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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.
*/
// Name Tree (Name Prefix Hash Table)
#include "name-tree.hpp"
#include "core/logger.hpp"
namespace nfd {
NFD_LOG_INIT("NameTree");
namespace name_tree {
// Interface of different hash functions
uint32_t
hashName(const Name& prefix)
{
// fixed value. Used for debugging only.
uint32_t ret = 0;
// Boost hash
// requires the /boost/functional/hash.hpp header file
// TODO: improve hash efficiency with Name type
boost::hash<std::string> stringHash;
ret = stringHash(prefix.toUri());
return ret;
}
} // namespace name_tree
NameTree::NameTree(size_t nBuckets)
: m_nItems(0)
, m_nBuckets(nBuckets)
, m_loadFactor(0.5)
, m_resizeFactor(2)
{
m_resizeThreshold = static_cast<size_t>(m_loadFactor *
static_cast<double>(m_nBuckets));
// array of node pointers
m_buckets = new name_tree::Node*[m_nBuckets];
// Initialize the pointer array
for (size_t i = 0; i < m_nBuckets; i++)
m_buckets[i] = 0;
}
NameTree::~NameTree()
{
for (size_t i = 0; i < m_nBuckets; i++)
{
if (m_buckets[i] != 0)
delete m_buckets[i];
}
delete [] m_buckets;
}
// insert() is a private function, and called by only lookup()
std::pair<shared_ptr<name_tree::Entry>, bool>
NameTree::insert(const Name& prefix)
{
NFD_LOG_DEBUG("insert " << prefix);
uint32_t hashValue = name_tree::hashName(prefix);
uint32_t loc = hashValue % m_nBuckets;
NFD_LOG_DEBUG("Name " << prefix << " hash value = " << hashValue << " location = " << loc);
// Check if this Name has been stored
name_tree::Node* node = m_buckets[loc];
name_tree::Node* nodePrev = node; // initialize nodePrev to node
for (node = m_buckets[loc]; node != 0; node = node->m_next)
{
if (static_cast<bool>(node->m_entry))
{
if (prefix == node->m_entry->m_prefix)
{
return std::make_pair(node->m_entry, false); // false: old entry
}
}
nodePrev = node;
}
NFD_LOG_DEBUG("Did not find " << prefix << ", need to insert it to the table");
// If no bucket is empty occupied, we need to create a new node, and it is
// linked from nodePrev
node = new name_tree::Node();
node->m_prev = nodePrev;
if (nodePrev == 0)
{
m_buckets[loc] = node;
}
else
{
nodePrev->m_next = node;
}
// Create a new Entry
shared_ptr<name_tree::Entry> entry(make_shared<name_tree::Entry>(prefix));
entry->setHash(hashValue);
node->m_entry = entry; // link the Entry to its Node
entry->m_node = node; // link the node to Entry. Used in eraseEntryIfEmpty.
return std::make_pair(entry, true); // true: new entry
}
// Name Prefix Lookup. Create Name Tree Entry if not found
shared_ptr<name_tree::Entry>
NameTree::lookup(const Name& prefix)
{
NFD_LOG_DEBUG("lookup " << prefix);
shared_ptr<name_tree::Entry> entry;
shared_ptr<name_tree::Entry> parent;
for (size_t i = 0; i <= prefix.size(); i++)
{
Name temp = prefix.getPrefix(i);
// insert() will create the entry if it does not exist.
