1 | // -*- C++ -*- |
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2 | |
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3 | // CoalesceableHeap: manages a range of coalesceable memory. |
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4 | |
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5 | #ifndef _COALESCEABLEHEAP_H_ |
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6 | #define _COALESCEABLEHEAP_H_ |
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7 | |
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8 | #include <assert.h> |
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9 | #include <new.h> |
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10 | |
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11 | #define MULTIPLE_HEAP_SUPPORT 0 |
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12 | #define USE_TOP 0 |
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13 | |
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14 | template <class SuperHeap> |
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15 | class RequireCoalesceable : public SuperHeap { |
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16 | public: |
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17 | |
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18 | // Some thin wrappers over Header methods. |
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19 | inline static int getHeap (void * ptr) { return Header::getHeader(ptr)->getHeap(); } |
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20 | inline static void setHeap (void * ptr, int h) { Header::getHeader(ptr)->setHeap(h); } |
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21 | inline static int getPrevHeap (void * ptr) { return Header::getHeader(ptr)->getPrevHeap(); } |
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22 | inline static void setPrevHeap (void * ptr, int h) { Header::getHeader(ptr)->setPrevHeap(h); } |
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23 | |
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24 | inline static size_t getSize (void * ptr) { return Header::getHeader(ptr)->getSize(); } |
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25 | |
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26 | inline static void setSize (void * ptr, size_t sz) { Header::getHeader(ptr)->setSize(sz); } |
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27 | inline static size_t getPrevSize (void * ptr) { return Header::getHeader(ptr)->getPrevSize(); } |
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28 | inline static void setPrevSize (void * ptr, size_t sz) { Header::getHeader(ptr)->setPrevSize(sz); } |
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29 | inline static void markFree (void * ptr) { Header::getHeader(ptr)->markFree(); } |
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30 | inline static void markInUse (void * ptr) { Header::getHeader(ptr)->markInUse(); } |
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31 | inline static void markPrevInUse (void * ptr) { Header::getHeader(ptr)->markPrevInUse(); } |
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32 | inline static void markMmapped (void * ptr) { Header::getHeader(ptr)->markMmapped(); } |
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33 | inline static int isFree (void * ptr) { return Header::getHeader(ptr)->isFree(); } |
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34 | inline static int isPrevFree (void * ptr) { return Header::getHeader(ptr)->isPrevFree(); } |
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35 | inline static int isMmapped (void * ptr) { return Header::getHeader(ptr)->isMmapped(); } |
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36 | inline static void * getNext (void * ptr) { return Header::getHeader(ptr)->getNext(); } |
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37 | inline static void * getPrev (void * ptr) { return Header::getHeader(ptr)->getPrev(); } |
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38 | |
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39 | |
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40 | // The Header for every object, allocated or freed. |
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41 | class Header { |
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42 | public: |
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43 | |
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44 | // Returns the start of the object (i.e., just past the header). |
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45 | inline static void * makeObject (void * buf, size_t prevsz, size_t sz) { |
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46 | Header * h = new (buf) Header (prevsz, sz); |
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47 | // Record this object as in use in the next header. |
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48 | h->markInUse(); |
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49 | // Record this object's size in the next header. |
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50 | h->getNextHeader()->setPrevSize (sz); |
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51 | return Header::getObject (h); |
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52 | } |
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53 | |
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54 | #if USE_TOP |
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55 | // Returns the start of the object, but without updating the next header. |
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56 | inline static void * makeTop (void * buf, size_t prevsz, size_t sz) { |
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57 | Header * h = new (buf) Header (prevsz, sz); |
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58 | // Pretend the previous object is in use to prevent us from |
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59 | // accidentally coalescing backwards with non-existent memory. |
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60 | h->markPrevInUse(); |
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61 | h->markInUse(); |
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62 | return Header::getObject (h); |
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63 | } |
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64 | #endif |
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65 | |
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66 | inline void sanityCheck (void) { |
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67 | #ifndef NDEBUG |
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68 | int headerSize = sizeof(Header); |
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69 | assert (headerSize <= sizeof(double)); |
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70 | assert (getSize() == getNextHeader()->getPrevSize()); |
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71 | assert (isFree() == getNextHeader()->isPrevFree()); |
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72 | assert (getNextHeader()->getPrev() == getObject(this)); |
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73 | #if 0 |
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74 | if (isPrevFree()) { |
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75 | assert (getPrevSize() == getHeader(getPrev())->getSize()); |
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76 | } |
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77 | #endif |
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78 | #endif |
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79 | } |
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80 | |
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81 | // Get the header for a given object. |
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82 | inline static Header * getHeader (const void * ptr) { return ((Header *) ptr - 1); } |
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83 | |
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84 | // Get the object for a given header. |
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85 | inline static void * getObject (const Header * hd) { return (void *) (hd + 1); } |
