2 * copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
4 * This file is part of FFmpeg.
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.
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.
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
24 * Memory handling functions
33 #include "attributes.h"
39 * @addtogroup lavu_mem
40 * Utilities for manipulating memory.
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.
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.
55 #if FF_API_DECLARE_ALIGNED
58 * @defgroup lavu_mem_macros Alignment Macros
59 * Helper macros for declaring aligned variables.
64 * @def DECLARE_ALIGNED(n,t,v)
65 * Declare a variable that is aligned in memory.
68 * DECLARE_ALIGNED(16, uint16_t, aligned_int) = 42;
69 * DECLARE_ALIGNED(32, uint8_t, aligned_array)[128];
71 * // The default-alignment equivalent would be
72 * uint16_t aligned_int = 42;
73 * uint8_t aligned_array[128];
76 * @param n Minimum alignment in bytes
77 * @param t Type of the variable (or array element)
78 * @param v Name of the variable
82 * @def DECLARE_ASM_ALIGNED(n,t,v)
83 * Declare an aligned variable appropriate for use in inline assembly code.
86 * DECLARE_ASM_ALIGNED(16, uint64_t, pw_08) = UINT64_C(0x0008000800080008);
89 * @param n Minimum alignment in bytes
90 * @param t Type of the variable (or array element)
91 * @param v Name of the variable
95 * @def DECLARE_ASM_CONST(n,t,v)
96 * Declare a static constant aligned variable appropriate for use in inline
100 * DECLARE_ASM_CONST(16, uint64_t, pw_08) = UINT64_C(0x0008000800080008);
103 * @param n Minimum alignment in bytes
104 * @param t Type of the variable (or array element)
105 * @param v Name of the variable
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
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
136 * @defgroup lavu_mem_attrs Function Attributes
137 * Function attributes applicable to memory handling functions.
139 * These function attributes can help compilers emit more useful warnings, or
140 * generate better code.
145 * @def av_malloc_attrib
146 * Function attribute denoting a malloc-like function.
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>
151 #if AV_GCC_VERSION_AT_LEAST(3,1)
152 #define av_malloc_attrib __attribute__((__malloc__))
154 #define av_malloc_attrib
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).
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);
167 * @param ... One or two parameter indexes, separated by a comma
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>
172 #if AV_GCC_VERSION_AT_LEAST(4,3)
173 #define av_alloc_size(...) __attribute__((alloc_size(__VA_ARGS__)))
175 #define av_alloc_size(...)
183 * @defgroup lavu_mem_funcs Heap Management
184 * Functions responsible for allocating, freeing, and copying memory.
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.
194 * Allocate a memory block with alignment suitable for all memory accesses
195 * (including vectors if available on the CPU).
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
202 void *av_malloc(size_t size) av_malloc_attrib av_alloc_size(1);
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
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
213 void *av_mallocz(size_t size) av_malloc_attrib av_alloc_size(1);
216 * Allocate a memory block for an array with av_malloc().
218 * The allocated memory will have size `size * nmemb` bytes.
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
226 av_alloc_size(1, 2) void *av_malloc_array(size_t nmemb, size_t size);
229 * Allocate a memory block for an array with av_mallocz().
231 * The allocated memory will have size `size * nmemb` bytes.
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
239 * @see av_malloc_array()
241 av_alloc_size(1, 2) void *av_mallocz_array(size_t nmemb, size_t size);
244 * Non-inlined equivalent of av_mallocz_array().
246 * Created for symmetry with the calloc() C function.
248 void *av_calloc(size_t nmemb, size_t size) av_malloc_attrib;
251 * Allocate, reallocate, or free a block of memory.
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`.
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
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
265 * @warning Unlike av_malloc(), the returned pointer is not guaranteed to be
267 * @see av_fast_realloc()
270 void *av_realloc(void *ptr, size_t size) av_alloc_size(2);
273 * Allocate, reallocate, or free a block of memory through a pointer to a
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`.
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
286 * @return Zero on success, an AVERROR error code on failure
288 * @warning Unlike av_malloc(), the allocated memory is not guaranteed to be
291 av_warn_unused_result
292 int av_reallocp(void *ptr, size_t size);
295 * Allocate, reallocate, or free a block of memory.
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
303 * buf = realloc(buf);
309 void *av_realloc_f(void *ptr, size_t nelem, size_t elsize);
312 * Allocate, reallocate, or free an array.
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`.
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
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
325 * @warning Unlike av_malloc(), the allocated memory is not guaranteed to be
327 * @see av_reallocp_array()
329 av_alloc_size(2, 3) void *av_realloc_array(void *ptr, size_t nmemb, size_t size);
332 * Allocate, reallocate, or free an array through a pointer to a pointer.
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`.
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
343 * @return Zero on success, an AVERROR error code on failure
345 * @warning Unlike av_malloc(), the allocated memory is not guaranteed to be
348 int av_reallocp_array(void *ptr, size_t nmemb, size_t size);
351 * Reallocate the given buffer if it is not large enough, otherwise do nothing.
353 * If the given buffer is `NULL`, then a new uninitialized buffer is allocated.
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
359 * A typical use pattern follows:
362 * uint8_t *buf = ...;
363 * uint8_t *new_buf = av_fast_realloc(buf, ¤t_size, size_needed);
365 * // Allocation failed; clean up original buffer
367 * return AVERROR(ENOMEM);
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
380 * @see av_fast_malloc()
382 void *av_fast_realloc(void *ptr, unsigned int *size, size_t min_size);
385 * Allocate a buffer, reusing the given one if large enough.
