diff --git a/include/ndnboost/iostreams/filter/symmetric.hpp b/include/ndnboost/iostreams/filter/symmetric.hpp
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+++ b/include/ndnboost/iostreams/filter/symmetric.hpp
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+// (C) Copyright 2008 CodeRage, LLC (turkanis at coderage dot com)
+// (C) Copyright 2003-2007 Jonathan Turkanis
+// 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/iostreams for documentation.
+
+// Contains the definitions of the class templates symmetric_filter,
+// which models DualUseFilter based on a model of the Symmetric Filter.
+
+//
+// Roughly, a Symmetric Filter is a class type with the following interface:
+//
+//   struct symmetric_filter {
+//       typedef xxx char_type;
+//
+//       bool filter( const char*& begin_in, const char* end_in,
+//                    char*& begin_out, char* end_out, bool flush )
+//       {
+//          // Consume as many characters as possible from the interval
+//          // [begin_in, end_in), without exhausting the output range
+//          // [begin_out, end_out). If flush is true, write as mush output
+//          // as possible. 
+//          // A return value of true indicates that filter should be called 
+//          // again. More precisely, if flush is false, a return value of 
+//          // false indicates that the natural end of stream has been reached
+//          // and that all filtered data has been forwarded; if flush is
+//          // true, a return value of false indicates that all filtered data 
+//          // has been forwarded.
+//       }
+//       void close() { /* Reset filter's state. */ }
+//   };
+//
+// Symmetric Filter filters need not be CopyConstructable.
+//
+
+#ifndef NDNBOOST_IOSTREAMS_SYMMETRIC_FILTER_HPP_INCLUDED
+#define NDNBOOST_IOSTREAMS_SYMMETRIC_FILTER_HPP_INCLUDED
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1020)
+# pragma once
+#endif
+
+#include <ndnboost/assert.hpp>
+#include <memory>                               // allocator, auto_ptr.
+#include <ndnboost/config.hpp>                     // NDNBOOST_DEDUCED_TYPENAME.
+#include <ndnboost/iostreams/char_traits.hpp>
+#include <ndnboost/iostreams/constants.hpp>        // buffer size.
+#include <ndnboost/iostreams/detail/buffer.hpp>
+#include <ndnboost/iostreams/detail/char_traits.hpp>
+#include <ndnboost/iostreams/detail/config/limits.hpp>
+#include <ndnboost/iostreams/detail/template_params.hpp>
+#include <ndnboost/iostreams/traits.hpp>
+#include <ndnboost/iostreams/operations.hpp>       // read, write.
+#include <ndnboost/iostreams/pipeline.hpp>
+#include <ndnboost/preprocessor/iteration/local.hpp>
+#include <ndnboost/preprocessor/punctuation/comma_if.hpp>
+#include <ndnboost/preprocessor/repetition/enum_binary_params.hpp>
+#include <ndnboost/preprocessor/repetition/enum_params.hpp>
+#include <ndnboost/shared_ptr.hpp>
+
+// Must come last.
+#include <ndnboost/iostreams/detail/config/disable_warnings.hpp>  // MSVC.
+
+namespace ndnboost { namespace iostreams {
+
+template< typename SymmetricFilter,
+          typename Alloc =
+              std::allocator<
+                  NDNBOOST_DEDUCED_TYPENAME char_type_of<SymmetricFilter>::type
+              > >
+class symmetric_filter {
+public:
+    typedef typename char_type_of<SymmetricFilter>::type      char_type;
+    typedef NDNBOOST_IOSTREAMS_CHAR_TRAITS(char_type)            traits_type;
+    typedef std::basic_string<char_type, traits_type, Alloc>  string_type;
+    struct category
+        : dual_use,
+          filter_tag,
+          multichar_tag,
+          closable_tag
+        { };
+
+    // Expands to a sequence of ctors which forward to impl.
