source: rtems/c/src/exec/score/src/heapallocate.c @ 08311cc3

4.104.114.84.95
Last change on this file since 08311cc3 was 08311cc3, checked in by Joel Sherrill <joel.sherrill@…>, on Nov 17, 1999 at 5:51:34 PM

Updated copyright notice.

  • Property mode set to 100644
File size: 2.8 KB
Line 
1/*
2 *  Heap Handler
3 *
4 *  COPYRIGHT (c) 1989-1999.
5 *  On-Line Applications Research Corporation (OAR).
6 *
7 *  The license and distribution terms for this file may be
8 *  found in the file LICENSE in this distribution or at
9 *  http://www.OARcorp.com/rtems/license.html.
10 *
11 *  $Id$
12 */
13
14
15#include <rtems/system.h>
16#include <rtems/score/sysstate.h>
17#include <rtems/score/heap.h>
18
19/*PAGE
20 *
21 *  _Heap_Allocate
22 *
23 *  This kernel routine allocates the requested size of memory
24 *  from the specified heap.
25 *
26 *  Input parameters:
27 *    the_heap  - pointer to heap header.
28 *    size      - size in bytes of the memory block to allocate.
29 *
30 *  Output parameters:
31 *    returns - starting address of memory block allocated
32 */
33
34void *_Heap_Allocate(
35  Heap_Control        *the_heap,
36  unsigned32           size
37)
38{
39  unsigned32  excess;
40  unsigned32  the_size;
41  Heap_Block *the_block;
42  Heap_Block *next_block;
43  Heap_Block *temporary_block;
44  void       *ptr;
45  unsigned32  offset;
46 
47  excess   = size % the_heap->page_size;
48  the_size = size + the_heap->page_size + HEAP_BLOCK_USED_OVERHEAD;
49 
50  if ( excess )
51    the_size += the_heap->page_size - excess;
52
53  if ( the_size < sizeof( Heap_Block ) )
54    the_size = sizeof( Heap_Block );
55
56  for ( the_block = the_heap->first;
57        ;
58        the_block = the_block->next ) {
59    if ( the_block == _Heap_Tail( the_heap ) )
60      return( NULL );
61    if ( the_block->front_flag >= the_size )
62      break;
63  }
64
65  if ( (the_block->front_flag - the_size) >
66       (the_heap->page_size + HEAP_BLOCK_USED_OVERHEAD) ) {
67    the_block->front_flag -= the_size;
68    next_block             = _Heap_Next_block( the_block );
69    next_block->back_flag  = the_block->front_flag;
70
71    temporary_block            = _Heap_Block_at( next_block, the_size );
72    temporary_block->back_flag =
73    next_block->front_flag     = _Heap_Build_flag( the_size,
74                                    HEAP_BLOCK_USED );
75    ptr = _Heap_Start_of_user_area( next_block );
76  } else {
77    next_block                = _Heap_Next_block( the_block );
78    next_block->back_flag     = _Heap_Build_flag( the_block->front_flag,
79                                   HEAP_BLOCK_USED );
80    the_block->front_flag     = next_block->back_flag;
81    the_block->next->previous = the_block->previous;
82    the_block->previous->next = the_block->next;
83    ptr = _Heap_Start_of_user_area( the_block );
84  }
85 
86  /*
87   * round ptr up to a multiple of page size
88   * Have to save the bump amount in the buffer so that free can figure it out
89   */
90 
91  offset = the_heap->page_size - (((unsigned32) ptr) & (the_heap->page_size - 1));
92  ptr = _Addresses_Add_offset( ptr, offset );
93  *(((unsigned32 *) ptr) - 1) = offset;
94
95#ifdef RTEMS_DEBUG
96  {
97      unsigned32 ptr_u32;
98      ptr_u32 = (unsigned32) ptr;
99      if (ptr_u32 & (the_heap->page_size - 1))
100          abort();
101  }
102#endif
103
104  return ptr;
105}
106
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