table: don't use shared_ptr in Measurements

refs #3164

Change-Id: I7705d00ac155b15b5db69809610b68e96360a0ae
diff --git a/daemon/table/measurements-accessor.cpp b/daemon/table/measurements-accessor.cpp
index 47b4fe2..68cf784 100644
--- a/daemon/table/measurements-accessor.cpp
+++ b/daemon/table/measurements-accessor.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2014-2015,  Regents of the University of California,
+ * Copyright (c) 2014-2016,  Regents of the University of California,
  *                           Arizona Board of Regents,
  *                           Colorado State University,
  *                           University Pierre & Marie Curie, Sorbonne University,
@@ -26,6 +26,7 @@
 #include "measurements-accessor.hpp"
 
 namespace nfd {
+namespace measurements {
 
 using fw::Strategy;
 
@@ -42,8 +43,8 @@
 {
 }
 
-shared_ptr<measurements::Entry>
-MeasurementsAccessor::filter(const shared_ptr<measurements::Entry>& entry) const
+Entry*
+MeasurementsAccessor::filter(Entry* entry) const
 {
   if (entry == nullptr) {
     return entry;
@@ -53,7 +54,8 @@
   if (&effectiveStrategy == m_strategy) {
     return entry;
   }
-  return shared_ptr<measurements::Entry>();
+  return nullptr;
 }
 
+} // namespace measurements
 } // namespace nfd
diff --git a/daemon/table/measurements-accessor.hpp b/daemon/table/measurements-accessor.hpp
index 9a280c2..244897b 100644
--- a/daemon/table/measurements-accessor.hpp
+++ b/daemon/table/measurements-accessor.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2014-2015,  Regents of the University of California,
+ * Copyright (c) 2014-2016,  Regents of the University of California,
  *                           Arizona Board of Regents,
  *                           Colorado State University,
  *                           University Pierre & Marie Curie, Sorbonne University,
@@ -33,9 +33,14 @@
 
 namespace fw {
 class Strategy;
-}
+} // namespace fw
+
+namespace measurements {
 
 /** \brief allows Strategy to access portion of Measurements table under its namespace
+ *
+ *  All public methods have the same semantics as the same method on \p Measurements,
+ *  but would return nullptr if the entry falls out of the strategy's authority.
  */
 class MeasurementsAccessor : noncopyable
 {
@@ -47,42 +52,41 @@
 
   /** \brief find or insert a Measurements entry for \p name
    */
-  shared_ptr<measurements::Entry>
+  Entry*
   get(const Name& name);
 
   /** \brief find or insert a Measurements entry for \p fibEntry->getPrefix()
    */
-  shared_ptr<measurements::Entry>
+  Entry*
   get(const fib::Entry& fibEntry);
 
   /** \brief find or insert a Measurements entry for \p pitEntry->getName()
    */
-  shared_ptr<measurements::Entry>
+  Entry*
   get(const pit::Entry& pitEntry);
 
   /** \brief find or insert a Measurements entry for child's parent
-   *  \retval nullptr if child is the root entry
    */
-  shared_ptr<measurements::Entry>
-  getParent(const measurements::Entry& child);
+  Entry*
+  getParent(const Entry& child);
 
   /** \brief perform a longest prefix match for \p name
    */
-  shared_ptr<measurements::Entry>
+  Entry*
   findLongestPrefixMatch(const Name& name,
-                         const measurements::EntryPredicate& pred =
-                             measurements::AnyEntry()) const;
+                         const EntryPredicate& pred =
+                             AnyEntry()) const;
 
   /** \brief perform a longest prefix match for \p pitEntry.getName()
    */
-  shared_ptr<measurements::Entry>
+  Entry*
   findLongestPrefixMatch(const pit::Entry& pitEntry,
-                         const measurements::EntryPredicate& pred =
-                             measurements::AnyEntry()) const;
+                         const EntryPredicate& pred =
+                             AnyEntry()) const;
 
   /** \brief perform an exact match
    */
-  shared_ptr<measurements::Entry>
+  Entry*
   findExactMatch(const Name& name) const;
 
