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mem.h
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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 
37 /**
38  * @addtogroup lavu_mem
39  * Utilities for manipulating memory.
40  *
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.
44  *
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.
50  *
51  * @{
52  *
53  * @defgroup lavu_mem_macros Alignment Macros
54  * Helper macros for declaring aligned variables.
55  * @{
56  */
57 
58 /**
59  * @def DECLARE_ALIGNED(n,t,v)
60  * Declare a variable that is aligned in memory.
61  *
62  * @code{.c}
63  * DECLARE_ALIGNED(16, uint16_t, aligned_int) = 42;
64  * DECLARE_ALIGNED(32, uint8_t, aligned_array)[128];
65  *
66  * // The default-alignment equivalent would be
67  * uint16_t aligned_int = 42;
68  * uint8_t aligned_array[128];
69  * @endcode
70  *
71  * @param n Minimum alignment in bytes
72  * @param t Type of the variable (or array element)
73  * @param v Name of the variable
74  */
75 
76 /**
77  * @def DECLARE_ASM_ALIGNED(n,t,v)
78  * Declare an aligned variable appropriate for use in inline assembly code.
79  *
80  * @code{.c}
81  * DECLARE_ASM_ALIGNED(16, uint64_t, pw_08) = UINT64_C(0x0008000800080008);
82  * @endcode
83  *
84  * @param n Minimum alignment in bytes
85  * @param t Type of the variable (or array element)
86  * @param v Name of the variable
87  */
88 
89 /**
90  * @def DECLARE_ASM_CONST(n,t,v)
91  * Declare a static constant aligned variable appropriate for use in inline
92  * assembly code.
93  *
94  * @code{.c}
95  * DECLARE_ASM_CONST(16, uint64_t, pw_08) = UINT64_C(0x0008000800080008);
96  * @endcode
97  *
98  * @param n Minimum alignment in bytes
99  * @param t Type of the variable (or array element)
100  * @param v Name of the variable
101  */
102 
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_CONST(n,t,v) static const t av_used __attribute__ ((aligned (FFMIN(n, 16)))) v
110 #elif defined(__GNUC__) || defined(__clang__)
111  #define DECLARE_ALIGNED(n,t,v) t __attribute__ ((aligned (n))) v
112  #define DECLARE_ASM_ALIGNED(n,t,v) t av_used __attribute__ ((aligned (n))) v
113  #define DECLARE_ASM_CONST(n,t,v) static const t av_used __attribute__ ((aligned (n))) v
114 #elif defined(_MSC_VER)
115  #define DECLARE_ALIGNED(n,t,v) __declspec(align(n)) t v
116  #define DECLARE_ASM_ALIGNED(n,t,v) __declspec(align(n)) t v
117  #define DECLARE_ASM_CONST(n,t,v) __declspec(align(n)) static const t v
118 #else
119  #define DECLARE_ALIGNED(n,t,v) t v
120  #define DECLARE_ASM_ALIGNED(n,t,v) t v
121  #define DECLARE_ASM_CONST(n,t,v) static const t v
122 #endif
123 
124 /**
125  * @}
126  */
127 
128 /**
129  * @defgroup lavu_mem_attrs Function Attributes
130  * Function attributes applicable to memory handling functions.
131  *
132  * These function attributes can help compilers emit more useful warnings, or
133  * generate better code.
134  * @{
135  */
136 
137 /**
138  * @def av_malloc_attrib
139  * Function attribute denoting a malloc-like function.
140  *
141  * @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>
142  */
143 
144 #if AV_GCC_VERSION_AT_LEAST(3,1)
145  #define av_malloc_attrib __attribute__((__malloc__))
146 #else
147  #define av_malloc_attrib
148 #endif
149 
150 /**
151  * @def av_alloc_size(...)
152  * Function attribute used on a function that allocates memory, whose size is
153  * given by the specified parameter(s).
