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"
38 * @addtogroup lavu_mem
39 * Utilities for manipulating memory.
41 * FFmpeg has several applications of memory that are not required of a typical
42 * program. For example, the computing-heavy components like video decoding and
43 * encoding can be sped up significantly through the use of aligned memory.
45 * However, for each of FFmpeg's applications of memory, there might not be a
46 * recognized or standardized API for that specific use. Memory alignment, for
47 * instance, varies wildly depending on operating systems, architectures, and
48 * compilers. Hence, this component of @ref libavutil is created to make
49 * dealing with memory consistently possible on all platforms.
53 * @defgroup lavu_mem_macros Alignment Macros
54 * Helper macros for declaring aligned variables.
59 * @def DECLARE_ALIGNED(n,t,v)
60 * Declare a variable that is aligned in memory.
63 * DECLARE_ALIGNED(16, uint16_t, aligned_int) = 42;
64 * DECLARE_ALIGNED(32, uint8_t, aligned_array)[128];
66 * // The default-alignment equivalent would be
67 * uint16_t aligned_int = 42;
68 * uint8_t aligned_array[128];
71 * @param n Minimum alignment in bytes
72 * @param t Type of the variable (or array element)
73 * @param v Name of the variable
77 * @def DECLARE_ASM_ALIGNED(n,t,v)
78 * Declare an aligned variable appropriate for use in inline assembly code.
81 * DECLARE_ASM_ALIGNED(16, uint64_t, pw_08) = UINT64_C(0x0008000800080008);
84 * @param n Minimum alignment in bytes
85 * @param t Type of the variable (or array element)
86 * @param v Name of the variable
90 * @def DECLARE_ASM_CONST(n,t,v)
91 * Declare a static constant aligned variable appropriate for use in inline
95 * DECLARE_ASM_CONST(16, uint64_t, pw_08) = UINT64_C(0x0008000800080008);
98 * @param n Minimum alignment in bytes
99 * @param t Type of the variable (or array element)
100 * @param v Name of the variable
103 #if defined(__INTEL_COMPILER) && __INTEL_COMPILER < 1110 || defined(__SUNPRO_C)
104 #define DECLARE_ALIGNED(n,t,v) t __attribute__ ((aligned (n))) v
105 #define DECLARE_ASM_ALIGNED(n,t,v) t __attribute__ ((aligned (n))) v
106 #define DECLARE_ASM_CONST(n,t,v) const t __attribute__ ((aligned (n))) v
107 #elif defined(__DJGPP__)
108 #define DECLARE_ALIGNED(n,t,v) t __attribute__ ((aligned (FFMIN(n, 16)))) v
109 #define DECLARE_ASM_ALIGNED(n,t,v) t av_used __attribute__ ((aligned (FFMIN(n, 16)))) v
110 #define DECLARE_ASM_CONST(n,t,v) static const t av_used __attribute__ ((aligned (FFMIN(n, 16)))) v
111 #elif defined(__GNUC__) || defined(__clang__)
112 #define DECLARE_ALIGNED(n,t,v) t __attribute__ ((aligned (n))) v
113 #define DECLARE_ASM_ALIGNED(n,t,v) t av_used __attribute__ ((aligned (n))) v
114 #define DECLARE_ASM_CONST(n,t,v) static const t av_used __attribute__ ((aligned (n))) v
115 #elif defined(_MSC_VER)
116 #define DECLARE_ALIGNED(n,t,v) __declspec(align(n)) t v
117 #define DECLARE_ASM_ALIGNED(n,t,v) __declspec(align(n)) t v
118 #define DECLARE_ASM_CONST(n,t,v) __declspec(align(n)) static const t v
120 #define DECLARE_ALIGNED(n,t,v) t v
121 #define DECLARE_ASM_ALIGNED(n,t,v) t v
122 #define DECLARE_ASM_CONST(n,t,v) static const t v
130 * @defgroup lavu_mem_attrs Function Attributes
131 * Function attributes applicable to memory handling functions.
133 * These function attributes can help compilers emit more useful warnings, or
134 * generate better code.
139 * @def av_malloc_attrib
140 * Function attribute denoting a malloc-like function.
142 * @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>
145 #if AV_GCC_VERSION_AT_LEAST(3,1)
146 #define av_malloc_attrib __attribute__((__malloc__))
148 #define av_malloc_attrib
152 * @def av_alloc_size(...)