   /** \brief extend lifetime of an entry
@@ -90,14 +94,17 @@
    *  The entry will be kept until at least now()+lifetime.
    */
   void
-  extendLifetime(measurements::Entry& entry, const time::nanoseconds& lifetime);
+  extendLifetime(Entry& entry, const time::nanoseconds& lifetime);
 
 private:
   /** \brief perform access control to Measurements entry
    *  \return entry if strategy has access to namespace, otherwise nullptr
    */
-  shared_ptr<measurements::Entry>
-  filter(const shared_ptr<measurements::Entry>& entry) const;
+  Entry*
+  filter(Entry* entry) const;
+
+  Entry*
+  filter(Entry& entry) const;
 
 private:
   Measurements& m_measurements;
@@ -105,57 +112,66 @@
   const fw::Strategy* m_strategy;
 };
 
-inline shared_ptr<measurements::Entry>
+inline Entry*
+MeasurementsAccessor::filter(Entry& entry) const
+{
+  return this->filter(&entry);
+}
+
+inline Entry*
 MeasurementsAccessor::get(const Name& name)
 {
   return this->filter(m_measurements.get(name));
 }
 
-inline shared_ptr<measurements::Entry>
+inline Entry*
 MeasurementsAccessor::get(const fib::Entry& fibEntry)
 {
   return this->filter(m_measurements.get(fibEntry));
 }
 
-inline shared_ptr<measurements::Entry>
+inline Entry*
 MeasurementsAccessor::get(const pit::Entry& pitEntry)
 {
   return this->filter(m_measurements.get(pitEntry));
 }
 
-inline shared_ptr<measurements::Entry>
-MeasurementsAccessor::getParent(const measurements::Entry& child)
+inline Entry*
+MeasurementsAccessor::getParent(const Entry& child)
 {
   return this->filter(m_measurements.getParent(child));
 }
 
-inline shared_ptr<measurements::Entry>
+inline Entry*
 MeasurementsAccessor::findLongestPrefixMatch(const Name& name,
-                                             const measurements::EntryPredicate& pred) const
+                                             const EntryPredicate& pred) const
 {
   return this->filter(m_measurements.findLongestPrefixMatch(name, pred));
 }
 
-inline shared_ptr<measurements::Entry>
+inline Entry*
 MeasurementsAccessor::findLongestPrefixMatch(const pit::Entry& pitEntry,
-                                             const measurements::EntryPredicate& pred) const
+                                             const EntryPredicate& pred) const
 {
   return this->filter(m_measurements.findLongestPrefixMatch(pitEntry, pred));
 }
 
-inline shared_ptr<measurements::Entry>
+inline Entry*
 MeasurementsAccessor::findExactMatch(const Name& name) const
 {
   return this->filter(m_measurements.findExactMatch(name));
 }
 
 inline void
-MeasurementsAccessor::extendLifetime(measurements::Entry& entry,
-                                     const time::nanoseconds& lifetime)
+MeasurementsAccessor::extendLifetime(Entry& entry, const time::nanoseconds& lifetime)
 {
   m_measurements.extendLifetime(entry, lifetime);
 }
 
+} // namespace measurements
+
+using measurements::MeasurementsAccessor;
+
 } // namespace nfd
 
 #endif // NFD_DAEMON_TABLE_MEASUREMENTS_ACCESSOR_HPP
diff --git a/daemon/table/measurements-entry.hpp b/daemon/table/measurements-entry.hpp
index 0c9bc48..8eb40ff 100644
--- a/daemon/table/measurements-entry.hpp
+++ b/daemon/table/measurements-entry.hpp
@@ -38,12 +38,11 @@
 class Entry;
 } // namespace name_tree
 
-class Measurements;
-
 namespace measurements {
 
-/** \class Entry
- *  \brief represents a Measurements entry
+class Measurements;
+
+/** \brief represents a Measurements entry
  */
 class Entry : public StrategyInfoHost, noncopyable
 {
@@ -64,7 +63,7 @@
 
   friend class nfd::NameTree;
   friend class nfd::name_tree::Entry;
-  friend class nfd::Measurements;
+  friend class Measurements;
 };
 
 inline const Name&
diff --git a/daemon/table/measurements.cpp b/daemon/table/measurements.cpp
index 5981371..60e4f8d 100644
--- a/daemon/table/measurements.cpp
+++ b/daemon/table/measurements.cpp
@@ -29,8 +29,7 @@
 #include "fib-entry.hpp"
 
 namespace nfd {
-
-using measurements::Entry;
+namespace measurements {
 
 Measurements::Measurements(NameTree& nameTree)
   : m_nameTree(nameTree)
@@ -38,37 +37,39 @@
 {
 }
 
