1/*
2 * copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
3 *
4 * This file is part of FFmpeg.
5 *
6 * FFmpeg is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
10 *
11 * FFmpeg is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with FFmpeg; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19 */
20
21/**
22 * @file
23 * @ingroup lavu_mem
24 * Memory handling functions
25 */
26
27#ifndef AVUTIL_MEM_H
28#define AVUTIL_MEM_H
29
30#include <limits.h>
31#include <stdint.h>
32
33#include "attributes.h"
34#include "error.h"
35#include "avutil.h"
36#include "version.h"
37
38/**
39 * @addtogroup lavu_mem
40 * Utilities for manipulating memory.
41 *
42 * FFmpeg has several applications of memory that are not required of a typical
43 * program. For example, the computing-heavy components like video decoding and
44 * encoding can be sped up significantly through the use of aligned memory.
45 *
46 * However, for each of FFmpeg's applications of memory, there might not be a
47 * recognized or standardized API for that specific use. Memory alignment, for
48 * instance, varies wildly depending on operating systems, architectures, and
49 * compilers. Hence, this component of @ref libavutil is created to make
50 * dealing with memory consistently possible on all platforms.
51 *
52 * @{
53 */
54
55#if FF_API_DECLARE_ALIGNED
56/**
57 *
58 * @defgroup lavu_mem_macros Alignment Macros
59 * Helper macros for declaring aligned variables.
60 * @{
61 */
62
63/**
64 * @def DECLARE_ALIGNED(n,t,v)
65 * Declare a variable that is aligned in memory.
66 *
67 * @code{.c}
68 * DECLARE_ALIGNED(16, uint16_t, aligned_int) = 42;
69 * DECLARE_ALIGNED(32, uint8_t, aligned_array)[128];
70 *
71 * // The default-alignment equivalent would be
72 * uint16_t aligned_int = 42;
73 * uint8_t aligned_array[128];
74 * @endcode
75 *
76 * @param n Minimum alignment in bytes
77 * @param t Type of the variable (or array element)
78 * @param v Name of the variable
79 */
80
81/**
82 * @def DECLARE_ASM_ALIGNED(n,t,v)
83 * Declare an aligned variable appropriate for use in inline assembly code.
84 *
85 * @code{.c}
86 * DECLARE_ASM_ALIGNED(16, uint64_t, pw_08) = UINT64_C(0x0008000800080008);
87 * @endcode
88 *
89 * @param n Minimum alignment in bytes
90 * @param t Type of the variable (or array element)
91 * @param v Name of the variable
92 */
93
94/**
95 * @def DECLARE_ASM_CONST(n,t,v)
96 * Declare a static constant aligned variable appropriate for use in inline
97 * assembly code.
98 *
99 * @code{.c}
100 * DECLARE_ASM_CONST(16, uint64_t, pw_08) = UINT64_C(0x0008000800080008);
101 * @endcode
102 *
103 * @param n Minimum alignment in bytes
104 * @param t Type of the variable (or array element)
105 * @param v Name of the variable
106 */
107
108#if defined(__INTEL_COMPILER) && __INTEL_COMPILER < 1110 || defined(__SUNPRO_C)
109 #define DECLARE_ALIGNED(n,t,v) t __attribute__ ((aligned (n))) v
110 #define DECLARE_ASM_ALIGNED(n,t,v) t __attribute__ ((aligned (n))) v
111 #define DECLARE_ASM_CONST(n,t,v) const t __attribute__ ((aligned (n))) v
112#elif defined(__DJGPP__)
113 #define DECLARE_ALIGNED(n,t,v) t __attribute__ ((aligned (FFMIN(n, 16)))) v
114 #define DECLARE_ASM_ALIGNED(n,t,v) t av_used __attribute__ ((aligned (FFMIN(n, 16)))) v
115 #define DECLARE_ASM_CONST(n,t,v) static const t av_used __attribute__ ((aligned (FFMIN(n, 16)))) v
116#elif defined(__GNUC__) || defined(__clang__)
117 #define DECLARE_ALIGNED(n,t,v) t __attribute__ ((aligned (n))) v
118 #define DECLARE_ASM_ALIGNED(n,t,v) t av_used __attribute__ ((aligned (n))) v
119 #define DECLARE_ASM_CONST(n,t,v) static const t av_used __attribute__ ((aligned (n))) v
120#elif defined(_MSC_VER)
121 #define DECLARE_ALIGNED(n,t,v) __declspec(align(n)) t v
122 #define DECLARE_ASM_ALIGNED(n,t,v) __declspec(align(n)) t v
123 #define DECLARE_ASM_CONST(n,t,v) __declspec(align(n)) static const t v
124#else
125 #define DECLARE_ALIGNED(n,t,v) t v
126 #define DECLARE_ASM_ALIGNED(n,t,v) t v
127 #define DECLARE_ASM_CONST(n,t,v) static const t v
128#endif
129
130/**
131 * @}
132 */
133#endif
134
135/**
136 * @defgroup lavu_mem_attrs Function Attributes
137 * Function attributes applicable to memory handling functions.
