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1
2 /* png.c - location for general purpose libpng functions
3 *
4 * libpng 1.0.1
5 * For conditions of distribution and use, see copyright notice in png.h
6 * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
7 * Copyright (c) 1996, 1997 Andreas Dilger
8 * Copyright (c) 1998, Glenn Randers-Pehrson
9 * March 15, 1998
10 */
11
12 #define PNG_INTERNAL
13 #define PNG_NO_EXTERN
14 #include "../png/png.h"
15
16 /* Version information for C files. This had better match the version
17 * string defined in png.h.
18 */
19 char png_libpng_ver[12] = "1.0.1";
20
21 /* Place to hold the signature string for a PNG file. */
22 png_byte FARDATA png_sig[8] = {137, 80, 78, 71, 13, 10, 26, 10};
23
24 /* Constant strings for known chunk types. If you need to add a chunk,
25 * add a string holding the name here. If you want to make the code
26 * portable to EBCDIC machines, use ASCII numbers, not characters.
27 */
28 png_byte FARDATA png_IHDR[5] = { 73, 72, 68, 82, '\0'};
29 png_byte FARDATA png_IDAT[5] = { 73, 68, 65, 84, '\0'};
30 png_byte FARDATA png_IEND[5] = { 73, 69, 78, 68, '\0'};
31 png_byte FARDATA png_PLTE[5] = { 80, 76, 84, 69, '\0'};
32 png_byte FARDATA png_bKGD[5] = { 98, 75, 71, 68, '\0'};
33 png_byte FARDATA png_cHRM[5] = { 99, 72, 82, 77, '\0'};
34 png_byte FARDATA png_gAMA[5] = {103, 65, 77, 65, '\0'};
35 png_byte FARDATA png_hIST[5] = {104, 73, 83, 84, '\0'};
36 png_byte FARDATA png_oFFs[5] = {111, 70, 70, 115, '\0'};
37 png_byte FARDATA png_pCAL[5] = {112, 67, 65, 76, '\0'};
38 png_byte FARDATA png_pHYs[5] = {112, 72, 89, 115, '\0'};
39 png_byte FARDATA png_sBIT[5] = {115, 66, 73, 84, '\0'};
40 png_byte FARDATA png_sRGB[5] = {115, 82, 71, 66, '\0'};
41 png_byte FARDATA png_tEXt[5] = {116, 69, 88, 116, '\0'};
42 png_byte FARDATA png_tIME[5] = {116, 73, 77, 69, '\0'};
43 png_byte FARDATA png_tRNS[5] = {116, 82, 78, 83, '\0'};
44 png_byte FARDATA png_zTXt[5] = {122, 84, 88, 116, '\0'};
45
46 /* arrays to facilitate easy interlacing - use pass (0 - 6) as index */
47
48 /* start of interlace block */
49 int FARDATA png_pass_start[] = {0, 4, 0, 2, 0, 1, 0};
50
51 /* offset to next interlace block */
52 int FARDATA png_pass_inc[] = {8, 8, 4, 4, 2, 2, 1};
53
54 /* start of interlace block in the y direction */
55 int FARDATA png_pass_ystart[] = {0, 0, 4, 0, 2, 0, 1};
56
57 /* offset to next interlace block in the y direction */
58 int FARDATA png_pass_yinc[] = {8, 8, 8, 4, 4, 2, 2};
59
60 /* Width of interlace block. This is not currently used - if you need
61 * it, uncomment it here and in png.h
62 int FARDATA png_pass_width[] = {8, 4, 4, 2, 2, 1, 1};
63 */
64
65 /* Height of interlace block. This is not currently used - if you need
66 * it, uncomment it here and in png.h
67 int FARDATA png_pass_height[] = {8, 8, 4, 4, 2, 2, 1};
68 */
69
70 /* Mask to determine which pixels are valid in a pass */
71 int FARDATA png_pass_mask[] = {0x80, 0x08, 0x88, 0x22, 0xaa, 0x55, 0xff};
72
73 /* Mask to determine which pixels to overwrite while displaying */
74 int FARDATA png_pass_dsp_mask[] = {0xff, 0x0f, 0xff, 0x33, 0xff, 0x55, 0xff};
75
76
77 /* Tells libpng that we have already handled the first "num_bytes" bytes
78 * of the PNG file signature. If the PNG data is embedded into another
79 * stream we can set num_bytes = 8 so that libpng will not attempt to read
80 * or write any of the magic bytes before it starts on the IHDR.
