name-tree-hashtable.hpp

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/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
 * Copyright (c) 2014-2022,  Regents of the University of California,
 *                           Arizona Board of Regents,
 *                           Colorado State University,
 *                           University Pierre & Marie Curie, Sorbonne University,
 *                           Washington University in St. Louis,
 *                           Beijing Institute of Technology,
 *                           The University of Memphis.
 *
 * This file is part of NFD (Named Data Networking Forwarding Daemon).
 * See AUTHORS.md for complete list of NFD authors and contributors.
 *
 * NFD is free software: you can redistribute it and/or modify it under the terms
 * of the GNU General Public License as published by the Free Software Foundation,
 * either version 3 of the License, or (at your option) any later version.
 *
 * NFD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
 * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
 * PURPOSE.  See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * NFD, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
 */
 
#ifndef NFD_DAEMON_TABLE_NAME_TREE_HASHTABLE_HPP
#define NFD_DAEMON_TABLE_NAME_TREE_HASHTABLE_HPP
 
#include "name-tree-entry.hpp"
 
namespace nfd::name_tree {
 
class Entry;
 
using HashValue = size_t;
 
using HashSequence = std::vector<HashValue>;
 
HashValue
computeHash(const Name& name, size_t prefixLen = std::numeric_limits<size_t>::max());
 
HashSequence
computeHashes(const Name& name, size_t prefixLen = std::numeric_limits<size_t>::max());
 
class Node : noncopyable
{
public:
  Node(HashValue h, const Name& name);
 
  ~Node();
 
public:
  const HashValue hash;
  Node* prev;
  Node* next;
  mutable Entry entry;
};
 
Node*
getNode(const Entry& entry);
 
template<typename N, typename F>
void
foreachNode(N* head, const F& func)
{
  N* node = head;
  while (node != nullptr) {
    N* next = node->next;
    func(node);
    node = next;
  }
}
 
struct HashtableOptions
{
  explicit
  HashtableOptions(size_t size = 16);
 
  size_t initialSize;
 
  size_t minSize;
 
  float expandLoadFactor = 0.5f;
 
  float expandFactor = 2.0f;
 
  float shrinkLoadFactor = 0.1f;
 
  float shrinkFactor = 0.5f;
};
 
class Hashtable
{
public:
  using Options = HashtableOptions;
 
  explicit
  Hashtable(const Options& options);
 
  ~Hashtable();
 
  size_t
  size() const
  {
    return m_size;
  }
 
  size_t
  getNBuckets() const
  {
    return m_buckets.size();
  }
 
  size_t
  computeBucketIndex(HashValue h) const
  {
    return h % this->getNBuckets();
  }
 
  const Node*
  getBucket(size_t bucket) const
  {
    BOOST_ASSERT(bucket < this->getNBuckets());
    return m_buckets[bucket]; // don't use m_bucket.at() for better performance
  }
 
  const Node*
  find(const Name& name, size_t prefixLen) const;
 
  const Node*
  find(const Name& name, size_t prefixLen, const HashSequence& hashes) const;
 
  std::pair<const Node*, bool>
  insert(const Name& name, size_t prefixLen, const HashSequence& hashes);
 
  void
  erase(Node* node);
 
private:
  void
  attach(size_t bucket, Node* node);
 
  void
  detach(size_t bucket, Node* node);
 
  std::pair<const Node*, bool>
  findOrInsert(const Name& name, size_t prefixLen, HashValue h, bool allowInsert);
 
  void
  computeThresholds();
 
  void
  resize(size_t newNBuckets);
 
private:
  std::vector<Node*> m_buckets;
  Options m_options;
  size_t m_size;
  size_t m_expandThreshold;
  size_t m_shrinkThreshold;
};
 
} // namespace nfd::name_tree
 
#endif // NFD_DAEMON_TABLE_NAME_TREE_HASHTABLE_HPP