Data Types

The OPC UA protocol defines 25 builtin data types and three ways of combining them into higher-order types: arrays, structures and unions. In open62541, the builtin data types are defined manually. All other data types are generated from standard XML definitions. Their exact definitions can be looked up at https://opcfoundation.org/UA/schemas/Opc.Ua.Types.bsd.xml.

For users that are new to open62541, take a look at the tutorial for working with data types before diving into the implementation details.

Builtin Types

#define UA_BUILTIN_TYPES_COUNT 25U

Boolean

A two-state logical value (true or false).

typedef bool UA_Boolean;
#define UA_TRUE true
#define UA_FALSE false

SByte

An integer value between -128 and 127.

typedef int8_t UA_SByte;
#define UA_SBYTE_MIN (-128)
#define UA_SBYTE_MAX 127

Byte

An integer value between 0 and 255.

typedef uint8_t UA_Byte;
#define UA_BYTE_MIN 0
#define UA_BYTE_MAX 255

Int16

An integer value between -32 768 and 32 767.

typedef int16_t UA_Int16;
#define UA_INT16_MIN (-32768)
#define UA_INT16_MAX 32767

UInt16

An integer value between 0 and 65 535.

typedef uint16_t UA_UInt16;
#define UA_UINT16_MIN 0
#define UA_UINT16_MAX 65535

Int32

An integer value between -2 147 483 648 and 2 147 483 647.

typedef int32_t UA_Int32;
#define UA_INT32_MIN (-2147483648)
#define UA_INT32_MAX 2147483647

UInt32

An integer value between 0 and 4 294 967 295.

typedef uint32_t UA_UInt32;
#define UA_UINT32_MIN 0
#define UA_UINT32_MAX 4294967295

Int64

An integer value between -9 223 372 036 854 775 808 and 9 223 372 036 854 775 807.

typedef int64_t UA_Int64;
#define UA_INT64_MIN ((int64_t)-9223372036854775808)
#define UA_INT64_MAX (int64_t)9223372036854775807

UInt64

An integer value between 0 and 18 446 744 073 709 551 615.

typedef uint64_t UA_UInt64;
#define UA_UINT64_MIN (int64_t)0
#define UA_UINT64_MAX (int64_t)18446744073709551615

Float

An IEEE single precision (32 bit) floating point value.

typedef float UA_Float;

Double

An IEEE double precision (64 bit) floating point value.

typedef double UA_Double;

StatusCode

A numeric identifier for a error or condition that is associated with a value or an operation. See the section StatusCodes for the meaning of a specific code.

typedef uint32_t UA_StatusCode;

typedef struct {
    UA_StatusCode code;      /* The numeric value of the StatusCode */
    const char* name;        /* The symbolic name */
    const char* explanation; /* Short message explaining the StatusCode */
} UA_StatusCodeDescription;

/* Returns the description of the StatusCode. Never returns NULL, but a generic
 * description for invalid StatusCodes instead. */
const UA_StatusCodeDescription *
UA_StatusCode_description(UA_StatusCode code);

static UA_INLINE const char *
UA_StatusCode_name(UA_StatusCode code) {
    return UA_StatusCode_description(code)->name;
}

static UA_INLINE const char *
UA_StatusCode_explanation(UA_StatusCode code) {
    return UA_StatusCode_description(code)->explanation;
}

String

A sequence of Unicode characters. Strings are just an array of UA_Byte.

typedef struct {
    size_t length; /* The length of the string */
    UA_Byte *data; /* The content (not null-terminated) */
} UA_String;

/* Copies the content on the heap. Returns a null-string when alloc fails */
UA_String UA_String_fromChars(char const src[]);

UA_Boolean UA_String_equal(const UA_String *s1, const UA_String *s2);

extern const UA_String UA_STRING_NULL;

UA_STRING returns a string pointing to the preallocated char-array. UA_STRING_ALLOC is shorthand for UA_String_fromChars and makes a copy of the char-array.

static UA_INLINE UA_String
UA_STRING(char *chars) {
    UA_String str; str.length = strlen(chars);
    str.data = (UA_Byte*)chars; return str;
}

#define UA_STRING_ALLOC(CHARS) UA_String_fromChars(CHARS)

DateTime

An instance in time. A DateTime value is encoded as a 64-bit signed integer which represents the number of 100 nanosecond intervals since January 1, 1601 (UTC).

typedef int64_t UA_DateTime;