153 * Function attribute used on a function that allocates memory, whose size is
154 * given by the specified parameter(s).
157 * void *av_malloc(size_t size) av_alloc_size(1);
158 * void *av_calloc(size_t nmemb, size_t size) av_alloc_size(1, 2);
161 * @param ... One or two parameter indexes, separated by a comma
163 * @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>
166 #if AV_GCC_VERSION_AT_LEAST(4,3)
167 #define av_alloc_size(...) __attribute__((alloc_size(__VA_ARGS__)))
169 #define av_alloc_size(...)
177 * @defgroup lavu_mem_funcs Heap Management
178 * Functions responsible for allocating, freeing, and copying memory.
180 * All memory allocation functions have a built-in upper limit of `INT_MAX`
181 * bytes. This may be changed with av_max_alloc(), although exercise extreme
182 * caution when doing so.
188 * Allocate a memory block with alignment suitable for all memory accesses
189 * (including vectors if available on the CPU).
191 * @param size Size in bytes for the memory block to be allocated
192 * @return Pointer to the allocated block, or `NULL` if the block cannot
196 void *av_malloc(size_t size) av_malloc_attrib av_alloc_size(1);
199 * Allocate a memory block with alignment suitable for all memory accesses
200 * (including vectors if available on the CPU) and zero all the bytes of the
203 * @param size Size in bytes for the memory block to be allocated
204 * @return Pointer to the allocated block, or `NULL` if it cannot be allocated
207 void *av_mallocz(size_t size) av_malloc_attrib av_alloc_size(1);
210 * Allocate a memory block for an array with av_malloc().
212 * The allocated memory will have size `size * nmemb` bytes.
214 * @param nmemb Number of element
215 * @param size Size of a single element
216 * @return Pointer to the allocated block, or `NULL` if the block cannot
220 av_alloc_size(1, 2) void *av_malloc_array(size_t nmemb, size_t size);
223 * Allocate a memory block for an array with av_mallocz().
225 * The allocated memory will have size `size * nmemb` bytes.
227 * @param nmemb Number of elements
228 * @param size Size of the single element
229 * @return Pointer to the allocated block, or `NULL` if the block cannot
233 * @see av_malloc_array()
235 av_alloc_size(1, 2) void *av_mallocz_array(size_t nmemb, size_t size);
238 * Non-inlined equivalent of av_mallocz_array().
240 * Created for symmetry with the calloc() C function.
242 void *av_calloc(size_t nmemb, size_t size) av_malloc_attrib;
245 * Allocate, reallocate, or free a block of memory.
247 * If `ptr` is `NULL` and `size` > 0, allocate a new block. If `size` is
248 * zero, free the memory block pointed to by `ptr`. Otherwise, expand or
249 * shrink that block of memory according to `size`.
251 * @param ptr Pointer to a memory block already allocated with
252 * av_realloc() or `NULL`
253 * @param size Size in bytes of the memory block to be allocated or
256 * @return Pointer to a newly-reallocated block or `NULL` if the block
257 * cannot be reallocated or the function is used to free the memory block
259 * @warning Unlike av_malloc(), the returned pointer is not guaranteed to be
261 * @see av_fast_realloc()
264 void *av_realloc(void *ptr, size_t size) av_alloc_size(2);
267 * Allocate, reallocate, or free a block of memory through a pointer to a
270 * If `*ptr` is `NULL` and `size` > 0, allocate a new block. If `size` is
271 * zero, free the memory block pointed to by `*ptr`. Otherwise, expand or
272 * shrink that block of memory according to `size`.
274 * @param[in,out] ptr Pointer to a pointer to a memory block already allocated
275 * with av_realloc(), or a pointer to `NULL`. The pointer
276 * is updated on success, or freed on failure.
277 * @param[in] size Size in bytes for the memory block to be allocated or
280 * @return Zero on success, an AVERROR error code on failure
282 * @warning Unlike av_malloc(), the allocated memory is not guaranteed to be
285 av_warn_unused_result
286 int av_reallocp(void *ptr, size_t size);
289 * Allocate, reallocate, or free a block of memory.
291 * This function does the same thing as av_realloc(), except:
292 * - It takes two size arguments and allocates `nelem * elsize` bytes,
293 * after checking the result of the multiplication for integer overflow.