-shared_ptr<Entry>
+Entry&
 Measurements::get(name_tree::Entry& nte)
 {
-  shared_ptr<Entry> entry = nte.getMeasurementsEntry();
-  if (entry != nullptr)
-    return entry;
+  Entry* entry = nte.getMeasurementsEntry();
+  if (entry != nullptr) {
+    return *entry;
+  }
 
-  entry = make_shared<Entry>(nte.getPrefix());
-  nte.setMeasurementsEntry(entry);
+  nte.setMeasurementsEntry(make_unique<Entry>(nte.getPrefix()));
   ++m_nItems;
+  entry = nte.getMeasurementsEntry();
 
   entry->m_expiry = time::steady_clock::now() + getInitialLifetime();
   entry->m_cleanup = scheduler::schedule(getInitialLifetime(),
                                          bind(&Measurements::cleanup, this, ref(*entry)));
 
-  return entry;
+  return *entry;
 }
 
-shared_ptr<Entry>
+Entry&
 Measurements::get(const Name& name)
 {
   shared_ptr<name_tree::Entry> nte = m_nameTree.lookup(name);
+  BOOST_ASSERT(nte != nullptr);
   return this->get(*nte);
 }
 
-shared_ptr<Entry>
+Entry&
 Measurements::get(const fib::Entry& fibEntry)
 {
   shared_ptr<name_tree::Entry> nte = m_nameTree.lookup(fibEntry);
   if (nte == nullptr) {
-    // must be Fib::s_emptyEntry that is unattched
+    // must be Fib::s_emptyEntry that is unattached
     BOOST_ASSERT(fibEntry.getPrefix().empty());
     nte = m_nameTree.lookup(fibEntry.getPrefix());
   }
@@ -77,36 +78,35 @@
   return this->get(*nte);
 }
 
-shared_ptr<Entry>
+Entry&
 Measurements::get(const pit::Entry& pitEntry)
 {
   shared_ptr<name_tree::Entry> nte = m_nameTree.lookup(pitEntry);
   BOOST_ASSERT(nte != nullptr);
-
   return this->get(*nte);
 }
 
-shared_ptr<Entry>
+Entry*
 Measurements::getParent(const Entry& child)
 {
-  if (child.getName().size() == 0) { // the root entry
+  if (child.getName().empty()) { // the root entry
     return nullptr;
   }
 
   shared_ptr<name_tree::Entry> nteChild = m_nameTree.lookup(child);
   shared_ptr<name_tree::Entry> nte = nteChild->getParent();
   BOOST_ASSERT(nte != nullptr);
-  return this->get(*nte);
+  return &this->get(*nte);
 }
 
 template<typename K>
-shared_ptr<Entry>
+Entry*
 Measurements::findLongestPrefixMatchImpl(const K& key,
-                                         const measurements::EntryPredicate& pred) const
+                                         const EntryPredicate& pred) const
 {
   shared_ptr<name_tree::Entry> match = m_nameTree.findLongestPrefixMatch(key,
-      [pred] (const name_tree::Entry& nte) -> bool {
-        shared_ptr<Entry> entry = nte.getMeasurementsEntry();
+      [&pred] (const name_tree::Entry& nte) -> bool {
+        Entry* entry = nte.getMeasurementsEntry();
         return entry != nullptr && pred(*entry);
       });
   if (match != nullptr) {
@@ -115,28 +115,29 @@
   return nullptr;
 }
 
-shared_ptr<Entry>
+Entry*
 Measurements::findLongestPrefixMatch(const Name& name,
-                                     const measurements::EntryPredicate& pred) const
+                                     const EntryPredicate& pred) const
 {
   return this->findLongestPrefixMatchImpl(name, pred);
 }
 
-shared_ptr<Entry>
+Entry*
 Measurements::findLongestPrefixMatch(const pit::Entry& pitEntry,
-                                     const measurements::EntryPredicate& pred) const
+                                     const EntryPredicate& pred) const
 {
   shared_ptr<name_tree::Entry> nte = m_nameTree.lookup(pitEntry);
   BOOST_ASSERT(nte != nullptr);
   return this->findLongestPrefixMatchImpl(nte, pred);
 }
 
-shared_ptr<Entry>
+Entry*
 Measurements::findExactMatch(const Name& name) const
 {
   shared_ptr<name_tree::Entry> nte = m_nameTree.lookup(name);
-  if (nte != nullptr)
+  if (nte != nullptr) {
     return nte->getMeasurementsEntry();
+  }
   return nullptr;
 }
 
