1 | // -*- C++ -*- |
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2 | |
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3 | #ifndef _EMPTYCLASS_H_ |
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4 | #define _EMPTYCLASS_H_ |
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5 | |
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6 | #include <stdio.h> // for stderr |
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7 | #include "check.h" |
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8 | #include "array.h" |
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9 | #include "hldefines.h" |
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10 | |
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11 | /** |
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12 | * @class EmptyClass |
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13 | * @brief Maintains superblocks organized by emptiness. |
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14 | */ |
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15 | |
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16 | namespace Hoard { |
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17 | |
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18 | template <class SuperblockType_, |
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19 | int EmptinessClasses> |
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20 | class EmptyClass { |
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21 | |
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22 | enum { SuperblockSize = sizeof(SuperblockType_) }; |
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23 | |
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24 | public: |
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25 | |
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26 | typedef SuperblockType_ SuperblockType; |
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27 | |
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28 | EmptyClass (void) |
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29 | { |
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30 | for (int i = 0; i <= EmptinessClasses + 1; i++) { |
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31 | _available(i) = 0; |
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32 | } |
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33 | } |
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34 | |
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35 | void dumpStats (void) { |
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36 | for (int i = 0; i <= EmptinessClasses + 1; i++) { |
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37 | SuperblockType * s = _available(i); |
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38 | if (s) { |
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39 | fprintf (stderr, "EmptyClass: emptiness class = %d\n", i); |
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40 | while (s) { |
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41 | s->dumpStats(); |
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42 | s = s->getNext(); |
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43 | } |
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44 | } |
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45 | } |
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46 | } |
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47 | |
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48 | |
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49 | SuperblockType * getEmpty (void) { |
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50 | Check<EmptyClass, MyChecker> check (this); |
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51 | SuperblockType * s = _available(0); |
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52 | if (s && |
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53 | (s->getObjectsFree() == s->getTotalObjects())) { |
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54 | // Got an empty one. Remove it. |
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55 | _available(0) = s->getNext(); |
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56 | if (_available(0)) { |
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57 | _available(0)->setPrev (0); |
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58 | } |
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59 | s->setPrev (0); |
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60 | s->setNext (0); |
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61 | return s; |
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62 | } |
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63 | return 0; |
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64 | } |
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65 | |
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66 | SuperblockType * get (void) { |
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67 | Check<EmptyClass, MyChecker> check (this); |
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68 | // Return as empty a superblock as possible |
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69 | // by iterating from the emptiest to the fullest available class. |
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70 | for (int n = 0; n < EmptinessClasses + 1; n++) { |
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71 | SuperblockType * s = _available(n); |
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72 | while (s) { |
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73 | assert (s->isValidSuperblock()); |
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74 | // Got one. Remove it. |
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75 | _available(n) = s->getNext(); |
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76 | if (_available(n)) { |
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77 | _available(n)->setPrev (0); |
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78 | } |
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79 | s->setPrev (0); |
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80 | s->setNext (0); |
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81 | |
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82 | #ifndef NDEBUG |
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83 | // Verify that this superblock is *gone* from the lists. |
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84 | for (int z = 0; z < EmptinessClasses + 1; z++) { |
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85 | SuperblockType * p = _available(z); |
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86 | while (p) { |
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87 | assert (p != s); |
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88 | p = p->getNext(); |
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89 | } |
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90 | } |
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91 | #endif |
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92 | |
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93 | // Ensure that we return a superblock that is as free as |
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94 | // possible. |
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95 | int cl = getFullness (s); |
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96 | if (cl > n) { |
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97 | put (s); |
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98 | SuperblockType * sNew = _available(n); |
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99 | assert (s != sNew); |
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100 | s = sNew; |
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101 | } else { |
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102 | return s; |
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103 | } |
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104 | } |
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105 | } |
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106 | return 0; |
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107 | } |
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108 | |
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109 | void put (SuperblockType * s) { |
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110 | Check<EmptyClass, MyChecker> check (this); |
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111 | |
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112 | #ifndef NDEBUG |
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113 | // Check to verify that this superblock is not already on one of the lists. |
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114 | for (int n = 0; n <= EmptinessClasses + 1; n++) { |
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115 | SuperblockType * p = _available(n); |
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116 | while (p) { |
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117 | assert (p != s); |
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118 | p = p->getNext(); |
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119 | } |
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120 | } |
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121 | #endif |
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122 | |
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123 | // Put on the appropriate available list. |
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124 | int cl = getFullness (s); |
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125 | |
