remove libasn1c dependency and use asn1c without libasn1c

TODO: re-introduce talloc integration for asn1 runtime

Change-Id: I2140509c5359727f304470249be2a726b9a8deb1
diff --git a/src/rspro/xer_encoder.c b/src/rspro/xer_encoder.c
new file mode 100644
index 0000000..aa7cf04
--- /dev/null
+++ b/src/rspro/xer_encoder.c
@@ -0,0 +1,67 @@
+/*-
+ * Copyright (c) 2003, 2004 Lev Walkin <vlm@lionet.info>. All rights reserved.
+ * Redistribution and modifications are permitted subject to BSD license.
+ */
+#include <asn_internal.h>
+#include <stdio.h>
+#include <errno.h>
+
+/*
+ * The XER encoder of any type. May be invoked by the application.
+ */
+asn_enc_rval_t
+xer_encode(asn_TYPE_descriptor_t *td, void *sptr,
+	enum xer_encoder_flags_e xer_flags,
+		asn_app_consume_bytes_f *cb, void *app_key) {
+	asn_enc_rval_t er, tmper;
+	const char *mname;
+	size_t mlen;
+	int xcan = (xer_flags & XER_F_CANONICAL) ? 1 : 2;
+
+	if(!td || !sptr) goto cb_failed;
+
+	mname = td->xml_tag;
+	mlen = strlen(mname);
+
+	_ASN_CALLBACK3("<", 1, mname, mlen, ">", 1);
+
+	tmper = td->xer_encoder(td, sptr, 1, xer_flags, cb, app_key);
+	if(tmper.encoded == -1) return tmper;
+
+	_ASN_CALLBACK3("</", 2, mname, mlen, ">\n", xcan);
+
+	er.encoded = 4 + xcan + (2 * mlen) + tmper.encoded;
+
+	_ASN_ENCODED_OK(er);
+cb_failed:
+	_ASN_ENCODE_FAILED;
+}
+
+/*
+ * This is a helper function for xer_fprint, which directs all incoming data
+ * into the provided file descriptor.
+ */
+static int
+xer__print2fp(const void *buffer, size_t size, void *app_key) {
+	FILE *stream = (FILE *)app_key;
+
+	if(fwrite(buffer, 1, size, stream) != size)
+		return -1;
+
+	return 0;
+}
+
+int
+xer_fprint(FILE *stream, asn_TYPE_descriptor_t *td, void *sptr) {
+	asn_enc_rval_t er;
+
+	if(!stream) stream = stdout;
+	if(!td || !sptr)
+		return -1;
+
+	er = xer_encode(td, sptr, XER_F_BASIC, xer__print2fp, stream);
+	if(er.encoded == -1)
+		return -1;
+
+	return fflush(stream);
+}