Added ndnboost::weak_ptr
diff --git a/ndn-cpp/common.hpp b/ndn-cpp/common.hpp
index c20f3d6..e477687 100644
--- a/ndn-cpp/common.hpp
+++ b/ndn-cpp/common.hpp
@@ -20,7 +20,7 @@
 namespace ndn { namespace ptr_lib = boost; }
 #else
 // Use the boost header files in this distribution that were extracted with:
-// cd <INCLUDE DIRECTORY WITH boost SUBDIRECTORY>; bcp --namespace=ndnboost shared_ptr make_shared <NDN-CPP ROOT>
+// cd <INCLUDE DIRECTORY WITH boost SUBDIRECTORY>; bcp --namespace=ndnboost shared_ptr make_shared weak_ptr <NDN-CPP ROOT>
 // Also needed to rename all '<boost/' to '<ndnboost/', and all '"boost/' to '"ndnboost/', and the boost subdirectory to ndnboost.
 #include <ndnboost/shared_ptr.hpp>
 #include <ndnboost/make_shared.hpp>
diff --git a/ndnboost/smart_ptr/weak_ptr.hpp b/ndnboost/smart_ptr/weak_ptr.hpp
new file mode 100644
index 0000000..0e268a8
--- /dev/null
+++ b/ndnboost/smart_ptr/weak_ptr.hpp
@@ -0,0 +1,253 @@
+#ifndef BOOST_SMART_PTR_WEAK_PTR_HPP_INCLUDED
+#define BOOST_SMART_PTR_WEAK_PTR_HPP_INCLUDED
+
+//
+//  weak_ptr.hpp
+//
+//  Copyright (c) 2001, 2002, 2003 Peter Dimov
+//
+// Distributed under the Boost Software License, Version 1.0. (See
+// accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+//
+//  See http://www.boost.org/libs/smart_ptr/weak_ptr.htm for documentation.
+//
+
+#include <memory> // boost.TR1 include order fix
+#include <ndnboost/smart_ptr/detail/shared_count.hpp>
+#include <ndnboost/smart_ptr/shared_ptr.hpp>
+
+namespace ndnboost
+{
+
+template<class T> class weak_ptr
+{
+private:
+
+    // Borland 5.5.1 specific workarounds
+    typedef weak_ptr<T> this_type;
+
+public:
+
+    typedef typename ndnboost::detail::sp_element< T >::type element_type;
+
+    weak_ptr() BOOST_NOEXCEPT : px(0), pn() // never throws in 1.30+
+    {
+    }
+
+//  generated copy constructor, assignment, destructor are fine...
+
+#if !defined( BOOST_NO_CXX11_RVALUE_REFERENCES )
+
+// ... except in C++0x, move disables the implicit copy
+
+    weak_ptr( weak_ptr const & r ) BOOST_NOEXCEPT : px( r.px ), pn( r.pn )
+    {
+    }
+
+    weak_ptr & operator=( weak_ptr const & r ) BOOST_NOEXCEPT
+    {
+        px = r.px;
+        pn = r.pn;
+        return *this;
+    }
+
+#endif
+
+//
+//  The "obvious" converting constructor implementation:
+//
+//  template<class Y>
+//  weak_ptr(weak_ptr<Y> const & r): px(r.px), pn(r.pn) // never throws
+//  {
+//  }
+//
+//  has a serious problem.
+//
+//  r.px may already have been invalidated. The px(r.px)
+//  conversion may require access to *r.px (virtual inheritance).
+//
+//  It is not possible to avoid spurious access violations since
+//  in multithreaded programs r.px may be invalidated at any point.
+//
+
+    template<class Y>
+#if !defined( BOOST_SP_NO_SP_CONVERTIBLE )
+
+    weak_ptr( weak_ptr<Y> const & r, typename ndnboost::detail::sp_enable_if_convertible<Y,T>::type = ndnboost::detail::sp_empty() )
+
+#else
+
+    weak_ptr( weak_ptr<Y> const & r )
+
+#endif
+    BOOST_NOEXCEPT : px(r.lock().get()), pn(r.pn)
+    {
+        ndnboost::detail::sp_assert_convertible< Y, T >();
+    }
+
+#if !defined( BOOST_NO_CXX11_RVALUE_REFERENCES )
+
+    template<class Y>
+#if !defined( BOOST_SP_NO_SP_CONVERTIBLE )
+
+    weak_ptr( weak_ptr<Y> && r, typename ndnboost::detail::sp_enable_if_convertible<Y,T>::type = ndnboost::detail::sp_empty() )
+
+#else
+
+    weak_ptr( weak_ptr<Y> && r )
+
+#endif
+    BOOST_NOEXCEPT : px( r.lock().get() ), pn( static_cast< ndnboost::detail::weak_count && >( r.pn ) )
+    {
+        ndnboost::detail::sp_assert_convertible< Y, T >();
+        r.px = 0;
+    }
+
+    // for better efficiency in the T == Y case
+    weak_ptr( weak_ptr && r )
+    BOOST_NOEXCEPT : px( r.px ), pn( static_cast< ndnboost::detail::weak_count && >( r.pn ) )
+    {
+        r.px = 0;
+    }
+
+    // for better efficiency in the T == Y case