154  *
155  * @code{.c}
156  * void *av_malloc(size_t size) av_alloc_size(1);
157  * void *av_calloc(size_t nmemb, size_t size) av_alloc_size(1, 2);
158  * @endcode
159  *
160  * @param ... One or two parameter indexes, separated by a comma
161  *
162  * @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>
163  */
164 
165 #if AV_GCC_VERSION_AT_LEAST(4,3)
166  #define av_alloc_size(...) __attribute__((alloc_size(__VA_ARGS__)))
167 #else
168  #define av_alloc_size(...)
169 #endif
170 
171 /**
172  * @}
173  */
174 
175 /**
176  * @defgroup lavu_mem_funcs Heap Management
177  * Functions responsible for allocating, freeing, and copying memory.
178  *
179  * All memory allocation functions have a built-in upper limit of `INT_MAX`
180  * bytes. This may be changed with av_max_alloc(), although exercise extreme
181  * caution when doing so.
182  *
183  * @{
184  */
185 
186 /**
187  * Allocate a memory block with alignment suitable for all memory accesses
188  * (including vectors if available on the CPU).
189  *
190  * @param size Size in bytes for the memory block to be allocated
191  * @return Pointer to the allocated block, or `NULL` if the block cannot
192  * be allocated
193  * @see av_mallocz()
194  */
196 
197 /**
198  * Allocate a memory block with alignment suitable for all memory accesses
199  * (including vectors if available on the CPU) and zero all the bytes of the
200  * block.
201  *
202  * @param size Size in bytes for the memory block to be allocated
203  * @return Pointer to the allocated block, or `NULL` if it cannot be allocated
204  * @see av_malloc()
205  */
207 
208 /**
209  * Allocate a memory block for an array with av_malloc().
210  *
211  * The allocated memory will have size `size * nmemb` bytes.
212  *
213  * @param nmemb Number of element
214  * @param size Size of a single element
215  * @return Pointer to the allocated block, or `NULL` if the block cannot
216  * be allocated
217  * @see av_malloc()
218  */
219 av_alloc_size(1, 2) void *av_malloc_array(size_t nmemb, size_t size);
220 
221 /**
222  * Allocate a memory block for an array with av_mallocz().
223  *
224  * The allocated memory will have size `size * nmemb` bytes.
225  *
226  * @param nmemb Number of elements
227  * @param size Size of the single element
228  * @return Pointer to the allocated block, or `NULL` if the block cannot
229  * be allocated
230  *
231  * @see av_mallocz()
232  * @see av_malloc_array()
233  */
234 av_alloc_size(1, 2) void *av_mallocz_array(size_t nmemb, size_t size);
235 
236 /**
237  * Non-inlined equivalent of av_mallocz_array().
238  *
239  * Created for symmetry with the calloc() C function.
240  */
241 void *av_calloc(size_t nmemb, size_t size) av_malloc_attrib;
242 
243 /**
244  * Allocate, reallocate, or free a block of memory.
245  *
246  * If `ptr` is `NULL` and `size` > 0, allocate a new block. If `size` is
247  * zero, free the memory block pointed to by `ptr`. Otherwise, expand or
248  * shrink that block of memory according to `size`.
249  *
250  * @param ptr Pointer to a memory block already allocated with
251  * av_realloc() or `NULL`
252  * @param size Size in bytes of the memory block to be allocated or
253  * reallocated
254  *
255  * @return Pointer to a newly-reallocated block or `NULL` if the block
256  * cannot be reallocated or the function is used to free the memory block
257  *
258  * @warning Unlike av_malloc(), the returned pointer is not guaranteed to be
259  * correctly aligned.
260  * @see av_fast_realloc()
261  * @see av_reallocp()
262  */
263 void *av_realloc(void *ptr, size_t size) av_alloc_size(2);
264 
265 /**
266  * Allocate, reallocate, or free a block of memory through a pointer to a
267  * pointer.
268  *
269  * If `*ptr` is `NULL` and `size` > 0, allocate a new block. If `size` is
270  * zero, free the memory block pointed to by `*ptr`. Otherwise, expand or
271  * shrink that block of memory according to `size`.
272  *
273  * @param[in,out] ptr Pointer to a pointer to a memory block already allocated
274  * with av_realloc(), or a pointer to `NULL`. The pointer
275  * is updated on success, or freed on failure.