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86 | |
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87 | inline void setPrevSize (const size_t sz){ _prevSize = sz >> SIZE_SHIFT; } |
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88 | inline size_t getPrevSize (void) const { return _prevSize << SIZE_SHIFT; } |
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89 | |
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90 | inline void markFree (void) { getNextHeader()->markPrevFree(); } |
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91 | inline void markInUse (void) { getNextHeader()->markPrevInUse(); } |
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92 | inline void markMmapped (void) { setIsMmapped(); } // _isMmapped = IS_MMAPPED; } |
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93 | inline void markNotMmapped (void) { setIsNotMmapped(); } // _isMmapped = NOT_MMAPPED; } |
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94 | inline int isFree (void) const { return getNextHeader()->isPrevFree(); } |
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95 | inline int isNextFree (void) const { return getNextHeader()->getNextHeader()->isPrevFree(); } |
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96 | inline int isMmapped (void) const { return getIsMmapped(); } // _isMmapped == IS_MMAPPED; } |
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97 | inline void * getPrev (void) const { return ((char *) this) - getPrevSize(); } |
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98 | inline void * getNext (void) const { return ((char *) (this + 2)) + getSize(); } |
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99 | |
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100 | inline void markPrevFree (void) { setPrevIsFree(); } // _prevStatus = FREE; } |
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101 | inline void markPrevInUse (void) { setPrevInUse(); } //_prevStatus = IN_USE; } |
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102 | inline int isPrevFree (void) const { return getPrevIsFree(); } // return _prevStatus == FREE; } |
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103 | inline void setSize (size_t sz) { |
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104 | _size = ((sz >> SIZE_SHIFT) << 2) | (_size & 3); |
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105 | } |
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106 | |
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107 | inline size_t getSize (void) const { |
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108 | return (_size >> 2) << SIZE_SHIFT; |
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109 | } |
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110 | |
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111 | // inline size_t getSize (void) const { return getSize(); } // return _size << SIZE_SHIFT; } |
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112 | // inline void setSize (const size_t sz) { setSize(sz); } // _size = sz >> SIZE_SHIFT; } |
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113 | |
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114 | #if MULTIPLE_HEAP_SUPPORT |
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115 | inline int getHeap (void) const { return _currHeap; } |
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116 | inline void setHeap (int h) { _currHeap = h; } |
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117 | inline int getPrevHeap (void) const { return _prevHeap; } |
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118 | inline void setPrevHeap (int h) { _prevHeap = h; } |
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119 | #else |
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120 | inline int getHeap (void) const { return 0; } |
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121 | inline void setHeap (int) { } |
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122 | inline int getPrevHeap (void) const { return 0; } |
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123 | inline void setPrevHeap (int) { } |
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124 | #endif |
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125 | |
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126 | |
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127 | private: |
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128 | |
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129 | inline Header (void) {} |
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130 | inline Header (size_t prevsz, size_t sz) |
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131 | : |
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132 | // Record sizes, shifting to account for "stolen bits". |
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133 | _prevSize (prevsz >> SIZE_SHIFT) |
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134 | #if 0 |
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135 | ,_size (sz >> SIZE_SHIFT), |
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136 | // Assume that objects are NOT mmapped. |
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137 | _isMmapped (NOT_MMAPPED) |
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138 | #if MULTIPLE_HEAP_SUPPORT |
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139 | , _prevHeap (0), |
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140 | _currHeap (0) |
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141 | #endif |
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142 | #endif |
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143 | { |
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144 | _size = 0; |
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145 | setSize (sz); |
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146 | setIsNotMmapped(); |
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147 | assert (sizeof(Header) <= sizeof(double)); |
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148 | } |
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149 | |
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150 | inline Header * getNextHeader (void) const { |
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151 | return ((Header *) ((char *) (this + 1) + getSize())); |
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152 | } |
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153 | |
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154 | // How many bits we can shift size over without losing information. |
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155 | // 3 = double-word alignment. |
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156 | enum { SIZE_SHIFT = 3 }; |
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157 | |
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158 | #if !(MULTIPLE_HEAP_SUPPORT) // original |
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159 | |
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160 | inline int getIsMmapped (void) const { |
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161 | return _size & 1; |
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162 | } |
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163 | |
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164 | inline void setIsMmapped (void) { |
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165 | _size |= 1; |
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166 | } |
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167 | |
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168 | inline void setIsNotMmapped (void) { |
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169 | _size &= ~1; |
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170 | } |
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171 | |
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172 | inline int getPrevIsFree (void) const { |
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173 | return _size & 2; |
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174 | } |
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175 | |
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176 | inline void setPrevIsFree (void) { |