138 *
139 * These function attributes can help compilers emit more useful warnings, or
140 * generate better code.
141 * @{
142 */
143
144/**
145 * @def av_malloc_attrib
146 * Function attribute denoting a malloc-like function.
147 *
148 * @see <a href="https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-g_t_0040code_007bmalloc_007d-function-attribute-3251">Function attribute `malloc` in GCC's documentation</a>
149 */
150
151#if AV_GCC_VERSION_AT_LEAST(3,1)
152 #define av_malloc_attrib __attribute__((__malloc__))
153#else
154 #define av_malloc_attrib
155#endif
156
157/**
158 * @def av_alloc_size(...)
159 * Function attribute used on a function that allocates memory, whose size is
160 * given by the specified parameter(s).
161 *
162 * @code{.c}
163 * void *av_malloc(size_t size) av_alloc_size(1);
164 * void *av_calloc(size_t nmemb, size_t size) av_alloc_size(1, 2);
165 * @endcode
166 *
167 * @param ... One or two parameter indexes, separated by a comma
168 *
169 * @see <a href="https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-g_t_0040code_007balloc_005fsize_007d-function-attribute-3220">Function attribute `alloc_size` in GCC's documentation</a>
170 */
171
172#if AV_GCC_VERSION_AT_LEAST(4,3)
173 #define av_alloc_size(...) __attribute__((alloc_size(__VA_ARGS__)))
174#else
175 #define av_alloc_size(...)
176#endif
177
178/**
179 * @}
180 */
181
182/**
183 * @defgroup lavu_mem_funcs Heap Management
184 * Functions responsible for allocating, freeing, and copying memory.
185 *
186 * All memory allocation functions have a built-in upper limit of `INT_MAX`
187 * bytes. This may be changed with av_max_alloc(), although exercise extreme
188 * caution when doing so.
189 *
190 * @{
191 */
192
193/**
194 * Allocate a memory block with alignment suitable for all memory accesses
195 * (including vectors if available on the CPU).
196 *
197 * @param size Size in bytes for the memory block to be allocated
198 * @return Pointer to the allocated block, or `NULL` if the block cannot
199 * be allocated
200 * @see av_mallocz()
201 */
202void *av_malloc(size_t size) av_malloc_attrib av_alloc_size(1);
203
204/**
205 * Allocate a memory block with alignment suitable for all memory accesses
206 * (including vectors if available on the CPU) and zero all the bytes of the
207 * block.
208 *
209 * @param size Size in bytes for the memory block to be allocated
210 * @return Pointer to the allocated block, or `NULL` if it cannot be allocated
211 * @see av_malloc()
212 */
213void *av_mallocz(size_t size) av_malloc_attrib av_alloc_size(1);
214
215/**
216 * Allocate a memory block for an array with av_malloc().
217 *
218 * The allocated memory will have size `size * nmemb` bytes.
219 *
220 * @param nmemb Number of element
221 * @param size Size of a single element
222 * @return Pointer to the allocated block, or `NULL` if the block cannot
223 * be allocated
224 * @see av_malloc()
225 */
226av_alloc_size(1, 2) void *av_malloc_array(size_t nmemb, size_t size);
227
228/**
229 * Allocate a memory block for an array with av_mallocz().
230 *
231 * The allocated memory will have size `size * nmemb` bytes.
232 *
233 * @param nmemb Number of elements
234 * @param size Size of the single element
235 * @return Pointer to the allocated block, or `NULL` if the block cannot
236 * be allocated
237 *
238 * @see av_mallocz()
239 * @see av_malloc_array()
240 */
241av_alloc_size(1, 2) void *av_mallocz_array(size_t nmemb, size_t size);
242
243/**
244 * Non-inlined equivalent of av_mallocz_array().
