diff --git a/mio/bin/t03.c b/mio/bin/t03.c
index 2b3729a..5166591 100644
--- a/mio/bin/t03.c
+++ b/mio/bin/t03.c
@@ -182,7 +182,7 @@ mio_logbfmt (mio, MIO_LOG_STDOUT, "\n");
 		mio_uch_t ddd[4] = { 'D', '\0', 'R', 'Q' };
 		mio_uch_t ddv[5] = { L'밝', L'혀', L'졌', L'는', L'데' };
 	
-		jsonwr = mio_jsonwr_open (mio, 0);
+		jsonwr = mio_jsonwr_open (mio, 0, MIO_JSONWR_FLAG_PRETTY);
 
 		mio_jsonwr_setwritecb (jsonwr, write_json_element, MIO_NULL);
 
diff --git a/mio/lib/json.c b/mio/lib/json.c
index 5d9cf79..fc57df8 100644
--- a/mio/lib/json.c
+++ b/mio/lib/json.c
@@ -719,7 +719,7 @@ void mio_json_close (mio_json_t* json)
 	mio_freemem (json->mio, json);
 }
 
-static int do_nothing_on_inst  (mio_json_t* json, mio_json_inst_t inst, mio_oow_t level, const mio_oocs_t* str)
+static int do_nothing_on_inst  (mio_json_t* json, mio_json_inst_t inst, mio_oow_t level, mio_oow_t index, mio_json_state_t container_state, const mio_oocs_t* str, void* ctx)
 {
 	return 0;
 }
@@ -828,14 +828,14 @@ static void pop_all_write_states (mio_jsonwr_t* jsonwr)
 	while (jsonwr->state_stack != &jsonwr->state_top) pop_write_state (jsonwr);
 }
 
-mio_jsonwr_t* mio_jsonwr_open (mio_t* mio, mio_oow_t xtnsize)
+mio_jsonwr_t* mio_jsonwr_open (mio_t* mio, mio_oow_t xtnsize, int flags)
 {
 	mio_jsonwr_t* jsonwr;
 
 	jsonwr = (mio_jsonwr_t*)mio_allocmem(mio, MIO_SIZEOF(*jsonwr) + xtnsize);
 	if (MIO_LIKELY(jsonwr))
 	{
-		if (mio_jsonwr_init(jsonwr, mio) <= -1)
+		if (mio_jsonwr_init(jsonwr, mio, flags) <= -1)
 		{
 			mio_freemem (mio, jsonwr);
 			return MIO_NULL;
@@ -860,12 +860,13 @@ static int write_nothing (mio_jsonwr_t* jsonwr, const mio_bch_t* dptr, mio_oow_t
 	return 0;
 }
 
-int mio_jsonwr_init (mio_jsonwr_t* jsonwr, mio_t* mio)
+int mio_jsonwr_init (mio_jsonwr_t* jsonwr, mio_t* mio, int flags)
 {
 	MIO_MEMSET (jsonwr, 0, MIO_SIZEOF(*jsonwr));
 
 	jsonwr->mio = mio;
 	jsonwr->writecb = write_nothing;
+	jsonwr->flags = flags;
 
 	jsonwr->state_top.state = MIO_JSON_STATE_START;
 	jsonwr->state_top.next = MIO_NULL;
@@ -1062,14 +1063,14 @@ static int write_uchars (mio_jsonwr_t* jsonwr, int escape, const mio_uch_t* ptr,
 
 #define WRITE_LINE_BREAK(jsonwr) WRITE_BYTES_NOESC(jsonwr, "\n", 1)
 
-#define WRITE_COMMA(jsonwr) do { WRITE_BYTES_NOESC(jsonwr, ",", 1); if (jsonwr->pretty) WRITE_LINE_BREAK(jsonwr); } while(0)
+#define WRITE_COMMA(jsonwr) do { WRITE_BYTES_NOESC(jsonwr, ",", 1); if (jsonwr->flags & MIO_JSONWR_FLAG_PRETTY) WRITE_LINE_BREAK(jsonwr); } while(0)
 
