1 /*****************************************************************************
2 *
3 * XVID MPEG-4 VIDEO CODEC
4 * - Aligned Memory Allocator -
5 *
6 * Copyright(C) 2002-2003 Edouard Gomez <ed.gomez@free.fr>
7 *
8 * This program is free software ; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License as published by
10 * the Free Software Foundation ; either version 2 of the License, or
11 * (at your option) any later version.
12 *
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY ; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 * GNU General Public License for more details.
17 *
18 * You should have received a copy of the GNU General Public License
19 * along with this program ; if not, write to the Free Software
20 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
21 *
22 * $Id: mem_align.c 1985 2011-05-18 09:02:35Z Isibaar $
23 *
24 ****************************************************************************/
25
26 #include <stdlib.h>
27 #include <stdio.h>
28 #include "mem_align.h"
29
30 /*****************************************************************************
31 * xvid_malloc
32 *
33 * This function allocates 'size' bytes (usable by the user) on the heap and
34 * takes care of the requested 'alignment'.
35 * In order to align the allocated memory block, the xvid_malloc allocates
36 * 'size' bytes + 'alignment' bytes. So try to keep alignment very small
37 * when allocating small pieces of memory.
38 *
39 * NB : a block allocated by xvid_malloc _must_ be freed with xvid_free
40 * (the libc free will return an error)
41 *
42 * Returned value : - NULL on error
43 * - Pointer to the allocated aligned block
44 *
45 ****************************************************************************/
46
47 void *
xvid_malloc(size_t size,uint8_t alignment)48 xvid_malloc(size_t size,
49 uint8_t alignment)
50 {
51 uint8_t *mem_ptr;
52
53 if (!alignment) {
54
55 /* We have not to satisfy any alignment */
56 if ((mem_ptr = (uint8_t *) malloc(size + 1)) != NULL) {
57
58 /* Store (mem_ptr - "real allocated memory") in *(mem_ptr-1) */
59 *mem_ptr = (uint8_t)1;
60
61 /* Return the mem_ptr pointer */
62 return ((void *)(mem_ptr+1));
63 }
64 } else {
65 uint8_t *tmp;
66
67 /* Allocate the required size memory + alignment so we
68 * can realign the data if necessary */
69 if ((tmp = (uint8_t *) malloc(size + alignment)) != NULL) {
70
71 /* Align the tmp pointer */
72 mem_ptr =
73 (uint8_t *) ((ptr_t) (tmp + alignment - 1) &
74 (~(ptr_t) (alignment - 1)));
75
76 /* Special case where malloc have already satisfied the alignment
77 * We must add alignment to mem_ptr because we must store
78 * (mem_ptr - tmp) in *(mem_ptr-1)
79 * If we do not add alignment to mem_ptr then *(mem_ptr-1) points
80 * to a forbidden memory space */
81 if (mem_ptr == tmp)
82 mem_ptr += alignment;
83
84 /* (mem_ptr - tmp) is stored in *(mem_ptr-1) so we are able to retrieve
85 * the real malloc block allocated and free it in xvid_free */
86 *(mem_ptr - 1) = (uint8_t) (mem_ptr - tmp);
87
88 /* Return the aligned pointer */
89 return ((void *)mem_ptr);
90 }
91 }
92
93 return(NULL);
94 }
95
96 /*****************************************************************************
97 * xvid_free
98 *
99 * Free a previously 'xvid_malloc' allocated block. Does not free NULL
100 * references.
101 *
102 * Returned value : None.
103 *
104 ****************************************************************************/
105
106 void
xvid_free(void * mem_ptr)107 xvid_free(void *mem_ptr)
108 {
109
110 uint8_t *ptr;
111
112 if (mem_ptr == NULL)
113 return;
114
115 /* Aligned pointer */
116 ptr = mem_ptr;
117
118 /* *(ptr - 1) holds the offset to the real allocated block
119 * we sub that offset os we free the real pointer */
120 ptr -= *(ptr - 1);
121
122 /* Free the memory */
123 free(ptr);
124 }
125