1 | /* heap.h |
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2 | * |
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3 | * This include file contains the information pertaining to the Heap |
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4 | * Handler. A heap is a doubly linked list of variable size |
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5 | * blocks which are allocated using the first fit method. Garbage |
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6 | * collection is performed each time a block is returned to the heap by |
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7 | * coalescing neighbor blocks. Control information for both allocated |
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8 | * and unallocated blocks is contained in the heap space. A heap header |
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9 | * contains control information for the heap. |
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10 | * |
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11 | * COPYRIGHT (c) 1989, 1990, 1991, 1992, 1993, 1994. |
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12 | * On-Line Applications Research Corporation (OAR). |
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13 | * All rights assigned to U.S. Government, 1994. |
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14 | * |
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15 | * This material may be reproduced by or for the U.S. Government pursuant |
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16 | * to the copyright license under the clause at DFARS 252.227-7013. This |
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17 | * notice must appear in all copies of this file and its derivatives. |
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18 | * |
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19 | * $Id$ |
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20 | */ |
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21 | |
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22 | #ifndef __RTEMS_HEAP_h |
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23 | #define __RTEMS_HEAP_h |
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24 | |
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25 | #ifdef __cplusplus |
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26 | extern "C" { |
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27 | #endif |
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28 | |
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29 | /* |
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30 | * Status codes for heap_extend |
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31 | */ |
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32 | |
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33 | typedef enum { |
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34 | HEAP_EXTEND_SUCCESSFUL, |
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35 | HEAP_EXTEND_ERROR, |
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36 | HEAP_EXTEND_NOT_IMPLEMENTED |
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37 | } Heap_Extend_status; |
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38 | |
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39 | /* |
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40 | * Constants used in the size/used field of each heap block to |
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41 | * indicate when a block is free or in use. |
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42 | */ |
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43 | |
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44 | #define HEAP_BLOCK_USED 1 /* indicates block is in use */ |
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45 | #define HEAP_BLOCK_FREE 0 /* indicates block is free */ |
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46 | |
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47 | /* |
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48 | * The size/used field value for the dummy front and back flags. |
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49 | */ |
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50 | |
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51 | #define HEAP_DUMMY_FLAG (0 + HEAP_BLOCK_USED) |
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52 | |
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53 | /* |
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54 | * The following constants reflect various requirements of the |
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55 | * heap data structures which impact the management of a heap. |
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56 | * |
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57 | * NOTE: Because free block overhead is greater than used block |
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58 | * overhead AND a portion of the allocated space is from |
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59 | * the extra free block overhead, the absolute lower bound |
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60 | * of the minimum fragment size is equal to the size of |
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61 | * the free block overhead. |
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62 | */ |
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63 | |
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64 | #define HEAP_OVERHEAD \ |
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65 | (sizeof( unsigned32 ) * 2) /* size dummy first and last blocks */ |
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66 | #define HEAP_BLOCK_USED_OVERHEAD \ |
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67 | (sizeof( void * ) * 2) /* num bytes overhead in used block */ |
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68 | #define HEAP_MINIMUM_SIZE \ |
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69 | (HEAP_OVERHEAD + sizeof (Heap_Block)) |
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70 | /* min number of bytes the user may */ |
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71 | /* specify for the heap size */ |
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72 | |
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73 | /* |
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74 | * The following defines the data structure used to manage |
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75 | * individual blocks in a heap. When the block is allocated, the |
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76 | * next and previous fields are not used by the Heap Handler |
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77 | * and thus the address returned for the block starts at |
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78 | * the address of the next field. |
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79 | * |
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80 | * NOTE: The next and previous pointers are only valid when the |
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81 | * block is free. Caution must be exercised to insure that |
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82 | * allocated blocks are large enough to contain them and |
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83 | * that they are not accidentally overwritten when the |
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84 | * block is actually allocated. |
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85 | */ |
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86 | |
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87 | typedef struct Heap_Block_struct Heap_Block; |
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88 | |
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89 | struct Heap_Block_struct { |
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90 | unsigned32 back_flag; /* size and status of prev block */ |
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91 | unsigned32 front_flag; /* size and status of block */ |
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92 | Heap_Block *next; /* pointer to next block */ |
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93 | Heap_Block *previous; /* pointer to previous block */ |
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94 | }; |
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95 | |
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96 | /* |
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97 | * The following defines the control block used to manage each heap. |
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98 | * |
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99 | * NOTE: |
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100 | * |
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101 | * This structure is layed out such that it can be used a a dummy |
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102 | * first and last block on the free block chain. The extra padding |
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103 | * insures the dummy last block is the correct size. |
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104 | * |
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105 | * The first Heap_Block starts at first while the second starts at |
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106 | * final. This is effectively the same trick as is used in the Chain |
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107 | * Handler. |
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108 | */ |
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109 | |
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110 | typedef struct { |
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111 | Heap_Block *start; /* first valid block address in heap */ |
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112 | Heap_Block *final; /* last valid block address in heap */ |
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113 | |
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114 | Heap_Block *first; /* pointer to first block in heap */ |
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115 | Heap_Block *permanent_null; /* always NULL pointer */ |
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116 | Heap_Block *last; /* pointer to last block in heap */ |
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117 | unsigned32 page_size; /* allocation unit */ |
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118 | unsigned32 reserved; |
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119 | } Heap_Control; |
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120 | |
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121 | /* |
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122 | * _Heap_Initialize |