294 * - It frees the input block in case of failure, thus avoiding the memory
295 * leak with the classic
297 * buf = realloc(buf);
303 void *av_realloc_f(void *ptr, size_t nelem, size_t elsize);
306 * Allocate, reallocate, or free an array.
308 * If `ptr` is `NULL` and `nmemb` > 0, allocate a new block. If
309 * `nmemb` is zero, free the memory block pointed to by `ptr`.
311 * @param ptr Pointer to a memory block already allocated with
312 * av_realloc() or `NULL`
313 * @param nmemb Number of elements in the array
314 * @param size Size of the single element of the array
316 * @return Pointer to a newly-reallocated block or NULL if the block
317 * cannot be reallocated or the function is used to free the memory block
319 * @warning Unlike av_malloc(), the allocated memory is not guaranteed to be
321 * @see av_reallocp_array()
323 av_alloc_size(2, 3) void *av_realloc_array(void *ptr, size_t nmemb, size_t size);
326 * Allocate, reallocate, or free an array through a pointer to a pointer.
328 * If `*ptr` is `NULL` and `nmemb` > 0, allocate a new block. If `nmemb` is
329 * zero, free the memory block pointed to by `*ptr`.
331 * @param[in,out] ptr Pointer to a pointer to a memory block already
332 * allocated with av_realloc(), or a pointer to `NULL`.
333 * The pointer is updated on success, or freed on failure.
334 * @param[in] nmemb Number of elements
335 * @param[in] size Size of the single element
337 * @return Zero on success, an AVERROR error code on failure
339 * @warning Unlike av_malloc(), the allocated memory is not guaranteed to be
342 int av_reallocp_array(void *ptr, size_t nmemb, size_t size);
345 * Reallocate the given buffer if it is not large enough, otherwise do nothing.
347 * If the given buffer is `NULL`, then a new uninitialized buffer is allocated.
349 * If the given buffer is not large enough, and reallocation fails, `NULL` is
350 * returned and `*size` is set to 0, but the original buffer is not changed or
353 * A typical use pattern follows:
356 * uint8_t *buf = ...;
357 * uint8_t *new_buf = av_fast_realloc(buf, ¤t_size, size_needed);
359 * // Allocation failed; clean up original buffer
361 * return AVERROR(ENOMEM);
365 * @param[in,out] ptr Already allocated buffer, or `NULL`
366 * @param[in,out] size Pointer to the size of buffer `ptr`. `*size` is
367 * updated to the new allocated size, in particular 0
368 * in case of failure.
369 * @param[in] min_size Desired minimal size of buffer `ptr`
370 * @return `ptr` if the buffer is large enough, a pointer to newly reallocated
371 * buffer if the buffer was not large enough, or `NULL` in case of
374 * @see av_fast_malloc()
376 void *av_fast_realloc(void *ptr, unsigned int *size, size_t min_size);
379 * Allocate a buffer, reusing the given one if large enough.
381 * Contrary to av_fast_realloc(), the current buffer contents might not be
382 * preserved and on error the old buffer is freed, thus no special handling to
383 * avoid memleaks is necessary.
385 * `*ptr` is allowed to be `NULL`, in which case allocation always happens if
386 * `size_needed` is greater than 0.
389 * uint8_t *buf = ...;
390 * av_fast_malloc(&buf, ¤t_size, size_needed);
392 * // Allocation failed; buf already freed
393 * return AVERROR(ENOMEM);
397 * @param[in,out] ptr Pointer to pointer to an already allocated buffer.
398 * `*ptr` will be overwritten with pointer to new
399 * buffer on success or `NULL` on failure
400 * @param[in,out] size Pointer to the size of buffer `*ptr`. `*size` is
401 * updated to the new allocated size, in particular 0
402 * in case of failure.
403 * @param[in] min_size Desired minimal size of buffer `*ptr`
405 * @see av_fast_mallocz()
407 void av_fast_malloc(void *ptr, unsigned int *size, size_t min_size);
410 * Allocate and clear a buffer, reusing the given one if large enough.
412 * Like av_fast_malloc(), but all newly allocated space is initially cleared.
413 * Reused buffer is not cleared.
415 * `*ptr` is allowed to be `NULL`, in which case allocation always happens if
416 * `size_needed` is greater than 0.
