[176] | 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 | |
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| 28 | // An "Obstack". |
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| 29 | |
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| 30 | #ifndef _HLOBSTACK_H_ |
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| 31 | #define _HLOBSTACK_H_ |
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| 32 | |
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| 33 | |
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| 34 | #ifdef __cplusplus |
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| 35 | |
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| 36 | #include <assert.h> |
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| 37 | #include <new> |
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| 38 | |
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| 39 | /** |
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| 40 | * @class ObstackHeap |
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| 41 | * @brief Implements obstack functionality (as in the GNU obstack library). |
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| 42 | */ |
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| 43 | |
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| 44 | namespace HL { |
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| 45 | |
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| 46 | template <int ChunkSize, class SuperHeap> |
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| 47 | class ObstackHeap : public SuperHeap { |
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| 48 | public: |
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| 49 | |
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| 50 | ObstackHeap (void) |
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| 51 | { |
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| 52 | // Get one chunk and set the current position marker. |
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| 53 | currentChunk = makeChunk (NULL, ChunkSize); |
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| 54 | currentBase = nextPos = (char *) (currentChunk + 1); |
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| 55 | assert (isValid()); |
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| 56 | } |
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| 57 | |
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| 58 | ~ObstackHeap (void) { |
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| 59 | // Free every chunk. |
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| 60 | assert (isValid()); |
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| 61 | ChunkHeader * ch = currentChunk; |
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| 62 | while (ch != NULL) { |
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| 63 | ChunkHeader * pch = ch->getPrevChunk(); |
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| 64 | // cout << "Freeing chunk " << ch << endl; |
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| 65 | SuperHeap::free (ch); |
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| 66 | ch = pch; |
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| 67 | } |
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| 68 | } |
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| 69 | |
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| 70 | // "Grow" the current object. |
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| 71 | // Returns a point in the object just before the current "grow". |
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| 72 | inline void * grow (size_t sz) { |
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| 73 | // If we've grown beyond the confines of this chunk, |
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| 74 | // get a new one. |
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| 75 | assert (isValid()); |
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| 76 | if ((int) ((char *) currentChunk->getLimit() - (char *) nextPos) < sz) { |
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| 77 | ChunkHeader * newCurrent = copyToNew(sz); |
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| 78 | if (newCurrent == NULL) |
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| 79 | return NULL; |
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| 80 | #if 0 |
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| 81 | // Now delete the previous chunk if this was the only object in it. |
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| 82 | if (deleteChunk != NULL) { |
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| 83 | SuperHeap::free (deleteChunk); |
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| 84 | } |
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| 85 | #endif |
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| 86 | assert (isValid()); |
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| 87 | } |
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| 88 | assert (((int) ((char *) currentChunk->getLimit() - (char *) nextPos) >= sz)); |
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| 89 | assert ((char *) (sz + nextPos) <= currentChunk->getLimit()); |
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| 90 | // Bump the pointer for the next object. |
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| 91 | void * prevNextPos = nextPos; |
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| 92 | nextPos += sz; |
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| 93 | assert (isValid()); |
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| 94 | return prevNextPos; |
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| 95 | } |
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| 96 | |
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| 97 | |
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| 98 | inline void * malloc (size_t sz) { |
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| 99 | assert (isValid()); |
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| 100 | if (currentChunk == NULL) { |
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| 101 | return NULL; |
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| 102 | } |
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| 103 | //sz = align(sz > 0 ? sz : 1); |
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| 104 | // If this object can't fit in the current chunk, |
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| 105 | // get another one. |
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| 106 | if ((int) ((char *) currentChunk->getLimit() - (char *) nextPos) < sz) { |
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| 107 | // Allocate a chunk that's large enough to hold the requested size. |
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| 108 | currentChunk = makeChunk (currentChunk, sz); |
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| 109 | if (currentChunk == NULL) { |
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| 110 | return NULL; |
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| 111 | } |
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| 112 | currentBase = nextPos = (char *) (currentChunk + 1); |
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| 113 | assert (isValid()); |
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| 114 | } |
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| 115 | assert (((int) ((char *) currentChunk->getLimit() - (char *) nextPos) >= sz)); |
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| 116 | assert ((char *) (sz + nextPos) <= currentChunk->getLimit()); |
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| 117 | // Bump the pointers forward. |
