Making Xerces parse a string instead of a file - c++

Question

I know how to create a complete dom from an xml file just using XercesDOMParser:
xercesc::XercesDOMParser parser = new xercesc::XercesDOMParser();
parser->parse(path_to_my_file);
parser->getDocument(); // From here on I can access all nodes and do whatever i want
Well, that works... but what if I'd want to parse a string? Something like
std::string myxml = "<root>...</root>";
xercesc::XercesDOMParser parser = new xercesc::XercesDOMParser();
parser->parse(myxml);
parser->getDocument(); // From here on I can access all nodes and do whatever i want
I'm using version 3. Looking inside the AbstractDOMParser I see that parse method and its overloaded versions, only parse files.
How can I parse from a string?

Answer 1

Create a MemBufInputSource and parse that:
xercesc::MemBufInputSource myxml_buf(myxml.c_str(), myxml.size(),
"myxml (in memory)");
parser->parse(myxml_buf);

Answer 2

Use the following overload of XercesDOMParser::parse():
void XercesDOMParser::parse(const InputSource& source);
passing it a MemBufInputSource:
MemBufInputSource src((const XMLByte*)myxml.c_str(), myxml.length(), "dummy", false);
parser->parse(src);

Answer 3

Im doing it another way. If this is incorrect, please tell me why. It seems to work.
This is what parse expects:
DOMDocument* DOMLSParser::parse(const DOMLSInput * source )
So you need to put in a DOMLSInput instead of a an InputSource:
xercesc::DOMImplementation * impl = xercesc::DOMImplementation::getImplementation();
xercesc::DOMLSParser *parser = (xercesc::DOMImplementationLS*)impl)->createLSParser(xercesc::DOMImplementation::MODE_SYNCHRONOUS, 0);
xercesc::DOMDocument *doc;
xercesc::Wrapper4InputSource source (new xercesc::MemBufInputSource((const XMLByte *) (myxml.c_str()), myxml.size(), "A name");
parser->parse(&source);

Answer 4

You may use MemBufInputSource as found in the xercesc/framework/MemBufInputSource.cpp, and the header file, MemBufInputSource.hpp contains extensive documentation, as similar to answers above:
#include <xercesc/framework/MemBufInputSource.hpp>
char* myXMLBufString = "<root>hello xml</root>";
MemBufInputSource xmlBuf((const XMLByte*)myXMLBufString, 23, "myXMLBufName", false);
But take note, this doesn't seem to work unless you first initialize the system, as below (taken from the xerces-c-3.2.3/samples/src/SAX2Count/SAX2Count.cpp)
bool recognizeNEL = false;
char localeStr[64];
memset(localeStr, 0, sizeof localeStr);
// Initialize the XML4C2 system
try {
if (strlen(localeStr)) {
XMLPlatformUtils::Initialize(localeStr);
} else {
XMLPlatformUtils::Initialize();
}
if (recognizeNEL) {
XMLPlatformUtils::recognizeNEL(recognizeNEL);
}
} catch (const XMLException& toCatch) {
XERCES_STD_QUALIFIER cerr << "Error during initialization! Message:\n"
<< StrX(toCatch.getMessage()) << XERCES_STD_QUALIFIER endl;
return 1;
}
Of course reading a file wouldn't require thinking about this type of prep since you just pass a file path to the program which the parser takes. So for those experiencing seg faults, this could be the answer.