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123 | * |
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124 | * DESCRIPTION: |
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125 | * |
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126 | * This routine initializes the_heap record to manage the |
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127 | * contiguous heap of size bytes which starts at starting_address. |
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128 | * Blocks of memory are allocated from the heap in multiples of |
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129 | * page_size byte units. |
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130 | */ |
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131 | |
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132 | unsigned32 _Heap_Initialize( |
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133 | Heap_Control *the_heap, |
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134 | void *starting_address, |
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135 | unsigned32 size, |
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136 | unsigned32 page_size |
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137 | ); |
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138 | |
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139 | /* |
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140 | * _Heap_Extend |
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141 | * |
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142 | * DESCRIPTION: |
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143 | * |
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144 | * This routine grows the_heap memory area using the size bytes which |
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145 | * begin at starting_address. |
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146 | */ |
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147 | |
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148 | Heap_Extend_status _Heap_Extend( |
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149 | Heap_Control *the_heap, |
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150 | void *starting_address, |
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151 | unsigned32 size, |
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152 | unsigned32 *amount_extended |
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153 | ); |
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154 | |
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155 | /* |
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156 | * _Heap_Allocate |
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157 | * |
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158 | * DESCRIPTION: |
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159 | * |
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160 | * DESCRIPTION: |
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161 | * |
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162 | * This function attempts to allocate a block of size bytes from |
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163 | * the_heap. If insufficient memory is free in the_heap to allocate |
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164 | * a block of the requested size, then NULL is returned. |
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165 | */ |
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166 | |
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167 | void *_Heap_Allocate( |
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168 | Heap_Control *the_heap, |
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169 | unsigned32 size |
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170 | ); |
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171 | |
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172 | /* |
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173 | * _Heap_Size_of_user_area |
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174 | * |
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175 | * DESCRIPTION: |
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176 | * |
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177 | * This kernel routine sets size to the size of the given heap block. |
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178 | * It returns TRUE if the starting_address is in the heap, and FALSE |
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179 | * otherwise. |
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180 | */ |
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181 | |
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182 | boolean _Heap_Size_of_user_area( |
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183 | Heap_Control *the_heap, |
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184 | void *starting_address, |
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185 | unsigned32 *size |
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186 | ); |
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187 | |
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188 | /* |
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189 | * _Heap_Free |
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190 | * |
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191 | * DESCRIPTION: |
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192 | * |
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193 | * This routine returns the block of memory which begins |
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194 | * at starting_address to the_heap. Any coalescing which is |
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195 | * possible with the freeing of this routine is performed. |
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196 | */ |
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197 | |
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198 | boolean _Heap_Free( |
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199 | Heap_Control *the_heap, |
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200 | void *start_address |
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201 | ); |
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202 | |
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203 | /* |
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204 | * _Heap_Walk |
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205 | * |
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206 | * DESCRIPTION: |
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207 | * |
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208 | * This routine walks the heap to verify its integrity. |
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209 | */ |
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210 | |
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211 | void _Heap_Walk( |
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212 | Heap_Control *the_heap, |
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213 | int source, |
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214 | boolean do_dump |
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215 | ); |
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216 | |
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217 | /* |
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218 | * _Heap_Head |
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219 | * |
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220 | * DESCRIPTION: |
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221 | * |
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222 | * This function returns the head of the specified heap. |
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223 | */ |
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224 | |
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225 | STATIC INLINE Heap_Block *_Heap_Head ( |
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226 | Heap_Control *the_heap |
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227 | ); |
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228 | |
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229 | /* |
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230 | * _Heap_Tail |
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231 | * |
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232 | * DESCRIPTION: |
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233 | * |
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234 | * This function returns the tail of the specified heap. |
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235 | */ |
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236 | |
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237 | STATIC INLINE Heap_Block *_Heap_Tail ( |
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238 | Heap_Control *the_heap |
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239 | ); |
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240 | |
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241 | /* |
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242 | * _Heap_Previous_block |
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243 | * |
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244 | * DESCRIPTION: |
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245 | * |
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246 | * This function returns the address of the block which physically |
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247 | * precedes the_block in memory. |
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248 | */ |
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249 | |
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250 | STATIC INLINE Heap_Block *_Heap_Previous_block ( |
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251 | Heap_Block *the_block |
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252 | ); |
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253 | |
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254 | /* |
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255 | * _Heap_Next_block |
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256 | * |
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257 | * DESCRIPTION: |
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258 | * |
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259 | * This function returns the address of the block which physically |
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260 | * follows the_block in memory. |
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261 | */ |
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262 | |
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263 | STATIC INLINE Heap_Block *_Heap_Next_block ( |
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264 | Heap_Block *the_block |