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| 118 | currentBase = nextPos; |
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| 119 | nextPos += sz; |
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| 120 | void * ptr = currentBase; |
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| 121 | finalize(); |
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| 122 | assert (isValid()); |
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| 123 | return (void *) ptr; |
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| 124 | } |
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| 125 | |
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| 126 | // Free everything allocated "after" ptr. |
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| 127 | // NB: Freeing NULL safely empties the entire obstack. |
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| 128 | inline void free (void * ptr) { |
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| 129 | assert (isValid()); |
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| 130 | // Free every chunk until we find the one that this pointer is in. |
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| 131 | // Then reset the current position to ptr. |
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| 132 | while (currentChunk != NULL && |
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| 133 | (((char *) currentChunk > (char *) ptr) || |
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| 134 | ((char *) currentChunk->getLimit() < (char *) ptr))) { |
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| 135 | ChunkHeader * pch = currentChunk; |
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| 136 | currentChunk = currentChunk->getPrevChunk(); |
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| 137 | SuperHeap::free (pch); |
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| 138 | } |
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| 139 | if (currentChunk != NULL) { |
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| 140 | currentBase = nextPos = (char *) ptr; |
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| 141 | assert (isValid()); |
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| 142 | } else { |
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| 143 | if (ptr != NULL) { |
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| 144 | // Something bad has happened -- we tried to free an item that |
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| 145 | // wasn't in any chunk. |
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| 146 | abort(); |
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| 147 | } else { |
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| 148 | // Get one chunk. |
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| 149 | currentChunk = makeChunk (NULL, ChunkSize); |
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| 150 | currentBase = nextPos = (char *) (currentChunk + 1); |
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| 151 | assert (isValid()); |
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| 152 | } |
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| 153 | } |
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| 154 | } |
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| 155 | |
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| 156 | |
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| 157 | inline void * getObjectBase (void) { |
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| 158 | assert (isValid()); |
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| 159 | return currentBase; |
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| 160 | } |
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| 161 | |
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| 162 | |
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| 163 | inline void finalize (void) { |
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| 164 | assert (isValid()); |
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| 165 | nextPos = (char *) align((int) nextPos); |
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| 166 | currentBase = nextPos; |
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| 167 | assert (isValid()); |
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| 168 | } |
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| 169 | |
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| 170 | |
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| 171 | private: |
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| 172 | |
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| 173 | |
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| 174 | inline int objectSize (void) { |
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| 175 | int diff = (int) (nextPos - currentBase); |
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| 176 | assert (diff >= 0); |
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| 177 | return diff; |
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| 178 | } |
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| 179 | |
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| 180 | |
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| 181 | int isValid (void) { |
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| 182 | // Verify class invariants. |
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| 183 | #ifndef NDEBUG |
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| 184 | bool c1 = (currentBase <= nextPos); |
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| 185 | assert (c1); |
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| 186 | bool c2 = (nextPos <= currentChunk->getLimit()); |
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| 187 | assert (c2); |
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| 188 | bool c3 = ((char *) currentChunk <= currentChunk->getLimit()); |
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| 189 | assert (c3); |
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| 190 | bool c4 = ((char *) currentChunk <= currentBase); |
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| 191 | assert (c4); |
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| 192 | bool c5 = (currentChunk != currentChunk->getPrevChunk()); |
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| 193 | assert (c5); |
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| 194 | bool c6 = (objectSize() >= 0); |
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| 195 | assert (c6); |
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| 196 | return (c1 && c2 && c3 && c4 && c5 && c6); |
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| 197 | #else |
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| 198 | return 1; |
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| 199 | #endif |
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| 200 | } |
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| 201 | |
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| 202 | // The header for every chunk. |
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| 203 | class ChunkHeader { |
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| 204 | public: |
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| 205 | inline ChunkHeader (ChunkHeader * prev, size_t sz) |
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| 206 | : _pastEnd ((char *) (this + 1) + sz), |
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| 207 | _prevChunk (prev) |
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| 208 | {} |
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| 209 | |
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| 210 | // Return the end of the current chunk. |