/* Multiply to convert units for time difference computations */
#define UA_USEC_TO_DATETIME 10LL
#define UA_MSEC_TO_DATETIME (UA_USEC_TO_DATETIME * 1000LL)
#define UA_SEC_TO_DATETIME (UA_MSEC_TO_DATETIME * 1000LL)

/* Datetime of 1 Jan 1970 00:00 UTC */
#define UA_DATETIME_UNIX_EPOCH (11644473600LL * UA_SEC_TO_DATETIME)

/* The current time */
UA_DateTime UA_DateTime_now(void);

/* CPU clock invariant to system time changes. Use only for time diffs, not
 * current time */
UA_DateTime UA_DateTime_nowMonotonic(void);

typedef struct UA_DateTimeStruct {
    UA_UInt16 nanoSec;
    UA_UInt16 microSec;
    UA_UInt16 milliSec;
    UA_UInt16 sec;
    UA_UInt16 min;
    UA_UInt16 hour;
    UA_UInt16 day;
    UA_UInt16 month;
    UA_UInt16 year;
} UA_DateTimeStruct;

UA_DateTimeStruct UA_DateTime_toStruct(UA_DateTime t);

UA_String UA_DateTime_toString(UA_DateTime t);

Guid

A 16 byte value that can be used as a globally unique identifier.

typedef struct {
    UA_UInt32 data1;
    UA_UInt16 data2;
    UA_UInt16 data3;
    UA_Byte   data4[8];
} UA_Guid;

UA_Boolean UA_Guid_equal(const UA_Guid *g1, const UA_Guid *g2);

extern const UA_Guid UA_GUID_NULL;

ByteString

A sequence of octets.

typedef UA_String UA_ByteString;

static UA_INLINE UA_Boolean
UA_ByteString_equal(const UA_ByteString *string1,
                    const UA_ByteString *string2) {
    return UA_String_equal((const UA_String*)string1,
                           (const UA_String*)string2);
}

/* Allocates memory of size length for the bytestring.
 * The content is not set to zero. */
UA_StatusCode
UA_ByteString_allocBuffer(UA_ByteString *bs, size_t length);

extern const UA_ByteString UA_BYTESTRING_NULL;

static UA_INLINE UA_ByteString
UA_BYTESTRING(char *chars) {
    UA_ByteString str; str.length = strlen(chars);
    str.data = (UA_Byte*)chars; return str;
}

static UA_INLINE UA_ByteString
UA_BYTESTRING_ALLOC(const char *chars) {
    UA_String str = UA_String_fromChars(chars); UA_ByteString bstr;
    bstr.length = str.length; bstr.data = str.data; return bstr;
}

XmlElement

An XML element.

typedef UA_String UA_XmlElement;

NodeId

An identifier for a node in the address space of an OPC UA Server.

enum UA_NodeIdType {
    UA_NODEIDTYPE_NUMERIC    = 0, /* In the binary encoding, this can also
                                     become 1 or 2 (2byte and 4byte encoding of
                                     small numeric nodeids) */
    UA_NODEIDTYPE_STRING     = 3,
    UA_NODEIDTYPE_GUID       = 4,
    UA_NODEIDTYPE_BYTESTRING = 5
};

typedef struct {
    UA_UInt16 namespaceIndex;
    enum UA_NodeIdType identifierType;
    union {
        UA_UInt32     numeric;
        UA_String     string;
        UA_Guid       guid;
        UA_ByteString byteString;
    } identifier;
} UA_NodeId;

extern const UA_NodeId UA_NODEID_NULL;

UA_Boolean UA_NodeId_isNull(const UA_NodeId *p);

UA_Boolean UA_NodeId_equal(const UA_NodeId *n1, const UA_NodeId *n2);

/* Returns a non-cryptographic hash for the NodeId */
UA_UInt32 UA_NodeId_hash(const UA_NodeId *n);

The following functions are shorthand for creating NodeIds.

