include/AD/rete/alphamem.h

   1 //////////////////////////////////////////////////////////////////////////////
   2 // NOTICE:
   3 //
   4 // ADLib, Prop and their related set of tools and documentation are in the
   5 // public domain.   The author(s) of this software reserve no copyrights on
   6 // the source code and any code generated using the tools.  You are encouraged
   7 // to use ADLib and Prop to develop software, in both academic and commercial
   8 // settings, and are welcomed to incorporate any part of ADLib and Prop into
   9 // your programs.
  10 //
  11 // Although you are under no obligation to do so, we strongly recommend that
  12 // you give away all software developed using our tools.
  13 //
  14 // We also ask that credit be given to us when ADLib and/or Prop are used in
  15 // your programs, and that this notice be preserved intact in all the source
  16 // code.
  17 //
  18 // This software is still under development and we welcome(read crave for)
  19 // any suggestions and help from the users.
  20 //
  21 // Allen Leung
  22 // 1994
  23 //////////////////////////////////////////////////////////////////////////////
  24
  25 #ifndef alpha_memory_h
  26 #define alpha_memory_h
  27
  28 #include <AD/rete/fact.h>   // database fact
  29 #include <AD/memory/mem.h>  // memory manager
  30
  31 //////////////////////////////////////////////////////////////////////////////
  32 //
  33 //  Alpha memory is used to cache facts that pass intra-object tests.
  34 //
  35 //////////////////////////////////////////////////////////////////////////////
  36 class AlphaMem {
  37
  38    AlphaMem(const AlphaMem&);         // no copy constructor
  39    void operator = (const AlphaMem&); // no assignment
  40
  41 protected:
  42
  43    int     count;     // number of facts in the list.
  44    int     capacity;  // number of facts that we can hold.
  45    Fact ** facts;     // list of facts.
  46
  47 public:
  48
  49    ///////////////////////////////////////////////////////////////////////////
  50    //  Constructor and destructor
  51    ///////////////////////////////////////////////////////////////////////////
  52    AlphaMem() : count(0), capacity(0), facts(0) {}
  53   ~AlphaMem() {}
  54
  55    ///////////////////////////////////////////////////////////////////////////
  56    //  Conversion.
  57    ///////////////////////////////////////////////////////////////////////////
  58    // inline operator Fact ** () const { return facts; }
  59    inline Fact ** get_facts () { return facts; }
  60
  61    ///////////////////////////////////////////////////////////////////////////
  62    //  Selectors
  63    ///////////////////////////////////////////////////////////////////////////
  64    inline int    size()               const { return count; }
  65    inline Fact * operator [] (int i)  const { return facts[i]; }
  66    inline int    find(const Fact * f) const
  67    {  for (int i = capacity - 1; i >= 0; i--)
  68          if (f == facts[i]) return i;
  69       return -1;
  70    }
  71
  72    ///////////////////////////////////////////////////////////////////////////
  73    //  Method to insert a new fact into the alpha memory.
  74    ///////////////////////////////////////////////////////////////////////////
  75    inline void add_fact(Mem& mem, Fact * f)
  76    {  if (count < capacity) {
  77          facts[count++] = f;
  78       } else {
  79          int     new_capacity = 4 + capacity * 3 / 2;
  80          Fact ** new_facts =
  81             (Fact**)mem.m_alloc(sizeof(Fact*) * new_capacity);
  82          for (int i = capacity - 1; i >= 0; i--) new_facts[i] = facts[i];
  83          mem.free(facts);
  84          new_facts[count++] = f;
  85          capacity           = new_capacity;
  86          facts              = new_facts;
  87       }
  88    }
  89
  90    ///////////////////////////////////////////////////////////////////////////
  91    //  Method to remove an old fact from the alpha memory.
  92    ///////////////////////////////////////////////////////////////////////////
  93    inline void remove_fact(int i) { facts[--count] = facts[i]; }
  94 };
  95
  96 #endif