add printf data sender

libtelnet.c

@@ -855,3 +855,20 @@ void libtelnet_begin_compress2(libtelnet_t *telnet) {
 	_event(telnet, LIBTELNET_EV_COMPRESS, 1, 0, 0, 0);
 #endif /* HAVE_ZLIB */
 }
+
+/* send formatted data through libtelnet_send_data */
+int libtelnet_send_printf(libtelnet_t *telnet, const char *fmt, ...) {
+	char buffer[4096];
+	va_list va;
+	int rs;
+
+	/* format */
+	va_start(va, fmt);
+	rs = vsnprintf(buffer, sizeof(buffer), fmt, va);
+	va_end(va);
+
+	/* send */
+	libtelnet_send_data(telnet, (unsigned char *)buffer, rs);
+
+	return rs;
+}

libtelnet.h

@@ -228,4 +228,13 @@ extern void libtelnet_send_subnegotiation(libtelnet_t *telnet,
 /* begin sending compressed data (server only) */
 extern void libtelnet_begin_compress2(libtelnet_t *telnet);
 
+/* send formatted data (through libtelnet_send_data) */
+#ifdef __GNUC__
+# define LIBTELNET_GNU_PRINTF(f,a) __attribute__((printf(f, a)))
+#else
+# define LIBTELNET_GNU_PRINTF(f,a)
+#endif
+
+extern int libtelnet_send_printf(libtelnet_t *telnet, const char *fmt, ...);
+
 #endif /* !defined(LIBTELNET_INCLUDE) */