Add new F1AP msg enc&dec library

Add a new target f1ap_lib that groups F1AP ASN.1 encoding&decoding for
messages defined f1ap_messages_types.h. The objective is to, for each
F1AP message,
- add encoder&decoder (similar to what already exists, but without
  mandatory message sending afterwards)
- eq_X() function that checks two messages for equality (to be used
  mostly in tests)
- cp_X() function that deep-copies a message, e.g., to be used when
  sending ITTI messages, instead of manual copying done currently
- free_X() function that frees the memory associated to a memory, to
  avoid memory leaks.

Each message will be tested, notably that encoding&decoding as well as
copying yield identical messages.

The actual message encoding & decoding, tests, and their use will be
done in the forthcoming commits.

openair2/F1AP/tests/f1ap_lib_test.c

@@ -0,0 +1,47 @@
+#include <stdlib.h>
+#include <stdint.h>
+#include <stdio.h>
+
+#include "common/utils/assertions.h"
+
+#include "f1ap_messages_types.h"
+#include "F1AP_F1AP-PDU.h"
+
+void exit_function(const char *file, const char *function, const int line, const char *s, const int assert)
+{
+  printf("detected error at %s:%d:%s: %s\n", file, line, function, s);
+  abort();
+}
+
+static F1AP_F1AP_PDU_t *f1ap_encode_decode(const F1AP_F1AP_PDU_t *enc_pdu)
+{
+  //xer_fprint(stdout, &asn_DEF_F1AP_F1AP_PDU, enc_pdu);
+
+  DevAssert(enc_pdu != NULL);
+  char errbuf[1024];
+  size_t errlen = sizeof(errbuf);
+  int ret = asn_check_constraints(&asn_DEF_F1AP_F1AP_PDU, enc_pdu, errbuf, &errlen);
+  AssertFatal(ret == 0, "asn_check_constraints() failed: %s\n", errbuf);
+
+  uint8_t msgbuf[16384];
+  asn_enc_rval_t enc = aper_encode_to_buffer(&asn_DEF_F1AP_F1AP_PDU, NULL, enc_pdu, msgbuf, sizeof(msgbuf));
+  AssertFatal(enc.encoded > 0, "aper_encode_to_buffer() failed\n");
+
+  F1AP_F1AP_PDU_t *dec_pdu = NULL;
+  asn_codec_ctx_t st = {.max_stack_size = 100 * 1000};
+  asn_dec_rval_t dec = aper_decode(&st, &asn_DEF_F1AP_F1AP_PDU, (void **)&dec_pdu, msgbuf, enc.encoded, 0, 0);
+  AssertFatal(dec.code == RC_OK, "aper_decode() failed\n");
+
+  //xer_fprint(stdout, &asn_DEF_F1AP_F1AP_PDU, dec_pdu);
+  return dec_pdu;
+}
+
+static void f1ap_msg_free(F1AP_F1AP_PDU_t *pdu)
+{
+  ASN_STRUCT_FREE(asn_DEF_F1AP_F1AP_PDU, pdu);
+}
+
+int main()
+{
+  return 0;
+}