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