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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>
*/
#include "cs.hpp"
#include <ndn-cpp-dev/util/crypto.hpp>
#define SKIPLIST_MAX_LAYERS 32
#define SKIPLIST_PROBABILITY 50 // 50% ( p = 1/2 )
NFD_LOG_INIT("ContentStore");
namespace nfd {
Cs::Cs(int nMaxPackets)
: m_nMaxPackets(nMaxPackets)
{
srand (time::now());
SkipListLayer* zeroLayer = new SkipListLayer();
m_skipList.push_back(zeroLayer);
}
Cs::~Cs()
{
/// \todo Fix memory leak
}
size_t
Cs::size() const
{
return (*m_skipList.begin())->size(); // size of the first layer in a skip list
}
void
Cs::setLimit(size_t nMaxPackets)
{
m_nMaxPackets = nMaxPackets;
while (isFull())
{
evictItem();
}
}
size_t
Cs::getLimit() const
{
return m_nMaxPackets;
}
//Reference: "Skip Lists: A Probabilistic Alternative to Balanced Trees" by W.Pugh
std::pair< shared_ptr<cs::Entry>, bool>
Cs::insertToSkipList(const Data& data, bool isUnsolicited)
{
NFD_LOG_INFO("insertToSkipList() " << data.getName());
NFD_LOG_DEBUG("SkipList size " << size());
shared_ptr<cs::Entry> entry = make_shared<cs::Entry>(data, isUnsolicited);
bool insertInFront = false;
bool isIterated = false;
SkipList::reverse_iterator topLayer = m_skipList.rbegin();
SkipListLayer::iterator updateTable[SKIPLIST_MAX_LAYERS];
SkipListLayer::iterator head = (*topLayer)->begin();
if ( !(*topLayer)->empty() )
{
//start from the upper layer towards bottom
int layer = m_skipList.size() - 1;
for (SkipList::reverse_iterator rit = topLayer; rit != m_skipList.rend(); ++rit)
{
//if we didn't do any iterations on the higher layers, start from the begin() again
if ( !isIterated )
head = (*rit)->begin();
updateTable[layer] = head;
if (head != (*rit)->end())
{
// it can happen when begin() contains the element in front of which we need to insert
if ( !isIterated && ((*head)->getName() >= entry->getName()) )
{
--updateTable[layer];
insertInFront = true;
}
else
{
SkipListLayer::iterator it = head;
while ((*it)->getName() < entry->getName())
{
head = it;
updateTable[layer] = it;
isIterated = true;
++it;
if (it == (*rit)->end())
break;
}
}
}
if (layer > 0)
head = (*head)->getIterators().find(layer - 1)->second; // move HEAD to the lower layer
layer--;
}
}
else
{
updateTable[0] = (*topLayer)->begin(); //initialization
}
head = updateTable[0];
++head; // look at the next slot to check if it contains a duplicate
bool isCsEmpty = (size() == 0);
bool isInBoundaries = (head != (*m_skipList.begin())->end());
bool isNameIdentical = false;
if (!isCsEmpty && isInBoundaries)
{
isNameIdentical = (*head)->getName() == entry->getName();
}
//check if this is a duplicate packet
if (isNameIdentical)
{
NFD_LOG_DEBUG("Duplicate name (with digest)");
(*head)->setData(data, entry->getDigest()); //updates stale time
return std::make_pair(*head, false);
}
NFD_LOG_DEBUG("Not a duplicate");
int randomLayer = pickRandomLayer();
if (randomLayer > (m_skipList.size() - 1))
{
while ( (m_skipList.size() - 1) < randomLayer)
{
SkipListLayer* newLayer = new SkipListLayer();
m_skipList.push_back(newLayer);
updateTable[(m_skipList.size() - 1)] = newLayer->begin();
}
}
int layer = 0;
for (SkipList::iterator i = m_skipList.begin(); i != m_skipList.end() && layer <= randomLayer; ++i)
{
if (updateTable[layer] == (*i)->end() && !insertInFront)
{
(*i)->push_back(entry);
SkipListLayer::iterator last = (*i)->end();
--last;