static UA_INLINE UA_NodeId
UA_NODEID_NUMERIC(UA_UInt16 nsIndex, UA_UInt32 identifier) {
    UA_NodeId id; id.namespaceIndex = nsIndex;
    id.identifierType = UA_NODEIDTYPE_NUMERIC;
    id.identifier.numeric = identifier; return id;
}

static UA_INLINE UA_NodeId
UA_NODEID_STRING(UA_UInt16 nsIndex, char *chars) {
    UA_NodeId id; id.namespaceIndex = nsIndex;
    id.identifierType = UA_NODEIDTYPE_STRING;
    id.identifier.string = UA_STRING(chars); return id;
}

static UA_INLINE UA_NodeId
UA_NODEID_STRING_ALLOC(UA_UInt16 nsIndex, const char *chars) {
    UA_NodeId id; id.namespaceIndex = nsIndex;
    id.identifierType = UA_NODEIDTYPE_STRING;
    id.identifier.string = UA_STRING_ALLOC(chars); return id;
}

static UA_INLINE UA_NodeId
UA_NODEID_GUID(UA_UInt16 nsIndex, UA_Guid guid) {
    UA_NodeId id; id.namespaceIndex = nsIndex;
    id.identifierType = UA_NODEIDTYPE_GUID;
    id.identifier.guid = guid; return id;
}

static UA_INLINE UA_NodeId
UA_NODEID_BYTESTRING(UA_UInt16 nsIndex, char *chars) {
    UA_NodeId id; id.namespaceIndex = nsIndex;
    id.identifierType = UA_NODEIDTYPE_BYTESTRING;
    id.identifier.byteString = UA_BYTESTRING(chars); return id;
}

static UA_INLINE UA_NodeId
UA_NODEID_BYTESTRING_ALLOC(UA_UInt16 nsIndex, const char *chars) {
    UA_NodeId id; id.namespaceIndex = nsIndex;
    id.identifierType = UA_NODEIDTYPE_BYTESTRING;
    id.identifier.byteString = UA_BYTESTRING_ALLOC(chars); return id;
}

ExpandedNodeId

A NodeId that allows the namespace URI to be specified instead of an index.

typedef struct {
    UA_NodeId nodeId;
    UA_String namespaceUri;
    UA_UInt32 serverIndex;
} UA_ExpandedNodeId;

The following functions are shorthand for creating ExpandedNodeIds.

static UA_INLINE UA_ExpandedNodeId
UA_EXPANDEDNODEID_NUMERIC(UA_UInt16 nsIndex, UA_UInt32 identifier) {
    UA_ExpandedNodeId id; id.nodeId = UA_NODEID_NUMERIC(nsIndex, identifier);
    id.serverIndex = 0; id.namespaceUri = UA_STRING_NULL; return id;
}

static UA_INLINE UA_ExpandedNodeId
UA_EXPANDEDNODEID_STRING(UA_UInt16 nsIndex, char *chars) {
    UA_ExpandedNodeId id; id.nodeId = UA_NODEID_STRING(nsIndex, chars);
    id.serverIndex = 0; id.namespaceUri = UA_STRING_NULL; return id;
}

static UA_INLINE UA_ExpandedNodeId
UA_EXPANDEDNODEID_STRING_ALLOC(UA_UInt16 nsIndex, const char *chars) {
    UA_ExpandedNodeId id; id.nodeId = UA_NODEID_STRING_ALLOC(nsIndex, chars);
    id.serverIndex = 0; id.namespaceUri = UA_STRING_NULL; return id;
}

static UA_INLINE UA_ExpandedNodeId
UA_EXPANDEDNODEID_STRING_GUID(UA_UInt16 nsIndex, UA_Guid guid) {
    UA_ExpandedNodeId id; id.nodeId = UA_NODEID_GUID(nsIndex, guid);
    id.serverIndex = 0; id.namespaceUri = UA_STRING_NULL; return id;
}

static UA_INLINE UA_ExpandedNodeId
UA_EXPANDEDNODEID_BYTESTRING(UA_UInt16 nsIndex, char *chars) {
    UA_ExpandedNodeId id; id.nodeId = UA_NODEID_BYTESTRING(nsIndex, chars);
    id.serverIndex = 0; id.namespaceUri = UA_STRING_NULL; return id;
}

static UA_INLINE UA_ExpandedNodeId
UA_EXPANDEDNODEID_BYTESTRING_ALLOC(UA_UInt16 nsIndex, const char *chars) {
    UA_ExpandedNodeId id; id.nodeId = UA_NODEID_BYTESTRING_ALLOC(nsIndex, chars);
    id.serverIndex = 0; id.namespaceUri = UA_STRING_NULL; return id;
}

QualifiedName

A name qualified by a namespace.

