spot  0.8.2
fixpool.hh
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00001 // Copyright (C) 2011 Laboratoire de Recherche et Developpement de
00002 // l'Epita (LRDE)
00003 //
00004 // This file is part of Spot, a model checking library.
00005 //
00006 // Spot is free software; you can redistribute it and/or modify it
00007 // under the terms of the GNU General Public License as published by
00008 // the Free Software Foundation; either version 2 of the License, or
00009 // (at your option) any later version.
00010 //
00011 // Spot is distributed in the hope that it will be useful, but WITHOUT
00012 // ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
00013 // or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
00014 // License for more details.
00015 //
00016 // You should have received a copy of the GNU General Public License
00017 // along with Spot; see the file COPYING.  If not, write to the Free
00018 // Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
00019 // 02111-1307, USA.
00020 
00021 #ifndef SPOT_MISC_FIXPOOL_HH
00022 #  define SPOT_MISC_FIXPOOL_HH
00023 
00024 #include <new>
00025 #include <cstddef>
00026 #include <cstdlib>
00027 #include <cassert>
00028 
00029 namespace spot
00030 {
00031 
00033   class fixed_size_pool
00034   {
00035   public:
00037     fixed_size_pool(size_t size)
00038       : freelist_(0), free_start_(0), free_end_(0), chunklist_(0)
00039     {
00040       const size_t alignement = 2 * sizeof(size_t);
00041       size_ = ((size >= sizeof(block_) ? size : sizeof(block_))
00042                + alignement - 1) & ~(alignement - 1);
00043     }
00044 
00046     ~fixed_size_pool()
00047     {
00048       while (chunklist_)
00049         {
00050           chunk_* prev = chunklist_->prev;
00051           free(chunklist_);
00052           chunklist_ = prev;
00053         }
00054     }
00055 
00057     void*
00058     allocate()
00059     {
00060       block_* f = freelist_;
00061       // If we have free blocks available, return the first one.
00062       if (f)
00063         {
00064           freelist_ = f->next;
00065           return f;
00066         }
00067 
00068       // Else, create a block out of the last chunk of allocated
00069       // memory.
00070 
00071       // If all the last chunk has been used, allocate one more.
00072       if (free_start_ + size_ > free_end_)
00073         {
00074           const size_t requested = (size_ > 128 ? size_ : 128) * 8192 - 64;
00075           chunk_* c = reinterpret_cast<chunk_*>(malloc(requested));
00076           if (!c)
00077             throw std::bad_alloc();
00078           c->prev = chunklist_;
00079           chunklist_ = c;
00080 
00081           free_start_ = c->data_ + size_;
00082           free_end_ = c->data_ + requested;
00083         }
00084 
00085       void* res = free_start_;
00086       free_start_ += size_;
00087       return res;
00088     }
00089 
00096     void
00097     deallocate (const void* ptr)
00098     {
00099       assert(ptr);
00100       block_* b = reinterpret_cast<block_*>(const_cast<void*>(ptr));
00101       b->next = freelist_;
00102       freelist_ = b;
00103     }
00104 
00105   private:
00106     size_t size_;
00107     struct block_ { block_* next; }* freelist_;
00108     char* free_start_;
00109     char* free_end_;
00110     // chunk = several agglomerated blocks
00111     union chunk_ { chunk_* prev; char data_[1]; }* chunklist_;
00112   };
00113 
00114 }
00115 
00116 #endif // SPOT_MISC_FIXPOOL_HH

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