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177 | _size |= 2; |
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178 | } |
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179 | |
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180 | inline void setPrevInUse (void) { |
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181 | _size &= ~2; |
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182 | } |
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183 | |
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184 | |
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185 | #if 1 |
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186 | // The size of the previous object. |
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187 | size_t _prevSize; |
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188 | |
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189 | // The size of the current object, with NOT_MMAPPED & IN_USE bits. |
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190 | size_t _size; |
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191 | |
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192 | #else |
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193 | // The size of the previous object. |
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194 | enum { NUM_BITS_STOLEN_FROM_PREVSIZE = 0 }; |
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195 | size_t _prevSize : sizeof(size_t) * 8 - NUM_BITS_STOLEN_FROM_PREVSIZE; |
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196 | |
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197 | // The size of the current object. |
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198 | enum { NUM_BITS_STOLEN_FROM_SIZE = 2 }; |
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199 | size_t _size : sizeof(size_t) * 8 - NUM_BITS_STOLEN_FROM_SIZE; |
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200 | |
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201 | // Is the current object mmapped? |
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202 | enum { NOT_MMAPPED = 0, IS_MMAPPED = 1 }; |
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203 | unsigned int _isMmapped : 1; |
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204 | |
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205 | // Is the previous object free or in use? |
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206 | enum { IN_USE = 0, FREE = 1 }; |
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207 | unsigned int _prevStatus : 1; |
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208 | #endif |
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209 | |
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210 | #else // new support for scalability... |
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211 | |
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212 | // Support for 2^5 = 32 heaps. |
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213 | enum { NUM_BITS_FOR_HEAP = 5 }; |
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214 | |
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215 | enum { NUM_BITS_STOLEN_FROM_SIZE = NUM_BITS_FOR_HEAP + 1 }; // 1 for isMmapped |
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216 | enum { NUM_BITS_STOLEN_FROM_PREVSIZE = NUM_BITS_FOR_HEAP + 1 }; // 1 for isPrevFree |
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217 | |
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218 | // Max object size. |
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219 | enum { MAX_OBJECT_SIZE = 1 << (sizeof(size_t) * 8 + SIZE_SHIFT - NUM_BITS_STOLEN_FROM_SIZE) }; |
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220 | |
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221 | //// word 1 //// |
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222 | |
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223 | // The size of the previous object. |
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224 | size_t _prevSize : sizeof(size_t) * 8 - NUM_BITS_STOLEN_FROM_PREVSIZE; |
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225 | |
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226 | // What's the previous heap? |
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227 | unsigned int _prevHeap : NUM_BITS_FOR_HEAP; |
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228 | |
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229 | // Is the previous object free or in use? |
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230 | enum { FREE = 0, IN_USE = 1 }; |
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231 | unsigned int _prevStatus : 1; |
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232 | |
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233 | //// word 2 //// |
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234 | |
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235 | // The size of the current object. |
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236 | size_t _size : sizeof(size_t) * 8 - NUM_BITS_STOLEN_FROM_SIZE; |
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237 | |
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238 | // What's the current heap? |
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239 | unsigned int _currHeap : NUM_BITS_FOR_HEAP; |
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240 | |
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241 | // Is the current object mmapped? |
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242 | enum { NOT_MMAPPED = 0, IS_MMAPPED = 1 }; |
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243 | unsigned int _isMmapped : 1; |
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244 | |
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245 | #endif |
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246 | }; |
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247 | |
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248 | }; |
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249 | |
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250 | |
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251 | |
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252 | template <class SuperHeap> |
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253 | class CoalesceableHeap : public RequireCoalesceable<SuperHeap> { |
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254 | public: |
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255 | |
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256 | CoalesceableHeap (void) |
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257 | #if USE_TOP |
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258 | : top (NULL) |
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259 | #endif |
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260 | { } |
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261 | |
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262 | inline void * malloc (size_t sz) { |
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263 | #if !USE_TOP |
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264 | void * buf = SuperHeap::malloc (sz + sizeof(Header)); |
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265 | if (buf == NULL) { |
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266 | return NULL; |
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267 | } else { |
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268 | Header * header = (Header *) buf; |
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269 | |
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270 | // |
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271 | // Assume that everything allocated is NOT mmapped. |
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272 | // It is the responsibility of a child layer |
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273 | // to mark mmapped objects as such. |
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274 | // |
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275 | |
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276 | header->markNotMmapped (); |
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277 | |