typedef struct {
    UA_UInt16 namespaceIndex;
    UA_String name;
} UA_QualifiedName;

static UA_INLINE UA_Boolean
UA_QualifiedName_isNull(const UA_QualifiedName *q) {
    return (q->namespaceIndex == 0 && q->name.length == 0);
}

static UA_INLINE UA_QualifiedName
UA_QUALIFIEDNAME(UA_UInt16 nsIndex, char *chars) {
    UA_QualifiedName qn; qn.namespaceIndex = nsIndex;
    qn.name = UA_STRING(chars); return qn;
}

static UA_INLINE UA_QualifiedName
UA_QUALIFIEDNAME_ALLOC(UA_UInt16 nsIndex, const char *chars) {
    UA_QualifiedName qn; qn.namespaceIndex = nsIndex;
    qn.name = UA_STRING_ALLOC(chars); return qn;
}

LocalizedText

Human readable text with an optional locale identifier.

typedef struct {
    UA_String locale;
    UA_String text;
} UA_LocalizedText;

static UA_INLINE UA_LocalizedText
UA_LOCALIZEDTEXT(char *locale, char *text) {
    UA_LocalizedText lt; lt.locale = UA_STRING(locale);
    lt.text = UA_STRING(text); return lt;
}

static UA_INLINE UA_LocalizedText
UA_LOCALIZEDTEXT_ALLOC(const char *locale, const char *text) {
    UA_LocalizedText lt; lt.locale = UA_STRING_ALLOC(locale);
    lt.text = UA_STRING_ALLOC(text); return lt;
}

NumericRange

NumericRanges are used to indicate subsets of a (multidimensional) array. They no official data type in the OPC UA standard and are transmitted only with a string encoding, such as “1:2,0:3,5”. The colon separates min/max index and the comma separates dimensions. A single value indicates a range with a single element (min==max).

typedef struct {
    UA_UInt32 min;
    UA_UInt32 max;
} UA_NumericRangeDimension;

typedef struct  {
    size_t dimensionsSize;
    UA_NumericRangeDimension *dimensions;
} UA_NumericRange;

Variant

Variants may contain values of any type together with a description of the content. See the section on Generic Type Handling on how types are described. The standard mandates that variants contain built-in data types only. If the value is not of a builtin type, it is wrapped into an ExtensionObject. open62541 hides this wrapping transparently in the encoding layer. If the data type is unknown to the receiver, the variant contains the original ExtensionObject in binary or XML encoding.

Variants may contain a scalar value or an array. For details on the handling of arrays, see the section on Array handling. Array variants can have an additional dimensionality (matrix, 3-tensor, …) defined in an array of dimension lengths. The actual values are kept in an array of dimensions one. For users who work with higher-dimensions arrays directly, keep in mind that dimensions of higher rank are serialized first (the highest rank dimension has stride 1 and elements follow each other directly). Usually it is simplest to interact with higher-dimensional arrays via UA_NumericRange descriptions (see Array handling).

To differentiate between scalar / array variants, the following definition is used. UA_Variant_isScalar provides simplified access to these checks.

  • arrayLength == 0 && data == NULL: undefined array of length -1
  • arrayLength == 0 && data == UA_EMPTY_ARRAY_SENTINEL: array of length 0
  • arrayLength == 0 && data > UA_EMPTY_ARRAY_SENTINEL: scalar value
  • arrayLength > 0: array of the given length

Variants can also be empty. Then, the pointer to the type description is NULL.

/* Forward declaration. See the section on Generic Type Handling */
struct UA_DataType;
typedef struct UA_DataType UA_DataType;

#define UA_EMPTY_ARRAY_SENTINEL ((void*)0x01)

typedef enum {
    UA_VARIANT_DATA,          /* The data has the same lifecycle as the
                                 variant */
    UA_VARIANT_DATA_NODELETE, /* The data is "borrowed" by the variant and
                                 shall not be deleted at the end of the
                                 variant's lifecycle. */
} UA_VariantStorageType;

typedef struct {
    const UA_DataType *type;      /* The data type description */
    UA_VariantStorageType storageType;
    size_t arrayLength;           /* The number of elements in the data array */
    void *data;                   /* Points to the scalar or array data */
    size_t arrayDimensionsSize;   /* The number of dimensions */
    UA_UInt32 *arrayDimensions;   /* The length of each dimension */
} UA_Variant;

