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) 2000-2005 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 _XALLOCHEAP_H_ |
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28 | #define _XALLOCHEAP_H_ |
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29 | |
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30 | namespace HL { |
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31 | |
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32 | template <int ArenaSize, class SuperHeap> |
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33 | class XallocHeap : public SuperHeap { |
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34 | |
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35 | public: |
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36 | |
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37 | inline XallocHeap (void) { |
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38 | start_of_array = (char *) SuperHeap::malloc (ArenaSize); |
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39 | end_of_array = start_of_array + align(sizeof(Nuggie)); |
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40 | size_lval(end_of_array) = 0; |
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41 | last_block = NULL; |
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42 | } |
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43 | |
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44 | inline ~XallocHeap (void) { |
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45 | SuperHeap::free (start_of_array); |
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46 | } |
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47 | |
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48 | inline void * malloc (size_t size) { |
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49 | char * old_end_of_array = end_of_array; |
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50 | end_of_array += align(size + sizeof(Nuggie)); |
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51 | if (old_end_of_array + size >= start_of_array + ArenaSize) { |
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52 | // We're out of memory. |
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53 | return NULL; |
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54 | } |
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55 | size_lval(end_of_array) = end_of_array - old_end_of_array; |
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56 | clear_use(end_of_array); /* this is not necessary, cause it will be zero */ |
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57 | set_use(old_end_of_array); |
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58 | last_block = old_end_of_array; |
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59 | return old_end_of_array; |
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60 | } |
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61 | |
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62 | inline void free (void * ptr) { |
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63 | char * p = (char *) ptr; |
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64 | char * q; |
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65 | /* At this point we could check that the in_use bit for this block |
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66 | is set, and also check that the size is right */ |
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67 | clear_use(p); /* mark this block as unused */ |
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68 | if (p == last_block) { |
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69 | while (1) { |
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70 | q = prev_block(p); |
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71 | if (q == p) { |
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72 | last_block = NULL; |
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73 | end_of_array = p; |
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74 | break; /* only happens when we get to the beginning */ |
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75 | } |
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76 | if (in_use(q)) { |
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77 | last_block = q; |
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78 | end_of_array = p; |
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79 | break; |
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80 | } |
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81 | p = q; |
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82 | } |
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83 | } |
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84 | } |
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85 | |
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86 | private: |
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87 | |
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88 | static inline size_t& size_lval (char * x) { |
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89 | return (((Nuggie *)(((char *)x) - sizeof(Nuggie)))->size); |
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90 | } |
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91 | |
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92 | static inline char * prev_block (char * x) { |
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93 | return (((char *) x) - (size_lval(x) & (~1))); |
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94 | } |
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95 | |
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96 | static inline int in_use (char * x) { |
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97 | return (size_lval(x) & (1)); |
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98 | } |
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99 | |
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100 | static inline void set_use (char * x) { |
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101 | (size_lval(x) |= (1)); |
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102 | } |
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103 | |
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104 | static inline void clear_use (char * x) { |
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105 | (size_lval(x) &= (~1)); |
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106 | } |
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107 | |
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108 | class Nuggie { |
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109 | public: |
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110 | size_t size; |
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111 | }; |
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112 | |
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113 | inline static size_t align (int sz) { |
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114 | return (sz + (sizeof(double) - 1)) & ~(sizeof(double) - 1); |
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115 | } |
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116 | |
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117 | char * end_of_array; |
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118 | char * start_of_array; |
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119 | char * last_block; |
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120 | }; |
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121 | |
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122 | }; |
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123 | |
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124 | |
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125 | #endif |
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