Type Definition paho_mqtt_sys::Persistence_containskey

type Persistence_containskey = Option<unsafe extern "C" fn(handle: *mut c_void, key: *mut c_char) -> c_int>;

@brief Returns whether any data has been persisted using the specified key.

@param handle The handle pointer from a successful call to Persistence_open(). @param key The string to be tested for existence in the store. @return Return 0 if the key was found in the store, otherwise return ::MQTTCLIENT_PERSISTENCE_ERROR.