examples/NodeFunctions.cpp File Reference

example: get info about generic Nodes More...

Include dependency graph for NodeFunctions.cpp:

Functions
void	printGenericInfo (Node n)
	Print generic Node info.
void	printSpecificInfo (Node n)
	Decode Node type and print type specific info.
int	main (int, char **)
	Example use of generic and specific Node functions.

---

Detailed Description

example: get info about generic Nodes

Also see listing at end of this page for source without line numbers (to cut&paste from).

/*** NodeFunctions.cpp example: get info about generic Nodes */
#include <iostream>
#include "E57Foundation.h"
using namespace e57;
using namespace std;

void printGenericInfo(Node n)
{
    cout << "  elementName    = " << n.elementName()              << endl;
    cout << "  pathName       = " << n.pathName()                 << endl;
    cout << "  parent name    = " << n.parent().pathName()        << endl;
    cout << "  isRoot         = " << n.isRoot()                   << endl;
    cout << "  isAttached     = " << n.isAttached()               << endl;
    cout << "  destImageFile  = " << n.destImageFile().fileName() << endl;
    cout << "  type           = " << n.type()                     << endl;
}

void printSpecificInfo(Node n)
{
    switch (n.type()) {
        case E57_STRUCTURE: {
            StructureNode s = static_cast<StructureNode>(n);
            StructureNode s2(n);
            StructureNode s3 = StructureNode(n);
            StructureNode s4 = (StructureNode)n;
            cout << "  StructureNode with " << s.childCount() << " children" << endl;
            printGenericInfo(s);
        }
        break;
        case E57_VECTOR: {
            VectorNode v = static_cast<VectorNode>(n);
            cout << "  VectorNode with " << v.childCount() << " children" << endl;
            printGenericInfo(v);
        }
        break;
        case E57_COMPRESSED_VECTOR: {
            CompressedVectorNode cv = static_cast<CompressedVectorNode>(n);
            cout << "  CompressedVectorNode with " << cv.childCount() << " children" << endl;
            printGenericInfo(cv);
        }
        break;
        case E57_INTEGER: {
            IntegerNode i = static_cast<IntegerNode>(n);
            cout << "  IntegerNode with value = " << i.value() << endl;
            printGenericInfo(i);
        }
        break;
        case E57_SCALED_INTEGER: {
            ScaledIntegerNode si = static_cast<ScaledIntegerNode>(n);
            cout << "  ScaledIntegerNode with rawValue = " << si.rawValue() << endl;
            printGenericInfo(si);
        }
        break;
        case E57_FLOAT: {
            FloatNode f = static_cast<FloatNode>(n);
            cout << "  FloatNode with value = " << f.value() << endl;
            printGenericInfo(f);
        }
        break;
        case E57_STRING: {
            StringNode s = static_cast<StringNode>(n);
            cout << "  StringNode with value = " << s.value() << endl;
            printGenericInfo(s);
        }
        break;
        case E57_BLOB: {
            BlobNode b = static_cast<BlobNode>(n);
            cout << "  BlobNode with length = " << b.byteCount() << endl;
            printGenericInfo(b);
        }
        break;
    }
}

int main(int /*argc*/, char** /*argv*/) {
    try {
        ImageFile imf("temp._e57", "w");
        StructureNode root = imf.root();

        // Add a String element in /child/grandchild
        StructureNode child   = StructureNode(imf);
        StringNode grandchild = StringNode(imf, "I'm a grandchild");
        root.set("child", child);
        child.set("grandchild", grandchild);

        cout << "root node:" << endl;
        printSpecificInfo(root);

        cout << "child node:" << endl;
        printSpecificInfo(child);

        cout << "grandchild node:" << endl;
        printSpecificInfo(grandchild);

        StructureNode unattached = StructureNode(imf);
        StringNode unattachedChild = StringNode(imf, "I'm a child of an unattached node");
        unattached.set("unattachedChild", unattachedChild);

        cout << "unattached node:" << endl;
        printSpecificInfo(unattached);

        cout << "unattached child node:" << endl;
        printSpecificInfo(unattachedChild);

        imf.close(); // don't forget to explicitly close the ImageFile
    } catch(E57Exception& ex) {
        ex.report(__FILE__, __LINE__, __FUNCTION__);
        return(-1);
    }
    return(0);
}

This example program illustrates the manipulation and interrogation of generic Nodes. A tree three levels deep is created and printed. See the HelloWorld.cpp example for discussion of the use of include files, constructing an ImageFile, and the try/catch block to handle exceptions.

In source lines 82-83, an new E57 file is opened for writing, and the predefined root node is fetched. On source line 86, a StructureNode is created, and a handle to it is saved in child. On source line 87, a StringNode is created, and a handle to it is saved in grandchild. The StructureNode is then attached to the root of the ImageFile, on source line 88, with a resulting absolute path name of "/child". Then, in source line 89, the StringNode is attached into the ImageFile tree with a resulting absolute path name of "/child/grandchild".