 #define PREACTION_FOR_VLAUE(jsonwr,sn) do { \
 	if (sn->state != MIO_JSON_STATE_IN_ARRAY && !(sn->state == MIO_JSON_STATE_IN_OBJECT && sn->obj_awaiting_val)) goto incompatible_inst; \
 	if (sn->index > 0 && sn->state == MIO_JSON_STATE_IN_ARRAY) WRITE_COMMA (jsonwr); \
 	sn->index++; \
 	sn->obj_awaiting_val = 0; \
-	if (jsonwr->pretty && sn->state == MIO_JSON_STATE_IN_ARRAY) WRITE_INDENT (jsonwr); \
+	if ((jsonwr->flags & MIO_JSONWR_FLAG_PRETTY) && sn->state == MIO_JSON_STATE_IN_ARRAY) WRITE_INDENT (jsonwr); \
 } while(0)
 
 #define WRITE_INDENT(jsonwr) do { mio_oow_t i; for (i = 0; i < jsonwr->state_stack->level; i++) WRITE_BYTES_NOESC (jsonwr, "\t", 1); } while(0)
@@ -1078,10 +1079,6 @@ int mio_jsonwr_write (mio_jsonwr_t* jsonwr, mio_json_inst_t inst, int is_uchars,
 {
 	mio_jsonwr_state_node_t* sn = jsonwr->state_stack;
 
