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.rtems.com/license/LICENSE. |
---|
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_Initialize |
---|
22 | * |
---|
23 | * This kernel routine initializes a heap. |
---|
24 | * |
---|
25 | * Input parameters: |
---|
26 | * the_heap - pointer to heap header |
---|
27 | * starting_address - starting address of heap |
---|
28 | * size - size of heap |
---|
29 | * page_size - allocatable unit of memory |
---|
30 | * |
---|
31 | * Output parameters: |
---|
32 | * returns - maximum memory available if RTEMS_SUCCESSFUL |
---|
33 | * 0 - otherwise |
---|
34 | * |
---|
35 | * This is what a heap looks like in memory immediately |
---|
36 | * after initialization: |
---|
37 | * |
---|
38 | * +--------------------------------+ |
---|
39 | * 0 | size = 0 | status = used | a.k.a. dummy back flag |
---|
40 | * +--------------------------------+ |
---|
41 | * 4 | size = size-8 | status = free | a.k.a. front flag |
---|
42 | * +--------------------------------+ |
---|
43 | * 8 | next = PERM HEAP_TAIL | |
---|
44 | * +--------------------------------+ |
---|
45 | * 12 | previous = PERM HEAP_HEAD | |
---|
46 | * +--------------------------------+ |
---|
47 | * | | |
---|
48 | * | memory available | |
---|
49 | * | for allocation | |
---|
50 | * | | |
---|
51 | * +--------------------------------+ |
---|
52 | * size - 8 | size = size-8 | status = free | a.k.a. back flag |
---|
53 | * +--------------------------------+ |
---|
54 | * size - 4 | size = 0 | status = used | a.k.a. dummy front flag |
---|
55 | * +--------------------------------+ |
---|
56 | */ |
---|
57 | |
---|
58 | uint32_t _Heap_Initialize( |
---|
59 | Heap_Control *the_heap, |
---|
60 | void *starting_address, |
---|
61 | uint32_t size, |
---|
62 | uint32_t page_size |
---|
63 | ) |
---|
64 | { |
---|
65 | Heap_Block *the_block; |
---|
66 | uint32_t the_size; |
---|
67 | |
---|
68 | if ( !_Heap_Is_page_size_valid( page_size ) || |
---|
69 | (size < HEAP_MINIMUM_SIZE) ) |
---|
70 | return 0; |
---|
71 | |
---|
72 | the_heap->page_size = page_size; |
---|
73 | the_size = size - HEAP_OVERHEAD; |
---|
74 | |
---|
75 | the_block = (Heap_Block *) starting_address; |
---|
76 | the_block->back_flag = HEAP_DUMMY_FLAG; |
---|
77 | the_block->front_flag = the_size; |
---|
78 | the_block->next = _Heap_Tail( the_heap ); |
---|
79 | the_block->previous = _Heap_Head( the_heap ); |
---|
80 | |
---|
81 | the_heap->start = the_block; |
---|
82 | the_heap->first = the_block; |
---|
83 | the_heap->permanent_null = NULL; |
---|
84 | the_heap->last = the_block; |
---|
85 | |
---|
86 | the_block = _Heap_Next_block( the_block ); |
---|
87 | the_block->back_flag = the_size; |
---|
88 | the_block->front_flag = HEAP_DUMMY_FLAG; |
---|
89 | the_heap->final = the_block; |
---|
90 | |
---|
91 | return ( the_size - HEAP_BLOCK_USED_OVERHEAD ); |
---|
92 | } |
---|