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| 211 | inline char * getLimit (void) { return _pastEnd; } |
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| 212 | |
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| 213 | // Return the previous chunk. |
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| 214 | inline ChunkHeader * getPrevChunk (void) { return _prevChunk; } |
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| 215 | |
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| 216 | private: |
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| 217 | // Just past the end of this chunk. |
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| 218 | char * _pastEnd; |
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| 219 | |
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| 220 | // Address of prior chunk. |
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| 221 | ChunkHeader * _prevChunk; |
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| 222 | }; |
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| 223 | |
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| 224 | |
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| 225 | inline static size_t align (int sz) { |
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| 226 | return (sz + (sizeof(double) - 1)) & ~(sizeof(double) - 1); |
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| 227 | } |
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| 228 | |
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| 229 | // Make a new chunk of at least sz bytes. |
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| 230 | inline ChunkHeader * makeChunk (ChunkHeader * ch, size_t sz) { |
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| 231 | // Round up the allocation size to at least one chunk. |
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| 232 | size_t allocSize |
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| 233 | = align((sz > ChunkSize - sizeof(ChunkHeader)) ? sz : ChunkSize - sizeof(ChunkHeader)); |
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| 234 | // Make a new chunk. |
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| 235 | ChunkHeader * newChunk |
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| 236 | = new (SuperHeap::malloc (sizeof(ChunkHeader) + allocSize)) ChunkHeader (ch, allocSize); |
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| 237 | return newChunk; |
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| 238 | } |
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| 239 | |
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| 240 | |
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| 241 | // Copy the current object to a new chunk. |
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| 242 | // sz = the minimum amount of extra space we need. |
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| 243 | inline ChunkHeader * copyToNew (size_t sz) { |
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| 244 | size_t obj_size = objectSize(); |
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| 245 | size_t new_size = obj_size + sz + (obj_size >> 3) + 100; |
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| 246 | //size_t new_size = 2 * (obj_size + sz); |
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| 247 | ChunkHeader * newChunk; |
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| 248 | #if 0 |
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| 249 | // This variable will hold the chunk to be deleted (if any). |
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| 250 | ChunkHeader * deleteChunk = NULL; |
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| 251 | // If this object was the only one in the chunk, |
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| 252 | // link back past this chunk. |
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| 253 | if (currentBase == (char *) (currentChunk + 1)) { |
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| 254 | newChunk = makeChunk (currentChunk->getPrevChunk(), new_size); |
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| 255 | deleteChunk = currentChunk; |
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| 256 | } else { |
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| 257 | newChunk = makeChunk (currentChunk, new_size); |
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| 258 | } |
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| 259 | #else |
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| 260 | newChunk = makeChunk (currentChunk, new_size); |
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| 261 | #endif |
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| 262 | if (newChunk == NULL) { |
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| 263 | currentChunk = NULL; |
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| 264 | return NULL; |
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| 265 | } |
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| 266 | // Copy the current object to the new chunk. |
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| 267 | memcpy ((char *) (newChunk + 1), currentBase, obj_size); |
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| 268 | currentChunk = newChunk; |
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| 269 | currentBase = (char *) (currentChunk + 1); |
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| 270 | nextPos = currentBase + obj_size; |
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| 271 | #if 0 |
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| 272 | if (deleteChunk != NULL) { |
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| 273 | SuperHeap::free (deleteChunk); |
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| 274 | } |
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| 275 | #endif |
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| 276 | return currentChunk; |
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| 277 | } |
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| 278 | |
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| 279 | |
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| 280 | // Current position in the current chunk. |
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| 281 | char * currentBase; |
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| 282 | |
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| 283 | // Where to add the next character to the current object. |
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| 284 | char * nextPos; |
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| 285 | |
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| 286 | // My current chunk. |
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| 287 | ChunkHeader * currentChunk; |
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| 288 | |
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| 289 | }; |
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| 290 | |
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| 291 | #endif // __cplusplus |
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| 292 | |
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| 293 | // The C version of the above (just large enough to hold all of the data structures). |
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| 294 | struct obstack { |
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| 295 | void * _dummy[3]; |
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| 296 | }; |
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| 297 | |
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| 298 | }; |
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| 299 | |
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| 300 | #endif // _HLOBSTACK_H_ |
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