\fIOutputArguments\fR child nodes are retrieved and stub procedures
are written using the browse path and argument information.
.TP
\fBopcua gentypes\fR \fIhandle\fR
.
Generates custom data type mappings using information obtained from analyzing
the address space derived from the client or server object \fIhandle\fR.
This feature is highly experimental and requires the tDOM package for parsing
XML. It can create encoders/decoders for simple structure data types defined
in the address space which perform a mapping from/to tcl dictionaries.
For further information, see the server_types.tcl and client_types.tcl scripts
in the examples directory. If this command is used, it should be invoked prior
to creating method stubs, since methods may require custom data types in their
arguments.
.TP
\fBopcua info\fR ?\fIhandle\fR?
.

method stub procedures and other information. That namespace is
tied to the life time of the client or server object.
.TP
\fBopcua parent\fR \fIhandle nodeid\fR
.
Returns the parent node identifier of the given node identifier \fInodeid\fR
on the client or server object \fIhandle\fR.
.TP
\fBopcua ptree\fR \fIhandle\fR ?\fInodeid\fR?
.
Returns information similar to \fBopcua tree\fR using the client
or server object \fIhandle\fR. The address space is traversed starting
at the node identifier \fInodeid\fR (the root node if omitted). The
result list is made up of browse path name, node identifier,
node class path, reference node identier, and type node identifier.
The browse path name is a path name like notation made up of the
browse names pointing to the final node as seen from the starting node.
Browse names are written as qualified names, i.e. including the
numeric namespace index if not in root namespace. Similarly, the
node class path is a path name like notation made up of the node
classes of all nodes along the path. The \fBopcua ptree\fR command
is used internally by the \fBopcua genstubs\fR command in order to
filter out objects and methods when creating stub Tcl commands to
invoke methods on objects.
.TP
\fBopcua read\fR \fIhandle nodeid\fR ?\fIattr\fR?
.
Performs a read operation on the client or server object \fIhandle\fR
and returns the value of attribute \fIattr\fR of the node identifier
\fInodeid\fR. If \fIattr\fR is omitted, it defaults to the \fIValue\fR
attribute.

their direction. A reference may be abbreviated as slash for
\fIHierarchicalReferences\fR or as dot for \fIAggregates\fR.
.TP
\fBopcua tree\fR \fIhandle\fR ?\fInodeid\fR?
.
Returns information similar to \fBopcua browse\fR using the client
or server object \fIhandle\fR. The address space is traversed starting
at the node identifier \fInodeid\fR (the root node if omitted). The
result list is made up of tree level (0-based), node identifier,
browse name (qualified name), display name (locale and text), node class,
reference node identifier, and type node identifier.
.TP
\fBopcua type\fR \fIhandle nodeid\fR ?\fIattr\fR?
.
Performs a read operation on the client or server object \fIhandle\fR

/*
 * topcua.c --
 *
 *      This file contains a proof of concept Tcl binding to the
 *	open62541 OPC/UA library (client and server).
 *
 * Copyright (c) 2018 Christian Werner <chw at ch minus werner dot de>
 *
 * See the file "license.terms" for information on usage and redistribution of
 * this file, and for a DISCLAIMER OF ALL WARRANTIES.
 */

    int nCmdObjs;			/* For the Tcl callback. */
    Tcl_Obj **cmdObjs;			/* Ditto. */
    int nSavedCmdObjs;			/* Ditto. */
    Tcl_Obj **savedCmdObjs;		/* Ditto. */
} UAQ;

/*
 * Structure representing an OPC/UA client or server.
 */

typedef struct UAH {
    struct UAI *uai;			/* Pointer to per-interp data. */
    Tcl_Interp *interp;			/* Interpreter for the client. */
    UA_Client *client;			/* Client connection handle. */
    UA_Server *server;			/* Server handle. */

	g->data4[4] = d[7];
	g->data4[5] = d[8];
	g->data4[6] = d[9];
	g->data4[7] = d[10];
	break;
    }
    case UA_NODEIDTYPE_BYTESTRING:
	if ((string[0] == '0') && (string[1] == 'x')) {
	    UA_ByteString *bs = &nodein->identifier.byteString;
	    char buffer[3];
	    int v;
	    Tcl_DString ds;