81 */
82 void
83 png_set_sig_bytes(png_structp png_ptr, int num_bytes)
84 {
85 png_debug(1, "in png_set_sig_bytes\n");
86 if (num_bytes > 8)
87 png_error(png_ptr, "Too many bytes for PNG signature.");
88
89 png_ptr->sig_bytes = num_bytes < 0 ? 0 : num_bytes;
90 }
91
92 /* Checks whether the supplied bytes match the PNG signature. We allow
93 * checking less than the full 8-byte signature so that those apps that
94 * already read the first few bytes of a file to determine the file type
95 * can simply check the remaining bytes for extra assurance. Returns
96 * an integer less than, equal to, or greater than zero if sig is found,
97 * respectively, to be less than, to match, or be greater than the correct
98 * PNG signature (this is the same behaviour as strcmp, memcmp, etc).
99 */
100 int
101 png_sig_cmp(png_bytep sig, png_size_t start, png_size_t num_to_check)
102 {
103 if (num_to_check > 8)
104 num_to_check = 8;
105 else if (num_to_check < 1)
106 return (0);
107
108 if (start > 7)
109 return (0);
110
111 if (start + num_to_check > 8)
112 num_to_check = 8 - start;
113
114 return ((int)(png_memcmp(&sig[start], &png_sig[start], num_to_check)));
115 }
116
117 /* (Obsolete) function to check signature bytes. It does not allow one
118 * to check a partial signature. This function will be removed in the
119 * future - use png_sig_cmp().
120 */
121 int
122 png_check_sig(png_bytep sig, int num)
123 {
124 return ((int)!png_sig_cmp(sig, (png_size_t)0, (png_size_t)num));
125 }
126
127 /* Function to allocate memory for zlib. */
128 voidpf
129 png_zalloc(voidpf png_ptr, uInt items, uInt size)
130 {
131 png_voidp ptr;
132 png_uint_32 num_bytes;
133
134 num_bytes = (png_uint_32)items * size;
135 ptr = (png_voidp)png_malloc((png_structp)png_ptr, num_bytes);
136 if (num_bytes > (png_uint_32)0x8000)
137 {
138 png_memset(ptr, 0, (png_size_t)0x8000L);
139 png_memset((png_bytep)ptr + (png_size_t)0x8000L, 0,
140 (png_size_t)(num_bytes - (png_uint_32)0x8000L));
141 }
142 else
143 {
144 png_memset(ptr, 0, (png_size_t)num_bytes);
145 }
146 return ((voidpf)ptr);
147 }
148
149 /* function to free memory for zlib */
150 void
151 png_zfree(voidpf png_ptr, voidpf ptr)
152 {
153 png_free((png_structp)png_ptr, (png_voidp)ptr);
154 }
155
156 /* Reset the CRC variable to 32 bits of 1's. Care must be taken
157 * in case CRC is > 32 bits to leave the top bits 0.
158 */
159 void
160 png_reset_crc(png_structp png_ptr)
161 {
162 png_ptr->crc = crc32(0, Z_NULL, 0);
163 }
164
165 /* Calculate the CRC over a section of data. We can only pass as
166 * much data to this routine as the largest single buffer size. We
167 * also check that this data will actually be used before going to the
168 * trouble of calculating it.
169 */
170 void
171 png_calculate_crc(png_structp png_ptr, png_bytep ptr, png_size_t length)
172 {
173 int need_crc = 1;
174
175 if (png_ptr->chunk_name[0] & 0x20) /* ancillary */
176 {
177 if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_MASK) ==
178 (PNG_FLAG_CRC_ANCILLARY_USE | PNG_FLAG_CRC_ANCILLARY_NOWARN))
179 need_crc = 0;
180 }
181 else /* critical */
182 {
183 if (png_ptr->flags & PNG_FLAG_CRC_CRITICAL_IGNORE)
184 need_crc = 0;
185 }
186
187 if (need_crc)
188 png_ptr->crc = crc32(png_ptr->crc, ptr, (uInt)length);
189 }
190
191 /* Allocate the memory for an info_struct for the application. We don't
192 * really need the png_ptr, but it could potentially be useful in the
193 * future. This should be used in favour of malloc(sizeof(png_info))
194 * and png_info_init() so that applications that want to use a shared
195 * libpng don't have to be recompiled if png_info changes size.