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126 | // printf ("put %x, cl = %d\n", s, cl); |
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127 | s->setPrev (0); |
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128 | s->setNext (_available(cl)); |
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129 | if (_available(cl)) { |
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130 | _available(cl)->setPrev (s); |
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131 | } |
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132 | _available(cl) = s; |
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133 | } |
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134 | |
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135 | INLINE MALLOC_FUNCTION void * malloc (size_t sz) { |
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136 | // Malloc from the fullest superblock first. |
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137 | for (int i = EmptinessClasses; i >= 0; i--) { |
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138 | SuperblockType * s = _available(i); |
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139 | // printf ("i\n"); |
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140 | if (s) { |
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141 | int oldCl = getFullness (s); |
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142 | void * ptr = s->malloc (sz); |
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143 | int newCl = getFullness (s); |
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144 | if (ptr) { |
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145 | if (oldCl != newCl) { |
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146 | transfer (s, oldCl, newCl); |
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147 | } |
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148 | return ptr; |
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149 | } |
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150 | } |
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151 | } |
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152 | return NULL; |
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153 | } |
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154 | |
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155 | INLINE void free (void * ptr) { |
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156 | Check<EmptyClass, MyChecker> check (this); |
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157 | SuperblockType * s = getSuperblock (ptr); |
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158 | int oldCl = getFullness (s); |
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159 | s->free (ptr); |
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160 | int newCl = getFullness (s); |
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161 | |
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162 | if (oldCl != newCl) { |
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163 | // Transfer. |
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164 | transfer (s, oldCl, newCl); |
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165 | } |
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166 | } |
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167 | |
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168 | /// Find the superblock (by bit-masking) that holds a given pointer. |
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169 | static INLINE SuperblockType * getSuperblock (void * ptr) { |
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170 | return SuperblockType::getSuperblock (ptr); |
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171 | } |
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172 | |
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173 | private: |
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174 | |
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175 | void transfer (SuperblockType * s, int oldCl, int newCl) |
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176 | { |
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177 | SuperblockType * prev = s->getPrev(); |
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178 | SuperblockType * next = s->getNext(); |
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179 | if (prev) { prev->setNext (next); } |
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180 | if (next) { next->setPrev (prev); } |
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181 | if (s == _available(oldCl)) { |
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182 | assert (prev == 0); |
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183 | _available(oldCl) = next; |
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184 | } |
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185 | s->setNext (_available(newCl)); |
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186 | s->setPrev (0); |
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187 | if (_available(newCl)) { _available(newCl)->setPrev (s); } |
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188 | _available(newCl) = s; |
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189 | } |
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190 | |
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191 | static INLINE int getFullness (SuperblockType * s) { |
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192 | // Completely full = EmptinessClasses + 1 |
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193 | // Completely empty (all available) = 0 |
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194 | int total = s->getTotalObjects(); |
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195 | int free = s->getObjectsFree(); |
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196 | if (total == free) { |
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197 | return 0; |
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198 | } else { |
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199 | return 1 + (EmptinessClasses * (total - free)) / total; |
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200 | } |
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201 | } |
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202 | |
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203 | /// Forward declarations for the sanity checker. |
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204 | /// @sa Check |
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205 | class MyChecker; |
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206 | friend class MyChecker; |
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207 | |
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208 | /// Precondition and postcondition checking. |
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209 | class MyChecker { |
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210 | public: |
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211 | #ifndef NDEBUG |
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212 | static void precondition (EmptyClass * e) { |
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213 | e->sanityCheckPre(); |
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214 | } |
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215 | static void postcondition (EmptyClass * e) { |
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216 | e->sanityCheck(); |
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217 | } |
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218 | #else |
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219 | static void precondition (EmptyClass *) {} |
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220 | static void postcondition (EmptyClass *) {} |
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221 | #endif |
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222 | }; |
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223 | |
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224 | void sanityCheckPre (void) { sanityCheck(); } |
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225 | |
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226 | void sanityCheck (void) { |
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227 | for (int i = 0; i <= EmptinessClasses + 1; i++) { |
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228 | SuperblockType * s = _available(i); |
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229 | while (s) { |
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230 | assert (getFullness(s) == i); |
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231 | s = s->getNext(); |
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232 | } |
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233 | } |
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234 | } |
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235 | |
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236 | /// The bins of superblocks, by emptiness class. |
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237 | /// @note index 0 = completely empty, EmptinessClasses + 1 = full |
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238 | Array<EmptinessClasses + 2, SuperblockType *> _available; |
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239 | |
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240 | }; |
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241 | |
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242 | } |
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243 | |
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244 | |
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245 | #endif |
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