Use realtime text when it is negotiated

This patch make use of wirte_text() realtime text instead of
send_text() if T.140 is in native formats. ASTERISK-17937

Review: https://reviewboard.asterisk.org/r/1356/


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/10@333681 65c4cc65-6c06-0410-ace0-fbb531ad65f3

CHANGES

@@ -24,6 +24,10 @@ Text Messaging
    The MESSAGE() dialplan function and MessageSend() application have been
    added to go along with this functionality.  More detailed usage information
    can be found on the Asterisk wiki (http://wiki.asterisk.org/).
+ * If real-time text support (T.140) is negotiated, it will be preferred for
+   sending text via the SendText application. For example, via SIP, messages
+   that were once sent via the SIP MESSAGE request would be sent via RTP if
+   T.140 text is negotiated for a call.
 
 Parking
 -------

main/channel.c

@@ -4586,9 +4586,29 @@ int ast_sendtext(struct ast_channel *chan, const char *text)
 		ast_channel_unlock(chan);
 		return -1;
 	}
+
+	if (ast_strlen_zero(text)) {
+		ast_channel_unlock(chan);
+		return 0;
+	}
+
 	CHECK_BLOCKING(chan);
-	if (chan->tech->send_text)
+	if (chan->tech->write_text && (ast_format_cap_has_type(chan->nativeformats, AST_FORMAT_TYPE_TEXT))) {
+		struct ast_frame f;
+
+		f.frametype = AST_FRAME_TEXT;
+		f.src = "DIALPLAN";
+		f.mallocd = AST_MALLOCD_DATA;
+		f.datalen = strlen(text);
+		f.data.ptr = ast_strdup(text);
+		f.offset = 0;
+		f.seqno = 0;
+
+		ast_format_set(&f.subclass.format, AST_FORMAT_T140, 0);
+		res = chan->tech->write_text(chan, &f);
+	} else if (chan->tech->send_text) {
 		res = chan->tech->send_text(chan, text);
+	}
 	ast_clear_flag(chan, AST_FLAG_BLOCKING);
 	ast_channel_unlock(chan);
 	return res;