diff --git a/c/unpack.h b/c/unpack.h
index 77fbd54d..779e2564 100644
--- a/c/unpack.h
+++ b/c/unpack.h
@@ -61,7 +61,8 @@ msgpack_zone* msgpack_unpacker_release_zone(msgpack_unpacker* mpac);
 
 void msgpack_unpacker_reset(msgpack_unpacker* mpac);
 
-static inline size_t msgpack_unpacker_parsed_size(const msgpack_unpacker* mpac);
+static inline size_t msgpack_unpacker_message_size(const msgpack_unpacker* mpac);
+
 
 
 typedef enum {
@@ -76,6 +77,8 @@ msgpack_unpack(const char* data, size_t len, size_t* off,
 		msgpack_zone* z, msgpack_object* result);
 
 
+static inline size_t msgpack_unpacker_parsed_size(const msgpack_unpacker* mpac);
+
 bool msgpack_unpacker_flush_zone(msgpack_unpacker* mpac);
 
 bool msgpack_unpacker_expand_buffer(msgpack_unpacker* mpac, size_t size);
@@ -102,6 +105,11 @@ void msgpack_unpacker_buffer_consumed(msgpack_unpacker* mpac, size_t size)
 	mpac->free -= size;
 }
 
+size_t msgpack_unpacker_message_size(const msgpack_unpacker* mpac)
+{
+	return mpac->parsed - mpac->off + mpac->used;
+}
+
 size_t msgpack_unpacker_parsed_size(const msgpack_unpacker* mpac)
 {
 	return mpac->parsed;
diff --git a/cpp/unpack.hpp b/cpp/unpack.hpp
index 0b7fe574..e140b36a 100644
--- a/cpp/unpack.hpp
+++ b/cpp/unpack.hpp
@@ -67,8 +67,8 @@ public:
 	/*! 5.3. after release_zone(), re-initialize unpacker */
 	void reset();
 
-	/*! 6. check if the parsed message size doesn't exceed assumption. */
-	size_t parsed_size() const;
+	/*! 6. check if the size of message doesn't exceed assumption. */
+	size_t message_size() const;
 
 
 	// Basic usage of the unpacker is as following:
@@ -112,6 +112,7 @@ public:
 public:
 	// These functions are usable when non-MessagePack message follows after
 	// MessagePack message.
+	size_t parsed_size() const;
 
 	/*! get address of the buffer that is not parsed */
 	char* nonparsed_buffer();
@@ -218,12 +219,17 @@ inline void unpacker::reset()
 	msgpack_unpacker_reset(this);
 }
 
+inline size_t unpacker::message_size() const
+{
+	return msgpack_unpacker_message_size(this);
+}
+
+
 inline size_t unpacker::parsed_size() const
 {
 	return msgpack_unpacker_parsed_size(this);
 }
 
-
 inline char* unpacker::nonparsed_buffer()
 {
 	return buf + off;