Source line 92 calls a routine printSpecificInfo that prints out information that is specific to the type of the node. However the format argument to the function is of type Node, and the type of actual argument provided is type StructureNode in source line 92. This type mis-match is resolved by the compiler by using the upcast function of StructureNode that can convert the handle into a generic Node. This conversion is silently by the compiler, as it is always type-safe. Once inside printSpecificInfo, the true type of n is temporarily lost. A Node handle does not have the member function to get how many children the underlying StructureNode object has. On source line 24, the true type of n is fetched, and used in a switch statement to protect against attempting to convert a generic Node handle to a handle of the incorrect underlying type (this attempt would fail with an exception). The generic Node handle is convert back to the correct underlying type (e.g. in source line 26) by calling a handle downcast function. Note that in source lines 27-29, three alternate syntaxes are given for calling the exact same downcast function. The specific handle is used to print out some information that can't be gotten using the generic handle. Then printGenericInfo is called to print out the state of seven generic Node attributes that are common to all Node types.

Some state of the three nodes ("/", "/child", and "/child/grandchild") are listed in the output lines 1-27. The two more nodes are created, but not attached to the root node, and some of their state is printed out in output lines 28-45. Note that the isAttached attribute is false for both nodes. When the try block ends in source line 111, all the constructed objects will be deleted. The two unattached nodes will not be saved in the E57 file, because the were not attached directly or indirectly to the ImageFile root node. This is reflected in the XML listing, where only three elements show up, instead of five. Also note that the two unattached nodes remember (see output lines 35 and 44) which destination ImageFile was declared during their creation, even though they never get attached to that file. It is not an error to fail to attach a node to the declared ImageFile (it's just wasteful).

The following console output is produced:

The XML section of the temp._e57 E57 file produced by this example program is as follows:

Here is the source code without line numbers to cut&paste from:

/*** NodeFunctions.cpp example: get info about generic Nodes */
#include <iostream>
#include "E57Foundation.h"
using namespace e57;
using namespace std;

void printGenericInfo(Node n)
{
    cout << "  elementName    = " << n.elementName()              << endl;
    cout << "  pathName       = " << n.pathName()                 << endl;
    cout << "  parent name    = " << n.parent().pathName()        << endl;
    cout << "  isRoot         = " << n.isRoot()                   << endl;
    cout << "  isAttached     = " << n.isAttached()               << endl;
    cout << "  destImageFile  = " << n.destImageFile().fileName() << endl;
    cout << "  type           = " << n.type()                     << endl;
}

void printSpecificInfo(Node n)
{
    switch (n.type()) {
        case E57_STRUCTURE: {
            StructureNode s = static_cast<StructureNode>(n);
            StructureNode s2(n);
            StructureNode s3 = StructureNode(n);
            StructureNode s4 = (StructureNode)n;
            cout << "  StructureNode with " << s.childCount() << " children" << endl;
            printGenericInfo(s);
        }
        break;
        case E57_VECTOR: {
            VectorNode v = static_cast<VectorNode>(n);
            cout << "  VectorNode with " << v.childCount() << " children" << endl;
            printGenericInfo(v);
        }
        break;
        case E57_COMPRESSED_VECTOR: {
            CompressedVectorNode cv = static_cast<CompressedVectorNode>(n);
            cout << "  CompressedVectorNode with " << cv.childCount() << " children" << endl;
            printGenericInfo(cv);
        }
        break;
        case E57_INTEGER: {
            IntegerNode i = static_cast<IntegerNode>(n);
            cout << "  IntegerNode with value = " << i.value() << endl;
            printGenericInfo(i);
        }
        break;
        case E57_SCALED_INTEGER: {
            ScaledIntegerNode si = static_cast<ScaledIntegerNode>(n);
            cout << "  ScaledIntegerNode with rawValue = " << si.rawValue() << endl;
            printGenericInfo(si);
        }
        break;
        case E57_FLOAT: {
            FloatNode f = static_cast<FloatNode>(n);
            cout << "  FloatNode with value = " << f.value() << endl;
            printGenericInfo(f);
        }
        break;
        case E57_STRING: {
            StringNode s = static_cast<StringNode>(n);
            cout << "  StringNode with value = " << s.value() << endl;
            printGenericInfo(s);
        }
        break;
        case E57_BLOB: {
            BlobNode b = static_cast<BlobNode>(n);
            cout << "  BlobNode with length = " << b.byteCount() << endl;
            printGenericInfo(b);
        }
        break;
    }
}

int main(int /*argc*/, char** /*argv*/) {
    try {
        ImageFile imf("temp._e57", "w");
        StructureNode root = imf.root();

        // Add a String element in /child/grandchild
        StructureNode child   = StructureNode(imf);
        StringNode grandchild = StringNode(imf, "I'm a grandchild");
        root.set("child", child);
        child.set("grandchild", grandchild);

        cout << "root node:" << endl;
        printSpecificInfo(root);

        cout << "child node:" << endl;
        printSpecificInfo(child);

        cout << "grandchild node:" << endl;
        printSpecificInfo(grandchild);

        StructureNode unattached = StructureNode(imf);
        StringNode unattachedChild = StringNode(imf, "I'm a child of an unattached node");
        unattached.set("unattachedChild", unattachedChild);

        cout << "unattached node:" << endl;
        printSpecificInfo(unattached);

        cout << "unattached child node:" << endl;
        printSpecificInfo(unattachedChild);

        imf.close(); // don't forget to explicitly close the ImageFile
    } catch(E57Exception& ex) {
        ex.report(__FILE__, __LINE__, __FUNCTION__);
        return(-1);
    }
    return(0);
}