276  * @param[in] size Size in bytes for the memory block to be allocated or
277  * reallocated
278  *
279  * @return Zero on success, an AVERROR error code on failure
280  *
281  * @warning Unlike av_malloc(), the allocated memory is not guaranteed to be
282  * correctly aligned.
283  */
285 int av_reallocp(void *ptr, size_t size);
286 
287 /**
288  * Allocate, reallocate, or free a block of memory.
289  *
290  * This function does the same thing as av_realloc(), except:
291  * - It takes two size arguments and allocates `nelem * elsize` bytes,
292  * after checking the result of the multiplication for integer overflow.
293  * - It frees the input block in case of failure, thus avoiding the memory
294  * leak with the classic
295  * @code{.c}
296  * buf = realloc(buf);
297  * if (!buf)
298  * return -1;
299  * @endcode
300  * pattern.
301  */
302 void *av_realloc_f(void *ptr, size_t nelem, size_t elsize);
303 
304 /**
305  * Allocate, reallocate, or free an array.
306  *
307  * If `ptr` is `NULL` and `nmemb` > 0, allocate a new block. If
308  * `nmemb` is zero, free the memory block pointed to by `ptr`.
309  *
310  * @param ptr Pointer to a memory block already allocated with
311  * av_realloc() or `NULL`
312  * @param nmemb Number of elements in the array
313  * @param size Size of the single element of the array
314  *
315  * @return Pointer to a newly-reallocated block or NULL if the block
316  * cannot be reallocated or the function is used to free the memory block
317  *
318  * @warning Unlike av_malloc(), the allocated memory is not guaranteed to be
319  * correctly aligned.
320  * @see av_reallocp_array()
321  */
322 av_alloc_size(2, 3) void *av_realloc_array(void *ptr, size_t nmemb, size_t size);
323 
324 /**
325  * Allocate, reallocate, or free an array through a pointer to a pointer.
326  *
327  * If `*ptr` is `NULL` and `nmemb` > 0, allocate a new block. If `nmemb` is
328  * zero, free the memory block pointed to by `*ptr`.
329  *
330  * @param[in,out] ptr Pointer to a pointer to a memory block already
331  * allocated with av_realloc(), or a pointer to `NULL`.
332  * The pointer is updated on success, or freed on failure.
333  * @param[in] nmemb Number of elements
334  * @param[in] size Size of the single element
335  *
336  * @return Zero on success, an AVERROR error code on failure
337  *
338  * @warning Unlike av_malloc(), the allocated memory is not guaranteed to be
339  * correctly aligned.
340  */
341 av_alloc_size(2, 3) int av_reallocp_array(void *ptr, size_t nmemb, size_t size);
342 
343 /**
344  * Reallocate the given buffer if it is not large enough, otherwise do nothing.
345  *
346  * If the given buffer is `NULL`, then a new uninitialized buffer is allocated.
347  *
348  * If the given buffer is not large enough, and reallocation fails, `NULL` is
349  * returned and `*size` is set to 0, but the original buffer is not changed or
350  * freed.
351  *
352  * A typical use pattern follows:
353  *
354  * @code{.c}
355  * uint8_t *buf = ...;
356  * uint8_t *new_buf = av_fast_realloc(buf, &current_size, size_needed);
357  * if (!new_buf) {
358  * // Allocation failed; clean up original buffer
359  * av_freep(&buf);
360  * return AVERROR(ENOMEM);
361  * }
362  * @endcode
363  *
364  * @param[in,out] ptr Already allocated buffer, or `NULL`
365  * @param[in,out] size Pointer to current size of buffer `ptr`. `*size` is
366  * changed to `min_size` in case of success or 0 in
367  * case of failure
368  * @param[in] min_size New size of buffer `ptr`
369  * @return `ptr` if the buffer is large enough, a pointer to newly reallocated
370  * buffer if the buffer was not large enough, or `NULL` in case of
371  * error
372  * @see av_realloc()
373  * @see av_fast_malloc()
374  */
375 void *av_fast_realloc(void *ptr, unsigned int *size, size_t min_size);
376 
377 /**
378  * Allocate a buffer, reusing the given one if large enough.