196 */
197 png_infop
198 png_create_info_struct(png_structp png_ptr)
199 {
200 png_infop info_ptr;
201
202 png_debug(1, "in png_create_info_struct\n");
203 if(png_ptr == NULL) return (NULL);
204 if ((info_ptr = (png_infop)png_create_struct(PNG_STRUCT_INFO)) != NULL)
205 {
206 png_info_init(info_ptr);
207 }
208
209 return (info_ptr);
210 }
211
212 /* This function frees the memory associated with a single info struct.
213 * Normally, one would use either png_destroy_read_struct() or
214 * png_destroy_write_struct() to free an info struct, but this may be
215 * useful for some applications.
216 */
217 void
218 png_destroy_info_struct(png_structp png_ptr, png_infopp info_ptr_ptr)
219 {
220 png_infop info_ptr = NULL;
221
222 png_debug(1, "in png_destroy_info_struct\n");
223 if (info_ptr_ptr != NULL)
224 info_ptr = *info_ptr_ptr;
225
226 if (info_ptr != NULL)
227 {
228 png_info_destroy(png_ptr, info_ptr);
229
230 png_destroy_struct((png_voidp)info_ptr);
231 *info_ptr_ptr = (png_infop)NULL;
232 }
233 }
234
235 /* Initialize the info structure. This is now an internal function (0.89)
236 * and applications using it are urged to use png_create_info_struct()
237 * instead.
238 */
239 void
240 png_info_init(png_infop info_ptr)
241 {
242 png_debug(1, "in png_info_init\n");
243 /* set everything to 0 */
244 png_memset(info_ptr, 0, sizeof (png_info));
245 }
246
247 /* This is an internal routine to free any memory that the info struct is
248 * pointing to before re-using it or freeing the struct itself. Recall
249 * that png_free() checks for NULL pointers for us.
250 */
251 void
252 png_info_destroy(png_structp png_ptr, png_infop info_ptr)
253 {
254 #if defined(PNG_READ_tEXt_SUPPORTED) || defined(PNG_READ_zTXt_SUPPORTED)
255 int i;
256
257 png_debug(1, "in png_info_destroy\n");
258 if (info_ptr->text != NULL)
259 {
260 for (i = 0; i < info_ptr->num_text; i++)
261 {
262 png_free(png_ptr, info_ptr->text[i].key);
263 }
264 png_free(png_ptr, info_ptr->text);
265 }
266 #endif
267 #if defined(PNG_READ_pCAL_SUPPORTED)
268 png_free(png_ptr, info_ptr->pcal_purpose);
269 png_free(png_ptr, info_ptr->pcal_units);
270 if (info_ptr->pcal_params != NULL)
271 {
272 for (i = 0; i < (int)info_ptr->pcal_nparams; i++)
273 {
274 png_free(png_ptr, info_ptr->pcal_params[i]);
275 }
276 png_free(png_ptr, info_ptr->pcal_params);
277 }
278 #endif
279
280 png_info_init(info_ptr);
281 }
282
283 /* This function returns a pointer to the io_ptr associated with the user
284 * functions. The application should free any memory associated with this
285 * pointer before png_write_destroy() or png_read_destroy() are called.
286 */
287 png_voidp
288 png_get_io_ptr(png_structp png_ptr)
289 {
290 return (png_ptr->io_ptr);
291 }
292
293 #if !defined(PNG_NO_STDIO)
294 /* Initialize the default input/output functions for the PNG file. If you
295 * use your own read or write routines, you can call either png_set_read_fn()
296 * or png_set_write_fn() instead of png_init_io().
297 */
298 void
299 png_init_io(png_structp png_ptr, FILE *fp)
300 {
301 png_debug(1, "in png_init_io\n");
302 png_ptr->io_ptr = (png_voidp)fp;
303 }
304 #endif