FFmpeg
 All Data Structures Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
mem.h
Go to the documentation of this file.
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  * memory handling functions
24  */
25 
26 #ifndef AVUTIL_MEM_H
27 #define AVUTIL_MEM_H
28 
29 #include <limits.h>
30 #include <stdint.h>
31 
32 #include "attributes.h"
33 #include "error.h"
34 #include "avutil.h"
35 
36 /**
37  * @addtogroup lavu_mem
38  * @{
39  */
40 
41 
42 #if defined(__INTEL_COMPILER) && __INTEL_COMPILER < 1110 || defined(__SUNPRO_C)
43  #define DECLARE_ALIGNED(n,t,v) t __attribute__ ((aligned (n))) v
44  #define DECLARE_ASM_CONST(n,t,v) const t __attribute__ ((aligned (n))) v
45 #elif defined(__TI_COMPILER_VERSION__)
46  #define DECLARE_ALIGNED(n,t,v) \
47  AV_PRAGMA(DATA_ALIGN(v,n)) \
48  t __attribute__((aligned(n))) v
49  #define DECLARE_ASM_CONST(n,t,v) \
50  AV_PRAGMA(DATA_ALIGN(v,n)) \
51  static const t __attribute__((aligned(n))) v
52 #elif defined(__GNUC__)
53  #define DECLARE_ALIGNED(n,t,v) t __attribute__ ((aligned (n))) v
54  #define DECLARE_ASM_CONST(n,t,v) static const t av_used __attribute__ ((aligned (n))) v
55 #elif defined(_MSC_VER)
56  #define DECLARE_ALIGNED(n,t,v) __declspec(align(n)) t v
57  #define DECLARE_ASM_CONST(n,t,v) __declspec(align(n)) static const t v
58 #else
59  #define DECLARE_ALIGNED(n,t,v) t v
60  #define DECLARE_ASM_CONST(n,t,v) static const t v
61 #endif
62 
63 #if AV_GCC_VERSION_AT_LEAST(3,1)
64  #define av_malloc_attrib __attribute__((__malloc__))
65 #else
66  #define av_malloc_attrib
67 #endif
68 
69 #if AV_GCC_VERSION_AT_LEAST(4,3)
70  #define av_alloc_size(...) __attribute__((alloc_size(__VA_ARGS__)))
71 #else
72  #define av_alloc_size(...)
73 #endif
74 
75 /**
76  * Allocate a block of size bytes with alignment suitable for all
77  * memory accesses (including vectors if available on the CPU).
78  * @param size Size in bytes for the memory block to be allocated.
79  * @return Pointer to the allocated block, NULL if the block cannot
80  * be allocated.
81  * @see av_mallocz()
82  */
84 
85 /**
86  * Helper function to allocate a block of size * nmemb bytes with
87  * using av_malloc()
88  * @param nmemb Number of elements
89  * @param size Size of the single element
90  * @return Pointer to the allocated block, NULL if the block cannot
91  * be allocated.
92  * @see av_malloc()
93  */
94 av_alloc_size(1, 2) static inline void *av_malloc_array(size_t nmemb, size_t size)
95 {
96  if (size <= 0 || nmemb >= INT_MAX / size)
97  return NULL;
98  return av_malloc(nmemb * size);
99 }
100 
101 /**
102  * Allocate or reallocate a block of memory.
103  * If ptr is NULL and size > 0, allocate a new block. If
104  * size is zero, free the memory block pointed to by ptr.
105  * @param ptr Pointer to a memory block already allocated with
106  * av_malloc(z)() or av_realloc() or NULL.
107  * @param size Size in bytes for the memory block to be allocated or
108  * reallocated.
109  * @return Pointer to a newly reallocated block or NULL if the block
110  * cannot be reallocated or the function is used to free the memory block.
111  * @see av_fast_realloc()
112  */
113 void *av_realloc(void *ptr, size_t size) av_alloc_size(2);
114 
115 /**
116  * Allocate or reallocate a block of memory.
117  * This function does the same thing as av_realloc, except:
118  * - It takes two arguments and checks the result of the multiplication for
119  * integer overflow.
120  * - It frees the input block in case of failure, thus avoiding the memory
121  * leak with the classic "buf = realloc(buf); if (!buf) return -1;".
