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/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/**
* Copyright (C) 2014 Named Data Networking Project
* See COPYING for copyright and distribution information.
*
* Author: Ilya Moiseenko <iliamo@ucla.edu>
*/
#ifndef NFD_TABLE_CS_HPP
#define NFD_TABLE_CS_HPP
#include "common.hpp"
#include "cs-entry.hpp"
namespace nfd {
typedef std::list< shared_ptr<cs::Entry> > SkipListLayer;
typedef std::list<SkipListLayer*> SkipList;
/** \brief represents Content Store
*/
class Cs : noncopyable
{
public:
explicit
Cs(int nMaxPackets = 65536); // ~500MB with average packet size = 8KB
~Cs();
/** \brief inserts a Data packet
* This method does not consider the payload of the Data packet.
*
* Packets are considered duplicate if the name matches.
* The new Data packet with the identical name, but a different payload
* is not placed in the Content Store
* \return{ whether the Data is added }
*/
bool
insert(const Data& data, bool isUnsolicited = false);
/** \brief finds the best match Data for an Interest
* \return{ the best match, if any; otherwise 0 }
*/
const Data*
find(const Interest& interest) const;
/** \brief deletes CS entry by the exact name
*/
void
erase(const Name& exactName);
/** \brief sets maximum allowed size of Content Store (in packets)
*/
void
setLimit(size_t nMaxPackets);
/** \brief returns maximum allowed size of Content Store (in packets)
* \return{ number of packets that can be stored in Content Store }
*/
size_t
getLimit() const;
/** \brief returns current size of Content Store measured in packets
* \return{ number of packets located in Content Store }
*/
size_t
size() const;
protected:
/** \brief removes one Data packet from Content Store based on replacement policy
* \return{ whether the Data was removed }
*/
bool
evictItem();
private:
/** \brief returns True if the Content Store is at its maximum capacity
* \return{ True if Content Store is full; otherwise False}
*/
bool
isFull() const;
/** \brief Computes the layer where new Content Store Entry is placed
*
* Reference: "Skip Lists: A Probabilistic Alternative to Balanced Trees" by W.Pugh
* \return{ returns random layer (number) in a skip list}
*/
int
pickRandomLayer() const;
/** \brief Inserts a new Content Store Entry in a skip list
* \return{ returns a pair containing a pointer to the CS Entry,
* and a flag indicating if the entry was newly created (True) or refreshed (False) }
*/
std::pair< shared_ptr<cs::Entry>, bool>
insertToSkipList(const Data& data, bool isUnsolicited = false);
/** \brief Removes a specific CS Entry from all layers of a skip list
* \return{ returns True if CS Entry was succesfully removed and False if CS Entry was not found}
*/
bool
eraseFromSkipList(shared_ptr<cs::Entry> entry);
/** \brief Prints contents of the skip list, starting from the top layer
*/
void
printSkipList() const;
/** \brief Implements child selector (leftmost, rightmost, undeclared).
* Operates on the first layer of a skip list.
*
* startingPoint must be less than Interest Name.
* startingPoint can be equal to Interest Name only when the item is in the begin() position.
*
* Iterates toward greater Names, terminates when CS entry falls out of Interest prefix.
* When childSelector = leftmost, returns first CS entry that satisfies other selectors.
* When childSelector = rightmost, it goes till the end, and returns CS entry that satisfies
* other selectors. Returned CS entry is the leftmost child of the rightmost child.
* \return{ the best match, if any; otherwise 0 }
*/
const Data*
selectChild(const Interest& interest, SkipListLayer::iterator startingPoint) const;
/** \brief checks if Content Store entry satisfies Interest selectors (MinSuffixComponents,
* MaxSuffixComponents, Implicit Digest, MustBeFresh)
* \return{ true if satisfies all selectors; false otherwise }
*/
bool
doesComplyWithSelectors(const Interest& interest, shared_ptr<cs::Entry> entry) const;
/** \brief interprets minSuffixComponent and name lengths to understand if Interest contains
* implicit digest of the data
* \return{ True if Interest name contains digest; False otherwise }
*/
bool
recognizeInterestWithDigest(const Interest& interest, shared_ptr<cs::Entry> entry) const;
private:
class StalenessComparator
{
public:
bool
operator() (shared_ptr<cs::Entry> entry1, shared_ptr<cs::Entry> entry2)
{
return entry1->getStaleTime() > entry2->getStaleTime();
}
};
SkipList m_skipList;
size_t m_nMaxPackets; //user defined maximum size of the Content Store in packets
std::queue< shared_ptr<cs::Entry> > m_unsolicitedContent; //FIFO for unsolicited Data
std::queue< shared_ptr<cs::Entry> > m_contentByArrival; //FIFO index
std::priority_queue< shared_ptr<cs::Entry>, std::vector< shared_ptr<cs::Entry> >, StalenessComparator> m_contentByStaleness; //index by staleness time
};
} // namespace nfd
#endif // NFD_TABLE_CS_HPP