RingRacers/libs/ACSVM/include/ACSVM/HashMapFixed.hpp

//-----------------------------------------------------------------------------
//
// Copyright (C) 2015 David Hill
//
// See COPYING for license information.
//
//-----------------------------------------------------------------------------
//
// HashMapFixed class.
//
//-----------------------------------------------------------------------------

#ifndef ACSVM__HashMapFixed_H__
#define ACSVM__HashMapFixed_H__

#include "Types.hpp"

#include <functional>
#include <new>


//----------------------------------------------------------------------------|
// Types                                                                      |
//

namespace ACSVM
{
   //
   // HashMapFixed
   //
   // Non-resizable hash map.
   //
   template<typename Key, typename T, typename Hash = std::hash<Key>>
   class HashMapFixed
   {
   public:
      struct Elem
      {
         Key   key;
         T     val;
         Elem *next;
      };

      using iterator   = Elem *;
      using size_type  = std::size_t;
      using value_type = Elem;


      HashMapFixed() : hasher{}, table{nullptr}, elemV{nullptr}, elemC{0} {}
      ~HashMapFixed() {free();}

      //
      // alloc
      //
      void alloc(size_type count)
      {
         if(elemV) free();

         if(!count) return;

         size_type sizeRaw = sizeof(Elem) * count + sizeof(Elem *) * count;

         elemC = count;
         elemV = static_cast<Elem *>(::operator new(sizeRaw));
      }

      // begin
      iterator begin() {return elemV;}

      //
      // build
      //
      void build()
      {
         // Initialize table.
         table = reinterpret_cast<Elem **>(elemV + elemC);
         for(Elem **elem = table + elemC; elem != table;)
            *--elem = nullptr;

         // Insert elements.
         for(Elem &elem : *this)
         {
            size_type hash = hasher(elem.key) % elemC;

            elem.next = table[hash];
            table[hash] = &elem;
         }
      }

      // empty
      bool empty() const {return !elemC;}

      // end
      iterator end() {return elemV + elemC;}

      //
      // find
      //
      T *find(Key const &key)
      {
         if(!table) return nullptr;

         for(Elem *elem = table[hasher(key) % elemC]; elem; elem = elem->next)
         {
            if(elem->key == key)
               return &elem->val;
         }

         return nullptr;
      }

      //
      // free
      //
      void free()
      {
         if(table)
         {
            for(Elem *elem = elemV + elemC; elem != elemV;)
               (--elem)->~Elem();

            table = nullptr;
         }

         ::operator delete(elemV);

         elemV = nullptr;
         elemC = 0;
      }

      // size
      size_type size() const {return elemC;}

   private:
      Hash hasher;

      Elem    **table;
      Elem     *elemV;
      size_type elemC;
   };
}

#endif//ACSVM__HashMapFixed_H__