1 | /* -*- C++ -*- */ |
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2 | |
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3 | #ifndef _SLOTHEAP_H_ |
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4 | #define _SLOTHEAP_H_ |
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5 | |
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6 | // NOTE: All size requests to malloc must be identical! |
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7 | |
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8 | /* |
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9 | |
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10 | A "slot" allocator. |
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11 | |
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12 | All allocations come from a fixed-size chunk of memory |
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13 | that is carved into a number of pieces. |
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14 | |
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15 | The "chunk" class must support the following methods: |
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16 | |
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17 | void * getSlot (void); // Returns NULL if there is no slot left. |
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18 | void putSlot (void *); // Puts a slot back into its chunk. |
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19 | |
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20 | */ |
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21 | |
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22 | #include <assert.h> |
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23 | |
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24 | #include "chunkheap.h" |
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25 | |
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26 | /* A "slot" heap. |
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27 | |
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28 | This heap reserves exactly one "chunk" that is divided into |
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29 | a number of fixed-size slots. When the chunk is used up, |
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30 | the heap requests another one. */ |
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31 | |
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32 | template <int chunkSize, int slotSize, class Super> |
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33 | class SlotInterface; |
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34 | |
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35 | template <int chunkSize, int slotSize, class Super> |
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36 | class SlotHeap : public SlotInterface<chunkSize, slotSize, ChunkHeap<chunkSize, slotSize, Super> >{}; |
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37 | |
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38 | template <int chunkSize, int slotSize, class Super> |
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39 | class SlotInterface : public Super { |
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40 | public: |
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41 | |
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42 | SlotInterface (void) |
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43 | : currentChunk (new (Super::malloc(chunkSize)) Chunk<chunkSize, slotSize>) |
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44 | {} |
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45 | |
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46 | inline void * malloc (size_t sz) { |
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47 | assert (sz == slotSize); |
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48 | // Use up all of the slots in one chunk, |
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49 | // and get another chunk if we need one. |
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50 | void * ptr = currentChunk->getSlot(); |
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51 | if (ptr == NULL) { |
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52 | // This chunk is empty -- get another one. |
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53 | currentChunk = new (Super::malloc(chunkSize)) Chunk<chunkSize, slotSize>; |
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54 | ptr = currentChunk->getSlot(); |
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55 | } |
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56 | assert (ptr != NULL); |
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57 | return ptr; |
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58 | } |
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59 | |
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60 | inline void free (void * ptr) { |
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61 | // If this object belongs to "our" chunk, |
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62 | // free it directly; otherwise, pass it up. |
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63 | if (getChunk(ptr) == currentChunk) { |
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64 | currentChunk->putSlot (ptr); |
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65 | } else { |
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66 | Super::free (ptr); |
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67 | } |
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68 | } |
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69 | |
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70 | private: |
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71 | |
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72 | Chunk<chunkSize, slotSize> * currentChunk; |
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73 | |
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74 | }; |
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75 | |
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76 | #endif |
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