std::pair<shared_ptr<name_tree::Entry>, bool> ret = insert(temp);
entry = ret.first;
if (ret.second == true)
{
m_nItems++; /* Increase the counter */
entry->m_parent = parent;
if (static_cast<bool>(parent))
{
parent->m_children.push_back(entry);
}
}
if (m_nItems > m_resizeThreshold)
{
resize(m_resizeFactor * m_nBuckets);
}
parent = entry;
}
return entry;
}
// Exact Match
shared_ptr<name_tree::Entry>
NameTree::findExactMatch(const Name& prefix) const
{
NFD_LOG_DEBUG("findExactMatch " << prefix);
uint32_t hashValue = name_tree::hashName(prefix);
uint32_t loc = hashValue % m_nBuckets;
NFD_LOG_DEBUG("Name " << prefix << " hash value = " << hashValue <<
" location = " << loc);
shared_ptr<name_tree::Entry> entry;
name_tree::Node* node = 0;
for (node = m_buckets[loc]; node != 0; node = node->m_next)
{
entry = node->m_entry;
if (static_cast<bool>(entry))
{
if (hashValue == entry->getHash() && prefix == entry->getPrefix())
{
return entry;
}
} // if entry
} // for node
// if not found, the default value of entry (null pointer) will be returned
entry.reset();
return entry;
}
// Longest Prefix Match
// Return the longest matching Entry address
// start from the full name, and then remove 1 name comp each time
shared_ptr<name_tree::Entry>
NameTree::findLongestPrefixMatch(const Name& prefix)
{
NFD_LOG_DEBUG("findLongestPrefixMatch " << prefix);
shared_ptr<name_tree::Entry> entry;
for (int i = prefix.size(); i >= 0; i--)
{
entry = findExactMatch(prefix.getPrefix(i));
if (static_cast<bool>(entry))
return entry;
}
return entry;
}
// return {false: this entry is not empty, true: this entry is empty and erased}
bool
NameTree::eraseEntryIfEmpty(shared_ptr<name_tree::Entry> entry)
{
BOOST_ASSERT(static_cast<bool>(entry));
NFD_LOG_DEBUG("eraseEntryIfEmpty " << entry->getPrefix());
// first check if this Entry can be erased
if (entry->getChildren().empty() &&
!(entry->getFibEntry()) &&
entry->getPitEntries().empty())
{
// update child-related info in the parent
shared_ptr<name_tree::Entry> parent = entry->getParent();
if (static_cast<bool>(parent))
{
std::vector<shared_ptr<name_tree::Entry> >& parentChildrenList =
parent->getChildren();
bool isFound = false;
size_t size = parentChildrenList.size();
for (size_t i = 0; i < size; i++)
{
if (parentChildrenList[i] == entry)
{
parentChildrenList[i] = parentChildrenList[size - 1];
parentChildrenList.pop_back();
isFound = true;
break;
}
}
BOOST_ASSERT(isFound == true);
}
// remove this Entry and its Name Tree Node
name_tree::Node* node = entry->m_node;
name_tree::Node* nodePrev = node->m_prev;
// configure the previous node
if (nodePrev != 0)
{
// link the previous node to the next node
nodePrev->m_next = node->m_next;
}
else
{
m_buckets[entry->getHash() % m_nBuckets] = node->m_next;
}
// link the previous node with the next node (skip the erased one)
if (node->m_next != 0)
{
node->m_next->m_prev = nodePrev;
node->m_next = 0;
}
BOOST_ASSERT(node->m_next == 0);
m_nItems--;
delete node;
if (static_cast<bool>(parent))
eraseEntryIfEmpty(parent);
return true;
} // if this entry is empty
return false; // if this entry is not empty
}
shared_ptr<std::vector<shared_ptr<name_tree::Entry> > >
NameTree::fullEnumerate()
{
NFD_LOG_DEBUG("fullEnumerate");
shared_ptr<std::vector<shared_ptr<name_tree::Entry> > > ret =
make_shared<std::vector<shared_ptr<name_tree::Entry> > >();
