table: ContentStore based on skip list
ref: #1212
Change-Id: Iaa13aa7c110c3cd059438bf553a19b4fcd07e137
diff --git a/daemon/table/cs.hpp b/daemon/table/cs.hpp
index 0db5ad7..e4c1ae6 100644
--- a/daemon/table/cs.hpp
+++ b/daemon/table/cs.hpp
@@ -2,6 +2,8 @@
/**
* 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
@@ -12,31 +14,144 @@
namespace nfd {
-/** \class Cs
- * \brief represents the ContentStore
+typedef std::list< shared_ptr<cs::Entry> > SkipListLayer;
+typedef std::list<SkipListLayer*> SkipList;
+
+/** \brief represents Content Store
*/
class Cs : noncopyable
{
public:
- Cs();
-
+ explicit
+ Cs(int nMaxPackets = 65536); // ~500MB with average packet size = 8KB
+
~Cs();
-
+
/** \brief inserts a Data packet
- * The caller should ensure that this Data packet is admittable,
- * ie. not unsolicited from a untrusted source.
- * This does not guarantee the Data is added to the cache;
- * even if the Data is added, it may be removed anytime in the future.
+ * 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);
-
+ 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);
+ 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