379  *
380  * Contrary to av_fast_realloc(), the current buffer contents might not be
381  * preserved and on error the old buffer is freed, thus no special handling to
382  * avoid memleaks is necessary.
383  *
384  * `*ptr` is allowed to be `NULL`, in which case allocation always happens if
385  * `size_needed` is greater than 0.
386  *
387  * @code{.c}
388  * uint8_t *buf = ...;
389  * av_fast_malloc(&buf, &current_size, size_needed);
390  * if (!buf) {
391  * // Allocation failed; buf already freed
392  * return AVERROR(ENOMEM);
393  * }
394  * @endcode
395  *
396  * @param[in,out] ptr Pointer to pointer to an already allocated buffer.
397  * `*ptr` will be overwritten with pointer to new
398  * buffer on success or `NULL` on failure
399  * @param[in,out] size Pointer to current size of buffer `*ptr`. `*size` is
400  * changed to `min_size` in case of success or 0 in
401  * case of failure
402  * @param[in] min_size New size of buffer `*ptr`
403  * @see av_realloc()
404  * @see av_fast_mallocz()
405  */
406 void av_fast_malloc(void *ptr, unsigned int *size, size_t min_size);
407 
408 /**
409  * Allocate and clear a buffer, reusing the given one if large enough.
410  *
411  * Like av_fast_malloc(), but all newly allocated space is initially cleared.
412  * Reused buffer is not cleared.
413  *
414  * `*ptr` is allowed to be `NULL`, in which case allocation always happens if
415  * `size_needed` is greater than 0.
416  *
417  * @param[in,out] ptr Pointer to pointer to an already allocated buffer.
418  * `*ptr` will be overwritten with pointer to new
419  * buffer on success or `NULL` on failure
420  * @param[in,out] size Pointer to current size of buffer `*ptr`. `*size` is
421  * changed to `min_size` in case of success or 0 in
422  * case of failure
423  * @param[in] min_size New size of buffer `*ptr`
424  * @see av_fast_malloc()
425  */
426 void av_fast_mallocz(void *ptr, unsigned int *size, size_t min_size);
427 
428 /**
429  * Free a memory block which has been allocated with a function of av_malloc()
430  * or av_realloc() family.
431  *
432  * @param ptr Pointer to the memory block which should be freed.
433  *
434  * @note `ptr = NULL` is explicitly allowed.
435  * @note It is recommended that you use av_freep() instead, to prevent leaving
436  * behind dangling pointers.
437  * @see av_freep()
438  */
439 void av_free(void *ptr);
440 
441 /**
442  * Free a memory block which has been allocated with a function of av_malloc()
443  * or av_realloc() family, and set the pointer pointing to it to `NULL`.
444  *
445  * @code{.c}
446  * uint8_t *buf = av_malloc(16);
447  * av_free(buf);
448  * // buf now contains a dangling pointer to freed memory, and accidental
449  * // dereference of buf will result in a use-after-free, which may be a
450  * // security risk.
451  *
452  * uint8_t *buf = av_malloc(16);
453  * av_freep(&buf);
454  * // buf is now NULL, and accidental dereference will only result in a
455  * // NULL-pointer dereference.
456  * @endcode
457  *
458  * @param ptr Pointer to the pointer to the memory block which should be freed
459  * @note `*ptr = NULL` is safe and leads to no action.
460  * @see av_free()
461  */
462 void av_freep(void *ptr);
463 
464 /**
465  * Duplicate a string.
466  *
467  * @param s String to be duplicated
468  * @return Pointer to a newly-allocated string containing a
469  * copy of `s` or `NULL` if the string cannot be allocated
470  * @see av_strndup()
471  */
472 char *av_strdup(const char *s) av_malloc_attrib;
473 
474 /**
475  * Duplicate a substring of a string.