-/* ============================= */
-jsonwr->pretty = 1;
-/* ============================= */
-
 	switch (inst)
 	{
 		case MIO_JSON_INST_START_ARRAY:
@@ -1090,9 +1087,9 @@ jsonwr->pretty = 1;
 			if (sn->index > 0) WRITE_COMMA (jsonwr);
 			sn->index++;
 			sn->obj_awaiting_val = 0;
-			if (jsonwr->pretty) WRITE_INDENT (jsonwr);
+			if (jsonwr->flags & MIO_JSONWR_FLAG_PRETTY) WRITE_INDENT (jsonwr);
 			WRITE_BYTES_NOESC (jsonwr, "[", 1); 
-			if (jsonwr->pretty) WRITE_LINE_BREAK (jsonwr);
+			if (jsonwr->flags & MIO_JSONWR_FLAG_PRETTY) WRITE_LINE_BREAK (jsonwr);
 			if (push_write_state(jsonwr, MIO_JSON_STATE_IN_ARRAY) <= -1) return -1;
 			jsonwr->state_stack->level++;
 			break;
@@ -1103,9 +1100,9 @@ jsonwr->pretty = 1;
 			if (sn->index > 0) WRITE_COMMA (jsonwr);
 			sn->index++;
 			sn->obj_awaiting_val = 0;
-			if (jsonwr->pretty) WRITE_INDENT (jsonwr);
+			if (jsonwr->flags & MIO_JSONWR_FLAG_PRETTY) WRITE_INDENT (jsonwr);
 			WRITE_BYTES_NOESC (jsonwr, "{", 1); 
-			if (jsonwr->pretty) WRITE_LINE_BREAK (jsonwr);
+			if (jsonwr->flags & MIO_JSONWR_FLAG_PRETTY) WRITE_LINE_BREAK (jsonwr);
 			if (push_write_state (jsonwr, MIO_JSON_STATE_IN_OBJECT) <= -1) return -1;
 			jsonwr->state_stack->level++;
 			break;
@@ -1113,7 +1110,7 @@ jsonwr->pretty = 1;
 		case MIO_JSON_INST_END_ARRAY:
 			if (sn->state != MIO_JSON_STATE_IN_ARRAY) goto incompatible_inst;
 			pop_write_state (jsonwr);
-			if (jsonwr->pretty) 
+			if (jsonwr->flags & MIO_JSONWR_FLAG_PRETTY) 
 			{
 				WRITE_LINE_BREAK (jsonwr);
 				WRITE_INDENT (jsonwr);
@@ -1122,7 +1119,7 @@ jsonwr->pretty = 1;
 			if (jsonwr->state_stack->state == MIO_JSON_STATE_START) 
 			{
 				/* end of json */
-				if (jsonwr->pretty) WRITE_LINE_BREAK (jsonwr);
+				if (jsonwr->flags & MIO_JSONWR_FLAG_PRETTY) WRITE_LINE_BREAK (jsonwr);
 				if (jsonwr->wbuf_len > 0 && flush_wbuf(jsonwr) <= -1) return -1;
 			}
 			break;
@@ -1130,7 +1127,7 @@ jsonwr->pretty = 1;
 		case MIO_JSON_INST_END_OBJECT:
 			if (sn->state != MIO_JSON_STATE_IN_OBJECT || sn->obj_awaiting_val) goto incompatible_inst;
 			pop_write_state (jsonwr);
-			if (jsonwr->pretty) 
+			if (jsonwr->flags & MIO_JSONWR_FLAG_PRETTY) 
 			{
 				WRITE_LINE_BREAK (jsonwr);
 				WRITE_INDENT (jsonwr);
@@ -1139,7 +1136,7 @@ jsonwr->pretty = 1;
 			if (jsonwr->state_stack->state == MIO_JSON_STATE_START) 
 			{
 				/* end of json */
-				if (jsonwr->pretty) WRITE_LINE_BREAK (jsonwr);
+				if (jsonwr->flags & MIO_JSONWR_FLAG_PRETTY) WRITE_LINE_BREAK (jsonwr);
 				if (jsonwr->wbuf_len > 0 && flush_wbuf(jsonwr) <= -1) return -1;
 			}
 			break;
@@ -1147,7 +1144,7 @@ jsonwr->pretty = 1;
 		case MIO_JSON_INST_KEY:
 			if (sn->state != MIO_JSON_STATE_IN_OBJECT || sn->obj_awaiting_val) goto incompatible_inst;
 			if (sn->index > 0) WRITE_COMMA (jsonwr);
-			if (jsonwr->pretty) WRITE_INDENT (jsonwr);
+			if (jsonwr->flags & MIO_JSONWR_FLAG_PRETTY) WRITE_INDENT (jsonwr);
 			WRITE_BYTES_NOESC (jsonwr, "\"", 1);
 			if (is_uchars) WRITE_UCHARS (jsonwr, 1, dptr, dlen);
 			else WRITE_BYTES_ESC (jsonwr, dptr, dlen);
@@ -1188,7 +1185,7 @@ jsonwr->pretty = 1;
 
 		default:
 		incompatible_inst:
-			flush_wbuf(jsonwr);
+			flush_wbuf (jsonwr);
 			mio_seterrbfmt (jsonwr->mio, MIO_EINVAL, "incompatiable write instruction - %d", (int)inst);
 			return -1;
 	}
@@ -1196,6 +1193,41 @@ jsonwr->pretty = 1;
 	return 0;
 }
 