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265 | ); |
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266 | |
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267 | /* |
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268 | * _Heap_Block_at |
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269 | * |
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270 | * DESCRIPTION: |
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271 | * |
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272 | * This function calculates and returns a block's location (address) |
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273 | * in the heap based upad a base address and an offset. |
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274 | */ |
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275 | |
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276 | STATIC INLINE Heap_Block *_Heap_Block_at( |
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277 | void *base, |
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278 | unsigned32 offset |
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279 | ); |
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280 | |
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281 | /*PAGE |
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282 | * |
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283 | * _Heap_User_Block_at |
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284 | * |
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285 | */ |
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286 | |
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287 | STATIC INLINE Heap_Block *_Heap_User_Block_at( |
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288 | void *base |
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289 | ); |
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290 | |
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291 | /* |
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292 | * _Heap_Is_previous_block_free |
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293 | * |
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294 | * DESCRIPTION: |
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295 | * |
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296 | * This function returns TRUE if the previous block of the_block |
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297 | * is free, and FALSE otherwise. |
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298 | */ |
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299 | |
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300 | STATIC INLINE boolean _Heap_Is_previous_block_free ( |
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301 | Heap_Block *the_block |
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302 | ); |
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303 | |
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304 | /* |
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305 | * _Heap_Is_block_free |
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306 | * |
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307 | * DESCRIPTION: |
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308 | * |
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309 | * This function returns TRUE if the block is free, and FALSE otherwise. |
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310 | */ |
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311 | |
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312 | STATIC INLINE boolean _Heap_Is_block_free ( |
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313 | Heap_Block *the_block |
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314 | ); |
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315 | |
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316 | /* |
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317 | * _Heap_Is_block_used |
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318 | * |
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319 | * DESCRIPTION: |
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320 | * |
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321 | * This function returns TRUE if the block is currently allocated, |
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322 | * and FALSE otherwise. |
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323 | */ |
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324 | |
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325 | STATIC INLINE boolean _Heap_Is_block_used ( |
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326 | Heap_Block *the_block |
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327 | ); |
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328 | |
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329 | /* |
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330 | * _Heap_Block_size |
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331 | * |
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332 | * DESCRIPTION: |
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333 | * |
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334 | * This function returns the size of the_block in bytes. |
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335 | */ |
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336 | |
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337 | STATIC INLINE unsigned32 _Heap_Block_size ( |
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338 | Heap_Block *the_block |
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339 | ); |
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340 | |
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341 | /* |
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342 | * _Heap_Start_of_user_area |
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343 | * |
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344 | * DESCRIPTION: |
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345 | * |
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346 | * This function returns the starting address of the portion of the block |
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347 | * which the user may access. |
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348 | */ |
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349 | |
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350 | STATIC INLINE void *_Heap_Start_of_user_area ( |
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351 | Heap_Block *the_block |
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352 | ); |
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353 | |
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354 | /* |
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355 | * _Heap_Is_block_in |
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356 | * |
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357 | * DESCRIPTION: |
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358 | * |
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359 | * This function returns TRUE if the_block is within the memory area |
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360 | * managed by the_heap, and FALSE otherwise. |
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361 | */ |
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362 | |
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363 | STATIC INLINE boolean _Heap_Is_block_in ( |
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364 | Heap_Control *the_heap, |
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365 | Heap_Block *the_block |
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366 | ); |
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367 | |
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368 | |
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369 | /* |
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370 | * _Heap_Is_page_size_valid |
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371 | * |
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372 | * DESCRIPTION: |
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373 | * |
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374 | * This function validates a specified heap page size. If the page size |
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375 | * is 0 or if lies outside a page size alignment boundary it is invalid |
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376 | * and FALSE is returned. Otherwise, the page size is valid and TRUE is |
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377 | * returned. |
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378 | */ |
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379 | |
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380 | STATIC INLINE boolean _Heap_Is_page_size_valid( |
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381 | unsigned32 page_size |
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382 | ); |
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383 | |
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384 | /* |
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385 | * _Heap_Build_flag |
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386 | * |
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387 | * DESCRIPTION: |
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388 | * |
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389 | * This function returns the block flag composed of size and in_use_flag. |
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390 | * The flag returned is suitable for use as a back or front flag in a |
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391 | * heap block. |
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392 | */ |
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393 | |
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394 | STATIC INLINE unsigned32 _Heap_Build_flag ( |
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395 | unsigned32 size, |
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396 | unsigned32 in_use_flag |
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397 | ); |
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398 | |
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399 | #include <rtems/core/heap.inl> |
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400 | |
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401 | #ifdef __cplusplus |
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402 | } |
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403 | #endif |
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404 | |
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405 | #endif |
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406 | /* end of include file */ |
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