245 *
246 * Created for symmetry with the calloc() C function.
247 */
248void *av_calloc(size_t nmemb, size_t size) av_malloc_attrib;
249
250/**
251 * Allocate, reallocate, or free a block of memory.
252 *
253 * If `ptr` is `NULL` and `size` > 0, allocate a new block. If `size` is
254 * zero, free the memory block pointed to by `ptr`. Otherwise, expand or
255 * shrink that block of memory according to `size`.
256 *
257 * @param ptr Pointer to a memory block already allocated with
258 * av_realloc() or `NULL`
259 * @param size Size in bytes of the memory block to be allocated or
260 * reallocated
261 *
262 * @return Pointer to a newly-reallocated block or `NULL` if the block
263 * cannot be reallocated or the function is used to free the memory block
264 *
265 * @warning Unlike av_malloc(), the returned pointer is not guaranteed to be
266 * correctly aligned.
267 * @see av_fast_realloc()
268 * @see av_reallocp()
269 */
270void *av_realloc(void *ptr, size_t size) av_alloc_size(2);
271
272/**
273 * Allocate, reallocate, or free a block of memory through a pointer to a
274 * pointer.
275 *
276 * If `*ptr` is `NULL` and `size` > 0, allocate a new block. If `size` is
277 * zero, free the memory block pointed to by `*ptr`. Otherwise, expand or
278 * shrink that block of memory according to `size`.
279 *
280 * @param[in,out] ptr Pointer to a pointer to a memory block already allocated
281 * with av_realloc(), or a pointer to `NULL`. The pointer
282 * is updated on success, or freed on failure.
283 * @param[in] size Size in bytes for the memory block to be allocated or
284 * reallocated
285 *
286 * @return Zero on success, an AVERROR error code on failure
287 *
288 * @warning Unlike av_malloc(), the allocated memory is not guaranteed to be
289 * correctly aligned.
290 */
291av_warn_unused_result
292int av_reallocp(void *ptr, size_t size);
293
294/**
295 * Allocate, reallocate, or free a block of memory.
296 *
297 * This function does the same thing as av_realloc(), except:
298 * - It takes two size arguments and allocates `nelem * elsize` bytes,
299 * after checking the result of the multiplication for integer overflow.
300 * - It frees the input block in case of failure, thus avoiding the memory
301 * leak with the classic
302 * @code{.c}
303 * buf = realloc(buf);
304 * if (!buf)
305 * return -1;
306 * @endcode
307 * pattern.
308 */
309void *av_realloc_f(void *ptr, size_t nelem, size_t elsize);
310
311/**
312 * Allocate, reallocate, or free an array.
313 *
314 * If `ptr` is `NULL` and `nmemb` > 0, allocate a new block. If
315 * `nmemb` is zero, free the memory block pointed to by `ptr`.
316 *
317 * @param ptr Pointer to a memory block already allocated with
318 * av_realloc() or `NULL`
319 * @param nmemb Number of elements in the array
320 * @param size Size of the single element of the array
321 *
322 * @return Pointer to a newly-reallocated block or NULL if the block
323 * cannot be reallocated or the function is used to free the memory block
324 *
325 * @warning Unlike av_malloc(), the allocated memory is not guaranteed to be
326 * correctly aligned.
327 * @see av_reallocp_array()
328 */
329av_alloc_size(2, 3) void *av_realloc_array(void *ptr, size_t nmemb, size_t size);
330
331/**
332 * Allocate, reallocate, or free an array through a pointer to a pointer.
333 *
334 * If `*ptr` is `NULL` and `nmemb` > 0, allocate a new block. If `nmemb` is
335 * zero, free the memory block pointed to by `*ptr`.
336 *
337 * @param[in,out] ptr Pointer to a pointer to a memory block already
338 * allocated with av_realloc(), or a pointer to `NULL`.
339 * The pointer is updated on success, or freed on failure.
340 * @param[in] nmemb Number of elements
341 * @param[in] size Size of the single element
342 *
343 * @return Zero on success, an AVERROR error code on failure
344 *
345 * @warning Unlike av_malloc(), the allocated memory is not guaranteed to be
346 * correctly aligned.
347 */
348int av_reallocp_array(void *ptr, size_t nmemb, size_t size);
349
350/**
351 * Reallocate the given buffer if it is not large enough, otherwise do nothing.
352 *
353 * If the given buffer is `NULL`, then a new uninitialized buffer is allocated.