+    #define NDNBOOST_PP_LOCAL_MACRO(n) \
+        NDNBOOST_IOSTREAMS_TEMPLATE_PARAMS(n, T) \
+        explicit symmetric_filter( \
+              int buffer_size NDNBOOST_PP_COMMA_IF(n) \
+              NDNBOOST_PP_ENUM_BINARY_PARAMS(n, const T, &t) ) \
+            : pimpl_(new impl(buffer_size NDNBOOST_PP_COMMA_IF(n) \
+                     NDNBOOST_PP_ENUM_PARAMS(n, t))) \
+            { NDNBOOST_ASSERT(buffer_size > 0); } \
+        /**/
+    #define NDNBOOST_PP_LOCAL_LIMITS (0, NDNBOOST_IOSTREAMS_MAX_FORWARDING_ARITY)
+    #include NDNBOOST_PP_LOCAL_ITERATE()
+    #undef NDNBOOST_PP_LOCAL_MACRO
+
+    template<typename Source>
+    std::streamsize read(Source& src, char_type* s, std::streamsize n)
+    {
+        using namespace std;
+        if (!(state() & f_read))
+            begin_read();
+
+        buffer_type&  buf = pimpl_->buf_;
+        int           status = (state() & f_eof) != 0 ? f_eof : f_good;
+        char_type    *next_s = s,
+                     *end_s = s + n;
+        while (true)
+        {
+            // Invoke filter if there are unconsumed characters in buffer or if
+            // filter must be flushed.
+            bool flush = status == f_eof;
+            if (buf.ptr() != buf.eptr() || flush) {
+                const char_type* next = buf.ptr();
+                bool done =
+                    !filter().filter(next, buf.eptr(), next_s, end_s, flush);
+                buf.ptr() = buf.data() + (next - buf.data());
+                if (done)
+                    return detail::check_eof(
+                               static_cast<std::streamsize>(next_s - s)
+                           );
+            }
+
+            // If no more characters are available without blocking, or
+            // if read request has been satisfied, return.
+            if ( (status == f_would_block && buf.ptr() == buf.eptr()) ||
+                 next_s == end_s )
+            {
+                return static_cast<std::streamsize>(next_s - s);
+            }
+
+            // Fill buffer.
+            if (status == f_good)
+                status = fill(src);
+        }
+    }
+
+    template<typename Sink>
+    std::streamsize write(Sink& snk, const char_type* s, std::streamsize n)
+    {
+        if (!(state() & f_write))
+            begin_write();
+
+        buffer_type&     buf = pimpl_->buf_;
+        const char_type *next_s, *end_s;
+        for (next_s = s, end_s = s + n; next_s != end_s; ) {
+            if (buf.ptr() == buf.eptr() && !flush(snk))
+                break;
+            if(!filter().filter(next_s, end_s, buf.ptr(), buf.eptr(), false)) {
+                flush(snk);
+                break;
+            }
+        }
+        return static_cast<std::streamsize>(next_s - s);
+    }
+
+    template<typename Sink>
+    void close(Sink& snk, NDNBOOST_IOS::openmode mode)
+    {
+        if (mode == NDNBOOST_IOS::out) {
+
+            if (!(state() & f_write))
+                begin_write();
+
+            // Repeatedly invoke filter() with no input.
+            try {
+                buffer_type&     buf = pimpl_->buf_;
+                char_type        dummy;
+                const char_type* end = &dummy;
+                bool             again = true;
+                while (again) {
+                    if (buf.ptr() != buf.eptr())
+                        again = filter().filter( end, end, buf.ptr(),
+                                                 buf.eptr(), true );
+                    flush(snk);
+                }
+            } catch (...) {
+                try { close_impl(); } catch (...) { }
+                throw;
+            }
+            close_impl();
+        } else {
+            close_impl();
+        }
+    }
+    SymmetricFilter& filter() { return *pimpl_; }
+    string_type unconsumed_input() const;
+
+// Give impl access to buffer_type on Tru64
+#if !NDNBOOST_WORKAROUND(__DECCXX_VER, NDNBOOST_TESTED_AT(60590042)) 
+    private:
+#endif
+    typedef detail::buffer<char_type, Alloc> buffer_type;
+private:
+    buffer_type& buf() { return pimpl_->buf_; }
+    const buffer_type& buf() const { return pimpl_->buf_; }
+    int& state() { return pimpl_->state_; }
+    void begin_read();
+    void begin_write();
+
+    template<typename Source>
+    int fill(Source& src)
+    {
+        std::streamsize amt = iostreams::read(src, buf().data(), buf().size());
+        if (amt == -1) {
+            state() |= f_eof;
+            return f_eof;
+        }
+        buf().set(0, amt);
+        return amt != 0 ? f_good : f_would_block;
+    }
+
+    // Attempts to write the contents of the buffer the given Sink.
