[176] | 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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