source: source/ariba/overlay/modules/chord/detail/chord_routing_table.hpp

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// [License]
#ifndef CHORD_ROUTING_TABLE_HPP_
#define CHORD_ROUTING_TABLE_HPP_

#include <vector>
#include <iostream>

#include <boost/foreach.hpp>

#include "distances.hpp"
#include "comparators.hpp"
#include "minimizer_table.hpp"

#include "ariba/Identifiers.h"

using namespace ariba;

using namespace distances;
using namespace comparators;
using namespace std;

// placeholders for route info and nodeid type
typedef ariba::NodeID nodeid_t;
typedef ariba::LinkID routeinfo_t;

/**
 * Implementation of a chord routing table.
*
 * @author Sebastian Mies <mies@tm.uka.de>
 */
class chord_routing_table {
private:
        typedef chord_routing_table self;
        typedef distance_compare<nodeid_t&, nodeid_t, ring_succ_distance>
                        succ_compare_type;
        typedef distance_compare<nodeid_t&, nodeid_t, ring_pred_distance>
                        pred_compare_type;
        typedef distance_compare<nodeid_t, nodeid_t, ring_distance>
                        finger_compare_type;

public:
        typedef minimizer_table<nodeid_t, succ_compare_type, self> succ_table;
        typedef minimizer_table<nodeid_t, pred_compare_type, self> pred_table;
        typedef minimizer_table<nodeid_t, finger_compare_type, self> finger_table;

        // a routing table entry
        class item {
        public:
                uint8_t ref_count;
                nodeid_t id;
                routeinfo_t info;
        };
        typedef vector<item> route_table;


private:
        // maximum number of fingers
        static const size_t max_fingers = 32;

        // the own node id
        nodeid_t id;
    
    // the own node id as routing item
    item own_id_item;

        // successor and predecessor tables
        succ_table succ;
        pred_table pred;
        finger_table* finger[max_fingers*2];

        // main routing table
        route_table table;

        // some internal flags
        item* item_added;
        item item_removed;
        bool item_removed_flag;
        bool simulate;

        // finds an item inside the routing table
        item* find_item(const nodeid_t& id) {
                BOOST_FOREACH( item& i, table )
                        if ( i.id == id ) return &i;
                return NULL;
        }

        /// Adds a item to the routing table
        item* add_item( const nodeid_t& id ) {
                item i;
                i.id = id;
                i.ref_count = 1;
                table.push_back(i);
                item_added = &table.back();
                return item_added;
        }

        /// Removes an item from the routing table
        bool remove_item( const nodeid_t& id ) {
                for (route_table::iterator i = table.begin(); i!=table.end(); i++) {
                        if ( (*i).id == id ) {
                                (*i).ref_count--;
                                if ((*i).ref_count == 0) {
                                        item_removed = *i;
                                        item_removed_flag = true;
                                        return true;
                                }
                                break;
                        }
                }
                return false;
        }

public:

        // handles events from minimizers
        template<class Table>
        void on_table( table_listener::type_ type, const Table& tab, typename Table::iterator pos ) {
                switch (type) {
                case table_listener::insert: {
                        item* i = find_item( *pos );
                        if (i == NULL) i = add_item( *pos ); else i->ref_count++;
                        break;
                }
                case table_listener::remove: {
                        remove_item(*pos);
                        break;
                }
                case table_listener::update:
                        break;
                }
        }


public:
        /// constructs the reactive chord routing table
        explicit chord_routing_table( const nodeid_t& id, int redundancy = 4 ) :
                id(id),
                succ( redundancy, succ_compare_type(this->id), *this ),
                pred( redundancy, pred_compare_type(this->id), *this )
    {
        // init reflexive item
        own_id_item.id = id;
        own_id_item.ref_count = 1;

                // create finger tables
                nodeid_t nid = Identifier(2);
                for (size_t i=0; i<max_fingers; i++) {
                        finger[i*2+0] =
                                new finger_table( redundancy,
                                                finger_compare_type(this->id - nid), *this);
                        finger[i*2+1] =
                                new finger_table( redundancy,
                                                finger_compare_type(this->id + nid), *this);
                        nid = nid << 1;
                }
        }

        virtual ~chord_routing_table() {
                BOOST_FOREACH( finger_table* f, this->finger){
                        delete f;
                }
        }

        /// check whether a node could fit the routing table
        bool is_insertable( const nodeid_t& value ) {
//              if (find_item(value)!=NULL) return false;
                bool is_insertable_ = false;
                is_insertable_ |= succ.insertable(value);
                is_insertable_ |= pred.insertable(value);
                for (size_t i=0; i<max_fingers*2; i++)
                        is_insertable_ |= finger[i]->insertable(value);
                return is_insertable_;
        }

