include/o3tl/vector_pool.hxx

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  19
  20 #ifndef INCLUDED_O3TL_VECTOR_POOL_HXX
  21 #define INCLUDED_O3TL_VECTOR_POOL_HXX
  22
  23 #include <utility>
  24 #include <vector>
  25
  26 namespace o3tl
  27 {
  28     namespace detail
  29     {
  30         template<typename ValueType, class Container> class simple_pool_impl :
  31             public Container
  32         {
  33             typedef typename Container::value_type value_type;
  34             std::ptrdiff_t mnFirstFreeIndex;
  35
  36         public:
  37             simple_pool_impl() :
  38                 mnFirstFreeIndex(-1)
  39             {}
  40
  41             std::ptrdiff_t alloc()
  42             {
  43                 return store(ValueType());
  44             }
  45
  46             std::ptrdiff_t store(const ValueType& rCopy)
  47             {
  48                 if( mnFirstFreeIndex != -1 )
  49                 {
  50                     std::ptrdiff_t nIdx=mnFirstFreeIndex;
  51                     mnFirstFreeIndex = this->at(mnFirstFreeIndex).nextFree;
  52                     this->at(nIdx).value = rCopy;
  53                     this->at(nIdx).nextFree = -1;
  54
  55                     return nIdx;
  56                 }
  57                 else
  58                 {
  59                     this->push_back(value_type(rCopy));
  60                     return this->size()-1;
  61                 }
  62             }
  63
  64             void free( std::ptrdiff_t nIdx )
  65             {
  66                 this->at(nIdx).nextFree = mnFirstFreeIndex;
  67                 mnFirstFreeIndex = nIdx;
  68             }
  69
  70             const ValueType& get( std::ptrdiff_t nIdx ) const
  71             {
  72                 return this->operator[](nIdx).value;
  73             }
  74             ValueType& get( std::ptrdiff_t nIdx )
  75             {
  76                 return this->operator[](nIdx).value;
  77             }
  78         };
  79
  80         template< typename ValueType > struct struct_from_value
  81         {
  82             struct type
  83             {
  84                 type() :
  85                     value(),
  86                     nextFree(-1)
  87                 {}
  88                 explicit type( ValueType val ) :
  89                     value(std::move(val)),
  90                     nextFree(-1)
  91                 {}
  92
  93                 ValueType      value;
  94                 std::ptrdiff_t nextFree;
  95             };
  96         };
  97     }
  98
  99     /** Simple vector-based memory pool allocator
 100
 101         This template can be used to provide simple pooled memory
 102         allocation from a container class that adheres to the stl
 103         random access container concept. Note that alloc/free works
 104         with _indices_ into the container!
 105
 106         @example
 107         <pre>
 108 vector_pool<type> myPool;
 109 int nIdx=myPool.alloc();
 110 myPool[nIdx] = myVal;
 111  ... do stuff ...
 112 myPool.free(nIdx);
 113         </pre>
 114      */
 115     template<typename ValueType> struct vector_pool :
 116         public detail::simple_pool_impl<ValueType,
 117                                        std::vector<typename detail::struct_from_value<ValueType>::type > >
 118     {};
 119 }
 120
 121 #endif /* INCLUDED_O3TL_VECTOR_POOL_HXX */
 122
 123 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */