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.OARcorp.com/rtems/license.html. |
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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_Extend |
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22 | * |
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23 | * This routine grows the_heap memory area using the size bytes which |
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24 | * begin at starting_address. |
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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 - pointer to the memory area. |
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29 | * size - size in bytes of the memory block to allocate. |
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30 | * |
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31 | * Output parameters: |
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32 | * *amount_extended - amount of memory added to the_heap |
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33 | */ |
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34 | |
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35 | Heap_Extend_status _Heap_Extend( |
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36 | Heap_Control *the_heap, |
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37 | void *starting_address, |
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38 | unsigned32 size, |
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39 | unsigned32 *amount_extended |
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40 | ) |
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41 | { |
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42 | Heap_Block *the_block; |
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43 | unsigned32 *p; |
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44 | |
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45 | /* |
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46 | * The overhead was taken from the original heap memory. |
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47 | */ |
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48 | |
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49 | Heap_Block *old_final; |
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50 | Heap_Block *new_final; |
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51 | |
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52 | /* |
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53 | * There are five possibilities for the location of starting |
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54 | * address: |
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55 | * |
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56 | * 1. non-contiguous lower address (NOT SUPPORTED) |
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57 | * 2. contiguous lower address (NOT SUPPORTED) |
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58 | * 3. in the heap (ERROR) |
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59 | * 4. contiguous higher address (SUPPORTED) |
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60 | * 5. non-contiguous higher address (NOT SUPPORTED) |
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61 | * |
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62 | * As noted, this code only supports (4). |
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63 | */ |
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64 | |
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65 | if ( starting_address >= (void *) the_heap->start && /* case 3 */ |
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66 | starting_address <= (void *) the_heap->final |
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67 | ) |
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68 | return HEAP_EXTEND_ERROR; |
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69 | |
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70 | if ( starting_address < (void *) the_heap->start ) { /* cases 1 and 2 */ |
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71 | |
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72 | return HEAP_EXTEND_NOT_IMPLEMENTED; /* cases 1 and 2 */ |
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73 | |
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74 | } else { /* cases 4 and 5 */ |
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75 | |
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76 | the_block = (Heap_Block *) |
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77 | _Addresses_Subtract_offset( starting_address, HEAP_OVERHEAD ); |
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78 | if ( the_block != the_heap->final ) |
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79 | return HEAP_EXTEND_NOT_IMPLEMENTED; /* case 5 */ |
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80 | } |
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81 | |
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82 | /* |
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83 | * Currently only case 4 should make it to this point. |
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84 | * The basic trick is to make the extend area look like a used |
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85 | * block and free it. |
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86 | */ |
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87 | |
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88 | *amount_extended = size; |
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89 | |
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90 | old_final = the_heap->final; |
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91 | new_final = _Addresses_Add_offset( old_final, size ); |
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92 | /* SAME AS: _Addresses_Add_offset( starting_address, size-HEAP_OVERHEAD ); */ |
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93 | |
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94 | the_heap->final = new_final; |
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95 | |
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96 | old_final->front_flag = |
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97 | new_final->back_flag = _Heap_Build_flag( size, HEAP_BLOCK_USED ); |
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98 | new_final->front_flag = HEAP_DUMMY_FLAG; |
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99 | |
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100 | /* |
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101 | * Must pass in address of "user" area |
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102 | * So add in the offset field. |
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103 | */ |
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104 | |
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105 | p = (unsigned32 *) &old_final->next; |
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106 | *p = sizeof(unsigned32); |
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107 | p++; |
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108 | _Heap_Free( the_heap, p ); |
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109 | |
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110 | return HEAP_EXTEND_SUCCESSFUL; |
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111 | } |
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112 | |
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