enum: Return boolean result for enum_from_name() lookup

Handling the result for enum_from_name() is difficult, as checking for
negative return values requires a cast if the enum type is unsigned. The new
signature clearly differentiates lookup result from lookup value.

Further, this actually allows to convert real -1 enum values, which could not
be distinguished from "not-found" and the -1 return value.

This also fixes several clang warnings where enums are unsigned.

src/libcharon/plugins/coupling/coupling_validator.c

@@ -202,6 +202,7 @@ METHOD(coupling_validator_t, destroy, void,
 coupling_validator_t *coupling_validator_create()
 {
 	private_coupling_validator_t *this;
+	hash_algorithm_t alg;
 	char *path, *hash;
 
 	INIT(this,
@@ -219,8 +220,13 @@ coupling_validator_t *coupling_validator_create()
 
 	hash = lib->settings->get_str(lib->settings,
 								  "%s.plugins.coupling.hash", "sha1", lib->ns);
-	this->hasher = lib->crypto->create_hasher(lib->crypto,
-							enum_from_name(hash_algorithm_short_names, hash));
+	if (!enum_from_name(hash_algorithm_short_names, hash, &alg))
+	{
+		DBG1(DBG_CFG, "unknown coupling hash algorithm: %s", hash);
+		destroy(this);
+		return NULL;
+	}
+	this->hasher = lib->crypto->create_hasher(lib->crypto, alg);
 	if (!this->hasher)
 	{
 		DBG1(DBG_CFG, "unsupported coupling hash algorithm: %s", hash);

src/libcharon/plugins/eap_radius/eap_radius_forward.c

@@ -362,8 +362,7 @@ static linked_list_t* parse_selector(char *selector)
 			vendor = atoi(token);
 			token = pos;
 		}
-		type = enum_from_name(radius_attribute_type_names, token);
-		if (type == -1)
+		if (!enum_from_name(radius_attribute_type_names, token, &type))
 		{
 			type = atoi(token);
 		}

src/libcharon/plugins/load_tester/load_tester_creds.c

@@ -465,7 +465,6 @@ load_tester_creds_t *load_tester_creds_create()
 		.private = load_issuer_key(),
 		.ca = load_issuer_cert(),
 		.cas = linked_list_create(),
-		.digest = enum_from_name(hash_algorithm_short_names, digest),
 		.psk = shared_key_create(SHARED_IKE,
 								 chunk_clone(chunk_create(psk, strlen(psk)))),
 		.pwd = shared_key_create(SHARED_EAP,
@@ -477,7 +476,7 @@ load_tester_creds_t *load_tester_creds_create()
 		this->cas->insert_last(this->cas, this->ca->get_ref(this->ca));
 	}
 
-	if (this->digest == -1)
+	if (!enum_from_name(hash_algorithm_short_names, digest, &this->digest))
 	{
 		DBG1(DBG_CFG, "invalid load-tester digest: '%s', using sha1", digest);
 		this->digest = HASH_SHA1;
@@ -487,4 +486,3 @@ load_tester_creds_t *load_tester_creds_create()
 
 	return &this->public;
 }
-

src/libcharon/plugins/stroke/stroke_socket.c

@@ -584,8 +584,7 @@ static void stroke_loglevel(private_stroke_socket_t *this,
 	}
 	else
 	{
-		group = enum_from_name(debug_names, msg->loglevel.type);
-		if ((int)group < 0)
+		if (!enum_from_name(debug_names, msg->loglevel.type, &group))
 		{
 			fprintf(out, "unknown type '%s'!\n", msg->loglevel.type);
 			return;

src/libcharon/plugins/vici/vici_query.c

@@ -729,8 +729,7 @@ CALLBACK(list_certs, vici_message_t*,
 	char *str;
 
 	str = request->get_str(request, "ANY", "type");
-	type = enum_from_name(certificate_type_names, str);
-	if (type == -1)
+	if (!enum_from_name(certificate_type_names, str, &type))
 	{
 		b = vici_builder_create();
 		return b->finalize(b);