	    Tcl_DStringInit(&ds);
	    string += 2;
	    while (1) {
		buffer[0] = string[0];
		if (string[0] == '\0') {
		    break;
		}
		buffer[1] = string[1];
		if (string[1] == '\0') {
		    break;
		}
		buffer[2] = '\0';
		if (sscanf(buffer, "%x", &v) != 1) {
		    break;
		}
		buffer[0] = v;
		Tcl_DStringAppend(&ds, buffer, 1);
		string += 2;
	    }
	    bs->length = Tcl_DStringLength(&ds);
	    if (bs->length > 0) {
		bs->data = (UA_Byte *) UA_malloc(bs->length);
		if (bs->data == NULL) {
		    bs->length = 0;
		    bs->data = (UA_Byte *) UA_EMPTY_ARRAY_SENTINEL;
		} else {
		    memcpy(bs->data, Tcl_DStringValue(&ds), bs->length);
		}
	    } else {
		bs->data = (UA_Byte *) UA_EMPTY_ARRAY_SENTINEL;
	    }
	    Tcl_DStringFree(&ds);
	} else {
	    UA_ByteString *bs = &nodein->identifier.byteString;

	    bs->length = strlen(string);
	    if (bs->length > 0) {
		bs->data = (UA_Byte *) UA_malloc(bs->length);
		if (bs->data == NULL) {
		    bs->length = 0;
		    bs->data = (UA_Byte *) UA_EMPTY_ARRAY_SENTINEL;
		} else {
		    memcpy(bs->data, string, bs->length);
		}
	    } else {
		bs->data = (UA_Byte *) UA_EMPTY_ARRAY_SENTINEL;
	    }
	}
	goto error;
    }
    return nodein;
error:
    if (interp != NULL) {
	Tcl_Obj *list[4];
	UA_StatusCode uaret = UA_STATUSCODE_BADINTERNALERROR;

 *
 *-------------------------------------------------------------------------
 */

static char *
PrintNodeId(const UA_NodeId *nodein, Tcl_DString *dsPtr)
{
    size_t i;
    char buffer[64];

    Tcl_DStringInit(dsPtr);
    if (nodein->namespaceIndex) {
	sprintf(buffer, "ns=%d;", nodein->namespaceIndex);
	Tcl_DStringAppend(dsPtr, buffer, -1);
    }

		nodein->identifier.guid.data4[4],
		nodein->identifier.guid.data4[5],
		nodein->identifier.guid.data4[6],
		nodein->identifier.guid.data4[7]);
	Tcl_DStringAppend(dsPtr, buffer, -1);
	break;
    case UA_NODEIDTYPE_BYTESTRING:

	Tcl_DStringAppend(dsPtr, "b=0x", 2);
	for (i = 0; i < nodein->identifier.byteString.length; i++) {
	    sprintf(buffer, "%02x", nodein->identifier.byteString.data[i]);
	    Tcl_DStringAppend(dsPtr, buffer, 2);
	}
	break;
    }
    return Tcl_DStringValue(dsPtr);
}

/*
 *-------------------------------------------------------------------------

}

/*
 *-------------------------------------------------------------------------
 *
 * DecodeToObj --
 *
 *	Decode a OPC/UA type to a Tcl_Obj.
 *
 * Results:
 *	A pointer to a Tcl_Obj (which is empty when decoding is not
 *	possible due to data type).
 *
 * Side effects:
 *	None.

	switch (ext->encoding) {
	case UA_EXTENSIONOBJECT_ENCODED_BYTESTRING:
	    p = PrintNodeId(&ext->content.encoded.typeId, &ds);
	    list[0] = Tcl_NewStringObj(p, -1);
	    Tcl_DStringFree(&ds);
	    if (ext->content.encoded.body.data != NULL) {

		list[1] =
		    Tcl_NewByteArrayObj(ext->content.encoded.body.data,
					ext->content.encoded.body.length);
	    } else {
		list[1] = Tcl_NewObj();
	    }
	    return Tcl_NewListObj(2, list);

		v->data4[6], v->data4[7]);
	return Tcl_NewStringObj(buffer, -1);
    }
    if (type == &UA_TYPES[UA_TYPES_BYTESTRING]) {
	UA_ByteString *v = (UA_ByteString *) data;

	if (v->data != NULL) {

	    return Tcl_NewByteArrayObj(v->data, v->length);
	}
	return Tcl_NewObj();
    }
    if (type == &UA_TYPES[UA_TYPES_XMLELEMENT]) {
	UA_String *v = (UA_String *) data;

}

/*
 *-------------------------------------------------------------------------
 *
 * EncodeFromObj --
 *
 *	Encode a Tcl_Obj to an OPC/UA type.
 *
 * Results:
 *	A pointer to an allocated OPC/UA value.
 *
 * Side effects:
 *	None.
 *
 *-------------------------------------------------------------------------
 */

}

/*
 *-------------------------------------------------------------------------
 *
 * MethodInvoke --
 *
 *	Method invocation callback from OPC/UA server.
 *
 * Results:
 *	UA_StatusCode.
 *
 * Side effects:
 *	Many, since Tcl code gets evaluated.
 *