@@ -144,10 +145,7 @@
 Measurements::extendLifetime(Entry& entry, const time::nanoseconds& lifetime)
 {
   shared_ptr<name_tree::Entry> nte = m_nameTree.lookup(entry);
-  if (nte == nullptr || nte->getMeasurementsEntry().get() != &entry) {
-    // entry is already gone; it is a dangling reference
-    return;
-  }
+  BOOST_ASSERT(nte != nullptr);
 
   time::steady_clock::TimePoint expiry = time::steady_clock::now() + lifetime;
   if (entry.m_expiry >= expiry) {
@@ -164,11 +162,12 @@
 Measurements::cleanup(Entry& entry)
 {
   shared_ptr<name_tree::Entry> nte = m_nameTree.lookup(entry);
-  if (nte != nullptr) {
-    nte->setMeasurementsEntry(nullptr);
-    m_nameTree.eraseEntryIfEmpty(nte);
-    m_nItems--;
-  }
+  BOOST_ASSERT(nte != nullptr);
+
+  nte->setMeasurementsEntry(nullptr);
+  m_nameTree.eraseEntryIfEmpty(nte);
+  --m_nItems;
 }
 
+} // namespace measurements
 } // namespace nfd
diff --git a/daemon/table/measurements.hpp b/daemon/table/measurements.hpp
index 5a61caa..cf9783d 100644
--- a/daemon/table/measurements.hpp
+++ b/daemon/table/measurements.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2014-2015,  Regents of the University of California,
+ * Copyright (c) 2014-2016,  Regents of the University of California,
  *                           Arizona Board of Regents,
  *                           Colorado State University,
  *                           University Pierre & Marie Curie, Sorbonne University,
@@ -41,35 +41,35 @@
 
 namespace measurements {
 
-/** \brief a predicate that accepts or rejects a \p Entry
+/** \brief a predicate that accepts or rejects an entry
  */
 typedef std::function<bool(const Entry&)> EntryPredicate;
 
-/** \brief an \p EntryPredicate that accepts any \p Entry
+/** \brief an \p EntryPredicate that accepts any entry
  */
 class AnyEntry
 {
 public:
   bool
-  operator()(const Entry& entry)
+  operator()(const Entry& entry) const
   {
     return true;
   }
 };
 
+/** \brief an \p EntryPredicate that accepts an entry if it has StrategyInfo of type T
+ */
 template<typename T>
 class EntryWithStrategyInfo
 {
 public:
   bool
-  operator()(const Entry& entry)
+  operator()(const Entry& entry) const
   {
     return entry.getStrategyInfo<T>() != nullptr;
   }
 };
 
-} // namespace measurements
-
 /** \brief represents the Measurements table
  */
 class Measurements : noncopyable
@@ -80,42 +80,40 @@
 
   /** \brief find or insert a Measurements entry for \p name
    */
-  shared_ptr<measurements::Entry>
+  Entry&
   get(const Name& name);
 
   /** \brief find or insert a Measurements entry for \p fibEntry.getPrefix()
    */
-  shared_ptr<measurements::Entry>
+  Entry&
   get(const fib::Entry& fibEntry);
 
   /** \brief find or insert a Measurements entry for \p pitEntry.getName()
    */
-  shared_ptr<measurements::Entry>
+  Entry&
   get(const pit::Entry& pitEntry);
 
   /** \brief find or insert a Measurements entry for child's parent
    *  \retval nullptr if child is the root entry
    */
-  shared_ptr<measurements::Entry>
-  getParent(const measurements::Entry& child);
+  Entry*
+  getParent(const Entry& child);
 
   /** \brief perform a longest prefix match for \p name
    */
-  shared_ptr<measurements::Entry>
+  Entry*
   findLongestPrefixMatch(const Name& name,
-                         const measurements::EntryPredicate& pred =
-                             measurements::AnyEntry()) const;
+                         const EntryPredicate& pred = AnyEntry()) const;
 
   /** \brief perform a longest prefix match for \p pitEntry.getName()
    */
-  shared_ptr<measurements::Entry>
+  Entry*
   findLongestPrefixMatch(const pit::Entry& pitEntry,
-                         const measurements::EntryPredicate& pred =
-                             measurements::AnyEntry()) const;
+                         const EntryPredicate& pred = AnyEntry()) const;
 