entry->setIterator(layer, last);
NFD_LOG_DEBUG("pushback " << &(*last));
}
else if (updateTable[layer] == (*i)->end() && insertInFront)
{
(*i)->push_front(entry);
entry->setIterator(layer, (*i)->begin());
NFD_LOG_DEBUG("pushfront ");
}
else
{
NFD_LOG_DEBUG("insertafter");
++updateTable[layer]; // insert after
SkipListLayer::iterator position = (*i)->insert(updateTable[layer], entry);
entry->setIterator(layer, position); // save iterator where item was inserted
}
layer++;
}
printSkipList();
return std::make_pair(entry, true);
}
bool
Cs::insert(const Data& data, bool isUnsolicited)
{
NFD_LOG_INFO("insert() " << data.getName());
if (isFull())
{
evictItem();
}
//pointer and insertion status
std::pair< shared_ptr<cs::Entry>, bool> entry = insertToSkipList(data, isUnsolicited);
//new entry
if (entry.first && (entry.second == true))
{
m_contentByArrival.push(entry.first);
m_contentByStaleness.push(entry.first);
if (entry.first->isUnsolicited())
m_unsolicitedContent.push(entry.first);
return true;
}
return false;
}
int
Cs::pickRandomLayer() const
{
int layer = -1;
int randomValue;
do
{
layer++;
randomValue = rand() % 100 + 1;
}
while ( (randomValue < SKIPLIST_PROBABILITY) && (layer < SKIPLIST_MAX_LAYERS) );
return layer;
}
bool
Cs::isFull() const
{
if (size() >= m_nMaxPackets) //size of the first layer vs. max size
return true;
return false;
}
bool
Cs::eraseFromSkipList(shared_ptr<cs::Entry> entry)
{
NFD_LOG_INFO("eraseFromSkipList() " << entry->getName());
NFD_LOG_DEBUG("SkipList size " << size());
bool isErased = false;
int layer = m_skipList.size() - 1;
for (SkipList::reverse_iterator rit = m_skipList.rbegin(); rit != m_skipList.rend(); ++rit)
{
const std::map<int, std::list< shared_ptr<cs::Entry> >::iterator>& iterators = entry->getIterators();
std::map<int, std::list< shared_ptr<cs::Entry> >::iterator>::const_iterator it = iterators.find(layer);
if (it != iterators.end())
{
(*rit)->erase(it->second);
entry->removeIterator(layer);
isErased = true;
}
layer--;
}
printSkipList();
//remove layers that do not contain any elements (starting from the second layer)
for (SkipList::iterator it = (++m_skipList.begin()); it != m_skipList.end();)
{
if ((*it)->empty())
{
it = m_skipList.erase(it);
}
else
++it;
}
return isErased;
}
bool
Cs::evictItem()
{
NFD_LOG_INFO("evictItem()");
//because there is a possibility that this item is in a queue, but no longer in skiplist
while ( !m_unsolicitedContent.empty() )
{
NFD_LOG_DEBUG("Evict from unsolicited queue");
shared_ptr<cs::Entry> entry = m_unsolicitedContent.front();
m_unsolicitedContent.pop();
bool isErased = eraseFromSkipList(entry);
if (isErased)
return true;
}
//because there is a possibility that this item is in a queue, but no longer in skiplist
int nIterations = size() * 0.01; // 1% of the Content Store
while ( !m_contentByStaleness.empty() )
{
NFD_LOG_DEBUG("Evict from staleness queue");
shared_ptr<cs::Entry> entry = m_contentByStaleness.top();
//because stale time could be updated by the duplicate packet
if (entry->getStaleTime() < time::now())
{
m_contentByStaleness.pop();
bool isErased = eraseFromSkipList(entry);
if (isErased)
return true;
}
else if ( (entry->getStaleTime() > time::now()) && entry->wasRefreshedByDuplicate() )
{
m_contentByStaleness.pop();
m_contentByStaleness.push(entry); // place in a right order
nIterations--;