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.
391 * `*ptr` is allowed to be `NULL`, in which case allocation always happens if
392 * `size_needed` is greater than 0.
395 * uint8_t *buf = ...;
396 * av_fast_malloc(&buf, ¤t_size, size_needed);
398 * // Allocation failed; buf already freed
399 * return AVERROR(ENOMEM);
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`
411 * @see av_fast_mallocz()
413 void av_fast_malloc(void *ptr, unsigned int *size, size_t min_size);
416 * Allocate and clear a buffer, reusing the given one if large enough.
418 * Like av_fast_malloc(), but all newly allocated space is initially cleared.
419 * Reused buffer is not cleared.
421 * `*ptr` is allowed to be `NULL`, in which case allocation always happens if
422 * `size_needed` is greater than 0.
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()
433 void av_fast_mallocz(void *ptr, unsigned int *size, size_t min_size);
436 * Free a memory block which has been allocated with a function of av_malloc()
437 * or av_realloc() family.
439 * @param ptr Pointer to the memory block which should be freed.
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.
446 void av_free(void *ptr);
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`.
453 * uint8_t *buf = av_malloc(16);
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
459 * uint8_t *buf = av_malloc(16);
461 * // buf is now NULL, and accidental dereference will only result in a
462 * // NULL-pointer dereference.
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.
469 void av_freep(void *ptr);
472 * Duplicate a string.
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
479 char *av_strdup(const char *s) av_malloc_attrib;
482 * Duplicate a substring of a string.
484 * @param s String to be duplicated
485 * @param len Maximum length of the resulting string (not counting the
487 * @return Pointer to a newly-allocated string containing a
488 * substring of `s` or `NULL` if the string cannot be allocated
490 char *av_strndup(const char *s, size_t len) av_malloc_attrib;
493 * Duplicate a buffer with av_malloc().
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
500 void *av_memdup(const void *p, size_t size);
503 * Overlapping memcpy() implementation.
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
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`.
513 void av_memcpy_backptr(uint8_t *dst, int back, int cnt);
520 * @defgroup lavu_mem_dynarray Dynamic Array
522 * Utilities to make an array grow when needed.
524 * Sometimes, the programmer would want to have an array that can grow when
525 * needed. The libavutil dynamic array utilities fill that need.
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.
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.
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
542 * type to_be_added = ...;
543 * type to_be_added2 = ...;
545 * av_dynarray_add(&array, &nb, &to_be_added);
547 * return AVERROR(ENOMEM);
549 * av_dynarray_add(&array, &nb, &to_be_added2);
551 * return AVERROR(ENOMEM);
555 * // &to_be_added == array[0]
556 * // &to_be_added2 == array[1]
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.
566 * type *array = NULL; //< an array of values
567 * int nb = 0; //< a variable to keep track of the length of the array
569 * type to_be_added = ...;
570 * type to_be_added2 = ...;
572 * type *addr = av_dynarray2_add((void **)&array, &nb, sizeof(*array), NULL);
574 * return AVERROR(ENOMEM);
575 * memcpy(addr, &to_be_added, sizeof(to_be_added));
577 * // Shortcut of the above.
578 * type *addr = av_dynarray2_add((void **)&array, &nb, sizeof(*array),
579 * (const void *)&to_be_added2);
581 * return AVERROR(ENOMEM);
585 * // to_be_added == array[0]
586 * // to_be_added2 == array[1]
595 * Add the pointer to an element to a dynamic array.
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.
601 * The array is reallocated when its size reaches powers of 2.
602 * Therefore, the amortized cost of adding an element is constant.
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`
607 * In case of failure, the array is freed, `*tab_ptr` is set to `NULL` and
608 * `*nb_ptr` is set to 0.
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()
615 void av_dynarray_add(void *tab_ptr, int *nb_ptr, void *elem);
618 * Add an element to a dynamic array.
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.
624 * @return >=0 on success, negative otherwise
625 * @see av_dynarray_add(), av_dynarray2_add()
627 av_warn_unused_result
628 int av_dynarray_add_nofree(void *tab_ptr, int *nb_ptr, void *elem);
631 * Add an element of size `elem_size` to a dynamic array.
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.
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`
639 * In case of failure, the array is freed, `*tab_ptr` is set to `NULL` and
640 * `*nb_ptr` is set to 0.
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.
649 * @return Pointer to the data of the element to copy in the newly allocated
651 * @see av_dynarray_add(), av_dynarray_add_nofree()
653 void *av_dynarray2_add(void **tab_ptr, int *nb_ptr, size_t elem_size,
654 const uint8_t *elem_data);
661 * @defgroup lavu_mem_misc Miscellaneous Functions
663 * Other functions related to memory allocation.
669 * Multiply two `size_t` values checking for overflow.
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
675 static inline int av_size_mult(size_t a, size_t b, size_t *r)
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);
687 * Set the maximum size that may be allocated in one block.
689 * The value specified with this function is effective for all libavutil's @ref
690 * lavu_mem_funcs "heap management functions."
692 * By default, the max value is defined as `INT_MAX`.
694 * @param max Value to be set as the new maximum size
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.
699 void av_max_alloc(size_t max);
706 #endif /* AVUTIL_MEM_H */