   /** \brief perform an exact match
    */
-  shared_ptr<measurements::Entry>
+  Entry*
   findExactMatch(const Name& name) const;
 
   static time::nanoseconds
@@ -126,23 +124,23 @@
    *  The entry will be kept until at least now()+lifetime.
    */
   void
-  extendLifetime(measurements::Entry& entry, const time::nanoseconds& lifetime);
+  extendLifetime(Entry& entry, const time::nanoseconds& lifetime);
 
   size_t
   size() const;
 
 private:
   void
-  cleanup(measurements::Entry& entry);
+  cleanup(Entry& entry);
 
-  shared_ptr<measurements::Entry>
+  Entry&
   get(name_tree::Entry& nte);
 
   /** \tparam K Name or shared_ptr<name_tree::Entry>
    */
   template<typename K>
-  shared_ptr<measurements::Entry>
-  findLongestPrefixMatchImpl(const K& key, const measurements::EntryPredicate& pred) const;
+  Entry*
+  findLongestPrefixMatchImpl(const K& key, const EntryPredicate& pred) const;
 
 private:
   NameTree& m_nameTree;
@@ -161,6 +159,10 @@
   return m_nItems;
 }
 
+} // namespace measurements
+
+using measurements::Measurements;
+
 } // namespace nfd
 
 #endif // NFD_DAEMON_TABLE_MEASUREMENTS_HPP
diff --git a/daemon/table/name-tree-entry.cpp b/daemon/table/name-tree-entry.cpp
index 3244059..b094e38 100644
--- a/daemon/table/name-tree-entry.cpp
+++ b/daemon/table/name-tree-entry.cpp
@@ -104,14 +104,14 @@
 }
 
 void
-Entry::setMeasurementsEntry(shared_ptr<measurements::Entry> measurementsEntry)
+Entry::setMeasurementsEntry(unique_ptr<measurements::Entry> measurementsEntry)
 {
   BOOST_ASSERT(measurementsEntry == nullptr || measurementsEntry->m_nameTreeEntry.expired());
 
   if (m_measurementsEntry != nullptr) {
     m_measurementsEntry->m_nameTreeEntry.reset();
   }
-  m_measurementsEntry = measurementsEntry;
+  m_measurementsEntry = std::move(measurementsEntry);
 
   if (m_measurementsEntry != nullptr) {
     m_measurementsEntry->m_nameTreeEntry = this->shared_from_this();
diff --git a/daemon/table/name-tree-entry.hpp b/daemon/table/name-tree-entry.hpp
index 7bade1f..2827926 100644
--- a/daemon/table/name-tree-entry.hpp
+++ b/daemon/table/name-tree-entry.hpp
@@ -114,9 +114,9 @@
   getPitEntries() const;
 
   void
-  setMeasurementsEntry(shared_ptr<measurements::Entry> measurementsEntry);
+  setMeasurementsEntry(unique_ptr<measurements::Entry> measurementsEntry);
 
-  shared_ptr<measurements::Entry>
+  measurements::Entry*
   getMeasurementsEntry() const;
 
   void
@@ -135,7 +135,7 @@
   std::vector<shared_ptr<Entry> > m_children; // Children pointers.
   unique_ptr<fib::Entry> m_fibEntry;
   std::vector<shared_ptr<pit::Entry> > m_pitEntries;
-  shared_ptr<measurements::Entry> m_measurementsEntry;
+  unique_ptr<measurements::Entry> m_measurementsEntry;
   unique_ptr<strategy_choice::Entry> m_strategyChoiceEntry;
 
   // get the Name Tree Node that is associated with this Name Tree Entry
@@ -205,10 +205,10 @@
   return m_pitEntries;
 }
 
-inline shared_ptr<measurements::Entry>
+inline measurements::Entry*
 Entry::getMeasurementsEntry() const
 {
-  return m_measurementsEntry;
+  return m_measurementsEntry.get();
 }
 
 inline strategy_choice::Entry*
diff --git a/daemon/table/name-tree.cpp b/daemon/table/name-tree.cpp
index bc7d7c7..bcf888e 100644
--- a/daemon/table/name-tree.cpp
+++ b/daemon/table/name-tree.cpp
@@ -269,7 +269,7 @@
 NameTree::lookup(const measurements::Entry& measurementsEntry) const
 {
   shared_ptr<name_tree::Entry> nte = this->getEntry(measurementsEntry);
-  BOOST_ASSERT(nte == nullptr || nte->getMeasurementsEntry().get() == &measurementsEntry);
+  BOOST_ASSERT(nte == nullptr || nte->getMeasurementsEntry() == &measurementsEntry);
   return nte;
 }