library/Native_Functions: add f_inet6_ntoa()

We have f_inet_ntoa() for converting IPv4 addresses to strings,
but so far there was no similar function for IPv6 addresses.

Change-Id: I0858cf8cb44a6673e19f3496c362d68fcdd7b18d

library/Native_FunctionDefs.cc

@@ -76,6 +76,19 @@ CHARSTRING f__inet__hntoa(const OCTETSTRING& in)
 	return CHARSTRING(str);
 }
 
+CHARSTRING f__inet6__ntoa(const OCTETSTRING& in)
+{
+	char buf[INET6_ADDRSTRLEN] = { 0 };
+	TTCN_Buffer ttcn_buffer(in);
+
+	const void *src = (const void *)ttcn_buffer.get_data();
+	const char *str = inet_ntop(AF_INET6, src, buf, sizeof(buf));
+	if (str == NULL)
+		fprintf(stderr, "inet_ntop failed: %s\n", strerror(errno));
+
+	return CHARSTRING((const char *)buf);
+}
+
 CHARSTRING f__str__tolower(const CHARSTRING& in)
 {
 	TTCN_Buffer ttcn_buffer(in);

library/Native_Functions.ttcn

@@ -11,6 +11,8 @@ module Native_Functions {
 	external function f_inet_ntoa(in octetstring oct) return charstring;
 	/* like inet_ntoa() but input is host byte order */
 	external function f_inet_hntoa(in octetstring oct) return charstring;
+	/* direct import of inet_ntop(AF_INET6) C function, input net byte order */
+	external function f_inet6_ntoa(in octetstring oct) return charstring;
 
 	/* convert content of charstring to lower-case using tolower(3) */
 	external function f_str_tolower(in charstring input) return charstring;