// if 1% of the CS are non-expired refreshed CS entries (allocated sequentially),
// then stop to prevent too many iterations
if ( nIterations <= 0 )
break;
}
else //no further item will be expired, stop
{
break;
}
}
//because there is a possibility that this item is in a queue, but no longer in skiplist
while ( !m_contentByArrival.empty() )
{
NFD_LOG_DEBUG("Evict from arrival queue");
shared_ptr<cs::Entry> entry = m_contentByArrival.front();
m_contentByArrival.pop();
bool isErased = eraseFromSkipList(entry);
if (isErased)
return true;
}
return false;
}
const Data*
Cs::find(const Interest& interest) const
{
NFD_LOG_INFO("find() " << interest.getName());
bool isIterated = false;
SkipList::const_reverse_iterator topLayer = m_skipList.rbegin();
SkipListLayer::iterator head = (*topLayer)->begin();
if ( !(*topLayer)->empty() )
{
//start from the upper layer towards bottom
int layer = m_skipList.size() - 1;
for (SkipList::const_reverse_iterator rit = topLayer; rit != m_skipList.rend(); ++rit)
{
//if we didn't do any iterations on the higher layers, start from the begin() again
if (!isIterated)
head = (*rit)->begin();
if (head != (*rit)->end())
{
// it happens when begin() contains the element we want to find
if ( !isIterated && (interest.getName().isPrefixOf((*head)->getName())) )
{
if (layer > 0)
{
layer--;
continue; // try lower layer
}
else
{
isIterated = true;
}
}
else
{
SkipListLayer::iterator it = head;
while ( (*it)->getName() < interest.getName() )
{
NFD_LOG_DEBUG((*it)->getName() << " < " << interest.getName());
head = it;
isIterated = true;
++it;
if (it == (*rit)->end())
break;
}
}
}
if (layer > 0)
{
head = (*head)->getIterators().find(layer - 1)->second; // move HEAD to the lower layer
}
else //if we reached the first layer
{
if ( isIterated )
return selectChild(interest, head);
}
layer--;
}
}
return 0;
}
// because skip list is a probabilistic data structure and the way it is traversed,
// there is no guarantee that startingPoint is an element preceding the leftmost child
const Data*
Cs::selectChild(const Interest& interest, SkipListLayer::iterator startingPoint) const
{
BOOST_ASSERT( startingPoint != (*m_skipList.begin())->end() );
if (startingPoint != (*m_skipList.begin())->begin())
{
BOOST_ASSERT( (*startingPoint)->getName() < interest.getName() );
}
NFD_LOG_INFO("selectChild() " << interest.getChildSelector() << " " << (*startingPoint)->getName());
bool hasLeftmostSelector = (interest.getChildSelector() <= 0);
bool hasRightmostSelector = !hasLeftmostSelector;
if (hasLeftmostSelector)
{
bool doesInterestContainDigest = recognizeInterestWithDigest(interest, *startingPoint);
bool isInPrefix = false;
if (doesInterestContainDigest)
{
isInPrefix = interest.getName().getPrefix(-1).isPrefixOf((*startingPoint)->getName());
}
else
{
isInPrefix = interest.getName().isPrefixOf((*startingPoint)->getName());
}
if (isInPrefix)
{
if (doesComplyWithSelectors(interest, *startingPoint))
{
return &(*startingPoint)->getData();
}
}
}
//iterate to the right
SkipListLayer::iterator rightmost = startingPoint;
if (startingPoint != (*m_skipList.begin())->end())
{
SkipListLayer::iterator rightmostCandidate = startingPoint;
Name currentChildPrefix("");
while (true)
{
++rightmostCandidate;
bool isInBoundaries = (rightmostCandidate != (*m_skipList.begin())->end());
bool isInPrefix = false;
bool doesInterestContainDigest = false;
if (isInBoundaries)
{
