diff --git a/ruby/unpack.c b/ruby/unpack.c
index e9d6494e..0f1af38f 100644
--- a/ruby/unpack.c
+++ b/ruby/unpack.c
@@ -18,10 +18,16 @@
 #include "ruby.h"
 #include "msgpack/unpack_define.h"
 
+static ID s_sysread;
 
 typedef struct {
 	int finished;
 	VALUE source;
+	size_t offset;
+	size_t parsed;
+	VALUE buffer;
+	VALUE stream;
+	VALUE streambuf;
 } unpack_user;
 
 
@@ -144,6 +150,9 @@ static void MessagePack_Unpacker_free(void* data)
 static void MessagePack_Unpacker_mark(msgpack_unpack_t *mp)
 {
 	unsigned int i;
+	rb_gc_mark(mp->user.buffer);
+	rb_gc_mark(mp->user.stream);
+	rb_gc_mark(mp->user.streambuf);
 	for(i=0; i < mp->top; ++i) {
 		rb_gc_mark(mp->stack[i].obj);
 		rb_gc_mark(mp->stack[i].map_key); /* maybe map_key is not initialized */
@@ -164,14 +173,32 @@ static VALUE MessagePack_Unpacker_reset(VALUE self)
 	UNPACKER(self, mp);
 	template_init(mp);
 	init_stack(mp);
-	unpack_user u = {0, Qnil};
-	mp->user = u;
+	mp->user.finished = 0;
 	return self;
 }
 
-static VALUE MessagePack_Unpacker_initialize(VALUE self)
+static VALUE MessagePack_Unpacker_initialize(int argc, VALUE *argv, VALUE self)
 {
-	return MessagePack_Unpacker_reset(self);
+	VALUE stream;
+	switch(argc) {
+	case 0:
+		stream = Qnil;
+		break;
+	case 1:
+		stream = argv[0];
+		break;
+	default:
+		rb_raise(rb_eArgError, "wrong number of arguments (%d for 0)", argc);
+	}
+
+	MessagePack_Unpacker_reset(self);
+	UNPACKER(self, mp);
+	mp->user.offset = 0;
+	mp->user.parsed = 0;
+	mp->user.buffer = rb_str_new("",0);
+	mp->user.stream = stream;
+	mp->user.streambuf = rb_str_new("",0);
+	return self;
 }
 
