Consistent::hashring, consistent hash.

implementation understanding of consistent hashing
1 namespace2 {3 4     classstringifyexception5     {6     };7 8Template <classT>9STD::stringStringify (Constt&t)Ten     { One std::ostringstream os; A         if(! (OS <<t)) -         { -             Throwstringifyexception (); the         } -         returnos.str (); -     } -  +Template <> -STD::stringStringify (ConstSTD::string&str) +     { A         returnstr; at     } -  -Template <> -STD::stringStringify (Const Char*Const&str) -     { -         returnstr; in     } - } to  + namespaceconsistent - { the  *     classemptyringexception $     {Panax Notoginseng     }; -  theTemplate <classNode,classData,classHash = hash_namespace::hash<Const Char*> > +     classhashring A     { the      Public: +typedef std::map<size_t, Node>Nodemap; -  $Hashring (unsignedintreplicas) $: Replicas_ (Replicas), Hash_ (hash_namespace::hash<Const Char*>()) -         { -         } the  -Hashring (unsignedintReplicas,Consthash&hash)Wuyi : Replicas_ (Replicas), hash_ (hash) the         { -         } Wu  -size_t AddNode (Constnode&node); About         voidRemoveNode (Constnode&node); $         Constnode& GetNode (Constdata& data)Const; -  -     Private: - Nodemap Ring_; A         ConstUnsignedintReplicas_; + Hash Hash_; the     }; -  $Template <classNode,classData,classHash> thesize_t Hashring<node, Data, Hash>::addnode (Constnode&node) the     { the size_t Hash; theSTD::stringNodestr =stringify (node); -          for(unsignedintR =0; R < Replicas_; r++)  in         { thehash = Hash_ ((nodestr +stringify (R)). C_STR ()); theRing_[hash] =node; About         } the         returnHash; the     } the  +Template <classNode,classData,classHash> -     voidHashring<node, Data, Hash>::removenode (Constnode&node) the     {BayiSTD::stringNodestr =stringify (node); the          for(unsignedintR =0; R < Replicas_; r++)  the         { -size_t hash = hash_ (Nodestr +stringify (R)). C_STR ()); - ring_.erase (hash); the         } the     } the  theTemplate <classNode,classData,classHash> -     Constnode& Hashring<node, Data, Hash>::getnode (Constdata& data)Const the     { the         if(Ring_.empty ()) the             Throwemptyringexception ();94  thesize_t hash =Hash_ (stringify (data). C_STR ()); the TypeName Nodemap::const_iterator it; the         //Look for the first node >= hash98it =Ring_.lower_bound (hash); About         if(It = =ring_.end ()) -         {101             //wrapped around; get the first node102it =Ring_.begin ();103         }104         returnIt->second; the     }106}

Consistent::hashring, consistent hash.