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278 | // |
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279 | // Record the size of this object in the current header |
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280 | // and the next. |
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281 | // |
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282 | |
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283 | header->setSize (sz); |
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284 | Header * nextHeader = Header::getHeader (header->getNext()); |
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285 | nextHeader->setSize (0); |
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286 | nextHeader->setPrevSize (sz); |
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287 | |
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288 | // |
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289 | // Mark the subsequent "object" as in use in order to prevent |
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290 | // accidental coalescing. |
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291 | // |
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292 | |
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293 | nextHeader->markInUse (); |
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294 | return Header::getObject (header); |
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295 | } |
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296 | #else |
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297 | |
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298 | if ((top == NULL) || (sz + sizeof(Header) > getSize(top))) { |
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299 | // There wasn't enough space in top. Get more memory (enough to |
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300 | // hold an extra header). |
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301 | void * buf = SuperHeap::malloc (sz + 2 * sizeof(Header)); |
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302 | if (buf == NULL) |
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303 | return NULL; |
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304 | void * ptr = Header::makeTop (buf, 0, sz); |
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305 | // Is this object contiguous with top? |
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306 | if ((top != NULL) && (getNext(top) == ptr)) { |
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307 | // It is contiguous. Extend top. |
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308 | setSize (top, getSize(top) + 2 * sizeof(Header) + sz); |
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309 | |
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310 | // printf ("Extended top by %d\n", getSize(ptr)); |
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311 | |
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312 | } else { |
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313 | // We got some non-contiguous memory. |
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314 | // For now, just abandon top. |
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315 | |
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316 | // printf ("Abandoning top.\n"); |
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317 | setSize (ptr, sz + sizeof(Header)); |
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318 | top = ptr; |
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319 | } |
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320 | } |
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321 | assert (getSize(top) >= sz + sizeof(Header)); |
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322 | // Carve out an sz object from top and advance top. |
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323 | size_t oldTopSize = getSize(top); |
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324 | void * newObject = top; |
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325 | setSize (newObject, sz); |
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326 | top = getNext (newObject); |
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327 | // Set top's new header. |
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328 | setSize (top, oldTopSize - sz - sizeof(Header)); |
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329 | setPrevSize (top, sz); |
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330 | // Mark the new top as in use to prevent it from being coalesced. |
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331 | |
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332 | markInUse (top); |
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333 | |
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334 | assert (getNext(newObject) == top); |
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335 | Header::getHeader(newObject)->sanityCheck(); |
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336 | //printf ("top = %x\n", top); |
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337 | assert (!isFree(top)); |
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338 | return newObject; |
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339 | #endif |
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340 | } |
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341 | |
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342 | inline void free (void * ptr) { |
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343 | assert (isFree(ptr)); |
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344 | #if USE_TOP |
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345 | // Try to extend top if this object is right before it. |
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346 | if (getNext(ptr) == top) { |
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347 | assert (getSize(ptr) == getPrevSize(top)); |
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348 | // Extend top backwards. |
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349 | setSize (ptr, getSize(ptr) + sizeof(Header) + getSize(top)); |
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350 | top = ptr; |
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351 | // printf ("free: top = %x\n", top); |
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352 | return; |
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353 | } |
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354 | #endif |
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355 | SuperHeap::free (Header::getHeader(ptr)); |
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356 | } |
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357 | |
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358 | |
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359 | #if USE_TOP |
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360 | inline void clear (void) { |
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361 | top = NULL; |
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362 | SuperHeap::clear (); |
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363 | } |
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364 | #endif |
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365 | |
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366 | private: |
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367 | |
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368 | #if USE_TOP |
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369 | // The top object allocated so far. |
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370 | void * top; |
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371 | #endif |
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372 | |
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373 | }; |
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374 | |
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375 | |
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376 | #endif // _COALESCEABLEHEAP_H_ |
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377 | |
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