/* Returns true if the variant has no value defined (contains neither an array
 * nor a scalar value).
 *
 * @param v The variant
 * @return Is the variant empty */
static UA_INLINE UA_Boolean
UA_Variant_isEmpty(const UA_Variant *v) {
    return v->type == NULL;
}

/* Returns true if the variant contains a scalar value. Note that empty variants
 * contain an array of length -1 (undefined).
 *
 * @param v The variant
 * @return Does the variant contain a scalar value */
static UA_INLINE UA_Boolean
UA_Variant_isScalar(const UA_Variant *v) {
    return (v->arrayLength == 0 && v->data > UA_EMPTY_ARRAY_SENTINEL);
}

/* Returns true if the variant contains a scalar value of the given type.
 *
 * @param v The variant
 * @param type The data type
 * @return Does the variant contain a scalar value of the given type */
static UA_INLINE UA_Boolean
UA_Variant_hasScalarType(const UA_Variant *v, const UA_DataType *type) {
    return UA_Variant_isScalar(v) && type == v->type;
}

/* Returns true if the variant contains an array of the given type.
 *
 * @param v The variant
 * @param type The data type
 * @return Does the variant contain an array of the given type */
static UA_INLINE UA_Boolean
UA_Variant_hasArrayType(const UA_Variant *v, const UA_DataType *type) {
    return (!UA_Variant_isScalar(v)) && type == v->type;
}

/* Set the variant to a scalar value that already resides in memory. The value
 * takes on the lifecycle of the variant and is deleted with it.
 *
 * @param v The variant
 * @param p A pointer to the value data
 * @param type The datatype of the value in question */
void
UA_Variant_setScalar(UA_Variant *v, void *p,
                     const UA_DataType *type);

/* Set the variant to a scalar value that is copied from an existing variable.
 * @param v The variant
 * @param p A pointer to the value data
 * @param type The datatype of the value
 * @return Indicates whether the operation succeeded or returns an error code */
UA_StatusCode
UA_Variant_setScalarCopy(UA_Variant *v, const void *p,
                         const UA_DataType *type);

/* Set the variant to an array that already resides in memory. The array takes
 * on the lifecycle of the variant and is deleted with it.
 *
 * @param v The variant
 * @param array A pointer to the array data
 * @param arraySize The size of the array
 * @param type The datatype of the array */
void
UA_Variant_setArray(UA_Variant *v, void *array,
                    size_t arraySize, const UA_DataType *type);

/* Set the variant to an array that is copied from an existing array.
 *
 * @param v The variant
 * @param array A pointer to the array data
 * @param arraySize The size of the array
 * @param type The datatype of the array
 * @return Indicates whether the operation succeeded or returns an error code */
UA_StatusCode
UA_Variant_setArrayCopy(UA_Variant *v, const void *array,
                        size_t arraySize, const UA_DataType *type);

/* Copy the variant, but use only a subset of the (multidimensional) array into
 * a variant. Returns an error code if the variant is not an array or if the
 * indicated range does not fit.
 *
 * @param src The source variant
 * @param dst The target variant
 * @param range The range of the copied data
 * @return Returns UA_STATUSCODE_GOOD or an error code */
UA_StatusCode
UA_Variant_copyRange(const UA_Variant *src, UA_Variant *dst,
                     const UA_NumericRange range);

/* Insert a range of data into an existing variant. The data array can't be
 * reused afterwards if it contains types without a fixed size (e.g. strings)
 * since the members are moved into the variant and take on its lifecycle.
 *
 * @param v The variant
 * @param dataArray The data array. The type must match the variant
 * @param dataArraySize The length of the data array. This is checked to match
 *        the range size.
 * @param range The range of where the new data is inserted
 * @return Returns UA_STATUSCODE_GOOD or an error code */
UA_StatusCode
UA_Variant_setRange(UA_Variant *v, void *array,
                    size_t arraySize, const UA_NumericRange range);

/* Deep-copy a range of data into an existing variant.
 *
 * @param v The variant
 * @param dataArray The data array. The type must match the variant
 * @param dataArraySize The length of the data array. This is checked to match
 *        the range size.
 * @param range The range of where the new data is inserted
 * @return Returns UA_STATUSCODE_GOOD or an error code */
UA_StatusCode
UA_Variant_setRangeCopy(UA_Variant *v, const void *array,
                        size_t arraySize, const UA_NumericRange range);

