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revision 1.2, Wed Mar 20 00:27:57 2002 UTC revision 1.12, Wed Nov 27 21:20:33 2002 UTC
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1    /*****************************************************************************
2     *
3     *  XVID MPEG-4 VIDEO CODEC
4     *  - Aligned memory allocator -
5     *
6     *  Copyright(C) 2002 Michael Militzer <isibaar@xvid.org>
7     *               2002 Edouard Gomez
8     *
9     *  This file is part of XviD, a free MPEG-4 video encoder/decoder
10     *
11     *  XviD is free software; you can redistribute it and/or modify it
12     *  under the terms of the GNU General Public License as published by
13     *  the Free Software Foundation; either version 2 of the License, or
14     *  (at your option) any later version.
15     *
16     *  This program is distributed in the hope that it will be useful,
17     *  but WITHOUT ANY WARRANTY; without even the implied warranty of
18     *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
19     *  GNU General Public License for more details.
20     *
21     *  You should have received a copy of the GNU General Public License
22     *  along with this program; if not, write to the Free Software
23     *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
24     *
25     *  Under section 8 of the GNU General Public License, the copyright
26     *  holders of XVID explicitly forbid distribution in the following
27     *  countries:
28     *
29     *    - Japan
30     *    - United States of America
31     *
32     *  Linking XviD statically or dynamically with other modules is making a
33     *  combined work based on XviD.  Thus, the terms and conditions of the
34     *  GNU General Public License cover the whole combination.
35     *
36     *  As a special exception, the copyright holders of XviD give you
37     *  permission to link XviD with independent modules that communicate with
38     *  XviD solely through the VFW1.1 and DShow interfaces, regardless of the
39     *  license terms of these independent modules, and to copy and distribute
40     *  the resulting combined work under terms of your choice, provided that
41     *  every copy of the combined work is accompanied by a complete copy of
42     *  the source code of XviD (the version of XviD used to produce the
43     *  combined work), being distributed under the terms of the GNU General
44     *  Public License plus this exception.  An independent module is a module
45     *  which is not derived from or based on XviD.
46     *
47     *  Note that people who make modified versions of XviD are not obligated
48     *  to grant this special exception for their modified versions; it is
49     *  their choice whether to do so.  The GNU General Public License gives
50     *  permission to release a modified version without this exception; this
51     *  exception also makes it possible to release a modified version which
52     *  carries forward this exception.
53     *
54     * $Id$
55     *
56     ****************************************************************************/
57    
58  #include <stdlib.h>  #include <stdlib.h>
59  #include <stdio.h>  #include <stdio.h>
60  #include "mem_align.h"  #include "mem_align.h"
61    
62  void *xvid_malloc(size_t size, uint8_t alignment)  /*****************************************************************************
63     * xvid_malloc
64     *
65     * This function allocates 'size' bytes (usable by the user) on the heap and
66     * takes care of the requested 'alignment'.
67     * In order to align the allocated memory block, the xvid_malloc allocates
68     * 'size' bytes + 'alignment' bytes. So try to keep alignment very small
69     * when allocating small pieces of memory.
70     *
71     * NB : a block allocated by xvid_malloc _must_ be freed with xvid_free
72     *      (the libc free will return an error)
73     *
74     * Returned value : - NULL on error
75     *                  - Pointer to the allocated aligned block
76     *
77     ****************************************************************************/
78    
79    void *
80    xvid_malloc(size_t size,
81                            uint8_t alignment)
82  {  {
83    uint8_t *mem_ptr;    uint8_t *mem_ptr;
84    
85    if(alignment == 0)          if (!alignment) {
86    {  
87                    /* We have not to satisfy any alignment */
88            if((mem_ptr = (uint8_t *) malloc(size + 1)) != NULL) {            if((mem_ptr = (uint8_t *) malloc(size + 1)) != NULL) {
89    
90                            /* Store (mem_ptr - "real allocated memory") in *(mem_ptr-1) */
91                  *mem_ptr = 0;                  *mem_ptr = 0;
92                  return (void *) mem_ptr++;  
93            }                          /* Return the mem_ptr pointer */
94                            return (void *)(mem_ptr+1);
95    
96    }    }
97    else  
98    {          } else {
99            uint8_t *tmp;            uint8_t *tmp;
100    
101                    /*
102                     * Allocate the required size memory + alignment so we
103                     * can realign the data if necessary
104                     */
105    
106            if((tmp = (uint8_t *) malloc(size + alignment)) != NULL) {            if((tmp = (uint8_t *) malloc(size + alignment)) != NULL) {
107                  mem_ptr = (uint8_t *) (((uint32_t) tmp / alignment) * alignment + alignment);  
108                  *(mem_ptr - 1) = (alignment - 1) - ((uint32_t) tmp % alignment);                          /* Align the tmp pointer */
109                            mem_ptr =
110                                    (uint8_t *) ((ptr_t) (tmp + alignment - 1) &
111                                                             (~(ptr_t) (alignment - 1)));
112    
113                            /*
114                             * Special case where malloc have already satisfied the alignment
115                             * We must add alignment to mem_ptr because we must store
116                             * (mem_ptr - tmp) in *(mem_ptr-1)
117                             * If we do not add alignment to mem_ptr then *(mem_ptr-1) points
118                             * to a forbidden memory space
119                             */
120                            if (mem_ptr == tmp)
121                                    mem_ptr += alignment;
122    
123                            /*
124                             * (mem_ptr - tmp) is stored in *(mem_ptr-1) so we are able to retrieve
125                             * the real malloc block allocated and free it in xvid_free
126                             */
127                            *(mem_ptr - 1) = (uint8_t) (mem_ptr - tmp);
128    
129                            /* Return the aligned pointer */
130                  return (void *) mem_ptr;                  return (void *) mem_ptr;
131    
132            }            }
133    }    }
134    
135    return NULL;    return NULL;
136    
137  }  }
138    
139  void xvid_free(void *mem_ptr)  /*****************************************************************************
140     * xvid_free
141     *
142     * Free a previously 'xvid_malloc' allocated block. Does not free NULL
143     * references.
144     *
145     * Returned value : None.
146     *
147     ****************************************************************************/
148    
149    void
150    xvid_free(void *mem_ptr)
151  {  {
   uint8_t *tmp;  
152    
153    tmp = (uint8_t *) mem_ptr - 1;          /* *(mem_ptr - 1) give us the offset to the real malloc block */
154    mem_ptr  = tmp - *tmp;          if (mem_ptr)
155                    free((uint8_t *) mem_ptr - *((uint8_t *) mem_ptr - 1));
156    
   free(mem_ptr);  
157  }  }

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