[cvs] / xvidcore / src / utils / mem_align.c Repository:
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Diff of /xvidcore/src/utils/mem_align.c

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revision 1.5, Sun Jun 9 11:23:13 2002 UTC revision 1.15.2.2, Mon Jun 9 13:55:38 2003 UTC
# Line 1  Line 1 
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     * $Id$
23     *
24     ****************************************************************************/
25    
26  #include <stdlib.h>  #include <stdlib.h>
27  #include <stdio.h>  #include <stdio.h>
28  #include "mem_align.h"  #include "mem_align.h"
29    
30  void *xvid_malloc(size_t size, uint8_t alignment)  /*****************************************************************************
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 *
48    xvid_malloc(size_t size,
49                            uint8_t alignment)
50  {  {
51          uint8_t *mem_ptr;          uint8_t *mem_ptr;
52    
53          if(!alignment)          if (!alignment) {
         {  
54    
55                  /* We have not to satisfy any alignment */                  /* We have not to satisfy any alignment */
56                  if((mem_ptr = (uint8_t *) malloc(size + 1)) != NULL)                  if ((mem_ptr = (uint8_t *) malloc(size + 1)) != NULL) {
                 {  
57    
58                          /* Store (mem_ptr - "real allocated memory") in *(mem_ptr-1) */                          /* Store (mem_ptr - "real allocated memory") in *(mem_ptr-1) */
59                          *mem_ptr = 0;                          *mem_ptr = 1;
60    
61                          /* Return the mem_ptr pointer */                          /* Return the mem_ptr pointer */
62                          return (void *) mem_ptr++;                          return (void *)(mem_ptr+1);
63    
64                  }                  }
65    
66          }          } else {
         else  
         {  
67                  uint8_t *tmp;                  uint8_t *tmp;
68    
69                  /*                  /*
# Line 31  Line 71 
71                   * can realign the data if necessary                   * can realign the data if necessary
72                   */                   */
73    
74                  if((tmp = (uint8_t *) malloc(size + alignment)) != NULL)                  if ((tmp = (uint8_t *) malloc(size + alignment)) != NULL) {
                 {  
75    
76                          /* Align the tmp pointer */                          /* Align the tmp pointer */
77                          mem_ptr = (uint8_t *)((uint32_t)(tmp + alignment - 1)&(~(uint32_t)(alignment - 1)));                          mem_ptr =
78                                    (uint8_t *) ((ptr_t) (tmp + alignment - 1) &
79                                                             (~(ptr_t) (alignment - 1)));
80    
81                          /*                          /*
82                           * Special case where malloc have already satisfied the alignment                           * Special case where malloc have already satisfied the alignment
# Line 44  Line 85 
85                           * If we do not add alignment to mem_ptr then *(mem_ptr-1) points                           * If we do not add alignment to mem_ptr then *(mem_ptr-1) points
86                           * to a forbidden memory space                           * to a forbidden memory space
87                           */                           */
88                          if(mem_ptr == tmp) mem_ptr += alignment;                          if (mem_ptr == tmp)
89                                    mem_ptr += alignment;
90    
91                          /*                          /*
92                           * (mem_ptr - tmp) is stored in *(mem_ptr-1) so we are able to retrieve                           * (mem_ptr - tmp) is stored in *(mem_ptr-1) so we are able to retrieve
# Line 62  Line 104 
104    
105  }  }
106    
107  void xvid_free(void *mem_ptr)  /*****************************************************************************
108     * xvid_free
109     *
110     * Free a previously 'xvid_malloc' allocated block. Does not free NULL
111     * references.
112     *
113     * Returned value : None.
114     *
115     ****************************************************************************/
116    
117    void
118    xvid_free(void *mem_ptr)
119  {  {
120    
121          /* *(mem_ptr - 1) give us the offset to the real malloc block */          /* *(mem_ptr - 1) give us the offset to the real malloc block */
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