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fei_Pool.hpp
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00004 //             FEI: Finite Element Interface to Linear Solvers
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00042 
00043 
00044 #ifndef _fei_Pool_hpp_
00045 #define _fei_Pool_hpp_
00046 
00047 #include "fei_macros.hpp"
00048 
00049 #include <cstdlib>
00050 
00051 #ifndef FEI_ALLOC_CHUNK_SIZE_K
00052 #define FEI_ALLOC_CHUNK_SIZE_K 512
00053 #endif
00054 
00055 //The macro FEI_ALLOC_CHUNK_SIZE_K determines the number
00056 //of kilobytes that each internally-allocated chunk of memory will
00057 //occupy. The fei_Pool object will then dispense "sub-chunks"
00058 //of memory having size determined by the argument to the class
00059 //constructor.
00060 
00061 class fei_Pool {
00062  public:
00063   fei_Pool(unsigned int n); // n is the size of elements
00064   ~fei_Pool();
00065 
00066   void* alloc(); //allocate one element
00067   void free(void* b); //put an element back into the pool
00068   struct Link { Link* next; };
00069 
00070  private:
00071   struct Chunk {
00072     //Stroustrup's comment:
00073     //slightly less than specified K so that a chunk will fit in
00074     //allocation area first to get stringent alignment
00075     enum { size = FEI_ALLOC_CHUNK_SIZE_K*1024-16 };
00076     char mem[size];
00077     Chunk* next;
00078   };
00079 
00080   Chunk* chunks;
00081   const unsigned int esize;
00082   Link* head;
00083 
00084   fei_Pool(const fei_Pool&);//private copy constructor
00085   fei_Pool& operator=(const fei_Pool&);//private assignment operator
00086   void grow(); //make pool larger
00087 };
00088 
00089 inline void* fei_Pool::alloc()
00090 {
00091   if (head == NULL) {
00092     grow();
00093   }
00094   Link* p = head; //return first element
00095   head = p->next;
00096   return p;
00097 }
00098 
00099 inline void fei_Pool::free(void* b)
00100 {
00101   Link* p = static_cast<Link*>(b);
00102   p->next = head; //put b back as first element
00103   head = p;
00104 }
00105 
00106 #endif
00107 
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