1 | /* |
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2 | * Heap Handler |
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3 | * |
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4 | * COPYRIGHT (c) 1989-1999. |
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5 | * On-Line Applications Research Corporation (OAR). |
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6 | * |
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7 | * The license and distribution terms for this file may be |
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8 | * found in the file LICENSE in this distribution or at |
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9 | * http://www.rtems.com/license/LICENSE. |
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10 | * |
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11 | * $Id$ |
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12 | */ |
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13 | |
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14 | |
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15 | #include <rtems/system.h> |
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16 | #include <rtems/score/sysstate.h> |
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17 | #include <rtems/score/heap.h> |
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18 | |
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19 | /*PAGE |
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20 | * |
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21 | * _Heap_Free |
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22 | * |
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23 | * This kernel routine returns the memory designated by the |
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24 | * given heap and given starting address to the memory pool. |
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25 | * |
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26 | * Input parameters: |
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27 | * the_heap - pointer to heap header |
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28 | * starting_address - starting address of the memory block to free. |
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29 | * |
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30 | * Output parameters: |
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31 | * TRUE - if starting_address is valid heap address |
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32 | * FALSE - if starting_address is invalid heap address |
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33 | */ |
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34 | |
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35 | boolean _Heap_Free( |
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36 | Heap_Control *the_heap, |
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37 | void *starting_address |
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38 | ) |
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39 | { |
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40 | Heap_Block *the_block; |
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41 | Heap_Block *next_block; |
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42 | uint32_t the_size; |
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43 | uint32_t next_size; |
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44 | Heap_Statistics *const stats = &the_heap->stats; |
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45 | boolean next_is_free; |
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46 | |
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47 | _Heap_Start_of_block( the_heap, starting_address, &the_block ); |
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48 | |
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49 | if ( !_Heap_Is_block_in( the_heap, the_block ) ) { |
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50 | _HAssert(starting_address == NULL); |
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51 | return( FALSE ); |
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52 | } |
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53 | |
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54 | the_size = _Heap_Block_size( the_block ); |
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55 | next_block = _Heap_Block_at( the_block, the_size ); |
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56 | |
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57 | if ( !_Heap_Is_prev_used( next_block ) ) { |
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58 | _HAssert(FALSE); |
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59 | return( FALSE ); |
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60 | } |
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61 | |
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62 | if ( !_Heap_Is_block_in( the_heap, next_block ) ) { |
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63 | _HAssert(FALSE); |
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64 | return( FALSE ); |
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65 | } |
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66 | |
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67 | next_size = _Heap_Block_size( next_block ); |
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68 | next_is_free = next_block < the_heap->final && |
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69 | !_Heap_Is_prev_used(_Heap_Block_at(next_block, next_size)); |
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70 | |
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71 | if ( !_Heap_Is_prev_used( the_block ) ) { |
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72 | uint32_t const prev_size = the_block->prev_size; |
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73 | Heap_Block *const prev_block = _Heap_Block_at( the_block, -prev_size ); |
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74 | |
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75 | if ( !_Heap_Is_block_in( the_heap, prev_block ) ) { |
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76 | _HAssert(FALSE); |
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77 | return( FALSE ); |
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78 | } |
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79 | |
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80 | /* As we always coalesce free blocks, the block that preceedes prev_block |
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81 | must have been used. */ |
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82 | if ( !_Heap_Is_prev_used ( prev_block) ) { |
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83 | _HAssert(FALSE); |
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84 | return( FALSE ); |
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85 | } |
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86 | |
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87 | if ( next_is_free ) { /* coalesce both */ |
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88 | uint32_t const size = the_size + prev_size + next_size; |
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89 | _Heap_Block_remove( next_block ); |
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90 | stats->free_blocks -= 1; |
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91 | prev_block->size = size | HEAP_PREV_USED; |
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92 | next_block = _Heap_Block_at( prev_block, size ); |
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93 | _HAssert(!_Heap_Is_prev_used( next_block)); |
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94 | next_block->prev_size = size; |
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95 | } |
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96 | else { /* coalesce prev */ |
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97 | uint32_t const size = the_size + prev_size; |
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98 | prev_block->size = size | HEAP_PREV_USED; |
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99 | next_block->size &= ~HEAP_PREV_USED; |
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100 | next_block->prev_size = size; |
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101 | } |
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102 | } |
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103 | else if ( next_is_free ) { /* coalesce next */ |
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104 | uint32_t const size = the_size + next_size; |
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105 | _Heap_Block_replace( next_block, the_block ); |
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106 | the_block->size = size | HEAP_PREV_USED; |
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107 | next_block = _Heap_Block_at( the_block, size ); |
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108 | next_block->prev_size = size; |
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109 | } |
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110 | else { /* no coalesce */ |
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111 | /* Add 'the_block' to the head of the free blocks list as it tends to |
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112 | produce less fragmentation than adding to the tail. */ |
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113 | _Heap_Block_insert_after( _Heap_Head( the_heap), the_block ); |
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114 | the_block->size = the_size | HEAP_PREV_USED; |
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115 | next_block->size &= ~HEAP_PREV_USED; |
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116 | next_block->prev_size = the_size; |
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117 | |
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118 | stats->free_blocks += 1; |
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119 | if ( stats->max_free_blocks < stats->free_blocks ) |
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120 | stats->max_free_blocks = stats->free_blocks; |
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121 | } |
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122 | |
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123 | stats->used_blocks -= 1; |
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124 | stats->free_size += the_size; |
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125 | stats->frees += 1; |
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126 | |
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127 | return( TRUE ); |
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128 | } |
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