122  */
123 void *av_realloc_f(void *ptr, size_t nelem, size_t elsize);
124 
125 /**
126  * Free a memory block which has been allocated with av_malloc(z)() or
127  * av_realloc().
128  * @param ptr Pointer to the memory block which should be freed.
129  * @note ptr = NULL is explicitly allowed.
130  * @note It is recommended that you use av_freep() instead.
131  * @see av_freep()
132  */
133 void av_free(void *ptr);
134 
135 /**
136  * Allocate a block of size bytes with alignment suitable for all
137  * memory accesses (including vectors if available on the CPU) and
138  * zero all the bytes of the block.
139  * @param size Size in bytes for the memory block to be allocated.
140  * @return Pointer to the allocated block, NULL if it cannot be allocated.
141  * @see av_malloc()
142  */
144 
145 /**
146  * Allocate a block of nmemb * size bytes with alignment suitable for all
147  * memory accesses (including vectors if available on the CPU) and
148  * zero all the bytes of the block.
149  * The allocation will fail if nmemb * size is greater than or equal
150  * to INT_MAX.
151  * @param nmemb
152  * @param size
153  * @return Pointer to the allocated block, NULL if it cannot be allocated.
154  */
155 void *av_calloc(size_t nmemb, size_t size) av_malloc_attrib;
156 
157 /**
158  * Helper function to allocate a block of size * nmemb bytes with
159  * using av_mallocz()
160  * @param nmemb Number of elements
161  * @param size Size of the single element
162  * @return Pointer to the allocated block, NULL if the block cannot
163  * be allocated.
164  * @see av_mallocz()
165  * @see av_malloc_array()
166  */
167 av_alloc_size(1, 2) static inline void *av_mallocz_array(size_t nmemb, size_t size)
168 {
169  if (size <= 0 || nmemb >= INT_MAX / size)
170  return NULL;
171  return av_mallocz(nmemb * size);
172 }
173 
174 /**
175  * Duplicate the string s.
176  * @param s string to be duplicated
177  * @return Pointer to a newly allocated string containing a
178  * copy of s or NULL if the string cannot be allocated.
179  */
180 char *av_strdup(const char *s) av_malloc_attrib;
181 
182 /**
183  * Free a memory block which has been allocated with av_malloc(z)() or
184  * av_realloc() and set the pointer pointing to it to NULL.
185  * @param ptr Pointer to the pointer to the memory block which should
186  * be freed.
187  * @see av_free()
188  */
189 void av_freep(void *ptr);
190 
191 /**
192  * Add an element to a dynamic array.
193  *
194  * @param tab_ptr Pointer to the array.
195  * @param nb_ptr Pointer to the number of elements in the array.
196  * @param elem Element to be added.
197  */
198 void av_dynarray_add(void *tab_ptr, int *nb_ptr, void *elem);
199 
200 /**
201  * Multiply two size_t values checking for overflow.
202  * @return 0 if success, AVERROR(EINVAL) if overflow.
203  */
204 static inline int av_size_mult(size_t a, size_t b, size_t *r)
205 {
206  size_t t = a * b;
207  /* Hack inspired from glibc: only try the division if nelem and elsize
208  * are both greater than sqrt(SIZE_MAX). */
209  if ((a | b) >= ((size_t)1 << (sizeof(size_t) * 4)) && a && t / a != b)
210  return AVERROR(EINVAL);
211  *r = t;
212  return 0;
213 }
214 
215 /**
216  * Set the maximum size that may me allocated in one block.
217  */
218 void av_max_alloc(size_t max);
219 
220 /**
221  * @brief deliberately overlapping memcpy implementation
222  * @param dst destination buffer
223  * @param back how many bytes back we start (the initial size of the overlapping window), must be > 0
224  * @param cnt number of bytes to copy, must be >= 0
225  *
226  * cnt > back is valid, this will copy the bytes we just copied,
227  * thus creating a repeating pattern with a period length of back.
228  */
229 void av_memcpy_backptr(uint8_t *dst, int back, int cnt);
230 
231 /**
232  * @}
233  */
234 
235 #endif /* AVUTIL_MEM_H */