1
2/* pngmem.c - stub functions for memory allocation
3 *
4 * Last changed in libpng 1.6.15 [November 20, 2014]
5 * Copyright (c) 1998-2002,2004,2006-2014 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 memory allocation.  Users who
14 * need special memory handling are expected to supply replacement
15 * functions for png_malloc() and png_free(), and to use
16 * png_create_read_struct_2() and png_create_write_struct_2() to
17 * identify the replacement functions.
18 */
19
20#include "pngpriv.h"
21
22void*	FXMEM_DefaultAlloc(int byte_size, int);
23void	FXMEM_DefaultFree(void* pointer, int);
24
25#if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
26/* Free a png_struct */
27void /* PRIVATE */
28png_destroy_png_struct(png_structrp png_ptr)
29{
30   if (png_ptr != NULL)
31   {
32      /* png_free might call png_error and may certainly call
33       * png_get_mem_ptr, so fake a temporary png_struct to support this.
34       */
35      png_struct dummy_struct = *png_ptr;
36      memset(png_ptr, 0, (sizeof *png_ptr));
37      png_free(&dummy_struct, png_ptr);
38
39#     ifdef PNG_SETJMP_SUPPORTED
40         /* We may have a jmp_buf left to deallocate. */
41         png_free_jmpbuf(&dummy_struct);
42#     endif
43   }
44}
45
46/* Allocate memory.  For reasonable files, size should never exceed
47 * 64K.  However, zlib may allocate more than 64K if you don't tell
48 * it not to.  See zconf.h and png.h for more information.  zlib does
49 * need to allocate exactly 64K, so whatever you call here must
50 * have the ability to do that.
51 */
52PNG_FUNCTION(png_voidp,PNGAPI
53png_calloc,(png_const_structrp png_ptr, png_alloc_size_t size),PNG_ALLOCATED)
54{
55   png_voidp ret;
56
57   ret = png_malloc(png_ptr, size);
58
59   if (ret != NULL)
60      memset(ret, 0, size);
61
62   return ret;
63}
64
65/* png_malloc_base, an internal function added at libpng 1.6.0, does the work of
66 * allocating memory, taking into account limits and PNG_USER_MEM_SUPPORTED.
67 * Checking and error handling must happen outside this routine; it returns NULL
68 * if the allocation cannot be done (for any reason.)
69 */
70PNG_FUNCTION(png_voidp /* PRIVATE */,
71png_malloc_base,(png_const_structrp png_ptr, png_alloc_size_t size),
72   PNG_ALLOCATED)
73{
74   /* Moved to png_malloc_base from png_malloc_default in 1.6.0; the DOS
75    * allocators have also been removed in 1.6.0, so any 16-bit system now has
76    * to implement a user memory handler.  This checks to be sure it isn't
77    * called with big numbers.
78    */
79#ifndef PNG_USER_MEM_SUPPORTED
80   PNG_UNUSED(png_ptr)
81#endif
82
83   /* Some compilers complain that this is always true.  However, it
84    * can be false when integer overflow happens.
85    */
86   if (size > 0 && size <= PNG_SIZE_MAX
87#     ifdef PNG_MAX_MALLOC_64K
88         && size <= 65536U
89#     endif
90      )
91   {
92#ifdef PNG_USER_MEM_SUPPORTED
93      if (png_ptr != NULL && png_ptr->malloc_fn != NULL)
94         return png_ptr->malloc_fn(png_constcast(png_structrp,png_ptr), size);
95
96      else
97#endif
98         return FXMEM_DefaultAlloc((int)size, 0);
99   }
100
101   else
102      return NULL;
103}
104
105#if defined(PNG_TEXT_SUPPORTED) || defined(PNG_sPLT_SUPPORTED) ||\
106   defined(PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED)
107/* This is really here only to work round a spurious warning in GCC 4.6 and 4.7
108 * that arises because of the checks in png_realloc_array that are repeated in
109 * png_malloc_array.
110 */
111static png_voidp
112png_malloc_array_checked(png_const_structrp png_ptr, int nelements,
113   size_t element_size)
114{
115   png_alloc_size_t req = nelements; /* known to be > 0 */
116
117   if (req <= PNG_SIZE_MAX/element_size)
118      return png_malloc_base(png_ptr, req * element_size);
119
120   /* The failure case when the request is too large */
121   return NULL;
122}
123
124PNG_FUNCTION(png_voidp /* PRIVATE */,
125png_malloc_array,(png_const_structrp png_ptr, int nelements,
126   size_t element_size),PNG_ALLOCATED)
127{
128   if (nelements <= 0 || element_size == 0)
129      png_error(png_ptr, "internal error: array alloc");
130
131   return png_malloc_array_checked(png_ptr, nelements, element_size);
132}
133
134PNG_FUNCTION(png_voidp /* PRIVATE */,
135png_realloc_array,(png_const_structrp png_ptr, png_const_voidp old_array,
136   int old_elements, int add_elements, size_t element_size),PNG_ALLOCATED)
137{
138   /* These are internal errors: */
139   if (add_elements <= 0 || element_size == 0 || old_elements < 0 ||
140      (old_array == NULL && old_elements > 0))
141      png_error(png_ptr, "internal error: array realloc");
142
143   /* Check for overflow on the elements count (so the caller does not have to
144    * check.)