476  *
477  * @param s String to be duplicated
478  * @param len Maximum length of the resulting string (not counting the
479  * terminating byte)
480  * @return Pointer to a newly-allocated string containing a
481  * substring of `s` or `NULL` if the string cannot be allocated
482  */
483 char *av_strndup(const char *s, size_t len) av_malloc_attrib;
484 
485 /**
486  * Duplicate a buffer with av_malloc().
487  *
488  * @param p Buffer to be duplicated
489  * @param size Size in bytes of the buffer copied
490  * @return Pointer to a newly allocated buffer containing a
491  * copy of `p` or `NULL` if the buffer cannot be allocated
492  */
493 void *av_memdup(const void *p, size_t size);
494 
495 /**
496  * Overlapping memcpy() implementation.
497  *
498  * @param dst Destination buffer
499  * @param back Number of bytes back to start copying (i.e. the initial size of
500  * the overlapping window); must be > 0
501  * @param cnt Number of bytes to copy; must be >= 0
502  *
503  * @note `cnt > back` is valid, this will copy the bytes we just copied,
504  * thus creating a repeating pattern with a period length of `back`.
505  */
506 void av_memcpy_backptr(uint8_t *dst, int back, int cnt);
507 
508 /**
509  * @}
510  */
511 
512 /**
513  * @defgroup lavu_mem_dynarray Dynamic Array
514  *
515  * Utilities to make an array grow when needed.
516  *
517  * Sometimes, the programmer would want to have an array that can grow when
518  * needed. The libavutil dynamic array utilities fill that need.
519  *
520  * libavutil supports two systems of appending elements onto a dynamically
521  * allocated array, the first one storing the pointer to the value in the
522  * array, and the second storing the value directly. In both systems, the
523  * caller is responsible for maintaining a variable containing the length of
524  * the array, as well as freeing of the array after use.
525  *
526  * The first system stores pointers to values in a block of dynamically
527  * allocated memory. Since only pointers are stored, the function does not need
528  * to know the size of the type. Both av_dynarray_add() and
529  * av_dynarray_add_nofree() implement this system.
530  *
531  * @code
532  * type **array = NULL; //< an array of pointers to values
533  * int nb = 0; //< a variable to keep track of the length of the array
534  *
535  * type to_be_added = ...;
536  * type to_be_added2 = ...;
537  *
538  * av_dynarray_add(&array, &nb, &to_be_added);
539  * if (nb == 0)
540  * return AVERROR(ENOMEM);
541  *
542  * av_dynarray_add(&array, &nb, &to_be_added2);
543  * if (nb == 0)
544  * return AVERROR(ENOMEM);
545  *
546  * // Now:
547  * // nb == 2
548  * // &to_be_added == array[0]
549  * // &to_be_added2 == array[1]
550  *
551  * av_freep(&array);
552  * @endcode
553  *
554  * The second system stores the value directly in a block of memory. As a
555  * result, the function has to know the size of the type. av_dynarray2_add()
556  * implements this mechanism.
557  *
558  * @code
559  * type *array = NULL; //< an array of values
560  * int nb = 0; //< a variable to keep track of the length of the array
561  *
562  * type to_be_added = ...;
563  * type to_be_added2 = ...;
564  *
565  * type *addr = av_dynarray2_add((void **)&array, &nb, sizeof(*array), NULL);
566  * if (!addr)
567  * return AVERROR(ENOMEM);
568  * memcpy(addr, &to_be_added, sizeof(to_be_added));
569  *
570  * // Shortcut of the above.
571  * type *addr = av_dynarray2_add((void **)&array, &nb, sizeof(*array),
572  * (const void *)&to_be_added2);
573  * if (!addr)
574  * return AVERROR(ENOMEM);
575  *
576  * // Now:
577  * // nb == 2
578  * // to_be_added == array[0]
579  * // to_be_added2 == array[1]
580  *
581  * av_freep(&array);
582  * @endcode
583  *
584  * @{
585  */
586 
587 /**
588  * Add the pointer to an element to a dynamic array.
589  *
590  * The array to grow is supposed to be an array of pointers to
591  * structures, and the element to add must be a pointer to an already
592  * allocated structure.
593  *
594  * The array is reallocated when its size reaches powers of 2.
