open62541/examples/tutorial_datatypes.c

/* This work is licensed under a Creative Commons CCZero 1.0 Universal License.
 * See http://creativecommons.org/publicdomain/zero/1.0/ for more information. */

/**
 * .. _types-tutorial:
 *
 * Working with Data Types
 * -----------------------
 *
 * OPC UA defines a type system for values that can be encoded in the protocol
 * messages. This tutorial shows some examples for available data types and
 * their use. See the section on :ref:`types` for the full definitions.
 *
 * Basic Data Handling
 * ^^^^^^^^^^^^^^^^^^^
 * This section shows the basic interaction patterns for data types. Make
 * sure to compare with the type definitions in ``ua_types.h``. */

#include "open62541.h"

static void
variables_basic(void) {
    /* Int32 */
    UA_Int32 i = 5;
    UA_Int32 j;
    UA_Int32_copy(&i, &j);

    UA_Int32 *ip = UA_Int32_new();
    UA_Int32_copy(&i, ip);
    UA_Int32_delete(ip);

    /* String */
    UA_String s;
    UA_String_init(&s); /* _init zeroes out the entire memory of the datatype */
    char *test = "test";
    s.length = strlen(test);
    s.data = (UA_Byte*)test;

    UA_String s2;
    UA_String_copy(&s, &s2);
    UA_String_deleteMembers(&s2); /* Copying heap-allocated the dynamic content */

    UA_String s3 = UA_STRING("test2");
    UA_String s4 = UA_STRING_ALLOC("test2"); /* Copies the content to the heap */
    UA_Boolean eq = UA_String_equal(&s3, &s4);
    UA_String_deleteMembers(&s4);
    if(!eq)
        return;

    /* Structured Type */
    UA_ReadRequest rr;
    UA_init(&rr, &UA_TYPES[UA_TYPES_READREQUEST]); /* Generic method */
    UA_ReadRequest_init(&rr); /* Shorthand for the previous line */

    rr.requestHeader.timestamp = UA_DateTime_now(); /* Members of a structure */

    rr.nodesToRead = (UA_ReadValueId *)UA_Array_new(5, &UA_TYPES[UA_TYPES_READVALUEID]);
    rr.nodesToReadSize = 5; /* Array size needs to be made known */

    UA_ReadRequest *rr2 = UA_ReadRequest_new();
    UA_copy(&rr, rr2, &UA_TYPES[UA_TYPES_READREQUEST]);
    UA_ReadRequest_deleteMembers(&rr);
    UA_ReadRequest_delete(rr2);
}

/**
 * NodeIds
 * ^^^^^^^
 * An OPC UA information model is made up of nodes and references between nodes.
 * Every node has a unique :ref:`nodeid`. NodeIds refer to a namespace with an
 * additional identifier value that can be an integer, a string, a guid or a
 * bytestring. */

static void
variables_nodeids(void) {
    UA_NodeId id1 = UA_NODEID_NUMERIC(1, 1234);
    id1.namespaceIndex = 3;

    UA_NodeId id2 = UA_NODEID_STRING(1, "testid"); /* the string is static */
    UA_Boolean eq = UA_NodeId_equal(&id1, &id2);
    if(eq)
        return;

    UA_NodeId id3;
    UA_NodeId_copy(&id2, &id3);
    UA_NodeId_deleteMembers(&id3);

    UA_NodeId id4 = UA_NODEID_STRING_ALLOC(1, "testid"); /* the string is copied
                                                            to the heap */
    UA_NodeId_deleteMembers(&id4);
}

/**
 * Variants
 * ^^^^^^^^
 * The datatype :ref:`variant` belongs to the built-in datatypes of OPC UA and
 * is used as a container type. A variant can hold any other datatype as a
 * scalar (except variant) or as an array. Array variants can additionally
 * denote the dimensionality of the data (e.g. a 2x3 matrix) in an additional
 * integer array. */

static void
variables_variants(void) {
    /* Set a scalar value */
    UA_Variant v;
    UA_Int32 i = 42;
    UA_Variant_setScalar(&v, &i, &UA_TYPES[UA_TYPES_INT32]);

    /* Make a copy */
    UA_Variant v2;
    UA_Variant_copy(&v, &v2);
    UA_Variant_deleteMembers(&v2);

    /* Set an array value */
    UA_Variant v3;
    UA_Double d[9] = {1.0, 2.0, 3.0,
                      4.0, 5.0, 6.0,
                      7.0, 8.0, 9.0};
    UA_Variant_setArrayCopy(&v3, d, 9, &UA_TYPES[UA_TYPES_DOUBLE]);

    /* Set array dimensions */
    v3.arrayDimensions = (UA_UInt32 *)UA_Array_new(2, &UA_TYPES[UA_TYPES_UINT32]);
    v3.arrayDimensionsSize = 2;
    v3.arrayDimensions[0] = 3;
    v3.arrayDimensions[1] = 3;
    UA_Variant_deleteMembers(&v3);
}

/** It follows the main function, making use of the above definitions. */

int main(void) {
    variables_basic();
    variables_nodeids();
    variables_variants();
    return 0;
}