+    // Returns true if at least on character was written.
+    template<typename Sink>
+    bool flush(Sink& snk)
+    {
+        typedef typename iostreams::category_of<Sink>::type  category;
+        typedef is_convertible<category, output>             can_write;
+        return flush(snk, can_write());
+    }
+
+    template<typename Sink>
+    bool flush(Sink& snk, mpl::true_)
+    {
+        std::streamsize amt =
+            static_cast<std::streamsize>(buf().ptr() - buf().data());
+        std::streamsize result =
+            ndnboost::iostreams::write(snk, buf().data(), amt);
+        if (result < amt && result > 0)
+            traits_type::move(buf().data(), buf().data() + result, amt - result);
+        buf().set(amt - result, buf().size());
+        return result != 0;
+    }
+
+    template<typename Sink>
+    bool flush(Sink&, mpl::false_) { return true;}
+
+    void close_impl();
+
+    enum flag_type {
+        f_read   = 1,
+        f_write  = f_read << 1,
+        f_eof    = f_write << 1,
+        f_good,
+        f_would_block
+    };
+
+    struct impl : SymmetricFilter {
+
+    // Expands to a sequence of ctors which forward to SymmetricFilter.
+    #define NDNBOOST_PP_LOCAL_MACRO(n) \
+        NDNBOOST_IOSTREAMS_TEMPLATE_PARAMS(n, T) \
+        impl( int buffer_size NDNBOOST_PP_COMMA_IF(n) \
+              NDNBOOST_PP_ENUM_BINARY_PARAMS(n, const T, &t) ) \
+            : SymmetricFilter(NDNBOOST_PP_ENUM_PARAMS(n, t)), \
+              buf_(buffer_size), state_(0) \
+            { } \
+        /**/
+    #define NDNBOOST_PP_LOCAL_LIMITS (0, NDNBOOST_IOSTREAMS_MAX_FORWARDING_ARITY)
+    #include NDNBOOST_PP_LOCAL_ITERATE()
+    #undef NDNBOOST_PP_LOCAL_MACRO
+
+        buffer_type  buf_;
+        int          state_;
+    };
+
+    shared_ptr<impl> pimpl_;
+};
+NDNBOOST_IOSTREAMS_PIPABLE(symmetric_filter, 2)
+
+//------------------Implementation of symmetric_filter----------------//
+
+template<typename SymmetricFilter, typename Alloc>
+void symmetric_filter<SymmetricFilter, Alloc>::begin_read()
+{
+    NDNBOOST_ASSERT(!(state() & f_write));
+    state() |= f_read;
+    buf().set(0, 0);
+}
+
+template<typename SymmetricFilter, typename Alloc>
+void symmetric_filter<SymmetricFilter, Alloc>::begin_write()
+{
+    NDNBOOST_ASSERT(!(state() & f_read));
+    state() |= f_write;
+    buf().set(0, buf().size());
+}
+
+template<typename SymmetricFilter, typename Alloc>
+void symmetric_filter<SymmetricFilter, Alloc>::close_impl()
+{
+    state() = 0;
+    buf().set(0, 0);
+    filter().close();
+}
+
+template<typename SymmetricFilter, typename Alloc>
+typename symmetric_filter<SymmetricFilter, Alloc>::string_type
+symmetric_filter<SymmetricFilter, Alloc>::unconsumed_input() const
+{ return string_type(buf().ptr(), buf().eptr()); }
+
+//----------------------------------------------------------------------------//
+
+} } // End namespaces iostreams, boost.
+
+#include <ndnboost/iostreams/detail/config/enable_warnings.hpp>  // MSVC.
+
+#endif // #ifndef NDNBOOST_IOSTREAMS_SYMMETRIC_FILTER_HPP_INCLUDED