptr - pointer to a png input data structure | |
121 | * io_ptr - pointer to user supplied structure containing info about | |
122 | * the input functions. May be NULL. | |
123 | * read_data_fn - pointer to a new input function that takes as its | |
124 | * arguments a pointer to a png_struct, a pointer to | |
125 | * a location where input data can be stored, and a 32-bit | |
126 | * unsigned int that is the number of bytes to be read. | |
127 | * To exit and output any fatal error messages the new write | |
128 | * function should call png_error(png_ptr, "Error msg"). | |
129 | * May be NULL, in which case libpng's default function will | |
130 | * be used. | |
131 | */ | |
0272a10d VZ |
132 | void PNGAPI |
133 | png_set_read_fn(png_structp png_ptr, png_voidp io_ptr, | |
134 | png_rw_ptr read_data_fn) | |
135 | { | |
b61cc19c PC |
136 | if (png_ptr == NULL) |
137 | return; | |
0272a10d VZ |
138 | png_ptr->io_ptr = io_ptr; |
139 | ||
b61cc19c | 140 | #ifdef PNG_STDIO_SUPPORTED |
0272a10d VZ |
141 | if (read_data_fn != NULL) |
142 | png_ptr->read_data_fn = read_data_fn; | |
143 | else | |
144 | png_ptr->read_data_fn = png_default_read_data; | |
145 | #else | |
146 | png_ptr->read_data_fn = read_data_fn; | |
147 | #endif | |
148 | ||
149 | /* It is an error to write to a read device */ | |
150 | if (png_ptr->write_data_fn != NULL) | |
151 | { | |
152 | png_ptr->write_data_fn = NULL; | |
153 | png_warning(png_ptr, | |
154 | "It's an error to set both read_data_fn and write_data_fn in the "); | |
155 | png_warning(png_ptr, | |
b61cc19c | 156 | "same structure. Resetting write_data_fn to NULL"); |
0272a10d VZ |
157 | } |
158 | ||
b61cc19c | 159 | #ifdef PNG_WRITE_FLUSH_SUPPORTED |
0272a10d VZ |
160 | png_ptr->output_flush_fn = NULL; |
161 | #endif | |
162 | } | |
163 | #endif /* PNG_READ_SUPPORTED */ |