for (int i = 0; i < m_nBuckets; i++)
{
for (name_tree::Node* node = m_buckets[i]; node != 0; node = node->m_next)
{
if (static_cast<bool>(node->m_entry))
{
ret->push_back(node->m_entry);
}
}
}
return ret;
}
// Helper function for partialEnumerate()
void
NameTree::partialEnumerateAddChildren(shared_ptr<name_tree::Entry> entry,
shared_ptr<std::vector<shared_ptr<name_tree::Entry> > > ret)
{
BOOST_ASSERT(static_cast<bool>(entry));
ret->push_back(entry);
for (size_t i = 0; i < entry->m_children.size(); i++)
{
shared_ptr<name_tree::Entry> temp = entry->m_children[i];
partialEnumerateAddChildren(temp, ret);
}
}
shared_ptr<std::vector<shared_ptr<name_tree::Entry> > >
NameTree::partialEnumerate(const Name& prefix)
{
NFD_LOG_DEBUG("partialEnumerate" << prefix);
shared_ptr<std::vector<shared_ptr<name_tree::Entry> > > ret =
make_shared<std::vector<shared_ptr<name_tree::Entry> > >();
// find the hash bucket corresponding to that prefix
shared_ptr<name_tree::Entry> entry = findExactMatch(prefix);
if (!static_cast<bool>(entry))
{
return ret;
}
else
{
// go through its children list via depth-first-search
ret->push_back(entry);
for (size_t i = 0; i < entry->m_children.size(); i++)
{
partialEnumerateAddChildren(entry->m_children[i], ret);
}
}
return ret;
}
// Hash Table Resize
void
NameTree::resize(size_t newNBuckets)
{
NFD_LOG_DEBUG("resize");
name_tree::Node** newBuckets = new name_tree::Node*[newNBuckets];
int count = 0;
// referenced ccnx hashtb.c hashtb_rehash()
name_tree::Node** pp = 0;
name_tree::Node* p = 0;
name_tree::Node* pre = 0;
name_tree::Node* q = 0; // record p->m_next
int i;
uint32_t h;
uint32_t b;
for (i = 0; i < newNBuckets; i++)
{
newBuckets[i] = 0;
}
for (i = 0; i < m_nBuckets; i++)
{
for (p = m_buckets[i]; p != 0; p = q)
{
count++;
q = p->m_next;
BOOST_ASSERT(static_cast<bool>(p->m_entry));
h = p->m_entry->m_hash;
b = h % newNBuckets;
for (pp = &newBuckets[b]; *pp != 0; pp = &((*pp)->m_next))
{
pre = *pp;
continue;
}
p->m_prev = pre;
p->m_next = *pp; // Actually *pp always == 0 in this case
*pp = p;
}
}
BOOST_ASSERT(count == m_nItems);
name_tree::Node** oldBuckets = m_buckets;
m_buckets = newBuckets;
delete oldBuckets;
m_nBuckets = newNBuckets;
m_resizeThreshold = (int)(m_loadFactor * (double)m_nBuckets);
}
// For debugging
void
NameTree::dump(std::ostream& output)
{
NFD_LOG_DEBUG("dump()");
name_tree::Node* node = 0;
shared_ptr<name_tree::Entry> entry;
using std::endl;
for (size_t i = 0; i < m_nBuckets; i++)
{
for (node = m_buckets[i]; node != 0; node = node->m_next)
{
entry = node->m_entry;
// if the Entry exist, dump its information
if (static_cast<bool>(entry))
{
output << "Bucket" << i << "\t" << entry->m_prefix.toUri() << endl;
output << "\t\tHash " << entry->m_hash << endl;
if (static_cast<bool>(entry->m_parent))
{
output << "\t\tparent->" << entry->m_parent->m_prefix.toUri();
}
else
{
output << "\t\tROOT";
}
output << endl;
if (entry->m_children.size() != 0)
{
output << "\t\tchildren = " << entry->m_children.size() << endl;
for (size_t j = 0; j < entry->m_children.size(); j++)
{
output << "\t\t\tChild " << j << " " <<
entry->m_children[j]->getPrefix() << endl;
}
}
} // if (static_cast<bool>(entry))
} // for node
} // for int i
output << "Bucket count = " << m_nBuckets << endl;
output << "Stored item = " << m_nItems << endl;
output << "--------------------------\n";
}
} // namespace nfd