ExtensionObject

ExtensionObjects may contain scalars of any data type. Even those that are unknown to the receiver. See the section on Generic Type Handling on how types are described. If the received data type is unkown, the encoded string and target NodeId is stored instead of the decoded value.

typedef enum {
    UA_EXTENSIONOBJECT_ENCODED_NOBODY     = 0,
    UA_EXTENSIONOBJECT_ENCODED_BYTESTRING = 1,
    UA_EXTENSIONOBJECT_ENCODED_XML        = 2,
    UA_EXTENSIONOBJECT_DECODED            = 3,
    UA_EXTENSIONOBJECT_DECODED_NODELETE   = 4 /* Don't delete the content
                                                 together with the
                                                 ExtensionObject */
} UA_ExtensionObjectEncoding;

typedef struct {
    UA_ExtensionObjectEncoding encoding;
    union {
        struct {
            UA_NodeId typeId;   /* The nodeid of the datatype */
            UA_ByteString body; /* The bytestring of the encoded data */
        } encoded;
        struct {
            const UA_DataType *type;
            void *data;
        } decoded;
    } content;
} UA_ExtensionObject;

DataValue

A data value with an associated status code and timestamps.

typedef struct {
    UA_Boolean    hasValue             : 1;
    UA_Boolean    hasStatus            : 1;
    UA_Boolean    hasSourceTimestamp   : 1;
    UA_Boolean    hasServerTimestamp   : 1;
    UA_Boolean    hasSourcePicoseconds : 1;
    UA_Boolean    hasServerPicoseconds : 1;
    UA_Variant    value;
    UA_StatusCode status;
    UA_DateTime   sourceTimestamp;
    UA_UInt16     sourcePicoseconds;
    UA_DateTime   serverTimestamp;
    UA_UInt16     serverPicoseconds;
} UA_DataValue;

DiagnosticInfo

A structure that contains detailed error and diagnostic information associated with a StatusCode.

typedef struct UA_DiagnosticInfo {
    UA_Boolean    hasSymbolicId          : 1;
    UA_Boolean    hasNamespaceUri        : 1;
    UA_Boolean    hasLocalizedText       : 1;
    UA_Boolean    hasLocale              : 1;
    UA_Boolean    hasAdditionalInfo      : 1;
    UA_Boolean    hasInnerStatusCode     : 1;
    UA_Boolean    hasInnerDiagnosticInfo : 1;
    UA_Int32      symbolicId;
    UA_Int32      namespaceUri;
    UA_Int32      localizedText;
    UA_Int32      locale;
    UA_String     additionalInfo;
    UA_StatusCode innerStatusCode;
    struct UA_DiagnosticInfo *innerDiagnosticInfo;
} UA_DiagnosticInfo;

Generic Type Handling

All information about a (builtin/structured) data type is stored in a UA_DataType. The array UA_TYPES contains the description of all standard-defined types. This type description is used for the following generic operations that work on all types:

  • void T_init(T *ptr): Initialize the data type. This is synonymous with zeroing out the memory, i.e. memset(ptr, 0, sizeof(T)).
  • T* T_new(): Allocate and return the memory for the data type. The value is already initialized.
  • UA_StatusCode T_copy(const T *src, T *dst): Copy the content of the data type. Returns UA_STATUSCODE_GOOD or UA_STATUSCODE_BADOUTOFMEMORY.
  • void T_deleteMembers(T *ptr): Delete the dynamically allocated content of the data type and perform a T_init to reset the type.
  • void T_delete(T *ptr): Delete the content of the data type and the memory for the data type itself.

Specializations, such as UA_Int32_new() are derived from the generic type operations as static inline functions.

typedef struct {
#ifdef UA_ENABLE_TYPENAMES
    const char *memberName;
#endif
    UA_UInt16 memberTypeIndex;    /* Index of the member in the array of data
                                     types */
    UA_Byte   padding;            /* How much padding is there before this
                                     member element? For arrays this is the
                                     padding before the size_t lenght member.
                                     (No padding between size_t and the
                                     following ptr.) */
    UA_Boolean namespaceZero : 1; /* The type of the member is defined in
                                     namespace zero. In this implementation,
                                     types from custom namespace may contain
                                     members from the same namespace or
                                     namespace zero only.*/
    UA_Boolean isArray       : 1; /* The member is an array */
} UA_DataTypeMember;