595  * Therefore, the amortized cost of adding an element is constant.
596  *
597  * In case of success, the pointer to the array is updated in order to
598  * point to the new grown array, and the number pointed to by `nb_ptr`
599  * is incremented.
600  * In case of failure, the array is freed, `*tab_ptr` is set to `NULL` and
601  * `*nb_ptr` is set to 0.
602  *
603  * @param[in,out] tab_ptr Pointer to the array to grow
604  * @param[in,out] nb_ptr Pointer to the number of elements in the array
605  * @param[in] elem Element to add
606  * @see av_dynarray_add_nofree(), av_dynarray2_add()
607  */
608 void av_dynarray_add(void *tab_ptr, int *nb_ptr, void *elem);
609 
610 /**
611  * Add an element to a dynamic array.
612  *
613  * Function has the same functionality as av_dynarray_add(),
614  * but it doesn't free memory on fails. It returns error code
615  * instead and leave current buffer untouched.
616  *
617  * @return >=0 on success, negative otherwise
618  * @see av_dynarray_add(), av_dynarray2_add()
619  */
621 int av_dynarray_add_nofree(void *tab_ptr, int *nb_ptr, void *elem);
622 
623 /**
624  * Add an element of size `elem_size` to a dynamic array.
625  *
626  * The array is reallocated when its number of elements reaches powers of 2.
627  * Therefore, the amortized cost of adding an element is constant.
628  *
629  * In case of success, the pointer to the array is updated in order to
630  * point to the new grown array, and the number pointed to by `nb_ptr`
631  * is incremented.
632  * In case of failure, the array is freed, `*tab_ptr` is set to `NULL` and
633  * `*nb_ptr` is set to 0.
634  *
635  * @param[in,out] tab_ptr Pointer to the array to grow
636  * @param[in,out] nb_ptr Pointer to the number of elements in the array
637  * @param[in] elem_size Size in bytes of an element in the array
638  * @param[in] elem_data Pointer to the data of the element to add. If
639  * `NULL`, the space of the newly added element is
640  * allocated but left uninitialized.
641  *
642  * @return Pointer to the data of the element to copy in the newly allocated
643  * space
644  * @see av_dynarray_add(), av_dynarray_add_nofree()
645  */
646 void *av_dynarray2_add(void **tab_ptr, int *nb_ptr, size_t elem_size,
647  const uint8_t *elem_data);
648 
649 /**
650  * @}
651  */
652 
653 /**
654  * @defgroup lavu_mem_misc Miscellaneous Functions
655  *
656  * Other functions related to memory allocation.
657  *
658  * @{
659  */
660 
661 /**
662  * Multiply two `size_t` values checking for overflow.
663  *
664  * @param[in] a,b Operands of multiplication
665  * @param[out] r Pointer to the result of the operation
666  * @return 0 on success, AVERROR(EINVAL) on overflow
667  */
668 static inline int av_size_mult(size_t a, size_t b, size_t *r)
669 {
670  size_t t = a * b;
671  /* Hack inspired from glibc: don't try the division if nelem and elsize
672  * are both less than sqrt(SIZE_MAX). */
673  if ((a | b) >= ((size_t)1 << (sizeof(size_t) * 4)) && a && t / a != b)
674  return AVERROR(EINVAL);
675  *r = t;
676  return 0;
677 }
678 
679 /**
680  * Set the maximum size that may be allocated in one block.
681  *
682  * The value specified with this function is effective for all libavutil's @ref
683  * lavu_mem_funcs "heap management functions."
684  *
685  * By default, the max value is defined as `INT_MAX`.
686  *
687  * @param max Value to be set as the new maximum size
688  *
689  * @warning Exercise extreme caution when using this function. Don't touch
690  * this if you do not understand the full consequence of doing so.
691  */
692 void av_max_alloc(size_t max);
693 
694 /**
695  * @}
696  * @}
697  */
698 
699 #endif /* AVUTIL_MEM_H */
void * av_realloc_f(void *ptr, size_t nelem, size_t elsize)
Allocate, reallocate, or free a block of memory.