+    weak_ptr & operator=( weak_ptr && r ) BOOST_NOEXCEPT
+    {
+        this_type( static_cast< weak_ptr && >( r ) ).swap( *this );
+        return *this;
+    }
+
+
+#endif
+
+    template<class Y>
+#if !defined( BOOST_SP_NO_SP_CONVERTIBLE )
+
+    weak_ptr( shared_ptr<Y> const & r, typename ndnboost::detail::sp_enable_if_convertible<Y,T>::type = ndnboost::detail::sp_empty() )
+
+#else
+
+    weak_ptr( shared_ptr<Y> const & r )
+
+#endif
+    BOOST_NOEXCEPT : px( r.px ), pn( r.pn )
+    {
+        ndnboost::detail::sp_assert_convertible< Y, T >();
+    }
+
+#if !defined(BOOST_MSVC) || (BOOST_MSVC >= 1300)
+
+    template<class Y>
+    weak_ptr & operator=( weak_ptr<Y> const & r ) BOOST_NOEXCEPT
+    {
+        ndnboost::detail::sp_assert_convertible< Y, T >();
+
+        px = r.lock().get();
+        pn = r.pn;
+
+        return *this;
+    }
+
+#if !defined( BOOST_NO_CXX11_RVALUE_REFERENCES )
+
+    template<class Y>
+    weak_ptr & operator=( weak_ptr<Y> && r ) BOOST_NOEXCEPT
+    {
+        this_type( static_cast< weak_ptr<Y> && >( r ) ).swap( *this );
+        return *this;
+    }
+
+#endif
+
+    template<class Y>
+    weak_ptr & operator=( shared_ptr<Y> const & r ) BOOST_NOEXCEPT
+    {
+        ndnboost::detail::sp_assert_convertible< Y, T >();
+
+        px = r.px;
+        pn = r.pn;
+
+        return *this;
+    }
+
+#endif
+
+    shared_ptr<T> lock() const BOOST_NOEXCEPT
+    {
+        return shared_ptr<T>( *this, ndnboost::detail::sp_nothrow_tag() );
+    }
+
+    long use_count() const BOOST_NOEXCEPT
+    {
+        return pn.use_count();
+    }
+
+    bool expired() const BOOST_NOEXCEPT
+    {
+        return pn.use_count() == 0;
+    }
+
+    bool _empty() const // extension, not in std::weak_ptr
+    {
+        return pn.empty();
+    }
+
+    void reset() BOOST_NOEXCEPT // never throws in 1.30+
+    {
+        this_type().swap(*this);
+    }
+
+    void swap(this_type & other) BOOST_NOEXCEPT
+    {
+        std::swap(px, other.px);
+        pn.swap(other.pn);
+    }
+
+    template<typename Y>
+    void _internal_aliasing_assign(weak_ptr<Y> const & r, element_type * px2)
+    {
+        px = px2;
+        pn = r.pn;
+    }
+
+    template<class Y> bool owner_before( weak_ptr<Y> const & rhs ) const BOOST_NOEXCEPT
+    {
+        return pn < rhs.pn;
+    }
+
+    template<class Y> bool owner_before( shared_ptr<Y> const & rhs ) const BOOST_NOEXCEPT
+    {
+        return pn < rhs.pn;
+    }
+
+// Tasteless as this may seem, making all members public allows member templates
+// to work in the absence of member template friends. (Matthew Langston)
+
+#ifndef BOOST_NO_MEMBER_TEMPLATE_FRIENDS
+
+private:
+
+    template<class Y> friend class weak_ptr;
+    template<class Y> friend class shared_ptr;
+
+#endif
+
+    element_type * px;            // contained pointer
+    ndnboost::detail::weak_count pn; // reference counter
+
+};  // weak_ptr
+
+template<class T, class U> inline bool operator<(weak_ptr<T> const & a, weak_ptr<U> const & b) BOOST_NOEXCEPT
+{
+    return a.owner_before( b );
+}
+
+template<class T> void swap(weak_ptr<T> & a, weak_ptr<T> & b) BOOST_NOEXCEPT
+{
+    a.swap(b);
+}
+
+} // namespace ndnboost
+
+#endif  // #ifndef BOOST_SMART_PTR_WEAK_PTR_HPP_INCLUDED
diff --git a/ndnboost/weak_ptr.hpp b/ndnboost/weak_ptr.hpp
new file mode 100644
index 0000000..d7bbb7d
--- /dev/null
+++ b/ndnboost/weak_ptr.hpp
@@ -0,0 +1,18 @@
+#ifndef BOOST_WEAK_PTR_HPP_INCLUDED
+#define BOOST_WEAK_PTR_HPP_INCLUDED
+
+//
+//  weak_ptr.hpp
+//
+//  Copyright (c) 2001, 2002, 2003 Peter Dimov
+//
+//  Distributed under the Boost Software License, Version 1.0.
+//  See accompanying file LICENSE_1_0.txt or copy at
+//  http://www.boost.org/LICENSE_1_0.txt
+//
+//  See http://www.boost.org/libs/smart_ptr/weak_ptr.htm for documentation.
+//
+
+#include <ndnboost/smart_ptr/weak_ptr.hpp>
+
+#endif  // #ifndef BOOST_WEAK_PTR_HPP_INCLUDED