struct UA_DataType {
#ifdef UA_ENABLE_TYPENAMES
    const char *typeName;
#endif
    UA_NodeId  typeId;           /* The nodeid of the type */
    UA_UInt16  memSize;          /* Size of the struct in memory */
    UA_UInt16  typeIndex;        /* Index of the type in the datatypetable */
    UA_Byte    membersSize;      /* How many members does the type have? */
    UA_Boolean builtin      : 1; /* The type is "builtin" and has dedicated de-
                                    and encoding functions */
    UA_Boolean pointerFree  : 1; /* The type (and its members) contains no
                                    pointers that need to be freed */
    UA_Boolean overlayable  : 1; /* The type has the identical memory layout in
                                    memory and on the binary stream. */
    UA_UInt16  binaryEncodingId; /* NodeId of datatype when encoded as binary */
    //UA_UInt16  xmlEncodingId;  /* NodeId of datatype when encoded as XML */
    UA_DataTypeMember *members;
};

Builtin data types can be accessed as UA_TYPES[UA_TYPES_XXX], where XXX is the name of the data type. If only the NodeId of a type is known, use the following method to retrieve the data type description.

/* Returns the data type description for the type's identifier or NULL if no
 * matching data type was found. */
const UA_DataType *
UA_findDataType(const UA_NodeId *typeId);

The following functions are used for generic handling of data types.

/* Allocates and initializes a variable of type dataType
 *
 * @param type The datatype description
 * @return Returns the memory location of the variable or NULL if no
 *         memory could be allocated */
void * UA_new(const UA_DataType *type);

/* Initializes a variable to default values
 *
 * @param p The memory location of the variable
 * @param type The datatype description */
static UA_INLINE void
UA_init(void *p, const UA_DataType *type) {
    memset(p, 0, type->memSize);
}

/* Copies the content of two variables. If copying fails (e.g. because no memory
 * was available for an array), then dst is emptied and initialized to prevent
 * memory leaks.
 *
 * @param src The memory location of the source variable
 * @param dst The memory location of the destination variable
 * @param type The datatype description
 * @return Indicates whether the operation succeeded or returns an error code */
UA_StatusCode
UA_copy(const void *src, void *dst, const UA_DataType *type);

/* Deletes the dynamically allocated content of a variable (e.g. resets all
 * arrays to undefined arrays). Afterwards, the variable can be safely deleted
 * without causing memory leaks. But the variable is not initialized and may
 * contain old data that is not memory-relevant.
 *
 * @param p The memory location of the variable
 * @param type The datatype description of the variable */
void UA_deleteMembers(void *p, const UA_DataType *type);

/* Frees a variable and all of its content.
 *
 * @param p The memory location of the variable
 * @param type The datatype description of the variable */
void UA_delete(void *p, const UA_DataType *type);

Array handling

In OPC UA, arrays can have a length of zero or more with the usual meaning. In addition, arrays can be undefined. Then, they don’t even have a length. In the binary encoding, this is indicated by an array of length -1.

In open62541 however, we use size_t for array lengths. An undefined array has length 0 and the data pointer is NULL. An array of length 0 also has length 0 but a data pointer UA_EMPTY_ARRAY_SENTINEL.

/* Allocates and initializes an array of variables of a specific type
 *
 * @param size The requested array length
 * @param type The datatype description
 * @return Returns the memory location of the variable or NULL if no memory
           could be allocated */
void * UA_Array_new(size_t size, const UA_DataType *type);

/* Allocates and copies an array
 *
 * @param src The memory location of the source array
 * @param size The size of the array
 * @param dst The location of the pointer to the new array
 * @param type The datatype of the array members
 * @return Returns UA_STATUSCODE_GOOD or UA_STATUSCODE_BADOUTOFMEMORY */
UA_StatusCode
UA_Array_copy(const void *src, size_t size, void **dst,
              const UA_DataType *type);

/* Deletes an array.
 *
 * @param p The memory location of the array
 * @param size The size of the array
 * @param type The datatype of the array members */
void UA_Array_delete(void *p, size_t size, const UA_DataType *type);

Random Number Generator

If UA_ENABLE_MULTITHREADING is defined, then the seed is stored in thread local storage. The seed is initialized for every thread in the server/client.

void UA_random_seed(UA_UInt64 seed);
UA_UInt32 UA_UInt32_random(void); /* no cryptographic entropy */
UA_Guid UA_Guid_random(void);     /* no cryptographic entropy */

Generated Data Type Definitions

The following data types were auto-generated from a definition in XML format.