 
@@ -249,6 +276,87 @@ static VALUE MessagePack_Unpacker_data(VALUE self)
 }
 
 
+static VALUE MessagePack_Unpacker_feed(VALUE self, VALUE data)
+{
+	UNPACKER(self, mp);
+	StringValue(data);
+	rb_str_cat(mp->user.buffer, RSTRING_PTR(data), RSTRING_LEN(data));
+	return Qnil;
+}
+
+static VALUE MessagePack_Unpacker_stream_get(VALUE self)
+{
+	UNPACKER(self, mp);
+	return mp->user.stream;
+}
+
+static VALUE MessagePack_Unpacker_stream_set(VALUE self, VALUE val)
+{
+	UNPACKER(self, mp);
+	return mp->user.stream = val;
+}
+
+static VALUE MessagePack_Unpacker_fill(VALUE self)
+{
+	UNPACKER(self, mp);
+
+	if(mp->user.stream == Qnil) {
+		return Qnil;
+	}
+
+	size_t len;
+	if(RSTRING_LEN(mp->user.buffer) == 0) {
+		rb_funcall(mp->user.stream, s_sysread, 2, LONG2FIX(64*1024), mp->user.buffer);
+		len = RSTRING_LEN(mp->user.buffer);
+	} else {
+		rb_funcall(mp->user.stream, s_sysread, 2, LONG2FIX(64*1024), mp->user.streambuf);
+		len = RSTRING_LEN(mp->user.streambuf);
+		rb_str_cat(mp->user.buffer, RSTRING_PTR(mp->user.streambuf), RSTRING_LEN(mp->user.streambuf));
+	}
+
+	return LONG2FIX(len);
+}
+
+static VALUE MessagePack_Unpacker_each(VALUE self)
+{
+	UNPACKER(self, mp);
+	int ret;
+
+#ifdef RETURN_ENUMERATOR
+	RETURN_ENUMERATOR(self, 0, 0);
+#endif
+
+	while(1) {
+		if(RSTRING_LEN(mp->user.buffer) <= mp->user.offset) {
+			do_fill:
+			{
+				VALUE len = MessagePack_Unpacker_fill(self);
+				if(len == Qnil || FIX2LONG(len) == 0) {
+					break;
+				}
+			}
+		}
+
+		mp->user.source = mp->user.buffer;
+		ret = template_execute(mp, RSTRING_PTR(mp->user.buffer), RSTRING_LEN(mp->user.buffer), &mp->user.offset);
+		mp->user.source = Qnil;
+
+		if(ret < 0) {
+			rb_raise(eUnpackError, "parse error.");
+		} else if(ret > 0) {
+			VALUE data = template_data(mp);
+			template_init(mp);
+			init_stack(mp);
+			rb_yield(data);
+		} else {
+			goto do_fill;
+		}
+	}
+
+	return Qnil;
+}
+
+
 static VALUE MessagePack_unpack_impl(VALUE args)
 {
 	msgpack_unpack_t* mp = (msgpack_unpack_t*)((VALUE*)args)[0];
@@ -292,7 +400,7 @@ static VALUE MessagePack_unpack_limit(VALUE self, VALUE data, VALUE limit)
 	msgpack_unpack_t mp;
 	template_init(&mp);
 	init_stack(&mp);
-	unpack_user u = {0, Qnil};
+	unpack_user u = {0, Qnil, 0, 0, Qnil, Qnil, Qnil};
 	mp.user = u;
 
 	rb_gc_disable();
@@ -313,17 +421,22 @@ static VALUE MessagePack_unpack(VALUE self, VALUE data)
 
 void Init_msgpack_unpack(VALUE mMessagePack)
 {
+	s_sysread = rb_intern("sysread");
 	eUnpackError = rb_define_class_under(mMessagePack, "UnpackError", rb_eStandardError);
 	cUnpacker = rb_define_class_under(mMessagePack, "Unpacker", rb_cObject);
 	rb_define_alloc_func(cUnpacker, MessagePack_Unpacker_alloc);
-	rb_define_method(cUnpacker, "initialize", MessagePack_Unpacker_initialize, 0);
+	rb_define_method(cUnpacker, "initialize", MessagePack_Unpacker_initialize, -1);
 	rb_define_method(cUnpacker, "execute", MessagePack_Unpacker_execute, 2);
 	rb_define_method(cUnpacker, "execute_limit", MessagePack_Unpacker_execute_limit, 3);
 	rb_define_method(cUnpacker, "finished?", MessagePack_Unpacker_finished_p, 0);
 	rb_define_method(cUnpacker, "data", MessagePack_Unpacker_data, 0);
 	rb_define_method(cUnpacker, "reset", MessagePack_Unpacker_reset, 0);
+	rb_define_method(cUnpacker, "feed", MessagePack_Unpacker_feed, 1);
+	rb_define_method(cUnpacker, "fill", MessagePack_Unpacker_fill, 0);
+	rb_define_method(cUnpacker, "each", MessagePack_Unpacker_each, 0);
+	rb_define_method(cUnpacker, "stream", MessagePack_Unpacker_stream_get, 0);
+	rb_define_method(cUnpacker, "stream=", MessagePack_Unpacker_stream_set, 1);
 	rb_define_module_function(mMessagePack, "unpack", MessagePack_unpack, 1);
 	rb_define_module_function(mMessagePack, "unpack_limit", MessagePack_unpack_limit, 2);
 }
 
-