145    */
146   if (add_elements <= INT_MAX - old_elements)
147   {
148      png_voidp new_array = png_malloc_array_checked(png_ptr,
149         old_elements+add_elements, element_size);
150
151      if (new_array != NULL)
152      {
153         /* Because png_malloc_array worked the size calculations below cannot
154          * overflow.
155          */
156         if (old_elements > 0)
157            memcpy(new_array, old_array, element_size*(unsigned)old_elements);
158
159         memset((char*)new_array + element_size*(unsigned)old_elements, 0,
160            element_size*(unsigned)add_elements);
161
162         return new_array;
163      }
164   }
165
166   return NULL; /* error */
167}
168#endif /* TEXT || sPLT || STORE_UNKNOWN_CHUNKS */
169
170/* Various functions that have different error handling are derived from this.
171 * png_malloc always exists, but if PNG_USER_MEM_SUPPORTED is defined a separate
172 * function png_malloc_default is also provided.
173 */
174PNG_FUNCTION(png_voidp,PNGAPI
175png_malloc,(png_const_structrp png_ptr, png_alloc_size_t size),PNG_ALLOCATED)
176{
177   png_voidp ret;
178
179   if (png_ptr == NULL)
180      return NULL;
181
182   ret = png_malloc_base(png_ptr, size);
183
184   if (ret == NULL)
185       png_error(png_ptr, "Out of memory"); /* 'm' means png_malloc */
186
187   return ret;
188}
189
190#ifdef PNG_USER_MEM_SUPPORTED
191PNG_FUNCTION(png_voidp,PNGAPI
192png_malloc_default,(png_const_structrp png_ptr, png_alloc_size_t size),
193   PNG_ALLOCATED PNG_DEPRECATED)
194{
195   png_voidp ret;
196
197   if (png_ptr == NULL)
198      return NULL;
199
200   /* Passing 'NULL' here bypasses the application provided memory handler. */
201   ret = png_malloc_base(NULL/*use malloc*/, size);
202
203   if (ret == NULL)
204      png_error(png_ptr, "Out of Memory"); /* 'M' means png_malloc_default */
205
206   return ret;
207}
208#endif /* USER_MEM */
209
210/* This function was added at libpng version 1.2.3.  The png_malloc_warn()
211 * function will issue a png_warning and return NULL instead of issuing a
212 * png_error, if it fails to allocate the requested memory.
213 */
214PNG_FUNCTION(png_voidp,PNGAPI
215png_malloc_warn,(png_const_structrp png_ptr, png_alloc_size_t size),
216   PNG_ALLOCATED)
217{
218   if (png_ptr != NULL)
219   {
220      png_voidp ret = png_malloc_base(png_ptr, size);
221
222      if (ret != NULL)
223         return ret;
224
225      png_warning(png_ptr, "Out of memory");
226   }
227
228   return NULL;
229}
230
231/* Free a pointer allocated by png_malloc().  If ptr is NULL, return
232 * without taking any action.
233 */
234void PNGAPI
235png_free(png_const_structrp png_ptr, png_voidp ptr)
236{
237   if (png_ptr == NULL || ptr == NULL)
238      return;
239
240#ifdef PNG_USER_MEM_SUPPORTED
241   if (png_ptr->free_fn != NULL)
242      png_ptr->free_fn(png_constcast(png_structrp,png_ptr), ptr);
243
244   else
245      png_free_default(png_ptr, ptr);
246}
247
248PNG_FUNCTION(void,PNGAPI
249png_free_default,(png_const_structrp png_ptr, png_voidp ptr),PNG_DEPRECATED)
250{
251   if (png_ptr == NULL || ptr == NULL)
252      return;
253#endif /* USER_MEM */
254
255   FXMEM_DefaultFree(ptr, 0);
256}
257
258#ifdef PNG_USER_MEM_SUPPORTED
259/* This function is called when the application wants to use another method
260 * of allocating and freeing memory.
261 */
262void PNGAPI
263png_set_mem_fn(png_structrp png_ptr, png_voidp mem_ptr, png_malloc_ptr
264  malloc_fn, png_free_ptr free_fn)
265{
266   if (png_ptr != NULL)
267   {
268      png_ptr->mem_ptr = mem_ptr;
269      png_ptr->malloc_fn = malloc_fn;
270      png_ptr->free_fn = free_fn;
271   }
272}
273
274/* This function returns a pointer to the mem_ptr associated with the user
275 * functions.  The application should free any memory associated with this
276 * pointer before png_write_destroy and png_read_destroy are called.
277 */
278png_voidp PNGAPI
279png_get_mem_ptr(png_const_structrp png_ptr)
280{
281   if (png_ptr == NULL)
282      return NULL;
283
284   return png_ptr->mem_ptr;
285}
286#endif /* USER_MEM */
287#endif /* READ || WRITE */
288