354 *
355 * If the given buffer is not large enough, and reallocation fails, `NULL` is
356 * returned and `*size` is set to 0, but the original buffer is not changed or
357 * freed.
358 *
359 * A typical use pattern follows:
360 *
361 * @code{.c}
362 * uint8_t *buf = ...;
363 * uint8_t *new_buf = av_fast_realloc(buf, &current_size, size_needed);
364 * if (!new_buf) {
365 * // Allocation failed; clean up original buffer
366 * av_freep(&buf);
367 * return AVERROR(ENOMEM);
368 * }
369 * @endcode
370 *
371 * @param[in,out] ptr Already allocated buffer, or `NULL`
372 * @param[in,out] size Pointer to the size of buffer `ptr`. `*size` is
373 * updated to the new allocated size, in particular 0
374 * in case of failure.
375 * @param[in] min_size Desired minimal size of buffer `ptr`
376 * @return `ptr` if the buffer is large enough, a pointer to newly reallocated
377 * buffer if the buffer was not large enough, or `NULL` in case of
378 * error
379 * @see av_realloc()
380 * @see av_fast_malloc()
381 */
382void *av_fast_realloc(void *ptr, unsigned int *size, size_t min_size);
383
384/**
385 * Allocate a buffer, reusing the given one if large enough.
386 *
387 * Contrary to av_fast_realloc(), the current buffer contents might not be
388 * preserved and on error the old buffer is freed, thus no special handling to
389 * avoid memleaks is necessary.
390 *
391 * `*ptr` is allowed to be `NULL`, in which case allocation always happens if
392 * `size_needed` is greater than 0.
393 *
394 * @code{.c}
395 * uint8_t *buf = ...;
396 * av_fast_malloc(&buf, &current_size, size_needed);
397 * if (!buf) {
398 * // Allocation failed; buf already freed
399 * return AVERROR(ENOMEM);
400 * }
401 * @endcode
402 *
403 * @param[in,out] ptr Pointer to pointer to an already allocated buffer.
404 * `*ptr` will be overwritten with pointer to new
405 * buffer on success or `NULL` on failure
406 * @param[in,out] size Pointer to the size of buffer `*ptr`. `*size` is
407 * updated to the new allocated size, in particular 0
408 * in case of failure.
409 * @param[in] min_size Desired minimal size of buffer `*ptr`
410 * @see av_realloc()
411 * @see av_fast_mallocz()
412 */
413void av_fast_malloc(void *ptr, unsigned int *size, size_t min_size);
414
415/**
416 * Allocate and clear a buffer, reusing the given one if large enough.
417 *
418 * Like av_fast_malloc(), but all newly allocated space is initially cleared.
419 * Reused buffer is not cleared.
420 *
421 * `*ptr` is allowed to be `NULL`, in which case allocation always happens if
422 * `size_needed` is greater than 0.
423 *
424 * @param[in,out] ptr Pointer to pointer to an already allocated buffer.
425 * `*ptr` will be overwritten with pointer to new
426 * buffer on success or `NULL` on failure
427 * @param[in,out] size Pointer to the size of buffer `*ptr`. `*size` is
428 * updated to the new allocated size, in particular 0
429 * in case of failure.
430 * @param[in] min_size Desired minimal size of buffer `*ptr`
431 * @see av_fast_malloc()
432 */
433void av_fast_mallocz(void *ptr, unsigned int *size, size_t min_size);
434
435/**
436 * Free a memory block which has been allocated with a function of av_malloc()
437 * or av_realloc() family.
438 *
439 * @param ptr Pointer to the memory block which should be freed.
440 *
441 * @note `ptr = NULL` is explicitly allowed.
442 * @note It is recommended that you use av_freep() instead, to prevent leaving
443 * behind dangling pointers.
444 * @see av_freep()
445 */
446void av_free(void *ptr);
447
448/**
449 * Free a memory block which has been allocated with a function of av_malloc()
450 * or av_realloc() family, and set the pointer pointing to it to `NULL`.
451 *
452 * @code{.c}
453 * uint8_t *buf = av_malloc(16);
454 * av_free(buf);
455 * // buf now contains a dangling pointer to freed memory, and accidental
456 * // dereference of buf will result in a use-after-free, which may be a
457 * // security risk.
458 *
459 * uint8_t *buf = av_malloc(16);
460 * av_freep(&buf);
461 * // buf is now NULL, and accidental dereference will only result in a
462 * // NULL-pointer dereference.
