1 | /** |
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2 | * @file |
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3 | * |
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4 | * @ingroup ScoreHeap |
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5 | * |
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6 | * @brief Heap Handler implementation. |
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7 | */ |
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8 | |
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9 | /* |
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10 | * COPYRIGHT (c) 1989-2007. |
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11 | * On-Line Applications Research Corporation (OAR). |
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12 | * |
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13 | * The license and distribution terms for this file may be |
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14 | * found in the file LICENSE in this distribution or at |
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15 | * http://www.rtems.com/license/LICENSE. |
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16 | * |
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17 | * $Id$ |
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18 | */ |
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19 | |
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20 | #if HAVE_CONFIG_H |
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21 | #include "config.h" |
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22 | #endif |
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23 | |
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24 | #include <rtems/system.h> |
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25 | #include <rtems/score/sysstate.h> |
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26 | #include <rtems/score/heap.h> |
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27 | |
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28 | bool _Heap_Free( Heap_Control *heap, void *alloc_begin_ptr ) |
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29 | { |
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30 | Heap_Statistics *const stats = &heap->stats; |
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31 | uintptr_t alloc_begin = (uintptr_t) alloc_begin_ptr; |
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32 | Heap_Block *block = |
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33 | _Heap_Block_of_alloc_area( alloc_begin, heap->page_size ); |
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34 | Heap_Block *next_block = NULL; |
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35 | uintptr_t block_size = 0; |
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36 | uintptr_t next_block_size = 0; |
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37 | bool next_is_free = false; |
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38 | |
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39 | if ( !_Heap_Is_block_in_heap( heap, block ) ) { |
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40 | return false; |
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41 | } |
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42 | |
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43 | block_size = _Heap_Block_size( block ); |
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44 | next_block = _Heap_Block_at( block, block_size ); |
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45 | |
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46 | if ( !_Heap_Is_block_in_heap( heap, next_block ) ) { |
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47 | _HAssert( false ); |
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48 | return false; |
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49 | } |
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50 | |
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51 | if ( !_Heap_Is_prev_used( next_block ) ) { |
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52 | _HAssert( false ); |
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53 | return false; |
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54 | } |
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55 | |
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56 | next_block_size = _Heap_Block_size( next_block ); |
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57 | next_is_free = next_block != heap->last_block |
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58 | && !_Heap_Is_prev_used( _Heap_Block_at( next_block, next_block_size )); |
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59 | |
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60 | if ( !_Heap_Is_prev_used( block ) ) { |
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61 | uintptr_t const prev_size = block->prev_size; |
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62 | Heap_Block * const prev_block = _Heap_Block_at( block, -prev_size ); |
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63 | |
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64 | if ( !_Heap_Is_block_in_heap( heap, prev_block ) ) { |
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65 | _HAssert( false ); |
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66 | return( false ); |
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67 | } |
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68 | |
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69 | /* As we always coalesce free blocks, the block that preceedes prev_block |
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70 | must have been used. */ |
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71 | if ( !_Heap_Is_prev_used ( prev_block) ) { |
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72 | _HAssert( false ); |
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73 | return( false ); |
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74 | } |
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75 | |
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76 | if ( next_is_free ) { /* coalesce both */ |
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77 | uintptr_t const size = block_size + prev_size + next_block_size; |
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78 | _Heap_Free_list_remove( next_block ); |
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79 | stats->free_blocks -= 1; |
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80 | prev_block->size_and_flag = size | HEAP_PREV_BLOCK_USED; |
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81 | next_block = _Heap_Block_at( prev_block, size ); |
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82 | _HAssert(!_Heap_Is_prev_used( next_block)); |
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83 | next_block->prev_size = size; |
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84 | } else { /* coalesce prev */ |
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85 | uintptr_t const size = block_size + prev_size; |
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86 | prev_block->size_and_flag = size | HEAP_PREV_BLOCK_USED; |
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87 | next_block->size_and_flag &= ~HEAP_PREV_BLOCK_USED; |
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88 | next_block->prev_size = size; |
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89 | } |
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90 | } else if ( next_is_free ) { /* coalesce next */ |
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91 | uintptr_t const size = block_size + next_block_size; |
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92 | _Heap_Free_list_replace( next_block, block ); |
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93 | block->size_and_flag = size | HEAP_PREV_BLOCK_USED; |
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94 | next_block = _Heap_Block_at( block, size ); |
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95 | next_block->prev_size = size; |
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96 | } else { /* no coalesce */ |
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97 | /* Add 'block' to the head of the free blocks list as it tends to |
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98 | produce less fragmentation than adding to the tail. */ |
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99 | _Heap_Free_list_insert_after( _Heap_Free_list_head( heap), block ); |
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100 | block->size_and_flag = block_size | HEAP_PREV_BLOCK_USED; |
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101 | next_block->size_and_flag &= ~HEAP_PREV_BLOCK_USED; |
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102 | next_block->prev_size = block_size; |
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103 | |
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104 | /* Statistics */ |
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105 | ++stats->free_blocks; |
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106 | if ( stats->max_free_blocks < stats->free_blocks ) { |
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107 | stats->max_free_blocks = stats->free_blocks; |
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108 | } |
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109 | } |
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110 | |
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111 | /* Statistics */ |
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112 | --stats->used_blocks; |
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113 | ++stats->frees; |
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114 | stats->free_size += block_size; |
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115 | |
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116 | return( true ); |
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117 | } |
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