1 | /* -*- C++ -*- */ |
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2 | |
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3 | #ifndef _CHUNK_H_ |
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4 | #define _CHUNK_H_ |
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5 | |
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6 | /* |
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7 | |
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8 | Heap Layers: An Extensible Memory Allocation Infrastructure |
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9 | |
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10 | Copyright (C) 2000-2003 by Emery Berger |
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11 | http://www.cs.umass.edu/~emery |
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12 | emery@cs.umass.edu |
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13 | |
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14 | This program is free software; you can redistribute it and/or modify |
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15 | it under the terms of the GNU General Public License as published by |
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16 | the Free Software Foundation; either version 2 of the License, or |
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17 | (at your option) any later version. |
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18 | |
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19 | This program is distributed in the hope that it will be useful, |
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20 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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21 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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22 | GNU General Public License for more details. |
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23 | |
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24 | You should have received a copy of the GNU General Public License |
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25 | along with this program; if not, write to the Free Software |
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26 | Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
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27 | |
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28 | */ |
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29 | |
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30 | #include <assert.h> |
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31 | |
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32 | namespace HL { |
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33 | |
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34 | template <int chunkSize, int slotSize> |
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35 | class Chunk { |
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36 | public: |
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37 | |
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38 | inline Chunk (void); |
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39 | |
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40 | // Get and put slots. |
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41 | // Get returns NULL if there are no slots available. |
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42 | inline void * getSlot (void); |
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43 | inline void putSlot (void *); |
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44 | |
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45 | // How many slots are there in total? |
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46 | inline static int getNumSlots (void); |
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47 | |
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48 | // How many slots are available? |
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49 | inline int getNumSlotsFree (void); |
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50 | |
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51 | // How many slots are available? |
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52 | inline int getNumSlotsInUse (void); |
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53 | |
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54 | // Find a chunk given its slot. |
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55 | inline static Chunk * getChunk (void *); |
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56 | |
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57 | class ChunkBlock { |
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58 | public: |
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59 | void setChunk (Chunk * ch) { _myChunk = ch; } |
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60 | Chunk * getChunk (void) { return _myChunk; } |
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61 | void setNext (ChunkBlock * n) { _next = n; } |
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62 | ChunkBlock * getNext (void) { return _next; } |
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63 | private: |
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64 | Chunk * _myChunk; // If allocated, point to the chunk. |
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65 | ChunkBlock * _next; // If not allocated, point to the next chunk block. |
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66 | }; |
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67 | |
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68 | // Find a chunk block for a given pointer. |
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69 | static inline ChunkBlock * getChunkBlock (void * ptr) { |
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70 | assert (ptr != NULL); |
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71 | return (ChunkBlock *) ptr - 1; |
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72 | } |
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73 | |
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74 | private: |
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75 | |
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76 | ChunkBlock * freeSlots; |
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77 | int numSlotsAvailable; |
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78 | |
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79 | static inline size_t align (size_t sz) { |
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80 | return (sz + (sizeof(double) - 1)) & ~(sizeof(double) - 1); |
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81 | } |
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82 | |
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83 | }; |
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84 | |
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85 | template <int chunkSize, int slotSize> |
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86 | Chunk<chunkSize, slotSize>::Chunk (void) |
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87 | : freeSlots (NULL), |
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88 | numSlotsAvailable (getNumSlots()) |
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89 | { |
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90 | //printf ("numSlots = %d\n", numSlots); |
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91 | int numSlots = getNumSlots(); |
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92 | assert (numSlots > 0); |
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93 | const int blksize = align(sizeof(ChunkBlock) + slotSize); |
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94 | //printf ("blksize = %d\n", blksize); |
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95 | // Carve up the chunk into a number of slots. |
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96 | ChunkBlock * b = (ChunkBlock *) (this + 1); |
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97 | for (int i = 0; i < numSlots; i++) { |
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98 | assert ((unsigned long) b < ((unsigned long) (this + 1) + blksize * numSlots)); |
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99 | new (b) ChunkBlock; |
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100 | b->setChunk (this); |
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101 | assert (b->getChunk() == this); |
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102 | b->setNext (freeSlots); |
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103 | freeSlots = b; |
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104 | b = (ChunkBlock *) ((char *) b + blksize); |
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105 | } |
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106 | } |
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107 | |
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108 | |
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109 | template <int chunkSize, int slotSize> |
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110 | void * Chunk<chunkSize, slotSize>::getSlot (void) |
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111 | { |
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112 | if (freeSlots == NULL) { |
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113 | assert (numSlotsAvailable == 0); |
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114 | return NULL; |
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115 | } |
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116 | assert (numSlotsAvailable > 0); |
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117 | ChunkBlock * b = freeSlots; |
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118 | freeSlots = freeSlots->getNext(); |
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119 | numSlotsAvailable--; |
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120 | b->setChunk (this); // FIX ME -- this should be unnecessary. |
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121 | b->setNext (NULL); |
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122 | void * ptr = (void *) (b + 1); |
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123 | Chunk<chunkSize, slotSize> * bch = getChunk(ptr); |
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124 | assert (bch == this); |
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125 | return (void *) (b + 1); |
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126 | } |
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127 | |
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128 | |
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129 | template <int chunkSize, int slotSize> |
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130 | void Chunk<chunkSize, slotSize>::putSlot (void * ptr) |
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131 | { |
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132 | ChunkBlock * b = getChunkBlock (ptr); |
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133 | assert (b->getChunk() == this); |
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134 | b->setNext (freeSlots); |
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135 | freeSlots = b; |
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136 | numSlotsAvailable++; |
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137 | assert (numSlotsAvailable <= getNumSlots()); |
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138 | } |
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139 | |
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140 | |
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141 | template <int chunkSize, int slotSize> |
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142 | int Chunk<chunkSize, slotSize>::getNumSlots (void) |
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143 | { |
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144 | return ((chunkSize - sizeof(Chunk)) / align (sizeof(ChunkBlock) + slotSize)); |
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145 | } |
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146 | |
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147 | |
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148 | template <int chunkSize, int slotSize> |
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149 | int Chunk<chunkSize, slotSize>::getNumSlotsFree (void) |
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150 | { |
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151 | return numSlotsAvailable; |
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152 | } |
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153 | |
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154 | |
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155 | template <int chunkSize, int slotSize> |
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156 | int Chunk<chunkSize, slotSize>::getNumSlotsInUse (void) |
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157 | { |
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158 | return getNumSlots() - numSlotsAvailable; |
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159 | } |
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160 | |
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161 | |
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162 | template <int chunkSize, int slotSize> |
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163 | Chunk<chunkSize, slotSize> * Chunk<chunkSize, slotSize>::getChunk (void * ptr) |
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164 | { |
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165 | ChunkBlock * ch = getChunkBlock (ptr); |
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166 | return ch->getChunk(); |
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167 | } |
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168 | |
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169 | }; |
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170 | |
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171 | #endif |
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