463 * @endcode
464 *
465 * @param ptr Pointer to the pointer to the memory block which should be freed
466 * @note `*ptr = NULL` is safe and leads to no action.
467 * @see av_free()
468 */
469void av_freep(void *ptr);
470
471/**
472 * Duplicate a string.
473 *
474 * @param s String to be duplicated
475 * @return Pointer to a newly-allocated string containing a
476 * copy of `s` or `NULL` if the string cannot be allocated
477 * @see av_strndup()
478 */
479char *av_strdup(const char *s) av_malloc_attrib;
480
481/**
482 * Duplicate a substring of a string.
483 *
484 * @param s String to be duplicated
485 * @param len Maximum length of the resulting string (not counting the
486 * terminating byte)
487 * @return Pointer to a newly-allocated string containing a
488 * substring of `s` or `NULL` if the string cannot be allocated
489 */
490char *av_strndup(const char *s, size_t len) av_malloc_attrib;
491
492/**
493 * Duplicate a buffer with av_malloc().
494 *
495 * @param p Buffer to be duplicated
496 * @param size Size in bytes of the buffer copied
497 * @return Pointer to a newly allocated buffer containing a
498 * copy of `p` or `NULL` if the buffer cannot be allocated
499 */
500void *av_memdup(const void *p, size_t size);
501
502/**
503 * Overlapping memcpy() implementation.
504 *
505 * @param dst Destination buffer
506 * @param back Number of bytes back to start copying (i.e. the initial size of
507 * the overlapping window); must be > 0
508 * @param cnt Number of bytes to copy; must be >= 0
509 *
510 * @note `cnt > back` is valid, this will copy the bytes we just copied,
511 * thus creating a repeating pattern with a period length of `back`.
512 */
513void av_memcpy_backptr(uint8_t *dst, int back, int cnt);
514
515/**
516 * @}
517 */
518
519/**
520 * @defgroup lavu_mem_dynarray Dynamic Array
521 *
522 * Utilities to make an array grow when needed.
523 *
524 * Sometimes, the programmer would want to have an array that can grow when
525 * needed. The libavutil dynamic array utilities fill that need.
526 *
527 * libavutil supports two systems of appending elements onto a dynamically
528 * allocated array, the first one storing the pointer to the value in the
529 * array, and the second storing the value directly. In both systems, the
530 * caller is responsible for maintaining a variable containing the length of
531 * the array, as well as freeing of the array after use.
532 *
533 * The first system stores pointers to values in a block of dynamically
534 * allocated memory. Since only pointers are stored, the function does not need
535 * to know the size of the type. Both av_dynarray_add() and
536 * av_dynarray_add_nofree() implement this system.
537 *
538 * @code
539 * type **array = NULL; //< an array of pointers to values
540 * int nb = 0; //< a variable to keep track of the length of the array
541 *
542 * type to_be_added = ...;
543 * type to_be_added2 = ...;
544 *
545 * av_dynarray_add(&array, &nb, &to_be_added);
546 * if (nb == 0)
547 * return AVERROR(ENOMEM);
548 *
549 * av_dynarray_add(&array, &nb, &to_be_added2);
550 * if (nb == 0)
551 * return AVERROR(ENOMEM);
552 *
553 * // Now:
554 * // nb == 2
555 * // &to_be_added == array[0]
556 * // &to_be_added2 == array[1]
557 *
558 * av_freep(&array);
559 * @endcode
560 *
561 * The second system stores the value directly in a block of memory. As a
562 * result, the function has to know the size of the type. av_dynarray2_add()
563 * implements this mechanism.
564 *
565 * @code
566 * type *array = NULL; //< an array of values
567 * int nb = 0; //< a variable to keep track of the length of the array
568 *
569 * type to_be_added = ...;
570 * type to_be_added2 = ...;
571 *
572 * type *addr = av_dynarray2_add((void **)&array, &nb, sizeof(*array), NULL);
573 * if (!addr)
574 * return AVERROR(ENOMEM);
575 * memcpy(addr, &to_be_added, sizeof(to_be_added));
576 *
577 * // Shortcut of the above.
578 * type *addr = av_dynarray2_add((void **)&array, &nb, sizeof(*array),
579 * (const void *)&to_be_added2);
580 * if (!addr)
581 * return AVERROR(ENOMEM);
582 *
583 * // Now:
584 * // nb == 2
585 * // to_be_added == array[0]
586 * // to_be_added2 == array[1]
587 *
588 * av_freep(&array);
589 * @endcode
590 *
591 * @{
592 */
593
594/**
595 * Add the pointer to an element to a dynamic array.