doesInterestContainDigest = recognizeInterestWithDigest(interest, *rightmostCandidate);
if (doesInterestContainDigest)
{
isInPrefix = interest.getName().getPrefix(-1).isPrefixOf((*rightmostCandidate)->getName());
}
else
{
isInPrefix = interest.getName().isPrefixOf((*rightmostCandidate)->getName());
}
}
if (isInPrefix)
{
if (doesComplyWithSelectors(interest, *rightmostCandidate))
{
if (hasLeftmostSelector)
{
return &(*rightmostCandidate)->getData();
}
if (hasRightmostSelector)
{
if (doesInterestContainDigest)
{
// get prefix which is one component longer than Interest name (without digest)
const Name& childPrefix = (*rightmostCandidate)->getName().getPrefix(interest.getName().size());
NFD_LOG_DEBUG("Child prefix" << childPrefix);
if ( currentChildPrefix.empty() || (childPrefix != currentChildPrefix) )
{
currentChildPrefix = childPrefix;
rightmost = rightmostCandidate;
}
}
else
{
// get prefix which is one component longer than Interest name
const Name& childPrefix = (*rightmostCandidate)->getName().getPrefix(interest.getName().size() + 1);
NFD_LOG_DEBUG("Child prefix" << childPrefix);
if ( currentChildPrefix.empty() || (childPrefix != currentChildPrefix) )
{
currentChildPrefix = childPrefix;
rightmost = rightmostCandidate;
}
}
}
}
}
else
break;
}
}
if (rightmost != startingPoint)
{
return &(*rightmost)->getData();
}
if (hasRightmostSelector) // if rightmost was not found, try starting point
{
bool doesInterestContainDigest = recognizeInterestWithDigest(interest, *startingPoint);
bool isInPrefix = false;
if (doesInterestContainDigest)
{
isInPrefix = interest.getName().getPrefix(-1).isPrefixOf((*startingPoint)->getName());
}
else
{
isInPrefix = interest.getName().isPrefixOf((*startingPoint)->getName());
}
if (isInPrefix)
{
if (doesComplyWithSelectors(interest, *startingPoint))
{
return &(*startingPoint)->getData();
}
}
}
return 0;
}
bool
Cs::doesComplyWithSelectors(const Interest& interest, shared_ptr<cs::Entry> entry) const
{
NFD_LOG_INFO("doesComplyWithSelectors()");
/// \todo The following detection is not correct
/// 1. If data name ends with 32-octet component doesn't mean that this component is digest
/// 2. Only min/max selectors (both 0) can be specified, all other selectors do not make sense
/// for interests with digest (though not sure if we need to enforce this)
bool doesInterestContainDigest = recognizeInterestWithDigest(interest, entry);
if ( doesInterestContainDigest )
{
const ndn::name::Component& last = interest.getName().get(-1);
const ndn::ConstBufferPtr& digest = entry->getDigest();
BOOST_ASSERT(digest->size() == last.value_size());
BOOST_ASSERT(digest->size() == ndn::crypto::SHA256_DIGEST_SIZE);
if (std::memcmp(digest->buf(), last.value(), ndn::crypto::SHA256_DIGEST_SIZE) != 0)
{
NFD_LOG_DEBUG("violates implicit digest");
return false;
}
}
if ( !doesInterestContainDigest )
{
if (interest.getMinSuffixComponents() >= 0)
{
int minDataNameLength = interest.getName().size() + interest.getMinSuffixComponents();
bool isSatisfied = minDataNameLength <= entry->getName().size();
if ( !isSatisfied )
{
NFD_LOG_DEBUG("violates minComponents");
return false;
}
}
if (interest.getMaxSuffixComponents() >= 0)
{
int maxDataNameLength = interest.getName().size() + interest.getMaxSuffixComponents();
bool isSatisfied = maxDataNameLength >= entry->getName().size();
if ( !isSatisfied )
{
NFD_LOG_DEBUG("violates maxComponents");
