diff --git a/cpp/test.cpp b/cpp/test.cpp
index 3756a05b..e236d0fe 100644
--- a/cpp/test.cpp
+++ b/cpp/test.cpp
@@ -169,7 +169,10 @@ int main(void)
 		msgpack::unpacker upk;
 		while(stream.good() && total_bytes > 0) {
 
+			// 1. reserve buffer
 			upk.reserve_buffer(RESERVE_SIZE);
+
+			// 2. read data to buffer() up to buffer_capacity() bytes
 			size_t sz = stream.readsome(
 					(char*)upk.buffer(),
 					upk.buffer_capacity());
@@ -179,14 +182,24 @@ int main(void)
 					<< upk.buffer_capacity() << " bytes"
 					<< std::endl;
 
+			// 3. specify the number of  bytes actually copied
 			upk.buffer_consumed(sz);
+
+			// 4. repeat execute() until it returns false
 			while( upk.execute() ) {
 				std::cout << "message parsed" << std::endl;
-				boost::scoped_ptr<msgpack::zone> pz(upk.release_zone());
+
+				// 5.1. take out the parsed object
 				msgpack::object o = upk.data();
-				upk.reset();
+
+				// 5.2. the parsed object is valid until the zone is deleted
+				boost::scoped_ptr<msgpack::zone> pz(upk.release_zone());
+
 				std::cout << o << std::endl;
 				++num_msg;
+
+				// 5.3 re-initialize unpacker
+				upk.reset();
 			}
 
 		}
diff --git a/cpp/unpack.cpp b/cpp/unpack.cpp
index 50550084..d4845938 100644
--- a/cpp/unpack.cpp
+++ b/cpp/unpack.cpp
@@ -82,7 +82,6 @@ void unpacker::expand_buffer(size_t len)
 		while(next_size < len + m_used) { next_size *= 2; }
 
 		// FIXME realloc?
-
 		void* tmp = malloc(next_size);
 		if(!tmp) { throw std::bad_alloc(); }
 		memcpy(tmp, m_buffer, m_used);
@@ -121,15 +120,16 @@ bool unpacker::execute()
 	} else if(ret == 0) {
 		return false;
 	} else {
+		expand_buffer(0);
 		return true;
 	}
 }
 
 zone* unpacker::release_zone()
 {
+	zone* nz = new zone();
 	zone* z = m_zone;
-	m_zone = NULL;
-	m_zone = new zone();
+	m_zone = nz;
 	m_ctx->user(m_zone);
 	return z;
 }
@@ -141,12 +141,12 @@ object unpacker::data()
 
 void unpacker::reset()
 {
+	if(m_off != 0) { expand_buffer(0); }
 	if(!m_zone->empty()) {
 		delete m_zone;
 		m_zone = NULL;
 		m_zone = new zone();
 	}
-	expand_buffer(0);
 	m_ctx->reset();
 }
 
diff --git a/cpp/unpack.hpp b/cpp/unpack.hpp
index df4a636c..ae536c97 100644
--- a/cpp/unpack.hpp
+++ b/cpp/unpack.hpp
@@ -24,15 +24,46 @@ public:
 	~unpacker();
 
 public:
+	/*! 1. reserve buffer. at least `len' bytes of capacity will be ready */
 	void reserve_buffer(size_t len);
+
+	/*! 2. read data to the buffer() up to buffer_capacity() bytes */
 	void* buffer();
 	size_t buffer_capacity() const;
+
+	/*! 3. specify the number of bytes actually copied */
 	void buffer_consumed(size_t len);
+
+	/*! 4. repeat execute() until it retunrs false */
 	bool execute();
-	zone* release_zone();  // never throw
+
+	/*! 5.1. if execute() returns true, take out the parsed object */
 	object data();
+
+	/*! 5.2. the parsed object is valid until the zone is deleted */
+	// Note that once release_zone() from unpacker, you must delete it
+	// otherwise the memrory will leak.
+	zone* release_zone();
+
+	/*! 5.3. after release_zone(), re-initialize unpacker */
 	void reset();
 
+public:
+	// These functions are usable when non-MessagePack message follows after
+	// MessagePack message.
+	// Note that there are no parsed buffer when execute() returned true.
+
+	/*! get address of buffer that is not parsed */
+	void* nonparsed_buffer();
+	size_t nonparsed_size() const;
+
+	/*! get the number of bytes that is already parsed */
+	size_t parsed_size() const;
+
+	/*! remove unparsed buffer from unpacker */
+	// Note that reset() leaves non-parsed buffer.
+	void remove_nonparsed_buffer();
+
 private:
 	zone* m_zone;
 
@@ -72,6 +103,19 @@ inline void unpacker::buffer_consumed(size_t len)
 }
 
 
+inline void* unpacker::nonparsed_buffer()
+	{ return (void*)(((char*)m_buffer)+m_off); }
+
+inline size_t unpacker::nonparsed_size() const
+	{ return m_used - m_off; }
+
+inline size_t unpacker::parsed_size() const
+	{ return m_off; }
+
+inline void unpacker::remove_nonparsed_buffer()
+	{ m_used = m_off; }
+
+
 inline object unpack(const void* data, size_t len, zone& z)
 {
 	return unpacker::unpack(data, len, z);