1 | // -*- C++ -*- |
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2 | |
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3 | /* |
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4 | |
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5 | Heap Layers: An Extensible Memory Allocation Infrastructure |
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6 | |
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7 | Copyright (C) 2000-2003 by Emery Berger |
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8 | http://www.cs.umass.edu/~emery |
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9 | emery@cs.umass.edu |
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10 | |
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11 | This program is free software; you can redistribute it and/or modify |
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12 | it under the terms of the GNU General Public License as published by |
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13 | the Free Software Foundation; either version 2 of the License, or |
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14 | (at your option) any later version. |
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15 | |
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16 | This program is distributed in the hope that it will be useful, |
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17 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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18 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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19 | GNU General Public License for more details. |
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20 | |
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21 | You should have received a copy of the GNU General Public License |
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22 | along with this program; if not, write to the Free Software |
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23 | Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
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24 | |
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25 | */ |
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26 | |
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27 | #ifndef _REDIRECTFREE_H_ |
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28 | #define _REDIRECTFREE_H_ |
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29 | |
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30 | #include "fred.h" |
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31 | #include "guard.h" |
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32 | |
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33 | namespace Hoard { |
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34 | |
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35 | /** |
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36 | * @class RedirectFree |
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37 | * @brief Routes free calls to the Superblock's owner heap. |
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38 | * @note We also lock the heap on calls to malloc. |
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39 | */ |
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40 | |
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41 | template <class Heap, |
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42 | typename SuperblockType_> |
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43 | class RedirectFree { |
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44 | public: |
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45 | |
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46 | enum { Alignment = (int) Heap::Alignment }; |
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47 | |
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48 | typedef SuperblockType_ SuperblockType; |
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49 | |
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50 | inline void * malloc (size_t sz) { |
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51 | return _theHeap.malloc (sz); |
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52 | } |
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53 | |
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54 | size_t getSize (void * ptr) { |
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55 | return Heap::getSize (ptr); |
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56 | } |
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57 | |
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58 | SuperblockType * getSuperblock (void * ptr) { |
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59 | return Heap::getSuperblock (ptr); |
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60 | } |
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61 | |
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62 | /// Free the given object, obeying the required locking protocol. |
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63 | static inline void free (void * ptr) { |
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64 | // Get the superblock header. |
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65 | SuperblockType * s = reinterpret_cast<SuperblockType *>(Heap::getSuperblock (ptr)); |
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66 | |
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67 | assert (s->isValidSuperblock()); |
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68 | |
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69 | // Find out who the owner is. |
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70 | |
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71 | typedef BaseHoardManager<SuperblockType> * baseHeapType; |
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72 | baseHeapType owner; |
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73 | |
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74 | s->lock(); |
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75 | |
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76 | // By acquiring the lock on the superblock (above), |
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77 | // we prevent it from moving up to a higher heap. |
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78 | // This eventually pins it down in one heap, |
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79 | // so this loop is guaranteed to terminate. |
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80 | // (It should generally take no more than two iterations.) |
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81 | |
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82 | for (;;) { |
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83 | owner = reinterpret_cast<baseHeapType>(s->getOwner()); |
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84 | assert (owner != NULL); |
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85 | assert (owner->isValid()); |
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86 | // Lock the owner. If ownership changed between these two lines, |
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87 | // we'll detect it and try again. |
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88 | owner->lock(); |
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89 | if (owner == reinterpret_cast<baseHeapType>(s->getOwner())) { |
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90 | owner->free (ptr); |
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91 | owner->unlock(); |
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92 | s->unlock(); |
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93 | return; |
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94 | } |
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95 | owner->unlock(); |
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96 | |
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97 | // Sleep a little. |
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98 | HL::Fred::yield(); |
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99 | } |
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100 | } |
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101 | |
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102 | private: |
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103 | |
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104 | Heap _theHeap; |
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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 | |
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110 | #endif |
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