return false;
}
}
}
if (interest.getMustBeFresh() && entry->getStaleTime() < time::now())
{
NFD_LOG_DEBUG("violates mustBeFresh");
return false;
}
if ( doesInterestContainDigest )
{
const ndn::name::Component& lastComponent = entry->getName().get(-1);
if ( !lastComponent.empty() )
{
if (interest.getExclude().isExcluded(lastComponent))
{
NFD_LOG_DEBUG("violates exclusion");
return false;
}
}
}
else
{
if (entry->getName().size() >= interest.getName().size() + 1)
{
const ndn::name::Component& nextComponent = entry->getName().get(interest.getName().size());
if ( !nextComponent.empty() )
{
if (interest.getExclude().isExcluded(nextComponent))
{
NFD_LOG_DEBUG("violates exclusion");
return false;
}
}
}
}
NFD_LOG_DEBUG("complies!");
return true;
}
bool
Cs::recognizeInterestWithDigest(const Interest& interest, shared_ptr<cs::Entry> entry) const
{
// only when min selector is not specified or specified with value of 0
// and Interest's name length is exactly the length of the name of CS entry
if (interest.getMinSuffixComponents() <= 0 &&
interest.getName().size() == (entry->getName().size()))
{
const ndn::name::Component& last = interest.getName().get(-1);
if (last.value_size() == ndn::crypto::SHA256_DIGEST_SIZE)
{
NFD_LOG_DEBUG("digest recognized");
return true;
}
}
return false;
}
void
Cs::erase(const Name& exactName)
{
NFD_LOG_INFO("insert() " << exactName);
NFD_LOG_DEBUG("SkipList size " << size());
bool isIterated = false;
SkipListLayer::iterator updateTable[SKIPLIST_MAX_LAYERS];
SkipList::reverse_iterator topLayer = m_skipList.rbegin();
SkipListLayer::iterator head = (*topLayer)->begin();
if ( !(*topLayer)->empty() )
{
//start from the upper layer towards bottom
int layer = m_skipList.size() - 1;
for (SkipList::reverse_iterator rit = topLayer; rit != m_skipList.rend(); ++rit)
{
//if we didn't do any iterations on the higher layers, start from the begin() again
if ( !isIterated )
head = (*rit)->begin();
updateTable[layer] = head;
if (head != (*rit)->end())
{
// it can happen when begin() contains the element we want to remove
if ( !isIterated && ((*head)->getName() == exactName) )
{
eraseFromSkipList(*head);
return;
}
else
{
SkipListLayer::iterator it = head;
while ((*it)->getName() < exactName)
{
head = it;
updateTable[layer] = it;
isIterated = true;
++it;
if ( it == (*rit)->end() )
break;
}
}
}
if (layer > 0)
head = (*head)->getIterators().find(layer - 1)->second; // move HEAD to the lower layer
layer--;
}
}
else
{
return;
}
head = updateTable[0];
++head; // look at the next slot to check if it contains the item we want to remove
bool isCsEmpty = (size() == 0);
bool isInBoundaries = (head != (*m_skipList.begin())->end());
bool isNameIdentical = false;
if (!isCsEmpty && isInBoundaries)
{
NFD_LOG_DEBUG("Identical? " << (*head)->getName());
isNameIdentical = (*head)->getName() == exactName;
}
if (isNameIdentical)
{
NFD_LOG_DEBUG("Found target " << (*head)->getName());
eraseFromSkipList(*head);
}
printSkipList();
}
void
Cs::printSkipList() const
{
NFD_LOG_INFO("print()");
//start from the upper layer towards bottom
int layer = m_skipList.size() - 1;
for (SkipList::const_reverse_iterator rit = m_skipList.rbegin(); rit != m_skipList.rend(); ++rit)
{
for (SkipListLayer::iterator it = (*rit)->begin(); it != (*rit)->end(); ++it)
{
NFD_LOG_DEBUG("Layer " << layer << " " << (*it)->getName());
}
layer--;
}
}
} //namespace nfd