1 | /* -*- C++ -*- */ |
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2 | |
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3 | /** |
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4 | * @class ZoneHeap |
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5 | * @brief A zone (or arena, or region) based allocator. |
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6 | * @author Emery Berger |
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7 | * @date June 2000 |
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8 | * |
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9 | * Uses the superclass to obtain large chunks of memory that are only |
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10 | * returned when the heap itself is destroyed. |
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11 | * |
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12 | */ |
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13 | |
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14 | #ifndef _ZONEHEAP_H_ |
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15 | #define _ZONEHEAP_H_ |
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16 | |
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17 | #include <assert.h> |
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18 | |
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19 | namespace HL { |
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20 | |
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21 | template <class Super, size_t ChunkSize> |
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22 | class ZoneHeap : public Super { |
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23 | public: |
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24 | |
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25 | ZoneHeap (void) |
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26 | : sizeRemaining (-1), |
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27 | currentArena (NULL), |
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28 | pastArenas (NULL) |
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29 | {} |
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30 | |
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31 | ~ZoneHeap (void) |
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32 | { |
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33 | // printf ("deleting arenas!\n"); |
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34 | // Delete all of our arenas. |
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35 | Arena * ptr = pastArenas; |
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36 | while (ptr != NULL) { |
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37 | void * oldPtr = (void *) ptr; |
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38 | ptr = ptr->nextArena; |
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39 | //printf ("deleting %x\n", ptr); |
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40 | Super::free (oldPtr); |
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41 | } |
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42 | if (currentArena != NULL) |
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43 | //printf ("deleting %x\n", currentArena); |
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44 | Super::free (currentArena); |
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45 | } |
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46 | |
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47 | inline void * malloc (size_t sz) { |
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48 | void * ptr = zoneMalloc (sz); |
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49 | return ptr; |
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50 | } |
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51 | |
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52 | /// Free in a zone allocator is a no-op. |
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53 | inline void free (void *) {} |
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54 | |
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55 | /// Remove in a zone allocator is a no-op. |
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56 | inline int remove (void *) { return 0; } |
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57 | |
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58 | |
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59 | private: |
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60 | |
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61 | inline static size_t align (int sz) { |
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62 | return (sz + (sizeof(double) - 1)) & ~(sizeof(double) - 1); |
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63 | } |
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64 | |
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65 | inline void * zoneMalloc (size_t sz) { |
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66 | void * ptr; |
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67 | // Round up size to an aligned value. |
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68 | sz = align (sz); |
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69 | // Get more space in our arena if there's not enough room in this one. |
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70 | if ((currentArena == NULL) || (sizeRemaining < (int) sz)) { |
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71 | // First, add this arena to our past arena list. |
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72 | if (currentArena != NULL) { |
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73 | currentArena->nextArena = pastArenas; |
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74 | pastArenas = currentArena; |
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75 | } |
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76 | // Now get more memory. |
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77 | size_t allocSize = ChunkSize; |
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78 | if (allocSize < sz) { |
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79 | allocSize = sz; |
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80 | } |
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81 | currentArena = |
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82 | (Arena *) Super::malloc (allocSize + sizeof(Arena)); |
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83 | if (currentArena == NULL) { |
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84 | return NULL; |
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85 | } |
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86 | currentArena->arenaSpace = (char *) (currentArena + 1); |
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87 | currentArena->nextArena = NULL; |
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88 | sizeRemaining = ChunkSize; |
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89 | } |
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90 | // Bump the pointer and update the amount of memory remaining. |
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91 | sizeRemaining -= sz; |
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92 | ptr = currentArena->arenaSpace; |
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93 | currentArena->arenaSpace += sz; |
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94 | assert (ptr != NULL); |
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95 | return ptr; |
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96 | } |
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97 | |
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98 | class Arena { |
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99 | public: |
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100 | Arena * nextArena; |
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101 | char * arenaSpace; |
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102 | double _dummy; // For alignment. |
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103 | }; |
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104 | |
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105 | /// Space left in the current arena. |
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106 | long sizeRemaining; |
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107 | |
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108 | /// The current arena. |
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109 | Arena * currentArena; |
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110 | |
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111 | /// A linked list of past arenas. |
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112 | Arena * pastArenas; |
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113 | }; |
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114 | |
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115 | } |
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116 | |
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117 | #endif |
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