        /// searches an item
        item* get( const nodeid_t& value ) {
                return find_item(value);
        }

        inline item* operator[] ( size_t index ) {
                return &table[index];
        }

        inline size_t size() const {
                return table.size();
        }

        /// adds a node
        item* insert( const nodeid_t& value ) {
                if (value==id) return NULL;
                item_added = NULL;
                item_removed_flag = false;
                succ.insert(value);
                pred.insert(value);
                for (size_t i=0; i<max_fingers*2; i++) finger[i]->insert(value);
                return item_added;
        }

        /// adds an orphan
        item* insert_orphan( const nodeid_t& value ) {
                item* it = find_item(value);
                if (it!=NULL) return it;
                item i;
                i.id = id;
                i.ref_count = 0;
                table.push_back(i);
                return &table.back();
        }

        /// removes an node
        const item* remove( const nodeid_t& value ) {
                item_removed_flag = false;
                succ.remove(value);
                pred.remove(value);
                for (size_t i=0; i<max_fingers*2; i++) finger[i]->remove(value);
                if (!item_removed_flag) remove_orphan(value);
                return item_removed_flag ? &item_removed : NULL;
        }

        /// removes an orphan
        item* remove_orphan( const nodeid_t& value ) {
                item_removed_flag = false;
                remove_item(value);
                return item_removed_flag ? &item_removed : NULL;
        }

        /// returns the next hop
        const item* get_next_hop( const nodeid_t& value, bool nts = false) {
                ring_distance distance;
                item* best_item = NULL;
                for (size_t i=0; i<table.size(); i++) {
                        item* curr = &table[i];
                        if (nts && curr->id == value) continue;

                        // not not include orphans into routing!
                        if (curr->ref_count==0) continue;

                        // check if we found a better item
                        if (best_item==NULL) {
                                best_item = curr;
                                continue;
                        } else {
                                if (distance(value, curr->id)<distance(value, best_item->id))
                                        best_item = curr;
                        }
                }

                if (best_item != NULL && distance(value, id)<distance(value, best_item->id))
                        return NULL;
                return best_item;
        }
        
        std::vector<const item*> get_next_2_hops( const nodeid_t& value)
    {
        ring_distance distance;
        item* best_item = &own_id_item;
        item* second_best_item = NULL;
        
        // find best and second best item
        for (size_t i=0; i<table.size(); i++)
        {
            item* curr = &table[i];

            // not not include orphans into routing!
            if (curr->ref_count==0) continue;

            // check if we found a better item
            // is best item
            if ( distance(value, curr->id) < distance(value, best_item->id) )
            {
                second_best_item = best_item;
                best_item = curr;
            }
            // is second best item
            else
            {
                if ( second_best_item == NULL )
                {
                    second_best_item = curr;
                    continue;
                }
                
                if ( distance(value, curr->id) < distance(value, second_best_item->id) )
                {
                    second_best_item = curr;
                }
            }
        }

        // prepare return vector
        std::vector<const item*> ret;
        if ( best_item != NULL )
        {
            ret.push_back(best_item);
        }
        if ( second_best_item != NULL )
        {
            ret.push_back(second_best_item);
        }
        
        return ret;
    }

        const nodeid_t* get_successor() {
                if (succ.size()==0) return NULL;
                return &succ.front();
        }

        const nodeid_t* get_predesessor() {
                if (pred.size()==0) return NULL;
                return &pred.front();
        }

        bool is_closest_to( const nodeid_t& value ) {
                ring_distance distance;
                nodeid_t delta = distance(value, id);
                if (get_successor() != NULL &&
                                delta > distance(value, *get_successor() ) ) return false;
                if (get_predesessor() != NULL &&
                                delta > distance(value, *get_predesessor() ) ) return false;
                return true;
        }

        /// returns the whole routing table
        vector<item>& get_table() {
                return table;
        }

        /// returns the last removed item
        const item* get_removed_item() const {
                return item_removed_flag ? &item_removed : NULL;
        }

        /// return successor table
        const succ_table& get_succ_table() const {
                return succ;
        }

        /// return predecessor table
        const pred_table& get_pred_table() const {
                return pred;
        }

        /// return finger table
        finger_table& get_finger_table( size_t index ) {
                return *finger[index];
        }

        /// return number of finger tables
        size_t get_finger_table_size() const {
                return max_fingers*2;
        }
};

/// output routing table
std::ostream& operator<<(std::ostream& s, const chord_routing_table& t) {
        s << "[pred=" << t.get_pred_table() << " succ=" << t.get_succ_table()
                        << "]";
        return s;
}

#endif /* CHORD_ROUTING_TABLE_HPP_ */