596 *
597 * The array to grow is supposed to be an array of pointers to
598 * structures, and the element to add must be a pointer to an already
599 * allocated structure.
600 *
601 * The array is reallocated when its size reaches powers of 2.
602 * Therefore, the amortized cost of adding an element is constant.
603 *
604 * In case of success, the pointer to the array is updated in order to
605 * point to the new grown array, and the number pointed to by `nb_ptr`
606 * is incremented.
607 * In case of failure, the array is freed, `*tab_ptr` is set to `NULL` and
608 * `*nb_ptr` is set to 0.
609 *
610 * @param[in,out] tab_ptr Pointer to the array to grow
611 * @param[in,out] nb_ptr Pointer to the number of elements in the array
612 * @param[in] elem Element to add
613 * @see av_dynarray_add_nofree(), av_dynarray2_add()
614 */
615void av_dynarray_add(void *tab_ptr, int *nb_ptr, void *elem);
616
617/**
618 * Add an element to a dynamic array.
619 *
620 * Function has the same functionality as av_dynarray_add(),
621 * but it doesn't free memory on fails. It returns error code
622 * instead and leave current buffer untouched.
623 *
624 * @return >=0 on success, negative otherwise
625 * @see av_dynarray_add(), av_dynarray2_add()
626 */
627av_warn_unused_result
628int av_dynarray_add_nofree(void *tab_ptr, int *nb_ptr, void *elem);
629
630/**
631 * Add an element of size `elem_size` to a dynamic array.
632 *
633 * The array is reallocated when its number of elements reaches powers of 2.
634 * Therefore, the amortized cost of adding an element is constant.
635 *
636 * In case of success, the pointer to the array is updated in order to
637 * point to the new grown array, and the number pointed to by `nb_ptr`
638 * is incremented.
639 * In case of failure, the array is freed, `*tab_ptr` is set to `NULL` and
640 * `*nb_ptr` is set to 0.
641 *
642 * @param[in,out] tab_ptr Pointer to the array to grow
643 * @param[in,out] nb_ptr Pointer to the number of elements in the array
644 * @param[in] elem_size Size in bytes of an element in the array
645 * @param[in] elem_data Pointer to the data of the element to add. If
646 * `NULL`, the space of the newly added element is
647 * allocated but left uninitialized.
648 *
649 * @return Pointer to the data of the element to copy in the newly allocated
650 * space
651 * @see av_dynarray_add(), av_dynarray_add_nofree()
652 */
653void *av_dynarray2_add(void **tab_ptr, int *nb_ptr, size_t elem_size,
654 const uint8_t *elem_data);
655
656/**
657 * @}
658 */
659
660/**
661 * @defgroup lavu_mem_misc Miscellaneous Functions
662 *
663 * Other functions related to memory allocation.
664 *
665 * @{
666 */
667
668/**
669 * Multiply two `size_t` values checking for overflow.
670 *
671 * @param[in] a,b Operands of multiplication
672 * @param[out] r Pointer to the result of the operation
673 * @return 0 on success, AVERROR(EINVAL) on overflow
674 */
675static inline int av_size_mult(size_t a, size_t b, size_t *r)
676{
677 size_t t = a * b;
678 /* Hack inspired from glibc: don't try the division if nelem and elsize
679 * are both less than sqrt(SIZE_MAX). */
680 if ((a | b) >= ((size_t)1 << (sizeof(size_t) * 4)) && a && t / a != b)
681 return AVERROR(EINVAL);
682 *r = t;
683 return 0;
684}
685
686/**
687 * Set the maximum size that may be allocated in one block.
688 *
689 * The value specified with this function is effective for all libavutil's @ref
690 * lavu_mem_funcs "heap management functions."
691 *
692 * By default, the max value is defined as `INT_MAX`.
693 *
694 * @param max Value to be set as the new maximum size
695 *
696 * @warning Exercise extreme caution when using this function. Don't touch
697 * this if you do not understand the full consequence of doing so.
698 */
699void av_max_alloc(size_t max);
700
701/**
702 * @}
703 * @}
704 */
705
706#endif /* AVUTIL_MEM_H */
707

source code of include/x86_64-linux-gnu/libavutil/mem.h