Avoid calls to strlen() when checking for empty strings.

Change-Id: I3de322006623483cbf20218da071a9da5d7b2e2b
Signed-off-by: Anmol Sarma <me@anmolsarma.in>

lib/mosquitto.c

@@ -150,7 +150,7 @@ int mosquitto_reinitialise(struct mosquitto *mosq, const char *id, bool clean_se
 	mosq->last_retry_check = 0;
 	mosq->clean_session = clean_session;
 	if(id){
-		if(strlen(id) == 0){
+		if(STREMPTY(id)){
 			return MOSQ_ERR_INVAL;
 		}
 		mosq->id = _mosquitto_strdup(id);
@@ -552,7 +552,7 @@ int mosquitto_publish(struct mosquitto *mosq, int *mid, const char *topic, int p
 	int queue_status;
 
 	if(!mosq || !topic || qos<0 || qos>2) return MOSQ_ERR_INVAL;
-	if(strlen(topic) == 0) return MOSQ_ERR_INVAL;
+	if(STREMPTY(topic)) return MOSQ_ERR_INVAL;
 	if(payloadlen < 0 || payloadlen > MQTT_MAX_PAYLOAD) return MOSQ_ERR_PAYLOAD_SIZE;
 
 	if(mosquitto_pub_topic_check(topic) != MOSQ_ERR_SUCCESS){

lib/mosquitto_internal.h

@@ -257,4 +257,6 @@ struct mosquitto {
 #endif
 };
 
+#define STREMPTY(str) (str[0] == '\0')
+
 #endif

src/conf.c

@@ -640,7 +640,7 @@ int _config_read_file_core(struct mqtt3_config *config, bool reload, const char
 					if(!key){
 						_mosquitto_log_printf(NULL, MOSQ_LOG_ERR, "Error: Out of memory.");
 						return MOSQ_ERR_NOMEM;
-					}else if(strlen(key) == 0){
+					}else if(STREMPTY(key)){
 						_mosquitto_log_printf(NULL, MOSQ_LOG_ERR, "Error: Invalid auth_opt_ config option.");
 						return MOSQ_ERR_INVAL;
 					}

src/read_handle.c

@@ -102,7 +102,7 @@ int mqtt3_handle_publish(struct mosquitto_db *db, struct mosquitto *context)
 	retain = (header & 0x01);
 
 	if(_mosquitto_read_string(&context->in_packet, &topic)) return 1;
-	if(strlen(topic) == 0){
+	if(STREMPTY(topic)){
 		/* Invalid publish topic, disconnect client. */
 		_mosquitto_free(topic);
 		return 1;

src/read_handle_server.c

@@ -236,7 +236,7 @@ int mqtt3_handle_connect(struct mosquitto_db *db, struct mosquitto *context)
 			rc = 1;
 			goto handle_connect_error;
 		}
-		if(strlen(will_topic) == 0){
+		if(STREMPTY(will_topic)){
 			rc = 1;
 			goto handle_connect_error;
 		}