+
+int mio_jsonwr_writeintmax (mio_jsonwr_t* jsonwr, mio_intmax_t v)
+{
+	mio_jsonwr_state_node_t* sn = jsonwr->state_stack;
+	mio_bch_t tmp[((MIO_SIZEOF_UINTMAX_T * MIO_BITS_PER_BYTE) / 3) + 3]; /* there can be a sign. so +3 instead of +2 */
+	mio_oow_t len;
+
+	PREACTION_FOR_VLAUE (jsonwr, sn);
+	len = mio_fmt_intmax_to_bcstr(tmp, MIO_COUNTOF(tmp), v, 10, 0, '\0', MIO_NULL);
+	WRITE_BYTES_NOESC (jsonwr, tmp, len);
+	return 0;
+
+incompatible_inst:
+	flush_wbuf (jsonwr);
+	mio_seterrbfmt (jsonwr->mio, MIO_EINVAL, "incompatiable integer write instruction");
+	return -1;
+}
+
+int mio_jsonwr_writeuintmax (mio_jsonwr_t* jsonwr, mio_uintmax_t v)
+{
+	mio_jsonwr_state_node_t* sn = jsonwr->state_stack;
+	mio_bch_t tmp[((MIO_SIZEOF_UINTMAX_T * MIO_BITS_PER_BYTE) / 3) + 2];
+	mio_oow_t len;
+
+	PREACTION_FOR_VLAUE (jsonwr, sn);
+	len = mio_fmt_uintmax_to_bcstr(tmp, MIO_COUNTOF(tmp), v, 10, 0, '\0', MIO_NULL);
+	WRITE_BYTES_NOESC (jsonwr, tmp, len);
+	return 0;
+
+incompatible_inst:
+	flush_wbuf (jsonwr);
+	mio_seterrbfmt (jsonwr->mio, MIO_EINVAL, "incompatiable integer write instruction");
+	return -1;
+}
+
 int mio_jsonwr_writerawuchars (mio_jsonwr_t* jsonwr, const mio_uch_t* dptr, mio_oow_t dlen)
 {
 	WRITE_UCHARS (jsonwr, 0, dptr, dlen);
diff --git a/mio/lib/mio-json.h b/mio/lib/mio-json.h
index eea0d16..f1bb77d 100644
--- a/mio/lib/mio-json.h
+++ b/mio/lib/mio-json.h
@@ -153,13 +153,19 @@ struct mio_jsonwr_state_node_t
 	mio_jsonwr_state_node_t* next;
 };
 
+enum mio_jsonwr_flag_t
+{
+	MIO_JSONWR_FLAG_PRETTY = (1 << 0)
+};
+typedef enum mio_jsonwr_flag_t mio_jsonwr_flag_t;
+
 struct mio_jsonwr_t
 {
 	mio_t* mio;
 	mio_jsonwr_writecb_t writecb;
 	mio_jsonwr_state_node_t state_top;
 	mio_jsonwr_state_node_t* state_stack;
-	int pretty;
+	int flags;
 
 	void* wctx;	
 	mio_bch_t wbuf[8192];
@@ -242,7 +248,8 @@ MIO_EXPORT int mio_json_feed (
 
 MIO_EXPORT mio_jsonwr_t* mio_jsonwr_open (
 	mio_t*             mio,
-	mio_oow_t          xtnsize
+	mio_oow_t          xtnsize,
+	int                flags
 );
 
 MIO_EXPORT void mio_jsonwr_close (
@@ -251,7 +258,8 @@ MIO_EXPORT void mio_jsonwr_close (
 
 MIO_EXPORT int mio_jsonwr_init (
 	mio_jsonwr_t* jsonwr,
-	mio_t*        mio
+	mio_t*        mio,
+	int           flags
 );
 
 MIO_EXPORT void mio_jsonwr_fini (
@@ -314,6 +322,15 @@ MIO_EXPORT int mio_jsonwr_write (
 #define mio_jsonwr_writestringwithucstr(jsonwr,dptr) mio_jsonwr_write(jsonwr, MIO_JSON_INST_STRING, 1, dptr, mio_count_ucstr(dptr))
 #define mio_jsonwr_writestringwithbcstr(jsonwr,dptr) mio_jsonwr_write(jsonwr, MIO_JSON_INST_STRING, 0, dptr, mio_count_bcstr(dptr))
 
+MIO_EXPORT int mio_jsonwr_writeintmax (
+	mio_jsonwr_t*     jsonwr,
+	mio_intmax_t      v
+);
+
+MIO_EXPORT int mio_jsonwr_writeuintmax (
+	mio_jsonwr_t*     jsonwr,
+	mio_uintmax_t     v
+);
 
 MIO_EXPORT int mio_jsonwr_writerawuchars (
 	mio_jsonwr_t*     jsonwr,