Implement Characteristic Value Read using UUID in the gatttool

Sub-procedure used to read a Characteristic Value when the client
only knows the characteristic UUID and doesn't know the handle.
More than one handle and attribute value pair can be returned,
it is up to the user define the handles range based on the service
handles range.

Usage example:
$gatttool --char-read --uuid=2a00 -i hcix -b xx:xx:xx:xx:xx:xx
diff --git a/attrib/gatt.c b/attrib/gatt.c
index 2c87daf..bca8b49 100644
--- a/attrib/gatt.c
+++ b/attrib/gatt.c
@@ -74,13 +74,22 @@
 guint gatt_discover_char(GAttrib *attrib, uint16_t start, uint16_t end,
 				GAttribResultFunc func, gpointer user_data)
 {
-	uint8_t pdu[ATT_DEFAULT_MTU];
 	uuid_t uuid;
-	guint16 plen;
 
 	sdp_uuid16_create(&uuid, GATT_CHARAC_UUID);
 
-	plen = enc_read_by_type_req(start, end, &uuid, pdu, sizeof(pdu));
+	return gatt_read_char_by_uuid(attrib, start, end, &uuid, func,
+							user_data);
+}
+
+guint gatt_read_char_by_uuid(GAttrib *attrib, uint16_t start, uint16_t end,
+					uuid_t *uuid, GAttribResultFunc func,
+					gpointer user_data)
+{
+	uint8_t pdu[ATT_DEFAULT_MTU];
+	guint16 plen;
+
+	plen = enc_read_by_type_req(start, end, uuid, pdu, sizeof(pdu));
 	if (plen == 0)
 		return 0;
 
diff --git a/attrib/gatt.h b/attrib/gatt.h
index 4e7d88b..1e1e628 100644
--- a/attrib/gatt.h
+++ b/attrib/gatt.h
@@ -41,3 +41,7 @@
 
 guint gatt_write_cmd(GAttrib *attrib, uint16_t handle, uint8_t *value, int vlen,
 				GDestroyNotify notify, gpointer user_data);
+
+guint gatt_read_char_by_uuid(GAttrib *attrib, uint16_t start, uint16_t end,
+				uuid_t *uuid, GAttribResultFunc func,
+				gpointer user_data);
diff --git a/attrib/gatttool.c b/attrib/gatttool.c
index e961431..d0ef6d3 100644
--- a/attrib/gatttool.c
+++ b/attrib/gatttool.c
@@ -398,10 +398,49 @@
 		g_main_loop_quit(event_loop);
 }
 
+static void char_read_by_uuid_cb(guint8 status, const guint8 *pdu,
+					guint16 plen, gpointer user_data)
+{
+	struct att_data_list *list;
+	int i;
+
+	if (status != 0) {
+		g_printerr("Read characteristics by UUID failed: %s\n",
+							att_ecode2str(status));
+		goto done;
+	}
+
+	list = dec_read_by_type_resp(pdu, plen);
+	if (list == NULL)
+		goto done;
+
+	for (i = 0; i < list->num; i++) {
+		uint8_t *value = list->data[i];
+		int j;
+
+		g_print("handle: 0x%04x \t value: ", att_get_u16(value));
+		value += 2;
+		for (j = 0; j < list->len - 2; j++, value++)
+			g_print("%02x ", *value);
+		g_print("\n");
+	}
+
+	att_data_list_free(list);
+
+done:
+	g_main_loop_quit(event_loop);
+}
+
 static gboolean characteristics_read(gpointer user_data)
 {
 	GAttrib *attrib = user_data;
 
+	if (opt_uuid != NULL) {
+		gatt_read_char_by_uuid(attrib, opt_start, opt_end, opt_uuid,
+						char_read_by_uuid_cb, attrib);
+		return FALSE;
+	}
+
 	if (opt_handle <= 0) {
 		g_printerr("A valid handle is required\n");
 		g_main_loop_quit(event_loop);