418 * @param[in,out] ptr Pointer to pointer to an already allocated buffer.
419 * `*ptr` will be overwritten with pointer to new
420 * buffer on success or `NULL` on failure
421 * @param[in,out] size Pointer to the size of buffer `*ptr`. `*size` is
422 * updated to the new allocated size, in particular 0
423 * in case of failure.
424 * @param[in] min_size Desired minimal size of buffer `*ptr`
425 * @see av_fast_malloc()
427 void av_fast_mallocz(void *ptr, unsigned int *size, size_t min_size);
430 * Free a memory block which has been allocated with a function of av_malloc()
431 * or av_realloc() family.
433 * @param ptr Pointer to the memory block which should be freed.
435 * @note `ptr = NULL` is explicitly allowed.
436 * @note It is recommended that you use av_freep() instead, to prevent leaving
437 * behind dangling pointers.
440 void av_free(void *ptr);
443 * Free a memory block which has been allocated with a function of av_malloc()
444 * or av_realloc() family, and set the pointer pointing to it to `NULL`.
447 * uint8_t *buf = av_malloc(16);
449 * // buf now contains a dangling pointer to freed memory, and accidental
450 * // dereference of buf will result in a use-after-free, which may be a
453 * uint8_t *buf = av_malloc(16);
455 * // buf is now NULL, and accidental dereference will only result in a
456 * // NULL-pointer dereference.
459 * @param ptr Pointer to the pointer to the memory block which should be freed
460 * @note `*ptr = NULL` is safe and leads to no action.
463 void av_freep(void *ptr);
466 * Duplicate a string.
468 * @param s String to be duplicated
469 * @return Pointer to a newly-allocated string containing a
470 * copy of `s` or `NULL` if the string cannot be allocated
473 char *av_strdup(const char *s) av_malloc_attrib;
476 * Duplicate a substring of a string.
478 * @param s String to be duplicated
479 * @param len Maximum length of the resulting string (not counting the
481 * @return Pointer to a newly-allocated string containing a
482 * substring of `s` or `NULL` if the string cannot be allocated
484 char *av_strndup(const char *s, size_t len) av_malloc_attrib;
487 * Duplicate a buffer with av_malloc().
489 * @param p Buffer to be duplicated
490 * @param size Size in bytes of the buffer copied
491 * @return Pointer to a newly allocated buffer containing a
492 * copy of `p` or `NULL` if the buffer cannot be allocated
494 void *av_memdup(const void *p, size_t size);
497 * Overlapping memcpy() implementation.
499 * @param dst Destination buffer
500 * @param back Number of bytes back to start copying (i.e. the initial size of
501 * the overlapping window); must be > 0
502 * @param cnt Number of bytes to copy; must be >= 0
504 * @note `cnt > back` is valid, this will copy the bytes we just copied,
505 * thus creating a repeating pattern with a period length of `back`.
507 void av_memcpy_backptr(uint8_t *dst, int back, int cnt);
514 * @defgroup lavu_mem_dynarray Dynamic Array
516 * Utilities to make an array grow when needed.
518 * Sometimes, the programmer would want to have an array that can grow when
519 * needed. The libavutil dynamic array utilities fill that need.
521 * libavutil supports two systems of appending elements onto a dynamically
522 * allocated array, the first one storing the pointer to the value in the
523 * array, and the second storing the value directly. In both systems, the
524 * caller is responsible for maintaining a variable containing the length of
525 * the array, as well as freeing of the array after use.
527 * The first system stores pointers to values in a block of dynamically
528 * allocated memory. Since only pointers are stored, the function does not need
529 * to know the size of the type. Both av_dynarray_add() and
530 * av_dynarray_add_nofree() implement this system.
533 * type **array = NULL; //< an array of pointers to values
534 * int nb = 0; //< a variable to keep track of the length of the array
536 * type to_be_added = ...;
537 * type to_be_added2 = ...;
539 * av_dynarray_add(&array, &nb, &to_be_added);
541 * return AVERROR(ENOMEM);
543 * av_dynarray_add(&array, &nb, &to_be_added2);
545 * return AVERROR(ENOMEM);
549 * // &to_be_added == array[0]
550 * // &to_be_added2 == array[1]
555 * The second system stores the value directly in a block of memory. As a
556 * result, the function has to know the size of the type. av_dynarray2_add()
557 * implements this mechanism.
