How to add an array of UA_String to the server in open62541

Question

I am trying to set up an OPC server using open62541. The examples are working and I was able to add my own variables to the server.

For this project I would like to add a server variable which is an array of UA_String. There are examples for primitive types like doubles, but none for strings.

How to add an array of strings to the server variables? And what about the memory management of those strings?

score 2 · Accepted Answer · answered Sep 06 '19 at 10:16

Here is a minimal example which shows how to add a variable node to the server. The variable node has an array with 2 entries:

#include <open62541/plugin/log_stdout.h>
#include <open62541/server.h>
#include <open62541/server_config_default.h>

#include <signal.h>
#include <stdlib.h>

static volatile UA_Boolean running = true;
static void stopHandler(int sig) {
    UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND, "received ctrl-c");
    running = false;
}

int main(void) {
    signal(SIGINT, stopHandler);
    signal(SIGTERM, stopHandler);

    // Server initialization
    UA_Server *server = UA_Server_new();
    UA_ServerConfig_setDefault(UA_Server_getConfig(server));

    // Attributes for variable node
    UA_VariableAttributes vattr = UA_VariableAttributes_default;

    // Here is the string array. Current size is 2
    const size_t array_size = 2;
    UA_String *values = (UA_String *) UA_Array_new(array_size, &UA_TYPES[UA_TYPES_STRING]);
    values[0] = UA_String_fromChars("Foo");
    values[1] = UA_String_fromChars("Bar");

    UA_Variant_setArray(&vattr.value, values, array_size, &UA_TYPES[UA_TYPES_STRING]);
    vattr.valueRank = UA_VALUERANK_ANY;
    // We want a 1-dimensional array with 2 values
    UA_UInt32 myArrayDimensions[1] = {array_size};
    vattr.value.arrayDimensions = myArrayDimensions;
    vattr.value.arrayDimensionsSize = 1;
    vattr.displayName = UA_LOCALIZEDTEXT("locale","myarray");
    UA_StatusCode retval = UA_Server_addVariableNode(server,
                                       UA_NODEID_STRING(1, "myarray"), // new node id
                                       UA_NODEID_NUMERIC(0, UA_NS0ID_OBJECTSFOLDER), // parent node
                                       UA_NODEID_NUMERIC(0, UA_NS0ID_ORGANIZES), // reference type
                                       UA_QUALIFIEDNAME(1, "myarray"), // node browse name
                                       UA_NODEID_NUMERIC(0, UA_NS0ID_BASEDATAVARIABLETYPE),
                                       vattr, NULL, NULL);
    if (retval != UA_STATUSCODE_GOOD) {
        // handle error
        printf("Error adding node");
    }

    // clean up
    UA_Array_delete(values, array_size, &UA_TYPES[UA_TYPES_STRING]);

    retval = UA_Server_run(server, &running);

    UA_Server_delete(server);
    return retval == UA_STATUSCODE_GOOD ? EXIT_SUCCESS : EXIT_FAILURE;
}

How to add an array of UA_String to the server in open62541

1 Answers1