Definition: mem.c:148
const char * s
Definition: avisynth_c.h:768
void av_max_alloc(size_t max)
Set the maximum size that may be allocated in one block.
Definition: mem.c:73
void * av_realloc(void *ptr, size_t size) 1(2)
Allocate, reallocate, or free a block of memory.
Definition: mem.c:135
const char * b
Definition: vf_curves.c:113
#define av_malloc_attrib
Function attribute denoting a malloc-like function.
Definition: mem.h:145
Convenience header that includes libavutil's core.
void * av_mallocz(size_t size) av_malloc_attrib 1(1)
Allocate a memory block with alignment suitable for all memory accesses (including vectors if availab...
Definition: mem.c:236
Macro definitions for various function/variable attributes.
void * av_calloc(size_t nmemb, size_t size) av_malloc_attrib
Non-inlined equivalent of av_mallocz_array().
Definition: mem.c:244
uint8_t
void av_memcpy_backptr(uint8_t *dst, int back, int cnt)
Overlapping memcpy() implementation.
Definition: mem.c:414
av_warn_unused_result int av_dynarray_add_nofree(void *tab_ptr, int *nb_ptr, void *elem)
Add an element to a dynamic array.
Definition: mem.c:294
ptrdiff_t size
Definition: opengl_enc.c:101
void * av_realloc_array(void *ptr, size_t nmemb, size_t size)
Definition: mem.c:198
error code definitions
#define AVERROR(e)
Definition: error.h:43
void av_freep(void *ptr)
Free a memory block which has been allocated with a function of av_malloc() or av_realloc() family...
Definition: mem.c:227
const char * r
Definition: vf_curves.c:111
void * av_memdup(const void *p, size_t size)
Duplicate a buffer with av_malloc().
Definition: mem.c:283
int av_reallocp_array(void *ptr, size_t nmemb, size_t size)
Definition: mem.c:205
void av_fast_malloc(void *ptr, unsigned int *size, size_t min_size)
Allocate a buffer, reusing the given one if large enough.
Definition: mem.c:483
void * av_malloc_array(size_t nmemb, size_t size)
Definition: mem.c:184
void av_fast_mallocz(void *ptr, unsigned int *size, size_t min_size)
Allocate and clear a buffer, reusing the given one if large enough.
Definition: mem.c:488
typedef void(APIENTRY *FF_PFNGLACTIVETEXTUREPROC)(GLenum texture)
void * av_fast_realloc(void *ptr, unsigned int *size, size_t min_size)
Reallocate the given buffer if it is not large enough, otherwise do nothing.
Definition: mem.c:464
av_warn_unused_result int av_reallocp(void *ptr, size_t size)
Allocate, reallocate, or free a block of memory through a pointer to a pointer.
Definition: mem.c:163
char * av_strdup(const char *s) av_malloc_attrib
Duplicate a string.
Definition: mem.c:251
void * av_dynarray2_add(void **tab_ptr, int *nb_ptr, size_t elem_size, const uint8_t *elem_data)
Add an element of size elem_size to a dynamic array.
Definition: mem.c:322
void av_free(void *ptr)
Free a memory block which has been allocated with a function of av_malloc() or av_realloc() family...
Definition: mem.c:218
#define av_warn_unused_result
Definition: attributes.h:56
void * av_malloc(size_t size) av_malloc_attrib 1(1)
Allocate a memory block with alignment suitable for all memory accesses (including vectors if availab...
Definition: mem.c:77
#define av_alloc_size(...)
Function attribute used on a function that allocates memory, whose size is given by the specified par...
Definition: mem.h:166
static int av_size_mult(size_t a, size_t b, size_t *r)
Multiply two size_t values checking for overflow.
Definition: mem.h:668
void av_dynarray_add(void *tab_ptr, int *nb_ptr, void *elem)
Add the pointer to an element to a dynamic array.
Definition: mem.c:308
int len
char * av_strndup(const char *s, size_t len) av_malloc_attrib
Duplicate a substring of a string.
Definition: mem.c:263
void * av_mallocz_array(size_t nmemb, size_t size)
Definition: mem.c:191