560 * type *array = NULL; //< an array of values
561 * int nb = 0; //< a variable to keep track of the length of the array
563 * type to_be_added = ...;
564 * type to_be_added2 = ...;
566 * type *addr = av_dynarray2_add((void **)&array, &nb, sizeof(*array), NULL);
568 * return AVERROR(ENOMEM);
569 * memcpy(addr, &to_be_added, sizeof(to_be_added));
571 * // Shortcut of the above.
572 * type *addr = av_dynarray2_add((void **)&array, &nb, sizeof(*array),
573 * (const void *)&to_be_added2);
575 * return AVERROR(ENOMEM);
579 * // to_be_added == array[0]
580 * // to_be_added2 == array[1]
589 * Add the pointer to an element to a dynamic array.
591 * The array to grow is supposed to be an array of pointers to
592 * structures, and the element to add must be a pointer to an already
593 * allocated structure.
595 * The array is reallocated when its size reaches powers of 2.
596 * Therefore, the amortized cost of adding an element is constant.
598 * In case of success, the pointer to the array is updated in order to
599 * point to the new grown array, and the number pointed to by `nb_ptr`
601 * In case of failure, the array is freed, `*tab_ptr` is set to `NULL` and
602 * `*nb_ptr` is set to 0.
604 * @param[in,out] tab_ptr Pointer to the array to grow
605 * @param[in,out] nb_ptr Pointer to the number of elements in the array
606 * @param[in] elem Element to add
607 * @see av_dynarray_add_nofree(), av_dynarray2_add()
609 void av_dynarray_add(void *tab_ptr, int *nb_ptr, void *elem);
612 * Add an element to a dynamic array.
614 * Function has the same functionality as av_dynarray_add(),
615 * but it doesn't free memory on fails. It returns error code
616 * instead and leave current buffer untouched.
618 * @return >=0 on success, negative otherwise
619 * @see av_dynarray_add(), av_dynarray2_add()
621 av_warn_unused_result
622 int av_dynarray_add_nofree(void *tab_ptr, int *nb_ptr, void *elem);
625 * Add an element of size `elem_size` to a dynamic array.
627 * The array is reallocated when its number of elements reaches powers of 2.
628 * Therefore, the amortized cost of adding an element is constant.
630 * In case of success, the pointer to the array is updated in order to
631 * point to the new grown array, and the number pointed to by `nb_ptr`
633 * In case of failure, the array is freed, `*tab_ptr` is set to `NULL` and
634 * `*nb_ptr` is set to 0.
636 * @param[in,out] tab_ptr Pointer to the array to grow
637 * @param[in,out] nb_ptr Pointer to the number of elements in the array
638 * @param[in] elem_size Size in bytes of an element in the array
639 * @param[in] elem_data Pointer to the data of the element to add. If
640 * `NULL`, the space of the newly added element is
641 * allocated but left uninitialized.
643 * @return Pointer to the data of the element to copy in the newly allocated
645 * @see av_dynarray_add(), av_dynarray_add_nofree()
647 void *av_dynarray2_add(void **tab_ptr, int *nb_ptr, size_t elem_size,
648 const uint8_t *elem_data);
655 * @defgroup lavu_mem_misc Miscellaneous Functions
657 * Other functions related to memory allocation.
663 * Multiply two `size_t` values checking for overflow.
665 * @param[in] a,b Operands of multiplication
666 * @param[out] r Pointer to the result of the operation
667 * @return 0 on success, AVERROR(EINVAL) on overflow
669 static inline int av_size_mult(size_t a, size_t b, size_t *r)
672 /* Hack inspired from glibc: don't try the division if nelem and elsize
673 * are both less than sqrt(SIZE_MAX). */
674 if ((a | b) >= ((size_t)1 << (sizeof(size_t) * 4)) && a && t / a != b)
675 return AVERROR(EINVAL);
681 * Set the maximum size that may be allocated in one block.
683 * The value specified with this function is effective for all libavutil's @ref
684 * lavu_mem_funcs "heap management functions."
686 * By default, the max value is defined as `INT_MAX`.
688 * @param max Value to be set as the new maximum size
690 * @warning Exercise extreme caution when using this function. Don't touch
691 * this if you do not understand the full consequence of doing so.
693 void av_max_alloc(size_t max);
700 #endif /* AVUTIL_MEM_H */