[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 | #ifndef _SLOPHEAP_H_ |
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| 29 | #define _SLOPHEAP_H_ |
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| 30 | |
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| 31 | /** |
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| 32 | * @class SlopHeap |
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| 33 | * |
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| 34 | * SlopHeap is designed to guarantee that you always have an extra N bytes |
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| 35 | * available after the most recent malloc. This is necessary for the current |
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| 36 | * coalescing support, which can look past the last allocated object. |
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| 37 | * |
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| 38 | * @param SuperHeap The parent heap. |
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| 39 | * @param SLOP The amount of extra memory required, in bytes. |
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| 40 | */ |
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| 41 | |
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| 42 | namespace HL { |
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| 43 | |
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| 44 | template <class SuperHeap, int SLOP = 16> |
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| 45 | class SlopHeap : public SuperHeap { |
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| 46 | public: |
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| 47 | SlopHeap (void) |
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| 48 | : remaining (0), |
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| 49 | ptr (NULL) |
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| 50 | {} |
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| 51 | |
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| 52 | inline void * malloc (const size_t nbytes) { |
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| 53 | |
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| 54 | // Put the usual case up front. |
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| 55 | if (nbytes <= remaining) { |
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| 56 | remaining -= nbytes; |
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| 57 | char * p = ptr; |
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| 58 | ptr += nbytes; |
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| 59 | return (void *) p; |
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| 60 | } |
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| 61 | |
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| 62 | // |
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| 63 | // We don't have enough space to satisfy the current |
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| 64 | // request, so get more memory. |
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| 65 | // |
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| 66 | |
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| 67 | return getMoreMemory(nbytes); |
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| 68 | } |
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| 69 | |
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| 70 | inline void clear (void) { |
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| 71 | ptr = NULL; |
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| 72 | remaining = 0; |
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| 73 | SuperHeap::clear (); |
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| 74 | } |
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| 75 | |
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| 76 | inline void free (void *) {} |
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| 77 | |
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| 78 | private: |
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| 79 | |
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| 80 | // Disabled. |
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| 81 | inline int remove (void *); |
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| 82 | |
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| 83 | void * getMoreMemory (size_t nbytes) { |
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| 84 | char * newptr = (char *) SuperHeap::malloc (nbytes + SLOP); |
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| 85 | |
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| 86 | if (newptr == NULL) { |
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| 87 | return NULL; |
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| 88 | } |
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| 89 | |
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| 90 | // |
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| 91 | // If this new memory is contiguous with the previous one, |
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| 92 | // reclaim the "slop". |
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| 93 | // |
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| 94 | |
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| 95 | if ((ptr != NULL) && (ptr + remaining + SLOP == newptr)) { |
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| 96 | remaining += SLOP; |
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| 97 | } else { |
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| 98 | ptr = newptr; |
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| 99 | remaining = 0; |
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| 100 | } |
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| 101 | char * p = ptr; |
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| 102 | ptr += nbytes; |
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| 103 | |
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| 104 | return (void *) p; |
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| 105 | } |
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| 106 | |
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| 107 | char * ptr; |
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| 108 | size_t remaining; |
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| 109 | |
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| 110 | }; |
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| 111 | |
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| 112 | } |
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| 113 | |
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| 114 | #endif |
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