MSXML. Get data as Base64 - c++

Question

I'm using C++ with MSXML and want to get data from XML file as Base64. I'm using this code:
hr = nodeList->get_item((long)i, (IXMLDOMNode **)&vXMLNode);
if ( FAILED(hr) )
throw "Unable to retrieve child node";
vXMLNode->put_dataType(_bstr_t("bin.base64"));
hr = vXMLNode->get_nodeTypedValue(&varValue);
if ( FAILED(hr) )
throw "Unable to retrieve 'xmltext' text";
So vXMLNode is a child node with data. Node type of vXMLNode is NODE_ELEMENT. If I check data type for this node, I get VT_NULL. Therefore I get my data as a string.
What is wrong in my code?

Answer 1

I believe the problem lies outside of your supplied sample code. Here's a working console program that uses nodeTypedValue. I hope this helps.
// Base64CPP.cpp : Defines the entry point for the console application.
// NOTE:
// This code is provided as is in the form of a sample with no warranties of any kind,
// either expressed or implied for any purpose. Use at your own risk.
#include "stdafx.h"
#include <TCHAR.H>
#include <stdio.h>
#include <sys/stat.h>
#include <fstream>
#include <string.h>
#include <atlbase.h>
#import <msxml4.dll> named_guids
using namespace MSXML2;
inline void EVAL_HR( HRESULT _hr )
{ if FAILED(_hr) throw(_hr); }
// Binary to Base64 Encoding
bool DoEncoding(LPCTSTR lpszXMLFile, LPCTSTR lpszBinFile)
{
bool bRetVal = false;
try
{
long lFileSize;
struct stat fileSizeVal;
// Get the file size
if (stat(lpszBinFile, &fileSizeVal) == 0)
{
lFileSize = fileSizeVal.st_size;
if(lFileSize <= 0)
return false;
}
else
return false;
// Instantiate XML DOMDocument
CComPtr<IXMLDOMDocument2> spXMLDoc;
CComPtr<MSXML2::IXMLDOMElement> spDataElement;
HRESULT hr = spXMLDoc.CoCreateInstance(CLSID_DOMDocument40);
EVAL_HR(hr);
spXMLDoc->loadXML(_T("<?xml version='1.0' encoding='UTF-8'?> <Data/>"));
// Prepare the top node to store binary data as base64
spDataElement = spXMLDoc->documentElement;
ATLASSERT(spDataElement != NULL && _T("Failed to get document element."));
hr = spDataElement->put_dataType(CComBSTR(_T("bin.base64")));
EVAL_HR(hr);
// Read the file into memory
std::ifstream binDataFile;
binDataFile.open(lpszBinFile, std::ios::binary);
binDataFile.seekg(std::ios::beg);
SAFEARRAY* psa = SafeArrayCreateVector( VT_UI1, 0L, lFileSize);
binDataFile.read((char*)psa->pvData, lFileSize);
binDataFile.close();
// Save the binary data into Data node
VARIANT var;
VariantInit(&var);
var.parray = psa;
var.vt = (VT_ARRAY | VT_UI1 );
spDataElement->nodeTypedValue = var;
// Save the XML Document
spXMLDoc->save(lpszXMLFile);
bRetVal = true;
}
catch(int)
{
//TODO: Error handling
printf(_T("Exception raised!"));
}
return bRetVal;
}
// Base64 to binary decoding
bool DoDecoding(LPCTSTR lpszXMLFile, LPCTSTR lpszBinFile)
{
bool bRetVal = false;
try
{
// Instantiate DOMDocument and load XML file
CComPtr<IXMLDOMDocument2> spXMLDoc;
CComPtr<MSXML2::IXMLDOMElement> spDataElement;
HRESULT hr = spXMLDoc.CoCreateInstance(CLSID_DOMDocument40);
EVAL_HR(hr);
CComVariant vtFileName = CComBSTR(lpszXMLFile);
spXMLDoc->load(vtFileName);
// ASSUMPTION: documentElement (top element) contains base64 data
spDataElement = spXMLDoc->documentElement;
ATLASSERT(spDataElement != NULL && _T("Failed to get document element."));
// Prepare the file for writing
std::ofstream binDataFile (lpszBinFile, std::ios::out | std::ios::binary);
// Save the binary data into data file
long lDataLength=0;
hr = SafeArrayGetUBound(spDataElement->nodeTypedValue.parray, 1, &lDataLength);
EVAL_HR(hr);
lDataLength++;
binDataFile.write((char*)(spDataElement->nodeTypedValue.parray->pvData), lDataLength);
binDataFile.close();
bRetVal = true;
}
catch(int)
{
//TODO: Error handling
printf(_T("Exception raised!"));
}
return bRetVal;
}
int main(int argc, char* argv[])
{
if(argc < 4)
{//insufficient parameters
printf(_T("\nSample app to encode/decode binary data as base64 XML using MSXML.\n"));
printf(_T("\nUsage:\tBase64CPP.exe <e>|<d> <XMLFileName> <BinaryDataFile>"));
printf(_T("\n\nExamples:"));
printf(_T("\n\tEncode binary data in 1.jpg and save as Base64 into 1.xml:"));
printf(_T("\n\t\tBase64CPP.exe e c:\\1.xml c:\\1.jpg\n"));
printf(_T("\n\tDecode base64 data in 1.xml and save as binary into 2.jpg:"));
printf(_T("\n\t\tBase64CPP.exe d c:\\1.xml c:\\2.jpg\n\n"));
return -1;
}
try
{
HRESULT hr = CoInitialize(NULL);
EVAL_HR(hr);
if(_tcsicmp(argv[1], _T("e")) == 0)
{
if(DoEncoding(argv[2], argv[3]))
printf(_T("Success. See %s for results."), argv[2]);
else
printf(_T("Failed."));
}
else
{
if(DoDecoding(argv[2], argv[3]))
printf(_T("Success. See %s for results."), argv[3]);
else
printf(_T("Failed."));
}
}
catch(int)
{
//TODO: Error handling
printf(_T("Exception raised!"));
}
CoUninitialize();
getchar();
return 0;
}